Hey guys~
My sisters LT was stomping around PISMO with her brand new FMF pipe on with no issues, but a ton of fun... Then for a stretch we were really on it hard, 4th gear deep in the power band and the LT craps out like it had just fouled a plug... After that it will not start. There is spark, and my compression read 80psi... ITs a damn mystery...

*what is the ideal compression for the LT250'87???

*what is the best jetting recipe for sea level~FMF pipe on stock bike 1987LT? MAIN & Pilot???(I THINK I'M LEAN ON TOP)

*gas is leaking out of the carb overflow when not running and gas left on?

*the carb is taken apart for cleaning and I would like to re-jet.


ANY IDEAS ON HOW TO GET HER RUNNING???

If I were a betting man, I'd say she blew. 80 lbs is no where close. It should be more like 150-170 lbs. Mine has 165 lbs and runs very strong.

What gas/oil ratio were you running?? If you never re-jetted after piping it you for sure blew her up.

Thanks for the reply CATMAN... the more the marrier!!!

WOW~ we are low on compression...

I was running 32-1 and WAS NOT RE-JETTED!!!(DAMNIT)

Nothing seized, but the plug looked like it was LEAN, and like I said 4th gear deep in the power band and then blaaaahhhhhhhhh!!!!

Could you advise on how big of a MAIN JET to run with on a stock carb, also what do LT250 riders re-jet the pilot too? I AM AT SEA LEVEL.


THanks again

Main.... 240-260 Needle.... raised 1 notch (clip lowered 1 notch) Leave the pilot alone. All you should really have to do is turn the air screw IN 1/2 to 1 full turn. I am only at 500-600 ft. above sea level, so these settings are basicly the same for both of us.

You said nothing seized, but when you tear the head & cylinder off you'll either find a hole in the piston or a badly burned/scored piston & cylinder wall. You're now looking at a new piston,rings, boring & honing job, etc.

It won't read 80 lbs comp. with a hole in the piston. 80 is pretty low though, and you might have other issues. It still could have seized and then freed back up again. Seeing as it won't start it is definately rebuild time. A good rule of thumb on 2-strokes, if you go up 10 on your main(i.e. 180 to 190 main) then go up one size on your pilot. Better to rich than lean, and you can always go back down later. The starting problems could also be something kind of simple, like your ground is bad or disconnected. Also, with the gas flowing out of you overflow, either the floats are stuck, or the little needle valve the float actuates may be damaged. They have a rubber tip that becomes hard over time and won't seal. Hope this helps[img]i/expressions/face-icon-small-smile.gif[/img]

Might just be the head gasket if its a cheapy they go alot. My engine is pretty moded and I go through like 1or 2 a year, I guess im cheap cuz i havent bought a copper one or a pro design cool head yet lol

It's not the head gasket. He said that the engine was never re-jetted after adding an FMF pipe. Don't re-jet a 4 stroke after adding a pipe.... can usually get away w/ that..... a 2 stroke never! Just changing the silencer MIGHT be o.k., but definatly not a full system.

yeah you melted the rings, expensive lesson, when you could have spent 20 min and 10 bucks on jets. Someone once told me it takes at least 100 psi for an engine to even start.

Uh Oh, I just got a 87 LT250R Brand new motor rebuild. Mods are below, (FMF pipe all the way back, bored .40 over, stock carb, Please help me with this correct jetting thing.... What is jetting? What do i need to do to correct mine?

Hey just wanted to thank everyone for their help and give an UPDATE:

Starting with the obvious(not for me LOL): The rings are toasted and gernaded, The piston is thrashed and mangled, the head is scarred badly as well as the cylinder wall. Definately needs a full blown bore! So who does the best work on LT's?