I bought this 2000 LT80 for my 6 year old and am giving it to him this weekend. I was having problems with it idling so I checked Compression 130 psi - Boiled the Carb - Sprayed WD-40 around the whole front of the engine/carb/case with no effects - Checked the Exhaust Pipe.

I seem to be having a problem with the Petcock since when the gas is ON it will Idle inconsistenly and fast then eventually die. When in PRIME it will Idle inconsistently Raise and Lower RPM's but stay idling much much longer.
When driving with the Petcock in the ON Position it seems the fuel in Carb gets used then runs out of gas. If running on PRIME the ATV still seems to Lean out and when I let off the gas it doesn't slow down it almost seems to speed up? This is after going WOT for 10-20 Seconds or so.

The only thing I haven't checked is the Needle Jet with the E-Clip. I kept reading that people were adjusting this but I couldn't figure where it was till I checked a diagram last night and it is part of the Throttle cable at the Top of the Carb. I plan on pulling that apart tonight to see where it is set at.

Any other thoughts or ideas?

Thanks!

 

A clip sure won't make it surge. (but yes, it's in the top)
It sounds like a seal leak.

 

Any suggestions on what I should do to find it?

 

I am trying to think of all the places to check after reading some of the posts about where to find an air leak.
Here is what I could come up with Left and Right Crankshaft Seal/Top and Bottom Cylinder Gaskets/Carb.

If it were either of the seals on the Cylinder this would've affected the Compression Test I did. Correct? I did get 130-135psi.

I really sprayed the carb with alot of WD-40 when I was testing this with no affect.

Just an FYI after running it for awhile yesterday in the garage and playing with the Idle Adjustment I did notice what appeared to be a couple drops of oil on the garage floor. I assumed it was from the exhaust but maybe not. I will have to look underneath it tonight to see if it's obvious.

If it's a crankshaft seal would this leak oil as well?

 

I checked for the leak tonight and sure enough it is leaking oil out of the Flywheel Side cover . I have ordered the crankshaft seal. I don't plan on ripping it apart until I get the part in since I am giving it to my boy for his birthday this Saturday. I'd rather not give it to him in pieces. :-)
I don't expect to see the part till early next week. No one had this in stock.

I also noticed oil built up on the case near the starter. Is this from the same leak or do you think both sides are leaking?

 

mine always has oil near the starter but my crank seals arent leaking, its usually because i will flip the quad on its side or on the grab bar to work on something and fuel will leak out of the carb when the air box is off or similar, not saying yours isnt leaking, its very possible, good luck and let us know how it goes.

btw there is an o'ring between the carb and the reed spacer, make sure thats there because that will cause an air leak

 

Gave the atv to the kid today and it was great. He did ok for his first time. He hit the house and ran into the bushes. Lol. The seal also came so I tore into the atv and the seal was fine. I found the base gasket of the cylinder was leaking now it's I am pieces till parts come. Boooo. Oh well what can you do. I'll let you know how it runs when I'm done.
Thanks

 

I got the parts in yesterday and put everything back together and it is running and idling like a champ. Thanks for all of the help!