Just bought this in a group purchase. Removed and cleaned carburetor . It'll idle great! Mid rpm to high rpm non existent. It'll backfire sometimes. I've adjusted the airmix and the needle is set to middle . Am I missing something here?

 

Erratic rpm can be lean jetting,float setting off,stopped up fuel valve not alowing enough fuel in the carb bowl or air leak related. Leaking intake manifold, head or base gaskets or crank seals leaking.You can first try some wd40,carb cleaner,etc and spray around these areas when it runs at a high rpm and see if engine rpm changes. To get to the crank seal that cause the most problems you have to pull the clutch cover and pull the backing plate back a little to spray around the engine seal. I'd also do a compression check to be on the safe side to see what condition the top end is on this old 2 stroke. If it helps any,here is the carb section pdf from the manual that you can look over.You have the VM34 carb.https://www.google.com/url?sa=t&rct=...U2gGlaHJWSIlbA

 

Sorry. I wasn't clear on my post. My rpm is not erratic it's boggy and won't go to high rpm.

 

I'd still check compression,look over the carb section in the manual and if this doesn't help,then a leak down test can track down any air leaks.Plus don't know how familiar you are with a 2 stroke operation.

 

got good compression, 112 PSI, still wont rev up , have tried every setting on the Needle 1-5, same results, but it will idle and move slowly ,

 

Unable to achieve mid to high rpm , engine has very low kms on it, wondering why the head is stamped 400 not 350

 

Compression is still not the greatest at 112psi,plus looks like someone may have installed a 400 top end on a 350 bottom end or swapped out engines. Both bottom ends are the same,only difference was the larger bore on the 400 that came out in 94. Again if you do a leak down,look over the carb section on the manual you may be able to narrow down what's wrong. Even simple things like checking reed pedals,plus if you pull the reed block out you can see if the piston has any damage especially around the bottom of the piston skirt. Best since you're not familiar with the 350/400 engines to look over the service manual. The trouble shooting guides can help. http://visit.tradebit.com/visit.php/...75/264162958/9