HELP vaccum problems after rebuild

where to start, I have a 1982 750E, i did the top end on my bike a year ago, had the head checked and valve job done, i talked to the guy and he had said to leave the valve clearance a little on the loose side for when the valve seats and valves wear in, spec is 0.08-0.18 and im at 0.20. The bike fires up and runs, #1 isn't firing, has fuel and spark, so i checked the leak down, has 2% and the compression is 155, 165, 165, 150. so then i check vacuum, on all the carbs at idle the needle jumps all over the gauge from vacuum to pressure until i open the throttle to around 3,000 rpm and it smooths out till around 5 inches of vacuum. i will admit i didn't recheck the cam timing when i had the valve cover back off. could i have it off one tooth? any info would help out a lot. thanks

It would be a good idea to check the ignition timing advance to make sure it is not stuck in the advanced position. It's easy to get at and should be lubed periodically anyway. If it was still in the advanced position when under 3000 rpms you would be getting spark too early. At 3000 and above it operates in the advanced position anyway, this may be why you are running good over 3000.

yea i have that cover off, ill give it a good look, but still does not explain why the vacuum gauge is fluttering from vacuum to pressure on all cylinders

rssuby2001 wrote:

yea i have that cover off, ill give it a good look, but still does not explain why the vacuum gauge is fluttering from vacuum to pressure on all cylinders

Are the necessary restrictors in the gauge hoses?

Good Luck!

you need one in the line to the vacuum gauge? this is my first bike motor i have done, im a car mechanic by day.... i have never needed one checking vacuum on a larger motor

i think i just found it, over looking stupid things like this upsets me, i just got a can of carb kleen just to check the carb holders, and they are leaking, gotta start there first