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dirtrider

Throttel body throttle shaft/cam install procedure_

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dirtrider

 


I  m-i-g-h-t have a possible work around for a home install without a GS-911 and a fiddly/feely/subjective procedure.

 

Caution: this is a work in progress but I thought I would toss it out here early  to be questioned/debated/tweaked/thought about.

 

My 1200 throttle bodies were just laying on my workbench waiting for new Bing shafts/cams to arrive so I decided to do a little repeatability testing.


These were non-molested original throttle bodies with intact Bing factory paint on the base idle screws.

 

First, I completely cleaned the throttle bores & throttle plates so ACCURATE measurements could be taken using thin feeler gauge stock.   (be real careful here to not get cleaning solvent into the stepper connector pin area or TPS pin area)—
Or just remove the steppers then  mark & remove the TPS.  Problem with removing the TPS before cleaning is that allows washing the TPS position marking paint off, or washing the  position locating marks off. I left both the steppers & TPS on but covered the pin areas & was careful to not saturate the steppers or TPS with solvent.

 

Next, carefully & with precision I  marked the TPS position to the L/H  body housing. (this is an important step). I used some thick white marking paint, then when dry used an X-acto knife to scribe a  thin precision line across the TPS housing onto the throttle body on both sides of the TPS. (be accurate as possible with this step)

 

QAD6nYX.jpg

 

On the R/H throttle body  I carefully pried the outer throttle shaft cover cap off. I used a very small achilles heel to evenly work it off by continually working it up & off as I continually worked around it.  (the cap was somewhat difficult to remove without damage)

 

jkt52vH.jpg

 

Both the TPS (L/H) side TB and the shaft cover cap (R/H) side TB  MUST be removed to access the retaining circlips under them (shafts are held in place by external circlips).  I didn’t remove the circlips just yet (just getting the access to them out of the way so I didn’t have to interrupt the shaft measurement & other work continuity).  

 

wK2epEY.jpg

 

On to the measurements & pre-work/post-work noted below___

 

I first inserted .0015” feeler stock between the top of  throttle plate & the throttle bore, I then did the same on the very bottom of the throttle plate.  (perfectly centered & straight). So had a .0015” feeler stock at both the very top & at very bottom of the closed throttle plate.

That allowed the throttle plate to fully close on the .0015" feeler stock. With the .0015” feeler stock the TB idle stop lever j-u-s-t contacted the idle stop screw with no gap.

 

Next, I then did the same thing, only this time used .002" thick feeler stock.  This allowed the throttle plate to close firmly on the .002” feeler stock BUT, it prevented the  TB idle stop lever from fully contacting the idle stop screw.

 

VXlZB3x.jpg

 

I then used different thickness feeler stock to measure the stop lever to base idle screw gap (it was right at .0015” stop arm to screw tip).

 

KTz0BR4.jpg

 

I then measured the other side throttle body  & it measured out to the exact same numbers (good, looks repeatable between sides & sort of tells me that Bing set them to the same base idle screw settings on both TB’s).

On these (my set) of throttle bodies it looks like Bing set the original factory throttle plate air gap to around .0015” (maybe slightly more but not much)  but not nearly as much as .002".

 

I then blued & scribe-marked the factory throttle plates along the edge of the throttle shaft  for position (mainly this is for accurate plate clocking position at re-install).

 

4N17ax2.jpg

 

I then unhooked both return springs,  then removed the shaft retention circlip & plastic washer, then removed the throttle plate & throttle shaft from the first throttle body. (caution: don’t lose the plastic outer hat-shaped collar that is under the shaft lever) 

 

Now for the reassembly/repeatability test___

 

I re-installed the original throttle shaft & throttle plate being extra careful to match the throttle plate scribe marks up to match the throttle shaft sides (this re-sets throttle plate ‘clocking' back to  where they were). Then I very lightly tightened the throttle plate screws (very lightly).

 

Once all above was verified I reinserted the .002" feeler stock between the top & bottom of the throttle plate to throttle bore & allowed the factory springs to close the throttle plate (I then backed the throttle plate screws out slightly (to allow throttle plate to self center in the throttle bore against the top & bottom .002” feeler stock. I then re-checked that the throttle plate  scribed lines were still aligned with the throttle shaft edges (important). Then fully tightened the throttle plate  screws. Then re-checked that the scribe lines still line up EXACTLY.

