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Spline inspection

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gottabmw

Someone wants to buy my '04 RT, but not until he inspects the splines. He wants to remove the starter to inspect the splines. I have misgiving about him doing that in the first place, but also I need to know if he can actually check them using this method.

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The Fabricator

Yes the splines can be checked through the hole where the starter goes. Did it to my 2000 R1150GS. Mine has more play than I would like. The most hazardous part is the power cable from the battery that runs direct to the starter. Short that out and see big sparks. Disconnect the ground cable at the battery first or VERY CAREFULLY disconnect power cable at starter and tape it very well to insulate it. If this fellow knows about the spline inspection, he probably knows about the power cable hazard. Have that conversation first.

 

There is no specification for spline play. It's a judgement call, especially through the hole.

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dirtrider
Someone wants to buy my '04 RT, but not until he inspects the splines. He wants to remove the starter to inspect the splines. I have misgiving about him doing that in the first place, but also I need to know if he can actually check them using this method.

 

Morning gottabmw

 

You can't actually INSPECT the splines by just removing the starter as the clutch disk pretty well covers the splines in the known wear area so not much to see or inspect.

 

You can measure then evaluate the clutch disk rotational movement on the stationary transmission input shaft then from that get an idea on the amount of clutch disk to input shaft wear. But you still can't tell how much trans input shaft spline wear vs clutch disk hub internal wear.

 

I'm not sure that I would let just anyone tear into my bike & remove the starter, or pry around in the clutch area. How do you know if this guy is qualified & not a total hack???

 

What happens if he decides that the splines are worn? Does he just leave you with a pile of parts & a partially disassembled bike? What happens if he is a total hack & breaks something expensive (who pays for the repairs?)

 

Personally, if it were my bike for sale I would charge a nominal fee to remove the plastic then remove the starter (myself) for the potential buyers inspection. If he buys the bike then he gets the nominal fee back, if he doesn't buy it then I keep the nominal fee for my time & effort.

 

If you are not comfortable doing the work yourself then suggest that you would be open to allowing a (qualified) dealer to inspect it-- Just too much can go wrong with allowing some unknown person with unknown mechanical skills to tear your bike apart.

 

 

 

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Mike279

I bought my bike using the known spline problem as part of my negotiations. I test drove the bike and the clutch was not 100 percent. I just figured it was coming apart after I bought it. I was buying it because the price was right and I planned on replacing whatever it needed. I did not ask to tear down the bike. I was in a better position just implying there was a problem. In the end, the money I saved negotiating paid for the new clutch and the splines were fine. I played the odds after reading a bunch on this site to figure they were probably good. Used bikes are priced according to the market and factors like the spline issue. I am sure the bike I bought would cost more if those issues were not present. I am a happy owner. Mike

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Cap

These are all good points:

1. So, you pull the starter and wiggle the clutch. Now what? There is no spec.

2. Letting someone else dismantle your bike is risky

3. Spline problems are priced-in to the market for used bikes.

 

I would let the potential buyer ride the bike. If you have done meticulous maintenance, I would show evidence, and assert that your price represents a good value. A knowledgeable buyer should accept these data inputs, and make their decision without tearing your bike apart. They can do that when they get it home.

 

 

In contrast, an internet mechanic might parrot something they saw on a forum like this one, and ask you to remove your starter so they can satisfy their curiosity before they walk away.

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AndyS
These are all good points:

1. So, you pull the starter and wiggle the clutch. Now what? There is no spec.

 

Well, I wouldn't let an unauthorised / unqualified stranger anywhere near my bike to work on it. However, if this was a selling point and the price was right, I would pull the starter myself and show the prospective buyer.

There is no spec, but a fair amount can be ascertained.

For example:

a/. The clutch friction material can just about be seen, so there is a clue as to clutch life remaining (if you know the known starting thickness and the thickness at which they are likely to start causing problems.

Some kind souls on this forum have previously furnished that information too!

b/. With the clutch lever pulled in and the bike in gear, using a screwdriver, the clutch disk can be pushed on its periphery and wiggled back and forth. There will be radial (rotational) movement, but the amount of movement can be a good indicator of gearbox input shaft spline/clutch disc spline wear.

 

 

2. Letting someone else dismantle your bike is risky
Yes it is.

3. Spline problems are priced-in to the market for used bikes.
Only if you know, or suspect you have a problem. MANY bikes have no such problems, so why would you factor that in?

