371xp idle problem

[machine31]

I am working on a 371xp that idles fine if I lay it on it's clutch side, but won' t idle right if it sits on it's base as it normally would. The idle will slowly creep from 2600+/- to 4000+/- and then when I stab throttle it has very lean bog until I rev several times and it returns to normal. Then it will repeat it over again. If I let it sit and idle it will eventually die. However, if I "rev out" it will clean up and it's good for another 20-30 seconds. It runs great at high rpm. I can set tune to conservative 12500rpm My guess is crank seals, but I don't get why being on it's side would make a difference. What would be the symptoms of gas tank vent? Any thoughts?

 

[huskihl]

I'd say it's the clutch side seal. When you lay it on that side, the mix in the case is helping to seal it off

 

[Adamski]

Ok I had the same symptoms on one this year. Turned out for me that the carb was leaking from the tiny hole that the spring is held in the carb body for the choke shaft. Does this make sense? It took me weeks to find.. I then pushed some jb weld down there with the end of the spring..

 

[Redfin]

Does the saw symptom the same when turned on flywheel side?

 

[machine31]

Actually not sure if it does it on otherside. Iwill have to check.
I thought the same thing with it getting somewhat sealed off. The carburetor thing is interesting. Thankyou for the replies...I figure I ain't the first to experience this problem and love hearing opinions and ideas that can speed up diagnosing it.

 

[machine31]

Ended up being a combination of leaking crank seal on clutch side and a leak between the carburetor and intake rubber boot. It just wouldnt seal. The metal insert stuck out and the plastic piece bowed.