 

I then removed the .002”feeler stock & verified that I still had the needed lateral movement in the throttle shaft with throttle plate open a little. (also verified that the square edges on throttle shaft align somewhat with the insides of the throttle bore.

 

XOk7KEH.jpg
 
I then opened & closed the throttle plate by using the cam to open/close it a few times  & even allowed it to snap closed a couple of times.

I then reinstalled the .002” feeler stock between the top & bottom of the throttle plate & throttle bore then allowed the throttle plate to close on the .002” feeler stock.

 

I then re-measured the gap between the base idle screw & the stop lever (it was back to the pre-work gap of .0015”.

This tells me the process can be repetitive if care is taken in the feeler stock placement & throttle plate clocking & alignment.

The above was just the preliminary to SEE if I could get the stock throttle plate & stock throttle shaft/cam back to where it was from the factory.—I would say that the repeatability test was a success.

 

Note: the above was only re-installing the original shaft/cam not the new shaft/cam -- but the new shaft/cam install used the same basic procedure, only I had to adjust the base idle screws to regain the .0015" stop lever to base idle screw gap.

 

I will add the new shaft/cam install  procedure as I define it.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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greiffster

DR,

I finally got around this weekend to swapping out my new Bing cams/shafts with your procedure.  Here is what I found.

 

Prior to the TB removal, I did check and note my stepper counts and cross balance in order to compare it after the new cams were installed.  I was out of balance some at 3000 rpm, but idle was good/very close.  Actually, I was a little surprised as my balance has been pretty steady on this bike.  I left it alone.

 

I did the left TB first and followed your procedure closely.  I second the idea of taking lots pictures of the TB prior to removal and prior to disassembly.  The electrical wiring runs on different sides of the throttle cable on either TB side (at least on the GS).  Having a couple photos can help avoid frustration.  Also, I would take special note of the orientation and hook points of the springs on the TB.  Finally, regarding the circle torsion spring, make sure that thing is routed correctly inside the white washer guides (for lack of a better description).  It can jump out of those guides easily during assembly.

 

So, on the left TB, using the 0015" feelers at top and bottom, the idle screw was still on the stop, but close.  But, using the 0020", I found that screw had come off the stop about the predicted 0015".  Now, it does get a bit tricky, because you can easily get different gaps depending on whether or not you let the throttle plates snap shut, gently close, or even apply a light amount of pressure with your finger on the plate itself to "set" the closure consistently.  I chose the latter method and found I could consistently get the same gap results.  I also used a very good led flashlight and tried to get a good visual of the ring of light around the throttle plates as it sat on the stop.

 

Removal and installation of the new cam/shaft was pretty straight forward.  I did scribe a good mark on the TPS, but the two screws holding it to the TB just re-aligned itself almost perfect when I screwed it back down.  There just doesn't seem to be much play in it?  Definitely, scribe some good sharpie marks on the throttle plate.  It sure helps as there is a lot of play in the holes of the plate.  Upon installation and centering of the plate, it was clear with my flashlight that I had to much gap.  With the 0020" feelers, the screw was just on the stop.  I turned my idle screw out about 180 degrees or half turn until I was back to a consistently testing 0015”.

 

The right TB was almost identical to the left upon removal.  I had the same 0015” with the 0020” feelers prior to disassembly.  Almost scary close.  The TB metal cap at the end of the shaft was stubborn to come off.  I have a couple of small pry bars similar to your picture and just couldn’t get enough bite on the lip to pry them off.  I laid the TB in an open vise so the cap was pointing down and used a sharp chisel and small hammer to tap it off.  That seemed to work better.  After assembly of the new cam/shaft, I had about a 0060-0070” gap at the idle screw.  Ultimately, I turned the screw in just over a full turn to get back to 0015”.  Maybe 370 degrees.

 

The bike runs the same. And the stepper values, idle rpm, and cross balance were basically the same after re-assembly.  I’ll report back if I notice any changes, but I did adjust my balance at the right side to take out the original unbalance at around 3000rpm.

 

A few take-aways.  First, if I ever see the guy who decided that the Oetiker style clamps were a good idea for the air intakes and TBs, I’ll probably punch him in the face.  I have two styles on my bike with the ones at the air box being different and the most difficult (you can get the TBs off without removing the clamp at the air box, but it is more difficult).