 

 

 

Edited by AndyS

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Cap
... the amount of movement can be a good indicator of gearbox input shaft spline/clutch disc spline wear.

 

 

But that's my point Andy -- for someone with a lot of experience, this might be useful data. But even under the best of circumstances it is equivocal evidence. A few well-intentioned people have reported what they found when they tried this, usually in fairly imprecise terms. Still fewer people have subsequently pulled the transmission off and reported the degree of wear on the spline that correlated with their imprecise view of the angular free-play when viewed through the starter hole. So, given a situation in which both buyer and seller are non-experts, I think this is a pointless exercise.

 

 

re: priced-in... Only if you know, or suspect you have a problem. MANY bikes have no such problems, so why would you factor that in?

 

Well, things might be different on your side of the pond. I'm speaking for buyers and sellers in the US who have heard of this potential issue, which would seem to be the case in this instance. The market price of oilhead RTs is really much lower than it should be, given their features and overall superb engineering and quality of materials. I took advantage of that when I bought my 2004 RT a few years ago, and will suffer the same penalty when I sell my pristine RT to some lucky rider. The buyer knows they are gambling: there is some small probability that the spline will strip and leave them with expensive repairs. So, the price is discounted accordingly, in approximate proportion to the risk. And back to the original question of starter-hole inspection: why do it if you already have a discounted sales price?

 

Cap

 

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catskill

If I was going to buy a 2004 Oilhead, I would want to do this inspection. Having owned an Oilhead for quite some time, I do realize that this bike does have a problem with destroying it's input shaft / clutch. If the owner wouldn't allow me to see it, I would either walk away or severely discount the bike. If I did see it, and I liked what I saw, I would offer a good price. The 2004 has a lot of great features other Oilheads don't. If the prospective buyer has owned an Oilhead, I would feel better about allowing them to look. But, if they haven't done this job before I wouldn't be so eager to allow this.

 

Once you have the starter out, this is what I look for:

 

1. You can get a good idea how much of the clutch has worn by using a caliper. Some people beat the bike and wear the clutch out in 30k miles. But, normally it should last 100k.

2. If they area around the input shaft has red dust, this is an indication that the input shaft is out of grease, and is most likely needs to be replaced.

3. You can also see if they put an aftermarket longer hub on for the clutch. This will reduce the potential problem with the input shaft.

4. If the input shaft has been greased at the proper mileage interval, you can often tell by seeing some grease near the input shaft.

5. If the starter solenoid is sticking, you might notice it. Simple fix.

6. if the crankshaft output seal is bad, then you will see oil in the housing. That will be a significant repair.

7. If the input shaft bearing or seal is bad you would have gear oil in the housing. Again, this is a significant repair.

 

But, having said this, the bike can look good through the starter hole, and the input shaft / clutch can still be damaged. So, this is not fool-proof test. The only real way to know is to pull the transmission out.

 

I think that the hardest part is getting the left cover off and then back on the bike. Removing the starter is easy.

 

I personally do this check every 10-12k miles on my own Oilhead.

 

If you couldn't put the bike back together yourself I would understand why you might now want to do this. It also depends upon the prospective buyer, and how much you trust him. If you could put the bike back together yourself, i would certainly allow it. The used bike market is very soft right now. It is certainly a buyers market.

 

Allowing it really depends upon all the parameters of your situation.

 

 

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Jim Moore

How mechanical are you? Would you be confident in removing the starter yourself before he arrives?

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Alan Sykes

Here's the relevant video :-

 

 

As AndyS says above, if the spline wear issue is a deal-breaker, then do the Tupperware-off, starter-motor removal job yourself in advance of the purchaser arriving to view the bike.

 

Dirt Rider laboriously makes the point from his comfy chair that this check won't tell you what the splines look like - obviously. But it is regarded by most EU Motorrad technicians as a quick and effective check on whether worrying-amounts of spline wear EXIST. And doing the job anyway by no means "leave(s) you with a pile of parts & a partially disassembled bike."

 

I won't go once more into the topic of how many USA-bound bikes were dropped in transit, thus mis-aligning the bell-housing-to-clutch-to-gearbox interfaces, because such damage was only a possibility. If your bike has such a mis-alignment, due either to transit accident or factory bungling, tough. But most bikes of the period 2003 onward were OK in that regard.

