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TB woes


rsjockey

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I am having trouble getting my idle to reach the 1100 rev range.

After following the archived tech articles on TB balancing it seems I am able to get a close balance with the twin max but idle is still low and rough.

Adjusting the air screws dosent change anything. If there is any change at all, there is a slight increase in idle with both screws ALL the way in but even that is low. Of course it stalls when adjusted mostly out.

To my knowledge the stop screws have never been touched.

At speed the bike runs well but stop lights are rough.

Any suggestions?

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Have you removed the idle air screws to inspect and clean them? Often the screws are gunked up and prevent you from adjusting them correctly.

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Sounds like a big un-metered air leak (leak between the intake valve and TB.

1. Check the securing bolts for the throttle stub pipe at the cylinder head.

2. Check the stub pipe clamps for snugness at the front of the TB

3. Replace the stub pipes. They age and crack allowing air to be introduced. Many times the cracks are barely visible until the stub pipes are removed.

 

All of this assumes you have good compression on both cylinders and the valves are adjusted.

 

No idle authority by adjusting the air bypass screws usually is a result of un-metered air being introduced.

 

Hope this helps.........

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sonofdennis

Old trick used to look for intake air leaks was to spray carb cleaner on all joints while motor is idling. If the leak is large enough the idle will change as the motor pulls in the fumes through leak. Of course probably not the safest way but I've been lucky with it over the years. It doesn't take much, don't drench the joints.

Anyone else use this method for vacuum leak detection?

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I am having trouble getting my idle to reach the 1100 rev range.

After following the archived tech articles on TB balancing it seems I am able to get a close balance with the twin max but idle is still low and rough.

Adjusting the air screws dosent change anything. If there is any change at all, there is a slight increase in idle with both screws ALL the way in but even that is low. Of course it stalls when adjusted mostly out.

To my knowledge the stop screws have never been touched.

At speed the bike runs well but stop lights are rough.

Any suggestions?

 

Rsjockey, what you are seeing doesn’t make perfect sense to me.. If you have no control of the idle by-pass air (brass screws) how did you get a decent TBI balance?

 

You say when you turn those screws in the idle maybe picks up a little? That is backwards of how they are supposed to work.. As you turn those screws in you should be slowing the idle down not speeding it up.. Those Brass screws control the amount of air that by-passes the throttle plate so opening them up (out direction) should add more air & therefore a higher idle speed..

 

Do as Edgarr said & remove the brass screws & clean them, then use carburetor cleaner & clean the passages in the throttle body air passages in the TBI’s.. For some reason it sounds like you are not getting more air when you turn them out..

 

If by chance those brass screw passages are clean (I have a feeling they are carboned shut) then suspect the air is being added but for some reason the fuel isn’t there (maybe check your TPS idle voltage or re-set your Moronic computer (1100 engine only).. This is doubtful though as it takes very little fuel to sustain a decent idle speed..

 

Twisty

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The screws and inlets are clean. The TPS is correct. I found a minor leak at the RH TB pulley shaft.

It is my understanding that the screws are just for idle adjustment. I guess thats why I can get a good balance at speed. The screw all the way in is a puzzler.

I'll investigate further for leaks. Thanks All.

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Not sure if this matters, but how far out are the screws when you start your TBS? I have an 1150 and usually start out at 1 1/2 turns out. That usually puts me at 1100-1150rpm right off the bat.

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