 

Just out of curiosity, I unscrewed the cam from the new shaft.  It is a still a snug fit, but not pressed on.  Perhaps this is part of a fix?  Maybe the pressing of the cam end and subsequent stretching of the metal also imparted some tensile stress to the plastic and over time, contributed to the fracture?  I’m sure Bing will tell us if we ask. :/

   

Upon further inspection of my old cams/shaft, they were both cracked on the back or insides as well, but, in different radial spots than on the front side.  I find this strange.  The one at the right TB had a jagged double stress crack.  I will note that even with the cracks, a total failure doesn’t see imminent.  The plastic cams still feel very firmly bonded to the metal.  I assume this is why we are seeing many cracked cams of these vintage bikes, but not too many failures.

 

 

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dirtrider
1 hour ago, greiffster said:

DR,

Just out of curiosity, I unscrewed the cam from the new shaft.  It is a still a snug fit, but not pressed on.  Perhaps this is part of a fix?  Maybe the pressing of the cam end and subsequent stretching of the metal also imparted some tensile stress to the plastic and over time, contributed to the fracture?  I’m sure Bing will tell us if we ask.

   

 

 

 

 

Morning Mike

 

Thanks for the update, please keep us posted on how it works out long-term? I will add your comments into the final procedure plus any other comments  that show up in this thread as more cams  are replaced by other riders.

 

Does the procedure need any other tweaking as far as missed steps, or difficult to understand areas?????

 

I have done (2 bikes) now using 'the' procedure (3rd one coming right up) & so far it has worked out good. 

 

I did call Bing on those screws & it wasn't the answer we were hoping for. Seems that Bing in Europe won't send the shafts & cams already assembled so Bing USA needs to assemble them here (therefore the screws) are used to pull the new cams onto the shafts & keep retain them there.

 

Added:  I guess that also confirms my fears that a rider can't 'JUST' install the shafts/cams without adjusting the base idle screws & have them be even close.

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greiffster

The procedure is pretty straight forward once you get started.  Having the TB in hand clears up any of the text that may otherwise be tricky to understand.  I would stress that point of visually inspecting the ring of light around the throttle plate, if only for a backup measurement.  I would bet I could come pretty close just on the visual.  I find about a half turn on the idle screw to be apparent with just a good light.

 

I don't think that Bing could manufacture the shafts/cams to tight enough tolerance to say 0020-0030" at the idle stop relative to the "plane" of the throttle plate.  First, you've got the rotation of the "square" edge of the cam fitting relative to the throttle plane (maybe it's zero, but it doesn't really matter)  How do you do that with limited tolerance to not have an amplified effect further away from the radius of the shaft (ie the stop).  And then the metal bent portion of the stop??  What is the tolerance of the machine bending that thing?  I'm actually quite surprised that they are as close as they are.

 

My big question is what affect does the bike feel if the screw is out/in by a certain amount?  IOW, how close is good enough?  My cams were within about a full turn on the screw (one was half).  Maybe I got two good cam/shaft replacements? Maybe they are all within that tolerance?  But what does one turn on the idle screw really do to the bike?

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greiffster
3 hours ago, dirtrider said:

I did call Bing on those screws & it wasn't the answer we were hoping for. Seems that Bing in Europe won't send the shafts & cams already assembled so Bing USA needs to assemble them here (therefore the screws) are used to pull the new cams onto the shafts & keep retain them there.

 

 

 

That screams BS to me.  :S

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dirtrider
4 minutes ago, greiffster said:

 

 

My big question is what affect does a the bike feel if the screw is out/in by a certain amount?  IOW, how close is good enough?  My cams were within about a full turn on the screw (one was half).  Maybe I got two good cam/shaft replacements? Maybe they are all within that tolerance?  But what does one turn on the idle screw really do to the bike?

 

 

Afternoon Mike

 

There has to be some wiggle room here but the base idle screws add a fixed amount of air then the steppers control what is needed (+/-) on top of the base air flow. (steppers can't go any lower than base idle screw settings allow)

 

SO__ the base idle air flow (screw position) must allow enough base flow  to allow the Steppers to go to their fixed cold-engine starting position (based on engine temp, & other sensor inputs) so the engine has enough cold start air flow to allow quick engine starting in any conditions or oil thickness & remain running long enough for the steppers to start reacting & control engine RPM's.