 

The estimable Chris Harris did a bit of a sweeper by suggesting before he fell seriously ill that early in the noughties, ALL 6-speed hydrau-actuated clutch bikes were mis-aligned at the factory, leading to premature spline failure. The majority were not.

 

AL in s.e. Spain

2004 Rockster; amazing Honda NC750S-DCT auto.

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Alan Sykes

Thanks Stan - what incredibly beautiful and clear fotos. Fantastic. You must be a pro-fotografer as well as a bike wrencher.

 

Esmir's hub-spacer project has come to an end since those enterprising machine-shops in Thailand and subsequently Italy decided to solve the problem of the too-short Sachs friction plate hub, by broaching and selling a deeper hub on a quality friction plate as a one-stop solution.

 

My genial acquaintance Manfred on the shop-floor in BMW Berlin-Spandau admitted over a few beers a few years ago that the problem was simply inept communication by BMW Motorrad buying office with Sachs in Slowakia by giving them the wrong dimensions for the plate's hub and thus Sachs supplied crates of them that were 5-and-a-half millis too short.

 

An issue that BMW has never either acknowledged or corrected since, and now of course their current boxer bikes are fitted with an out-sourced Chinese wet clutch following the total re-design of the 1200cc motor back in 2013. Problem gone....

 

Thanks again for pointing us at your exhaustive link.

 

AL in s.e. Spain

 

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dirtrider

Evening Alan

 

Makes a good story-- but,

 

Put me in the doubtful column on this one.

 

So you are saying that BMW sent incorrect specifications to the clutch disk supplier (this is possible), then received the incorrect pre-production (test) clutch disks & didn't catch the error, then ran the pre-production durability testing, post test teardown, & durability layout evaluation using the incorrect parts.

 

Then bought cases of incorrect clutch parts & installed them in production motorcycle's for almost 6 years.

 

Then kept buying incorrect clutch disks even when dealer warranty reports & warranty parts send back indicated incorrect parts were being installed.

 

Then bought many many more to use as replacement parts for the last 10+ years.

 

 

 

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Alan Sykes

Yep, absolutely, DR - that is the correct sequence of events as described by you in such detail above. That is precisely what happened.

The incorrectly-dimensioned hub clutch plates supplied by Sachs were fitted in Berlin year after year. Any subsequent dealer referrals either didn't happen or were ignored.

An executive engineers' team clearly had decided that the incorrect length of the hub was of insignificant importance to adversely affect the performance and durability of the clutch mechanism.

Another example of incompetence was the collapse of the rear suspension back in 2011 affecting all 1200cc RT models, causing a major recall.

It happens, old pal, even in The Fatherland.

 

Thanks for your swift reply. But tut-tut, I notice an intrusive apostrophe in your phrase "production motorcycles". You were writing a plural, not a possessive. Naughty, naughty......

 

AL in s.e. Spain

Edited by Alan Sykes

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dirtrider
Yep, absolutely, DR - that is the correct sequence of events as described by you in such detail above. That is precisely what happened.

The incorrectly-dimensioned hub clutch plates supplied by Sachs were fitted in Berlin year after year.

An executive engineers' team clearly had decided that the incorrect length of the hub was of insignificant importance to adversely affect the performance and durability of the clutch mechanism.

Another example of incompetence was the collapse of the rear suspension back in 2011 affecting all 1200cc RT models, causing a major recall.

It happens, old pal, even in The Fatherland.

 

AL in s.e. Spain

 

Evening Alan

 

It still doesn't ring right to me.

 

If it was known early on then WHY didn't BMW simply make a running change & phase the correctly dimensioned parts into production bikes as correct parts became available. They did this on the 1100 clutch, did it on the 1200 final drive & rear pinion bearing, did it on the 1200 drive shaft, did it on the 1200 engine accessory shaft (major & expensive change on this one).

 

I can sort of see an engineering decision to go with the short parts if they thought it would work but definitely can't see them staying with the short parts once they got field feedback that it wasn't working & they were getting many spline failures. Even for the arrogant German BMW company that simply doesn't hold water in my book.

 

The short clutch disk (mistake) doesn't then explain why there were many many 1150 bikes that had no failures (if short was bad then why wouldn't all of the 1150's have shown some form of early failure), the short disk hub doesn't explain the angular spline wear seen on the failed units, or explain the lack of re-failures on the 1150 bikes that had the trans to engine aligned properly, or explain why the 1150 bikes that I have personally found with failed splines (& measured for alignment) showed a basic misalignment problem.

