i bought an 87 lt80 a month ago and i cant get it to run right.

what it does:
starts up quick with the choke on, but i have to mess with the choke and restart it a few times before it will idle on its own. once its warmed up, she idles all day long with the choke off. whether its cold or warmed up, it boggs and will die if i dont let off on the throttle right away. if i give it just a little throttle, it surges for a half second and then just runs a little past idle and wont move. get this though. if i take off the snorkle that goes from the air cleaner to the carb, it goes like a rapped ape after it surges a bit.

what ive done:
new top end (piston, rings, cylinder head and base gasket) the piston was not put in backwards and i have good compression. 120psi. new crank seals, rebuilt the carb 4 times. i found a guy who had a used carb, reeds and muffler from an '04 lt80. rebuilt that carb, put it, the reeds and muffler on. runs exactly the same. i even moved the e-clip on the main jet to every position. air cleaner is brand new and all passageways are clean. i took the o-ring out of the petcock and leave it on prime. it's getting plenty of fuel. new spark plug too. the o-ring in between the carb and reeds is new. like an idiot, when i took out the reed assembly, i didn't pay attention to whether they were facing up or down in the engine. i have them facing up. im an ase certified mechanic and do alot of chainsaw tuning but i am at a loss with this thing. i have a good solid blue spark. like i said earlier, she runs good after some surging with the air cleaner off.
i noticed that the three holes for the screws that hold the stator on are oblong, so you can adjust timing. any advice on how advanced the timing should be? HELP

 

The timing marks are at the 9O'clock position. Align the marks.
Your correct, the reed faces up.
Please explain how you rebuilt the carbs.
Something stupid, try closing the gap on the plug a lil.
I'll think..

 

the plug gap was originally .028. i changed it to .022 and when i started it, i could turn the choke off right away and it would idle without dying instead of playing with the choke a bit till it warmed up. then for about 15 seconds it drove great, then same issue with it bogging. i changed the gap to .025. same issue. when i rebuilt both carbs, i took everything out. pilot jet, needle jet, float needle, and the brass tube that the needle slides into. that tube was gummed up on both carbs. sprayed carb cleaner in every little orfice those carbs had and used my compressor to blow out everything. when i bought it the guy said he had it bored out. i brought it home and had 90psi for compression. i took the top end off and it was bored because the piston had the 05 marking on the top, but he put it in backwards and the piston, rings and cylinder got chewed up. i honed it out and put the new piston and rings in. however, when i honed it, there were still some score marks by the intake/exhaust ports. i didn't want to hone it out too much. as it is, i think i am hearing some piston slap. now it's 115-120psi. i've got a used jug that is stock bore and no scoring. i might have to hone it and get a new piston and rings (again). i was hoping to avoid that. im starting to hemorrhage money with this thing.

 

Check the stator. It should be around 185 ohms.

 

checked the stator 186-187 ohms. when i replaced the crank seal on that side, i also clean the surface rust on the rotor and stator. the whole thing with it running great with the air cleaner disconnected is still bothering me. even though the air filter is new (i also ran it with the air filter box connected but no air filter and it ran bad) is it possible that with it connected there's enough vacuum being created that an air leak somewhere else (like crankcase gasket) is causing a problem? i used to have a vacuum/pressure tester, but i let someone borrow it years ago and never saw it again. by the way lt80, i've been following your posts since i got this machine, and was hoping you would reply to my posts. you seem to know all the querks with these things. thanks for replying

 

to the guy called lt80. youve mentioned in some other threads about boiling the carb. i might give that a try. i've read a bunch of different methods on the web. what is yours?

 

I'd try boiling it. Seems to work.
I've never needed to boil one but that's not to say some don't need it.
Again, well worth the try IMO.
What jets do you have in the carb?

 

ok mr. lt80, i think we're on to something. i've taken apart and cleaned both carbs i had several times now. the quad's been sitting for a week and this morning i decided to take it off and boil it. when i took the bowl off, there was a bunch of brown dirt and flakes in it. this is the same stuff i saw on the petcock when i first took it off. i took the petcock off today and it was full of this brown stuff so i flushed out the tank, got rid of the cheap little stone lawnmower filter i put on (they never seem to filter right) and put on a paper filter. put it all back together and it ran the same. so i decided for the heck of it to move the e-clip again on the needle one position richer and the quad could get out of its own way, barely. so i kept moving the e-clip until it was at its richest setting. now she goes pretty good at half throttle. full throttle causes it to bogg but not die. i read your post about seeing what size the jet was, but it was after i had put the carb back on. im going to guess its stock, seeing how it ran the same using both carbs. if it is what size would it be. i would like to go at least one size bigger. could this be just from boring it one size over? thanks again for your responses.

 

The boring shouldn't affect it one bit.
Someone else had this problem a year or so ago. Wish I could remember about that.
Stock jetting is 17.5 or 20 pilot and 92.5 main.
Does it still run better w/air tube removed?
Which way did you move the clip to get it to run the best? (up or down let's make sure we're on the same page)
How about the carb vent? Could the line to it be plugged?
Your welcome.

 

it ran good, through half throttle today with the air filter connected. the e-clip is at the last groove on the bottom of the needle going towards the point on the needle. you mentioned vent tube. when i got the quad, there were two tubes blocked of with vacuum caps. one was for the petcock, the other i'm not sure. i looked up a diagram on the net and they called it "hose". wow, great discription! anyway, is that the one your calling the carb vent? just curious, ive heard people say to check the float level. i don't really see how to adjust it. its not like other floats, where you can bend the metal tab for the float needle. this one is attached in a way that it looks like any adjustment would snap the plastic the tab is attached to. by the way, fyi, the oil injection is bypassed. using 32:1 fuel. the brass fitting in the carb for the oil injection is blocked of.