Lost a cam??

[bikerphil]

No change in the idle mixture screw for me has meant a leak at the intake boot/head.

[3Phase]

I'm trying to figure out how you went from a hammered camshaft to a carburetor problem and why you would even try to synch the carbs on an engine with a hammered camshaft.

Did the camshaft un-hammer itself; valves and buckets were good so you dropped in a new cam or... what?

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[XS1100 Newbie]

Scott. It ended up that the bucket was nicked a little bit. Got it all cleared, and the cam measured fine. I went into the carbs to try to find the 3 year old problem of not being able to go above 7000 on the tach. The rebuild went fine i thought. The bike pulls hard all the way to 9000 now, but the idle sucked, and i could not get it to synch. Number three would not adjust. Pulled the carbs again to look at all passages, and parts. Found nothing wrong. I am waiting on the new carb holders to eliminate the possibility of a vac. leak there. We will see what happens then. It sure felt good to run it up to redline.

[3Phase]

Okay, so it wasn't the camshaft fairy!

Set up a box fan to keep the engine cool then pull the left-hand engine cover to watch the vacuum advance and see if it's moving at idle. If the vacuum advance moves at idle the carbs are out of synch or there is something else wrong and the throttle plates have to be opened far enough to uncover the vacuum advance port at idle.

If it's not just the carbs out of synch stop trying to synch the carbs or you'll drive yourself crazy! Find and fix the problem, then come back and synch the carbs.


The #3 carb is the baseline carb that the other carbs follow. To set the #3 carb you have back off the main idle speed screw (lower the idle speed) to get more vacuum; turn it in (raise the idle speed) and you'll get less vacuum.

Don't worry about idle RPM yet, just find the highest vacuum you can get on the #3 carb that still allows the engine to keep running, then try to adjust vacuum on the other three carbs to match #3 and see if the idle speed comes up to something close to ~1000 RPM.

Drop the idle to ~600/800 RPM, then slowly open and close the mixture screws while you listen for a rich lope or a lean roll, depending on which way you're turning the mixture screws.

Do it all again.

Keep doing it until the vacuum advance doesn't move, there is good, even vacuum on all four carbs and the engine revs and returns cleanly without hanging or stalling.


Go ride!


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[XS1100 Newbie]

Thanks Scott. The carb holders should be here tomorrow. I will button it up and hope for the best.

[XS1100 Newbie]

Installed the new carb holders, and new problems, along with old problems. No1, and 3, won't adjust, 2 and 4 adjust, but can only screw out 1 1/2 turns before it starts running rough. Vacuum varies between 5 inches on 3, to 10 inches on 1. I think this POS is telling me it wants to be parted out! Lose my ass, but get rid of the frustration.

[motoman]

Installed the new carb holders, and new problems, along with old problems. No1, and 3, won't adjust, 2 and 4 adjust, but can only screw out 1 1/2 turns before it starts running rough. Vacuum varies between 5 inches on 3, to 10 inches on 1. I think this POS is telling me it wants to be parted out! Lose my ass, but get rid of the frustration.

Sounds like some new vacuum leaks may have been created. If you have a little propane torch, unlit close following around the boot to head mount may find it for you. Can of WD-40 would be second choice to do same check, but if very low intake leak somwhere doesn't always prove itself to work. Starting fluid seems to ariate around enough that it can give false rises with idle. JAT.