 

Like I said above, good story, but to me it is just that-- a story without merit.

 

 

 

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Paul101

When my 2002 R1150RS had 117kkm, I was seeing what appeared to me about 1/4 inch of clutch disk movement when checking thru the starter opening. This was 5 years ago. This prompted me to take her apart for a spline inspection. I found the clutch disk approximated 50% worn, with angular wear. The input shaft was also worn. Its hard to estimate, but I would guess perhaps 15%. It also showed the angular wear. I decided to a new disk, clutch plate, pressure plate and spring were required. The pressure plate has three bars or straps which mount it to the clutch housing with bolts through the housing cover. In other words these bars are sandwiched between the clutch housing and the housing cover. I measured the clutch housing to ensure it had no run out was not warped. It wasn't. I also noticed that it did not have any indentations for the pressure plate bars either. This didn't seem right. If there is no space for the bars, something has to give and warp when its all bolted together right? So I decided to file some groves in the clutch cover so the assembly would bolt together flat. At the end of last years riding season, I checked the disk movement through the starter opening again. I marked some masking tape in 1/16 and 1/8 inch increments. (approximately) I taped it to the housing cover and took a video with my cell phone. The movement is perhaps a little more than 1/16, but less than 1/8 inch. In any case the bike now had over 202kkm on it. That 85kkm on the new clutch disk, plate and housing cover. I decided to open it up for inspection and lube. Much to my surprise, I found the new clutch plate had negligible wear. The transmission input shaft looked essentially the same as did 5 years ago. So the question is, how come the original clutch disk splines were worn 50% after 117,000km, yet the replacement disk shows almost no wear at 85,000km? Good lube? If anyone is interested, I will try to find the before are after photos and see if I can attach them.

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AndyS
....

My genial acquaintance Manfred on the shop-floor in BMW Berlin-Spandau admitted over a few beers a few years ago that the problem was simply inept communication by BMW Motorrad buying office with Sachs in Slowakia by giving them the wrong dimensions for the plate's hub and thus Sachs supplied crates of them that were 5-and-a-half millis too short.

 

An issue that BMW has never either acknowledged or corrected since, and now of course their current boxer bikes are fitted with an out-sourced Chinese wet clutch following the total re-design of the 1200cc motor back in 2013. Problem gone....

 

 

Wait, do you know the date you had this conversation with your genial acquaintance? It must have been April the 1st.

You can't really believe that story can you?

That could be true for possible one batch, but not for continued production over various model updates.

 

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Alan Sykes

Well, AndyS, I DID believe Manfred's explanation at the time, despite the slight fog of remembrance and the few jars of Berliner Kindl Weisse that we indulged in that evening long ago.

 

But what an interesting discussion this turns out to be. The issue of angular misalignment between plate and shaft causing premature spline wear has all been exhaustively discussed on some of our 'sister' forums :- ADV Rider, Pelikan Parts and UKGSer. Some of the explanations gone into, come from some extremely knowledgeable and experienced boxer bike riders and wrenchers.

 

And Paul's story above is a true "How Come ?" I can offer no comment on why his experience came about.

 

And so, may I point out that my first impulse is not to doubt the veracity of any proposal or explanation vouched by a fellow poster - unlike what seems to be the case here....

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AndyS

Well, we differ then. Because, I struggle to believe that a company such as BMW has too much to lose by just blundering along with the 'incorrect' part for years on end.

As a design engineer, when there is a chance to improve something, it will be done at the first oppertunity with an R2, R3 revision as required. Just as BMW do with each model year we sometimes see tiny changes (such as the Wethead coolant drain hole moving. It was no fanfare, but it happened none the less. Let's face it, a clutch issue is somewhat more important than a piddly little drain hole).

