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Throttle balance HELP!!


Leo

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Doing a throttle balance on '96 R1100RT using a Carbtune. No matter how I turn the brass idle adjusters I cannot get an idle balance. The right side cylinder has lower vacuum than the left. Have checked throttle cable seating. Swapped the carbtune hoses to other side and low vacuum stays with RH side. The closest I can get is with RH screw fully clockwise and about 1 turn out on LH. Any suggestions will be gladly acted upon.

Thanks in anticipation.

Ross Geoghegan

Alice Springs

Central Australia.

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ShovelStrokeEd

A bunch of things come to mind.

 

The first being that your cross over cable (I don't recall when the changeover to the junction box was made) is not properly adjusted that can do it. The right side throttle body is being held open. Slack the adjuster a bit and see if that helps.

 

Of course, the motor must be in perfect mechanical condition as well. Valves properly adjusted, spark plugs in good shape, injectors clean and spraying properly and no air leaks.

 

Does the

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ShovelStrokeEd

A bunch of things come to mind.

 

The first being that your cross over cable (I don't recall when the changeover to the junction box was made) is not properly adjusted that can do it. The right side throttle body is being held open. Slack the adjuster a bit and see if that helps.

 

Of course, the motor must be in perfect mechanical condition as well. Valves properly adjusted, spark plugs in good shape, injectors clean and spraying properly and no air leaks.

 

Does the screw on the RH body impact idle speed at all? The lower vacuum would indicate that the right cylinder is working harder than the left.

 

Look carefully at the idle stop screws, even pushing on the lever a little bit and make sure both are fully against their repsective seats. Over time, the little set screw can dig itself an indent in the stop and you may have to wind up doing a zero=zero procedure. A search on that phrase will get you the procedure.

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As Ed alluded to, its important that you start from the beginning, and that means everything must be clean w/no debris gumming up the works. Ensure to pull the brass screws and air tubes to give 'em a good cleaning, and to provide access to the inside of the throttle bodies to tidy everything up in there. Careful when reinstalling the tubes as the O-rings will want to pinch up, giving a bad seal.

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Stan Walker

Any suggestions will be gladly acted upon.

 

Ed, I believe all the '96's have the crossover cable setup.

 

First off, you must do things in the proper order.

1) Adjust valves

2) Have good plugs, etc.

3) Warm up the engine to 5 bars!!! Don't forget to have a big fan for cooling the engine.

4) Insure that the throttle cable (left side) has some free play, less is better but it MUST have some. The crossover cable should be adjusted to take all free play out of it but still allow the right side throttle slide to hit bottom on the idle stop.

5) Do the off-idle sync first. You adjust the crossover cable for this one.

6) When you are done both throttle slides must still contact their stops when at idle, if not, you will have trouble adjusting the idle sync.

7) Do the idle sync. It is dependent on having (6) be true.

 

 

To achieve (6) you may have to settle for something less than perfect off-idle sync if your right side cylinder is weaker running than your left cylinder. It implies that there is something wrong. Valves, rings, dirty injector, air leak, or just luck of the draw. You can either fix it or live with it.

 

With the later throttle setup using the junction box you can skew the adjustments and have either throttle slide come off the idle stop before the other. This is not possible to achieve with the earlier crossover setup. You cannot adjust it to have the right TB slide lift before the left side.

 

Of course if both cylinders are working equally hard then this isn't a problem.

 

By the way, in 73,000 miles on my '96 I've yet to clean the BBS's. Or to measure the number of turns they are out. Just a sync and go type of guy, I guess.

 

Stan

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Doing a throttle balance on '96 R1100RT using a Carbtune. No matter how I turn the brass idle adjusters I cannot get an idle balance. The right side cylinder has lower vacuum than the left. Have checked throttle cable seating. Swapped the carbtune hoses to other side and low vacuum stays with RH side. The closest I can get is with RH screw fully clockwise and about 1 turn out on LH. Any suggestions will be gladly acted upon.

Thanks in anticipation.

Ross Geoghegan

Alice Springs

Central Australia.

 

Ross,

How many miles on it? The throttle body shafts wear and can cause vacuum leaks. See if there is ANY play in the right side shaft.

 

Mick

Tucson

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The throttle body shafts wear and can cause vacuum leaks. See if there is ANY play in the right side shaft.

 

My butterfly shaft is worn on the right side throttle body. Does indeed make a good sync difficult if not impossible. Does anyone know if these can be rebushed, or do you need to replace the whole TB? If so, do you need to buy them paired?

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Mine had same paroblem and had to replace whole tottle body and BMW dont do the parts on their own

 

Take a look at this thread, it seems you can buy a kit direct from Bing.

 

Andy thumbsup.gif

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