after going through entire engine of a 92 lt80 replacing all bearings & seals boring to 50.5 with a wiseco piston & rings, rejetting main & pilot jet to 90 & 15 the bike has good throttle response in all ranges, but I have one little aggravating problem. When the throttle is shut off suddenly the engine dies without going to idle. the engine will start back up immediately and idles perfectly I have tried increasing idle speed but this doesn't correct the problem I have also gone to premix using amsoil synthetic. I got this atv for my "grands" so I don't have any past experience with quads or 2 strokes to fall back on, any suggestions would be appreciated. Thanks

 

Welcome to the forums. [img]i/expressions/face-icon-small-smile.gif[/img]
Put the 17.5 pilot jet back in and see if that helps.
Make sure the o-ring is in place on the black insulator when the carb is re-installed.
Needle in middle position.
Let us know, We'll help. [img]i/expressions/face-icon-small-smile.gif[/img]

 

Thanks for the response. I have had the carb back off three times to change main and pilot jets, and to reset float level, actually four times as I tried two different float levels. The o ring is glued in place, so I feel pretty confident it is still correct. I was told by local dealer that the pilot jets only come in increments of five, they only had 15, 20 25 & 30 available, there was a 20 in the carb when I got it about 3 mos. ago, again I know very little about any two stroke so I took their word. I have tried moving the clip on the needle on all but the richest setting and cant prevent the stalling. I still haven't took the time to pull the plug right after a stall, but I have checked it to determine the mixture, I still think it may be a little rich currently runnning between 35 & 40%. I didnt wan't to take a chance of going too lean with the rebuild plugs are cheaper than cylinders. any more suggestions would be appreciated. thanks again

 

Ok,,,,One more stupid question. Does the pipe flow freely? Could it be plugged? Remove and blow through with your mouth. If there is any restriction, stick it in a fire till red hot, then blow it out with compressed air.
You have me wondering about pilot jet sizes. On my modded motors I run a 37.5 pilot. I think you should run a stock pilot till we get this figured out. A 90 main is fine as they are jetted fat stock.
Next thing is to look for is air leaks. Spray carb cleaner around the front clutch/stator/carb/and where the motor splits in 1/2. See if it changes the idle speed.
If it still isn't right, I recommend pulling the head of and seeing if that Weisco 4 corner siezed. It's too common....FYI: up to 1.5 over, stock zuki pistons are a much wiser choice.I'm not ragging on you, just info [img]i/expressions/face-icon-small-smile.gif[/img]
Your doing good gramps [img]i/expressions/face-icon-small-happy.gif[/img]

 

Thanks again , the pipe is original and it was smoking heavy when I bought it so it could be plugged up, the motor really responded great at lower rpm ranges after I changed to 15 pilot, before it really wasnt clearing out until it finally got up to higher rpm. I don't have the manual here with me but I believe the stock size is 20. I had sprayed wd40 around the carb and reed block without any changes it used to work on auto. manifolds, but I will try the cleaner around the case & carb again. the engine has only been run for about an hour since the rebuild. what would be a normal breakin prcedure for these engines? It seems to have very good power and idles smoothly without any noise and turns over without any noticeable drag when starting. anyway the ideas should keep me busy for a few days I'm sure anything done will make an improvement as it didn't look like any maintenance had been done , it was in pretty sorry shape internally especially in clutch areas. one last ? the restrictor in the carb, is it the washer that the needle clip sits on? thanks again

 

The carb restrictor is a brass piece.It's about 1/2 inch wide and would resemble a very wide ring for your finger. It's between the slide and the cap. I doubt you have it still.

 

sorry I can't stay at this for any length of time, seems like work is always more important. Yes the restrictor would be gone then, there's one other change I had made that I forgot about, the main is an 85 I forgot that I changed it when I changed the pilot that may be the reason the low range power got better instead of the pilot change. I will look into that more when I go back to the 20. What effect would going to a 25 have on idle? Thanks again

 

After checking for leaks , none were found. I changed the pilot back to the 20 and the low end response was again bad, but this time I finally got my mind around the function of the pilot jet. So I went back into the carb once more and changed the main to an 80 to compensate for the larger pilot, now the the power is good from top to bottom , and the engine will come down to idle like I wanted. Thanks for the responses.