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dirtrider
When my 2002 R1150RS had 117kkm, I was seeing what appeared to me about 1/4 inch of clutch disk movement when checking thru the starter opening. This was 5 years ago. This prompted me to take her apart for a spline inspection. I found the clutch disk approximated 50% worn, with angular wear. The input shaft was also worn. Its hard to estimate, but I would guess perhaps 15%. It also showed the angular wear. I decided to a new disk, clutch plate, pressure plate and spring were required. The pressure plate has three bars or straps which mount it to the clutch housing with bolts through the housing cover. In other words these bars are sandwiched between the clutch housing and the housing cover. I measured the clutch housing to ensure it had no run out was not warped. It wasn't. I also noticed that it did not have any indentations for the pressure plate bars either. This didn't seem right. If there is no space for the bars, something has to give and warp when its all bolted together right? So I decided to file some groves in the clutch cover so the assembly would bolt together flat. At the end of last years riding season, I checked the disk movement through the starter opening again. I marked some masking tape in 1/16 and 1/8 inch increments. (approximately) I taped it to the housing cover and took a video with my cell phone. The movement is perhaps a little more than 1/16, but less than 1/8 inch. In any case the bike now had over 202kkm on it. That 85kkm on the new clutch disk, plate and housing cover. I decided to open it up for inspection and lube. Much to my surprise, I found the new clutch plate had negligible wear. The transmission input shaft looked essentially the same as did 5 years ago. So the question is, how come the original clutch disk splines were worn 50% after 117,000km, yet the replacement disk shows almost no wear at 85,000km? Good lube? If anyone is interested, I will try to find the before are after photos and see if I can attach them.

 

Morning Paul

 

I guess I don't really understand what you did as the 1150 clutch housing should already have depressions for the pressure plate straps to ride in.

 

It sort of sounds like either someone had machined your clutch housing porches flat or someone was trying to mix in an 1100 clutch housing (not even sure that is possible).

 

In any case at 117,000 km on first spline wear (not even a failure) your bike sure isn't one of the spline failure prone 1150 bikes.

 

IXjRSny.jpg

 

 

 

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Paul101
When my 2002 R1150RS had 117kkm, I was seeing what appeared to me about 1/4 inch of clutch disk movement when checking thru the starter opening. This was 5 years ago. This prompted me to take her apart for a spline inspection. I found the clutch disk approximated 50% worn, with angular wear. The input shaft was also worn. Its hard to estimate, but I would guess perhaps 15%. It also showed the angular wear. I decided to a new disk, clutch plate, pressure plate and spring were required. The pressure plate has three bars or straps which mount it to the clutch housing with bolts through the housing cover. In other words these bars are sandwiched between the clutch housing and the housing cover. I measured the clutch housing to ensure it had no run out was not warped. It wasn't. I also noticed that it did not have any indentations for the pressure plate bars either. This didn't seem right. If there is no space for the bars, something has to give and warp when its all bolted together right? So I decided to file some groves in the clutch cover so the assembly would bolt together flat. At the end of last years riding season, I checked the disk movement through the starter opening again. I marked some masking tape in 1/16 and 1/8 inch increments. (approximately) I taped it to the housing cover and took a video with my cell phone. The movement is perhaps a little more than 1/16, but less than 1/8 inch. In any case the bike now had over 202kkm on it. That 85kkm on the new clutch disk, plate and housing cover. I decided to open it up for inspection and lube. Much to my surprise, I found the new clutch plate had negligible wear. The transmission input shaft looked essentially the same as did 5 years ago. So the question is, how come the original clutch disk splines were worn 50% after 117,000km, yet the replacement disk shows almost no wear at 85,000km? Good lube? If anyone is interested, I will try to find the before are after photos and see if I can attach them.

 

Morning Paul

 

I guess I don't really understand what you did as the 1150 clutch housing should already have depressions for the pressure plate straps to ride in.

 

It sort of sounds like either someone had machined your clutch housing porches flat or someone was trying to mix in an 1100 clutch housing (not even sure that is possible).

 

 

In any case at 117,000 km on first spline wear (not even a failure) your bike sure isn't one of the spline failure prone 1150 bikes.

 

IXjRSny.jpg

 

 

 

 

Hi DR,

 

Yes I agree, those depressions should have been there, but they weren't. (unfortunately I didn't think to take a picture) They was a visible line, but the depth was almost immeasurable. When assembling the parts on the workbench, an air gap was clearly visible. That is why I concluded that something has to give and warp when bolting it all together. I am the original owner, so I can be certain no one else has opened her up. It is my contention that this part was not stamped properly. What are the chances this was the only one made this way? I agree my bike wasn't one of the ones with early spline failure. But I wonder if the angular wear I saw on the clutch and spline was a exacerbated due to the missing depression on the housing? As my pictures will show, clutch disk #2 shows very little wear after 85k compared to the original one. The replacement disk is an aftermarket Seibenrock. I suppose its possible the hub is made of a harder metal. But if that were the case I would assume the input shaft would suffer more wear as a result. That doesn't appear to be the case. I will try to post pictures as soon as I figure out how to do that.

