laganm21

Here is the problem that i am having the Motor Starts fine and idle the same way But once you give it gas it starts to take off then u let off the throttle and than it goes even faster and faster till it takes it sweet time to rev back down acts like the severo is stuck open but it not i put a new carb on it well used new to me the old one was shot the carb is a 3 neddle flush set carb please help i have try everythng

hrdcoreglf

Are you sure you clutch is not staying engaged as you engine is trying to rev down?

laganm21

No i am not would that cause the truck to speed up even though the throttle is closed

hrdcoreglf

No it would not cause it to speed up, just not throttle down when you let off the trigger. If you are actually speeding up when you release the trigger I would say you probably have an air leak in the engine somewhere. you can use a little red silicone sealer ( used to seal oxygen sensor on regular engines ) where the carb meets the block, where your HSN body meets the carb, your backplate, check you have a good seal on your glow plug. Check all of these places for leaks before you replace anything.

laganm21

would missing the head gasket cause this problem

hrdcoreglf

If is missing a head shim then yes there could be an air leak there. It also changes the compression rating in the combustion chamber. First make sure engine is free of fuel. Get yourself a carb cap and exhaust cap, put a piece of clean fuel tubing on the fuel intake on the HSN (make sure the fuel tubing is long enough so that you can rotate the engine to inspect it ). Cap them up put a little soapy water on the areas I mentioned, one area at a time and blow into the carb. If you see bubbles then you have found your air leak. You can also check your exhuast seals.

Anthoop

The most common cause of air leaks on the Hyper.21 engine is the carb. needle ''o'' rings, replace them. You can also purchase a sealing grease that will also help. However you should also seal the other parts of the engine (as above) as standard practice....and you should never run without the appropriate headshims as they not only help to seal but also provide the correct clearance.
Also worth checking that the midrange needle is set correctly.....remove the hsn housing and check that (with the mrn flush) the hole in the midrange needle is visble.....make sense?....If not there is a diagram somewhere on the Ofna forum.

cltcrns

http://www.ofna.com/forum/viewtopic.php?t=4339
Link for what Anthoop is referring to, very helpfull for a new Hyper owner.