I can't believe that my butterfly spindle might be worn

[Ian]

Two weeks ago when I did my last zero zero TB adjustment I was getting around 50mv TPS voltage variance each time I snapped the throttle closed. The variance was always to a lower voltage. Without doubt the cable had 1mm free play after closing and slight rotation of the throttle only moved the cable but did not move the cam.

 

When the throttle is closed the cam is against the stop whose locknut is tight

 

I have ridden 26,000 and I am not happy to think that the LH spindle or its sleeve bearing is sufficiently worn to cause this.

 

Is there any other explanation, e.g. could the butterfly be slack?

 

There is no surging and the engine is running very smooth. The only problem is excessive use of the clutch to ensure smooth riding at very low speed.

 

regards,

 

Ian

 

 

 

[AndyS]

What do you mean "excessive use of the clutch to ensure smooth riding at very low speed"?

 

Andy

[Ian]

Andy,

 

Just that although idle and 4K sync is spot on there is a tendancy for the engine to snatch as I completely close the throttle then open up slightly. For example when I'm circling around looking for a level parking spot. I don't like riding on full lock anyhow but when a snatch occurs it makes my heart miss a beat.

 

I have reset my TPS voltage back from (Lentini) 400mv to 380mv but I have left my ignition fully advanced as reported last month.

 

Valve lash is standard but I recall Rob saying that opening it up to double gave him more "control" at low speed. I tried it five years ago but the increased tapping noise annoyed me.

 

I just don't want to strip out the spindle if it is not the culprit.

 

regards,

 

Ian

[philbytx]

Ian,

Driveline lash and two big jugs make the boxer motor a little "different" when you are at idle/just off idle!

 

I am assuming you are in 1st gear in these scenarios and are occasionally feathering the clutch?

 

It really sounds like you have everything where it should be but it may be that you are just trying to dial out something that you just can't. Perhaps the best thing to do is to find another boxer motor owner with some miles under his belt and have him ride your bike and, perhaps, you ride his?

 

 

[AndyS]

Andy,

 

Just that although idle and 4K sync is spot on there is a tendancy for the engine to snatch as I completely close the throttle then open up slightly. For example when I'm circling around looking for a level parking spot. I don't like riding on full lock anyhow but when a snatch occurs it makes my heart miss a beat.

....Ian

 

Ian, remember that these bikes have no flywheel(worth calling a flywheel), and so when running real low revs you are asking the fuel injection to do things that the flywheel might be doing on other big bikes. So, as the revs fall off the engine has to do some quick thinking to prevent a stall, so it gives a slightly bigger gob of fuel and hence the lumpiness in these unusual conditions. I know my two bikes have done the same with the low speed, feet up, U turn, scenario.

 

Andy

[Ian]

Andy and Phil,

 

Thanks for the replies. I'm feeling a little better now and have reminded myself that I am 10 years older than when I first learned to full lock circle on my new R1100RT.

 

regards,

 

Ian

 

 

[philbytx]

Yup! It sucks getting old mate

[Ken H.]

Is there any other explanation,

Yes, it's possible the TPS itself is bad.

[Ian]

When doing my zero-zero the TPS adjustment appeared very stable as I closed in on 0.007mV and then again when I'm reading the full range from 380mv to 4.5V.

 

Can anyone tell me how the rotating part of the tps is attached to the butterfly spindle? Perhaps looseness here is causing the reading variance on butterfly closing.

 

Were it not that the bike has only done 26,800 miles I would not hesitate in stripping out the LH TB to see if the shaft/sleeve is worn

 

regards,

 

Ian

[OoPEZoO]

The end of the shaft has two flat spots on it that fit tightly into a notch in the TPS module. It is a tight enough fit that I was worried that I was going to break something when I was taking mine apart.

 

 

If you have a wear issue, I don't think it would be there. My personal situation right now is with wear on the pulley side of the left throttle body. The shaft has a notch worn in it, and the bushing is deformed. This is allowing a lot of axial play in the shaft and was causing my TPS voltage to be very erratic. I just got new bushings yesterday from McMastercarr, and I should have the full rebuild kits from Bing early next week.

 

BUT, like you said.....I wouldn't expect wear on a bike with low mileage like yours. I have ~125k miles on mine, so I kind of expect things like this from time to time.

 

On the bright side, it only takes about 15 minutes to tear the throttle body apart if you want to check it out. The only downside is that you then have to go back and do another zero-zero and throttle body sync when you put it back together.

[Ian]

Keith,

 

Can the TB be removed with removing the airbox?