 

 

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nrp
Yep, absolutely, DR - that is the correct sequence of events as described by you in such detail above. That is precisely what happened.

The incorrectly-dimensioned hub clutch plates supplied by Sachs were fitted in Berlin year after year. Any subsequent dealer referrals either didn't happen or were ignored.

An executive engineers' team clearly had decided that the incorrect length of the hub was of insignificant importance to adversely affect the performance and durability of the clutch mechanism.

Another example of incompetence was the collapse of the rear suspension back in 2011 affecting all 1200cc RT models, causing a major recall.

It happens, old pal, even in The Fatherland.

 

AL in s.e. Spain

 

I can totally understand the engineering/service/purchasing/management that allowed the shorter spline hub to continue thru the entire production cycle of this series of bikes. Remember the engineering decision tree that has a branch (Does anybody know?) that probably applies here. As an engineer, I'll have to admit I would have made the same decision to use the shorter spline housings, although I would like to think I would have have quietly changed the spec. The problem remains misalignment, not spline engagement, with maybe a contribution from assembly lubrication. It is good to hear there are still Manfreds in the company.

 

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Paul101

shaft and clutch pictures as promised. I believe the pictures clearly show the shaft has little if any additional wear since replacing the original clutch and riding another 85000km (to total of 202000km) The new clutch disk also shows very little wear, just slight scuffing at the section closest to the disk. The splines furthest from the disk have no made contact with the shaft. The shaft is shiny furthest from the transmission case, and rusty where the angular wear is closest to the case. This suggests to me that the angular wear has been eliminated. I saw no evidence of the moly grease I applied in 2013. The last picture shows one of the three spots where the clutch plate strap is located. This is where I filed the clutch housing so the straps would fit flush and not force the housing or clutch cover to bend upon tightening the bolts. I am open to theory's on why the input shaft and new clutch disk are showing almost no new or additional wear. Was it he application of moly lube? The installation of a new clutch disk by Seinbenrock? Or the filling of a gap in the housing for the clutch plate straps?

 

Original clutch disk after 117000km

 

http://s1217.photobucket.com/user/pkalichman/media/clutch%20117000km%202013.jpg.html?sort=3&o=2

 

New clutch after 85000km

 

http://s1217.photobucket.com/user/pkalichman/media/clutch%20disk%2085000km%202017.jpg.html?sort=3&o=1

 

Shaft at 117000km

 

http://s1217.photobucket.com/user/pkalichman/media/shaft%20117000km%202013.jpg.html?sort=3&o=5

 

Shaft at 202000km (1)

 

http://s1217.photobucket.com/user/pkalichman/media/clutch%20disk%2085000km%202017.jpg.html?sort=3&o=1

 

Shaft at 202000km (2)

 

http://s1217.photobucket.com/user/pkalichman/media/shaft%20202000km%202017f.jpg.html?sort=3&o=0

 

housing with filed depression for clutch plate strap

 

http://s1217.photobucket.com/user/pkalichman/media/clutch%20housing.jpg.html?sort=3&o=4

 

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Jim Moore

Great pictures! IMO those don't look like the "classic" six-speed clutch spline issue. The splines are typically more dished out in the usual case. Good for you though. It looks like your repair is working out.

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nrp

The so-called clutch plate straps are there to form a drive connection system between the two engine-side clutch elements in a way that accommodates angular misalignment as well as a small amount of axial (plunge) travel. Since everything rotates together (hopefully) there is no need to file the mounting surfaces for the straps (I would call them flex plates). The use of three tangential flexes like that is traditional engineering practice where plunge and angular alignment must be accommodated.

 

In normal operation the three flex plates are under tension when the engine is driving the rear wheel although I once saw a dyno test on a user's bike that buckled one or more of those flex plates. Needless to say that dyno test was soon over. Some body or thing got into a torsional resonance that caused one or more of the flex plates to buckle. I really can't figure out why it happened but it obviously did.

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dirtrider
The so-called clutch plate straps are there to form a drive connection system between the two engine-side clutch elements in a way that accommodates angular misalignment as well as a small amount of axial (plunge) travel. Since everything rotates together (hopefully) there is no need to file the mounting surfaces for the straps (I would call them flex plates). The use of three tangential flexes like that is traditional engineering practice where plunge and angular alignment must be accommodated.

