WHELP....its back together WITH a starter this time...new pull rope too...but it still wont run right...starts...wont rev up...wont idle...about 1/4 throttle i can get it kinda going...event took off the exhaust and tried it..will run a bit same same...got any thoughts?? im thinking carb...it is 20 years old...kid did clean it and put it together with a kit
....i did try again moving the clip up and down a couple notches...AND can you run that thing with the breather off? i keep putting it back on as i try to start it...PITA..

 

I wouldn't always trust someone else's work or what they claimed to have done on the carb. If you still have good compression as you mentioned earlier(140 psi) has new seals,has good spark(stator plate in same position as before) and good fuel supply to the carb,then sounds like the carb is the first thing I'd check into.Along with pulling the black wire from the reverse limiter that I mentioned earlier that can short out and cause problems. Yes on the old 2 strokes you can test them with out the air box in place. Couple videos that you can use as a guide on the carb.

 

thanks again...i pulled that wire...im gonna take the carb apart myself....i do work on small engines but not this kinda....ill give it a go...see what happens.

 

WHELP...im about done for now...it can sit and ill think about it...runs same as day i got it...put choke on..pops..take it off...runs like 10 seconds and done...not smooth either...i have no clue whats wrong with this thing...carb was clean...i soaked it over night anyway and used air and carb clean on it after...put all back together...same same...just like the day i bought it...this evening i tried moving the needle up and down a few notches and taking the idle air screw out and in 1/4 turn here and there...same same...the compression was low...so that helped....the seal under the clutch was shot..so that had to help...but it still runs same

 

Think it might be time then to look at that top end even though you say you have 120psi which is close to the limit one needs to run right. If the stator plate is set right,has good spark,has new crank seals,good air and fuel supply,carb is clean and ok,the only thing left is either a head or base gasket leaking or a piston problem.Plus looking back at your first post where you honed the cylinder out and installed new rings,this may be the problem area. Usually you can't get by with this on most two strokes if the piston to cylinder clearance is excessive to begin with. May have too much gap between the piston and rings to the cylinder walls. Ring end gap is supposed to be between .007-.015 and if the piston to cylinder clearance is close to .004 or larger,this could be the major problem.

 

the rings were not that tight...were like 14...the piston i dont know...but i got 140 psi in a wet test...120 dry...i figured that was good...but piston clearance could be bad..well...ill save some pennies and have that done...wont be for a bit...couple weeks...i can have it bored for 78 dollars and a 20 over kit for 60 bucks...if it dont run after that...ILL GET THE GUN OUT....oh yeah..plus ill need another top end kit thats about 20-40 bucks..thanks for the help again....ill keep plugging along...oh yeah...another question...i was reading that that cdi box can do some weird stuff....but i have good spark..mine also kinda loads up and backfires...but thats not its fault...i moved the clip up and down...but it does backfire

 

Just disconnect the black kill wire from the cdi along with the limiter black wire you already pulled and see if any difference. If not then I'd still suspect the top end. No good test on a cdi as you need to test out the stator and coil first and if the cdi is suspect,then change it out with a "known" good one as the manuals say.

 

ok...thanks...ill pull the black wire...i already did the rev thingy black wire. but its not my luck for something simple...i did buy it for almost nothing and others have worked on it already...next stop....top end. thanks again.

 

pulled the jug and piston...took to machine shop...guy says its 6 thou out...could clean it up with 10 over...but i found a kit for 20 0ver with gaskets so thats what its gonna be...again WISH ME LUCK....

 

Kind of what I was thinking from your first post. Just hard to just hone out a 2 stroke and install new rings on an old piston.Hopefully this will solve your problems. Be sure to bleed the 10mm bolt on the head to remove any air pockets from the coolant or the new top end can over heat very quick on the 400.I've seen that happen often when people forget.Good luck.