Problem with #2 at idle

[Pfreen]

It’s really interesting when you start sucking brake fluid into the engine. Ask me how I know.

[vxah]

What about the camshafts? Are they original or Re ground? I’ve had quite a few “not so good” quality cams cause this type of issue over the years with various engines. It’s usually standard aftermarket replacements that have been fitted, and the engine just won’t idle smoothly anymore. All down to the accuracy of the lobes, you might set the valve timing up on number one cylinder but is number two the same? You might well get a near enough identical compression reading but that’s done at wide open throttle not closed throttle and pulling a vacuum. You know that “hot” cams with lots of overlap have poor intake vacuum at low revs so what if one cylinder has more overlap?

[CG901]

Cams are original and after measurement are within spec. No surface abrasion - cracks or signs of excessive wear.

[CG901]

Once resolved, I will post what is found to be the cause and remedy.

[pabbage]

Did you ever get anywhere with this? I’m having a similar sounding issue (albeit on cylinder 1) and am running out of ideas. Looking for inspiration!

[CG901]

pabbage - I’d like to offer some inspiration but unable to as yet. I have been advised I could have an air bleed at the end of the butterfly spindle. A few years ago I replaced the original spindle bearings with sealed type and may have omitted the leather sealing washers thinking that sealed bearings would serve the same purpose. If the sealed bearings were permitting sufficient air to cause my issues, then why on only one cylinder?
I am working on this today and may have to remove both webers and add the leather washers to rule them out as contributing to the symptoms.
I hope your problem is more easily resolved.

[CG901]

Update - I have found some success by adjusting the idle mixture screws only after having achieved an extremely low idle (400 revs). Had to adjust in and out until the minimum turnout produced the same revs as further turns out. (~1 turn out on each idle mixture screw). I was likely ‘cheating’ but had to turn in the speed screw on the heretofore problematic weber (cyls 1-2) to balance both carbs with the synchrometer. Then adjusting the center linkage screw to assure both carb’s butterflies opened simultaneously. After a test drive, the engine had lost it rough idle and idles right at 800 revs. I hope it stays with this adjustment!

[pabbage]

Progress! good news. (Though I don't think I quite understand the mechanism of why dropping the rpm helped)

[CG901]

dropping the rpm helped me hear changes in rpm from adjusting the idle mixture screws far better than what I had always done (1000-1500 rpm).

[pabbage]

dropping the rpm helped me hear changes in rpm from adjusting the idle mixture screws far better than what I had always done (1000-1500 rpm).

ahhh I see! Great.

[mbell]

I bought a cheap digital tacho, that is very helpful for that as measures to nearest ~10rpm.

https://www.amazon.com/Maintenance-Tach ... B07MXXLXFP

Not as cheap as just turn the rpm down thou.