 

regards,

 

Ian

[Boffin]

Assuming you meant without removing the airbox, then yes.

The clamps on the intake tubes are loosened and then the intake tubes pushed back into the airbox, allowing the TBs to come off.

 

Andy

[OoPEZoO]

Like Andy said......Yes, the throttle bodies can easily be removed without disturbing the airbox.

[Ian]

Oops! Yes I meant without as the BMW manual is not explicit in this area.

 

thanks,

 

Ian

[Ian]

Keith,

 

...that is good news. Just curious but has anyone ever worked out how to measure the specified 10deg angle of the butterfly opening?

 

regards,

 

Ian

[OoPEZoO]

If you are refering to the angle of the butterfly valve when at idle, then everything I have read says to zero out the TPS and then set the throttle stop to get ~.385V measured from the TPS. From my understanding, that should get you right where you want to be.

 

I don't think you could easily do a physical measurement. The only thing we really have to go off of is the voltage put out by the TPS. As long as your TPS has been properly zeroed, and your shaft/bushings are not worn, then it should be trust worthy enough to believe. If you get erratic or unrepeatable numbers then its time to investigate further.

[Ian]

Keith,

 

I am well aware of the TPS voltage. My curiousity was only because BMW state the 10deg figure in their manual and since I have already done my zero zero I was wondering if I could check this against the angle whenever I have the tb off the bike

 

Ian

[Peter Parts]

Where is Twisty1?

 

Gosh, you hear a lot of... "gee, they all do that" and other lame apologies for ill-tuned engines.

 

It sounds to me like your engine isn't in a good state of tune. For example, trying to get some HP like you are doing because BMW leaves it on the table (they've kept a 3 degree ignition timing safety zone as long as I can remember) can lead to lumpy running at the low rev end.

 

You can test your timing by varying your octane. Try some super high octane (and ensuring clean gas in the tank) - that will in effect retard your backyard-advanced-adjusted timing. High octane really helps in the lowest end although low octane may add HP otherwise.

 

What kind of meter are you using to measure the TPS? Can't use a low input impedance VOM. Can you get stable measurements in a TPS test-scenario when you ought to expect them?

 

TPS is measured with the engine stopped. A rattling bearing changing the TPS voltage might be detectable by testing with the engine running and/or manually shoving the butterfly around by grabbing the butterfly crank while you watch the DVM.

 

Doing zero=zero by the book, eh?

 

Ben

[Ian]

Where is Twisty1?

 

Gosh, you hear a lot of... "gee, they all do that" and other lame apologies for ill-tuned engines.

 

It sounds to me like your engine isn't in a good state of tune. For example, trying to get some HP like you are doing because BMW leaves it on the table (they've kept a 3 degree ignition timing safety zone as long as I can remember) can lead to lumpy running at the low rev end.

 

You can test your timing by varying your octane. Try some super high octane (and ensuring clean gas in the tank) - that will in effect retard your backyard-advanced-adjusted timing. High octane really helps in the lowest end although low octane may add HP otherwise.

 

What kind of meter are you using to measure the TPS? Can't use a low input impedance VOM. Can you get stable measurements in a TPS test-scenario when you ought to expect them?

 

TPS is measured with the engine stopped. A rattling bearing changing the TPS voltage might be detectable by testing with the engine running and/or manually shoving the butterfly around by grabbing the butterfly crank while you watch the DVM.

 

Doing zero=zero by the book, eh?

 

Ben

 

Ben,

 

Not often I am confused by a reply and especially whether the reply is directed to the OP or other?

 

"where is Twisty1?"

 

...is over my head

 

"Gosh, you hear a lot of... "gee, they all do that" and other lame apologies for ill-tuned engines"

 

...is over my head

 

"It sounds to me like your engine isn't in a good state of tune. For example, trying to get some HP like you are doing because BMW leaves it on the table (they've kept a 3 degree ignition timing safety zone as long as I can remember) can lead to lumpy running at the low rev end"

 

...I have full advance set, premium fuel, no pre-ignition and no desire to seek maximum power. I am a qualified electrical and electronics technician engineer and my UT70D 80000 count DMM is more than capable of any TPS measurement.

 

(okay so now I see that you are replying to me although your earlier comments are as useful as Hieroglyphics

 

I have already investigated the TPS voltage problem (at 26K miles!) by fondling the butterfly cam which is why I posted in the first place.

 

"Doing zero=zero by the book, eh?"

 

... How am I supposed to interpret your comment? Are you denigrating Rob's legacy or enquiring if I complied?

 

Ian