 

On the other end the base air flow must be low enough to allow the engine idle to drop low enough at hot-engine, thin oil, high atmospheric pressure to it can get to low RPM command (plus not have the steppers bottomed out at 0 counts).  

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dirtrider
5 minutes ago, greiffster said:

 

That screams BS to me.  :S

 

 

Afternoon Mike

 

Actually it doesn't to me as I was thinking of buying only the cams & that was going to be the way that I was going to install/retain the new cams on the original shafts.

 

In fact now that I have a couple of sets of shafts with broken cams I am probably going to start installing new cams on those shafts then rotate those into the next bike that needs cams replaced.   

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greiffster

Update:

After a good road trip and 800+ miles after the cam/shaft replacement, I cannot say I've noticed any difference in performance. The idle is the same steady and smooth 1150rpm-ish as it was prior to the swap.  The bike starts the same.  I did a small adjustment to the TB balance to take out an off idle (around 3000rpm) imbalance.  But, I assume that the base idle adjustment wouldn't have much effect off idle that far anyway.  I'm pretty confident this method is going to yield consistently good results.

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dirtrider
7 hours ago, greiffster said:

Update:

After a good road trip and 800+ miles after the cam/shaft replacement, I cannot say I've noticed any difference in performance. The idle is the same steady and smooth 1150rpm-ish as it was prior to the swap.  The bike starts the same.  I did a small adjustment to the TB balance to take out an off idle (around 3000rpm) imbalance.  But, I assume that the base idle adjustment wouldn't have much effect off idle that far anyway.  I'm pretty confident this method is going to yield consistently good results.

 

 

Morning Mike

 

Thanks for the follow up (sounds like your bike is working good).

 

The two 1200 bikes that I have done using that procedure have also worked out good with no detectable before/after differences.

 

I have a 3rd & 4th bike to do with the 3rd coming up shortly & the 4th later this spring. (probably more as more riders inspect their 1200 TB cams)

 

I hope this procedure pans out long term as there seems to be a LOT of 1200 bikes now turning up with cracked TB cams.   

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SHIMHEAD

Hello Dirtrider,

     Thought I would add my 2 cents here. Assuming good mechanical engine condition, no intake air leaks, etc. Use stepper counts as a baseline for idle air flow combined stepper passage/throttle stop adjustment. Post cam install, do a live stop adjustment to achieve the same stepper counts as before. Theoretically this should achieve the same base idle airflow around the throttle plate well within the acceptable range of factory adjustment?? Looking for your thoughts. Maybe try it this way and compare to the careful measure/record/reset to measurement process. Of course clean throttle bodies and stepper passages, as well as fully functional steppers would be pre-requisites.

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dirtrider
2 minutes ago, SHIMHEAD said:

Hello Dirtrider,

     Thought I would add my 2 cents here. Assuming good mechanical engine condition, no intake air leaks, etc. Use stepper counts as a baseline for idle air flow combined stepper passage/throttle stop adjustment. Post cam install, do a live stop adjustment to achieve the same stepper counts as before. Theoretically this should achieve the same base idle airflow around the throttle plate well within the acceptable range of factory adjustment?? Looking for your thoughts. Maybe try it this way and compare to the careful measure/record/reset to measurement process. Of course clean throttle bodies and stepper passages, as well as fully functional steppers would be pre-requisites.

 

 

Afternoon SHIMHEAD

 

That is basically the way I did the first  ones a while back,  problem is that is way more complicated & fiddly  than it sounds at first thought. That is also what drove me to try & find a simpler way that even a cave man can do it.

 

Then if the TB's are cleaned during the throttle shaft/cam work that can skew the baseline numbers as being totally useful.

 

That way works as I have done it that way but I was really looking for a much simpler way that could be done without the need for GS-911, or need of a lot of post work fiddly adjustments.

 

 

 

 

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Mike T

Replaced my Throttle Body cams yesterday. Procedure very helpful so thanks very much for that. The hardest part was getting the aluminum cap off the right TB. I ended up using Mike's suggestion of a small coal chisel and small hammer to tap the cap off. It just caught the edge. Be careful when putting the TB in a vice. Very soft metal that will get marked up easily. Tip: when removing the TB's from the bike there is a stainless clip that releases the throttle cables from the black plastic TB housing so no need to loosen the lock nut on the cable (like I did).   Another Tip: I used a large paper clip to reattach the round cam spring end piece . You can easily grab the bent end to lift it up back on the new cam bracket. 