 

In normal operation the three flex plates are under tension when the engine is driving the rear wheel although I once saw a dyno test on a user's bike that buckled one or more of those flex plates. Needless to say that dyno test was soon over. Some body or thing got into a torsional resonance that caused one or more of the flex plates to buckle. I really can't figure out why it happened but it obviously did.

 

Morning nrp

 

I can sort of understand how that could happen on a rolling drum type chassis dyno as there is a lot of energy stored in that heavy rolling drum.

 

On throttle up those straps are pulling in a tension direction so there is no way they can buckle or bend but after a wide open throttle run-up & the throttle is quickly chopped (suddenly closed) all that stored energy in that fast spinning very heavy rolling drum instantly back drives the closed throttle engine back through the clutch so now those 3 little straps are being forced in the opposite (bending) direction.

 

Obviously those 3 straps only carry 1/2 of the clutch torque but the mass of that rolling drum will back-drive the engine for quite a while (longer than just closing the throttle while riding)

so there is more chance for the clutch to slip a little on back drive from the dyno).

 

I haven't ever seen this happen but can sort of understand how it possibly could.

 

Re-read Paul's postings a couple of times (I didn't get it right away either) where he mentions that the reason that he filed the clutch housing depressions deeper (where the straps attach) was because the depressions weren't deep enough to prevent the strap thickness from allowing the housing cover to bolt down evenly therefore allowing the housing cover to wobble slightly. The clutch cover is what the clutch disk actually seats against on an engaged clutch so if the clutch cover wobbles so does the clutch disk.

 

You also have to think 1150 clutch on this as the 1100 "early" clutch is WAY different as the straps are actually designed to pinch between the clutch housing & housing cover, or the later 1100 clutch as the straps mount to different location on the clutch housing.

 

On the 1150 the straps mount over a pin out on the very end of the mounting pads & get pinched between the clutch housing & housing cover so IF those straps sit a bit proud (like Paul says his did) they could conceivably prevent the housing cover from bolting down flat to the clutch housing.

 

If you aren't familiar with the 1150 assembled clutch then let me know & I will post up a picture of an assembled 1150 clutch to look at.

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Paul101

DR,

 

Thanks for translating my explanation into understandable English! I haven't come across any forums that mentioned any clutch housings that had shallow depressions for the pressure plate straps, so I wanted to get my findings out there.

 

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dirtrider
DR,

 

Thanks for translating my explanation into understandable English! I haven't come across any forums that mentioned any clutch housings that had shallow depressions for the pressure plate straps, so I wanted to get my findings out there.

 

Morning Paul.

 

It is a good find--

 

I haven't seen that shallow depression (mis-stamped housing) on any of the early spline failure bikes that I have worked on (I haven't worked on that many spline failed bikes but enough to get some idea anyhow).

 

You would think that if your apparent mis-stamped clutch cover was (the) main spline wear issue then it wouldn't have gone 117,000km with only showing moderate to light spline wear. I have seen total spline failures in less than 40,000km with a clutch cover that looked to have proper depressions & the housing cover bolted down nice and flat.

 

On the early (low km) failed ones that I have measured the trans/engine alignment the trans to engine alignment was found to be excessive for what I consider to be long life spline joint operation. Unfortunately I only measured the off-set & not the angular misalignment.

 

If you would have installed another stock clutch disk then your second spline inspection would have more meaning, but by installing a different type disk with a possible different hub material, or possible different spline broaching fit/profile makes the wear comparison much less meaningful.

 

If there is a slight trans to engine misalignment then possibly installing a different design clutch disk might also make a difference if there is more flex in the new disk that allows more trans to engine off-set with less radial spline loading, or possibly allows less orbital loading of the spline joint.

 

It would be nice to know for sure if what you found really made THE difference but including the different design clutch disk & using a bike that shows very little spline wear in 117,000km makes determining wear improvement from a sample of 1 very difficult.

 

It is still a good find & something we will all need to a look out for in the future. In the past I usually just bolt the housing cover on using a couple of bolts (with pressure plate not installed) then visually look to see if there is space or gap where the straps seat, then make darn sure that the housing cover bolts down flat with the straps in place, but I haven't actually measured the pocket depression depth vs strap thickness.

 

In any case it does look like what you did to your bike was a success as your new inspection looks good.

 

Are you planning another inspection in the future? If so please post another follow up here.

 

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