Engine Trouble Peculiar Noise

[mepsinas]

My carburetor-to-manifold screw was a little loose; maybe the minor air leak started again and that's the symptom/cause.

 

[Wrench]

Sometimes the carb mounting flange will get warped usually from overtightening the mounting nuts or bolts. Causing a slight intake air leak.

By resurfacing the carb flange it can be corrected. Resurface the carb flange just like ya would resurface a head

 

[mepsinas]

If it goes away again, maybe just need some loctite blue?

 

[Wrench]

If it goes away again, maybe just need some loctite blue?

Did ya check your carb flange for a flat surface?

Don't use Locktite, for maintenance reasons you don't want those nuts to be hard to take off or put back on easily.

Use a nut that looks like this and don't overtighten it. The nut is made to grip the surface and not loosen.
When used on an aluminum flange they grip real good

 

[mepsinas]

Sometimes the carb mounting flange will get warped usually from overtightening the mounting nuts or bolts. Causing a slight intake air leak.

By resurfacing the carb flange it can be corrected. Resurface the carb flange just like ya would resurface a head

I though I could find a specific location to resurface and cannot. My best guess is that I'd sand down here, to make the carb fit on the manifold more snugly.

 

[mepsinas]

... like put a piece of sandpaper on a glass surface and rub that edge down some. Am I in the ballpark?

 

[mepsinas]

I assume it's not the carb itself, because I tried putting the one from my other bicycle on it (same basic kit brand; that never gave me any problems on other engine), and it only corrected it for like a day, then started up again.

 

[mepsinas]

... then I used a thin strip of polyethylene (HDPE) as a sealant over the manifold lip, where the carb grips. Apparently it lasted longer but is now failing. I was thinking the loosening of the screw caused it; and that if I made that lip of the carb a little shorter, the manifold would have room to bottom out on the carb (and I probably wouldn't need the strip of HDPE as a sealant... which probably is relevant to the screw loosening).

 

[Wrench]

I though I could find a specific location to resurface and cannot. My best guess is that I'd sand down here, to make the carb fit on the manifold more snugly.

OH, you got a slip on carb it should be fine.
The nut's I mentioned would be for the intake manifold then.

 

[mepsinas]

... maybe double-nut the carburetor instead of loctite blue?