 

Both of my original TB's butterfly valves showed an equal amount of light all the way around them inside the TB when you shined a light behind them.  Left and Right looked to be the same and had a .0015 gap top and bottom as predicted. Very important to mark the brass butterfly valves with sharpie to show where the cam post is attached to them (as indicated with photos above.) I ended up making no adjustments to either stop screw. Did a TB sync using a manometer. The idle was off from side to side (not sure if this was true before). I decided to leave it as is since it idled smoothly and was at 1150 rpms. I did have to adjust the right side cable at 1800RPM to sync the the TBs using a GS-911. Took a short test ride and bike runs better than before with no issues noted.  

 

Thanks Guys for all the excellent info!

 

BTW, both cams had one or two cracks on outside of the cam and the Left TB had a crack on the inside as well. Everything still very tight and probably would have lasted a quite a while but better to fix at my convenience without paying for towing and have peace of mind. 

 

If anyone near Boulder, CO needs help with replacing theirs I'd be happy to assist. 

 

Cheers

 

Mike 

 

 

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dirtrider
13 hours ago, Mike T said:

Replaced my Throttle Body cams yesterday. Procedure very helpful so thanks very much for that. The hardest part was getting the aluminum cap off the right TB. I ended up using Mike's suggestion of a small coal chisel and small hammer to tap the cap off. It just caught the edge. Be careful when putting the TB in a vice. Very soft metal that will get marked up easily. Tip: when removing the TB's from the bike there is a stainless clip that releases the throttle cables from the black plastic TB housing so no need to loosen the lock nut on the cable (like I did).   Another Tip: I used a large paper clip to reattach the round cam spring end piece . You can easily grab the bent end to lift it up back on the new cam bracket. 

 

Both of my original TB's butterfly valves showed an equal amount of light all the way around them inside the TB when you shined a light behind them.  Left and Right looked to be the same and had a .0015 gap top and bottom as predicted. Very important to mark the brass butterfly valves with sharpie to show where the cam post is attached to them (as indicated with photos above.) I ended up making no adjustments to either stop screw. Did a TB sync using a manometer. The idle was off from side to side (not sure if this was true before). I decided to leave it as is since it idled smoothly and was at 1150 rpms. I did have to adjust the right side cable at 1800RPM to sync the the TBs using a GS-911. Took a short test ride and bike runs better than before with no issues noted.  

 

 

Morning Mike

 

Thanks for the feedback after replacing your cams. This is the type of feedback that we are looking for.

 

Removing that cap does seem to be a pain in a$$, I have done a couple more since I posted the above & like yours, seem to be running/working great.

 

I have been able to get all the caps off using my small Achilles heel (sp) & working around  the cap but not everybody has a small achilleas heel  in their tool kit (so the chisel option should probably be added to the procedure).

 

On clamping the TB's into a vise, I usually use small pieces of 1/4" thick plywood  on each end of the TB (inlet & outlet ends)  then clamp them in the vise longways (they seem quite strong in that direction so not much chance of crushing the TB) but it does take a slightly larger vise to get them to fit that direction.

 

Please post a long term follow up after riding the bike for a month or so.

 

 

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lkraus
7 minutes ago, dirtrider said:

...using my small achilleas heel & working around  the cap but not everybody has a small achilleas heel  in their tool kit...

OK, Google was no help. 

What is an achilleas heel?

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dirtrider
1 hour ago, lkraus said:

OK, Google was no help. 

What is an achilleas heel?

 

 

Morning Larry

 

It should read  "Achilles heel"   (at least it did until my spell check militated it)  ---I'll fix that now!

 

This little devil (picture only shows the lower part of it  but I'm sure that you have seen them before). I don't even know what the technical  name is  but we have been calling them Achilles heels  forever.

 

Put  ----      Achilles heel pry bar           --- into Google

 

jkt52vH.jpg

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lkraus

Got it. I think I have a couple bars like that in a box lot I picked up at an auction.

 

I'll attribute "militated" to your mutilating spell checker, too. ;)

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dirtrider
2 hours ago, lkraus said:

Got it. I think I have a couple bars like that in a box lot I picked up at an auction.

 

I'll attribute "militated" to your mutilating spell checker, too. ;)

 

Afternoon Larry

 

That was an on-purpose but I guess it wasn't funny? 

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