Topic: Vacuum wierdness ????

[grumpy]

I was synching the 750 K3 last night.
I got them even at idle but when I gas it the vacuum on 1, 3, and 4 increases but #2  goes down (less vaccum).
How can that be?
The only thing I can think of is it's a valve not closing but if that's the case wouldn't there be a discrepancy at idle, too?

All tappets are to spec, strobe timed, new carb manifold rubbers, no apparent air leaks...
WTF

 

[meb1948]

What kind of vacuum gauge are you using?  Have you swapped the vacuum hose between cylinder #2 and another cylinder to make sure you don't have a gauge problem?

Mark.

[grumpy]

I've got a dial gauge set (ie not the mercury type)
Didn't think about swapping gauges but I kinda doubt that's the issue.
#2 has always had problems so the wierdness is likely in the motor.
I'll try swapping gauges, though.

[grumpy]

Just did a gauge swap - the gauges are fine....


So, where's the leak??

[TwoTired]

Sticky valve guide.  Weak or broken valve spring.  Both would delay/prevent full closure of a valve which would get worse with increasing RPM.

Cheers,