1989 LT250R

LAST SEASON:
Freshly Rebuilt Motor at end of last season (October), only rode 1 weekend…quad started easy and ran good except it wouldn’t hold an idle without feathering throttle.

THIS SEASON:
Went to start last weekend and got nothing out of the motor, found out that there was no spark. Traced problem back to pickup coil – replaced pickup coil on stator and strong blue spark returned. All other stator components checked to be in good shape. After doing this engine started on a few kicks, still didn’t idle, but ran OK driving it around the yard. Put it away determined to fix idle problem another day.

Went to start again another day and nothing. Still getting spark and getting fuel. Compression is 150 psi. Worse yet, the kickstarter has started kicking back like a horse. Very painful on the foot. Have tried starting this 3 separate days now, no change, almost always kickback, never starts. Have tried with and without choke, with and without throttle, brand new plug a few times, gas down the plug hole, etc.

WHAT I HAVE DONE THUS FAR/NOTABLES:
- Compression is right around 150 psi in multiple tests
- Has fresh gas, mixed 32:1 (a week old)
- Used multiple new spark plugs (BR8ES)
- Kill switch seems to be working just fine
- Air filter doesn’t seem to be clogged at all, tried starting with and without filter, no difference
- Shouldn’t be any air leaks, motor rebuild included new seals throughout
- Timing was checked and is correct, all stator and coil ohm measurements checked and are correct (spark is great, nice and blue anyways)
- Checked Flywheel key, it isn't sheared
- Carburetor removed and cleaned twice, checked float level (good) and needle/seat (good), jet needle (good, has no grooves), the first time there was partial clogging of pilot jet and main jet, blew those out good, second time all looked perfect in there
- Jetting is stock (30 pilot jet, 240 main jet)
- this is an 89 quadracer with the smaller cylinder intake (6-bolt style and 6 reed style)


Any ideas here? Kickback is confusing and painful. Let me know your thoughts, thank you.

 

Try pull starting it. What is the engine/air temp when it was starting and not starting? Kickback is backfiring, either timing or jetting. Sounds like jetting. Have you tried using starting fluid? If you are getting fire, timed right, it has to be in your fuel/air mix or delivery. Check for cracks in intake boot.

 

Air temp hasn't changed much.... it was probably 40 degrees when it started the first time, 40 degrees when it kicked back the first time, and 50 degrees when it continued kicking back on other attempts.

I haven't tried using starting fluid, but have put gas down the plug hole a few different times (doesn't do anything differently).

Sorry to be a fool here, and not trying to say you're wrong (just trying to understand this), but how does poor jetting cause kickback on a 2-stroke?

I will give pull starting a try next chance I get, and I will check the intake boot for cracks.

 

Well, I'm not sure anyone is going to believe this (mostly because I can't believe it), but here goes....

Checked timing today with a dial indicator (to find TDC) and a timing light (to see where it is sparking). The difference should be the advance, right? . That difference, measured via the dial indicator, is .2" (just over 5 mm). 5 mm!?!?!?!? This is a ridiculous amount of initial timing, especially on a 2-stroke. Most I am aware of are somewhere between 1-2 mm.

Degrees wise, based on a rough measurement, this is somewhere over 20 degrees. Per manual, initial timing should be 6 degrees, final timing should be 11 degrees.

Where to next? Is this even possible?

 

You're right, kickback sounds more like a timing problem, but you said that checked out. check it again. I just rebuilt a 230s and was sure my build was good but I was lashing my valves exhaust TDC instead of intake TDC. Simple screw up on my part, a real mother to find. I know your 2 stroke is different, but fuel+fire+timing=braaap. Check your exhaust and make sure there isnt a mouse nest or mud daubber clump in there. (Trying to think outside the box) That might cause your kickback? Can you adjust your timing? I mean everything is pointing to timing its seems to me and you too.

 

Thanks for the help Burnpile. You were right, it was DEFINITELY TIMING.

Problem solved, I had the wires flipped / backwards on the pulsar coil. This made the ignition out of time, in this case advancing the timing the length of the exterior flywheel magnet....about 20 degrees of advance. The advanced timing caused the kickback. What was actually happening was it was firing waaay before the piston reached TDC, pushing the piston back down (and in turn, pushing the kick starter into the bottom of my foot, HARD).

Switched wires around last night and timing returned to normal. Quad is RUNNING JUST FINE other than a poor idle, but I believe that to be an air/fuel issue.

To be clear for anyone else reading this post in the future, pay close attention to which wire is which coming out of the pickup coil. It appears that each wire coming out of it, if sent to the CDI box, will fire but they will fire at different times. If the wire that is supposed to be the "ground" is sent to the CDI, then it will spark / fire at the BEGINNING OF THE ROTATION OF THE EXTERIOR MAGNET ON THE FLYWHEEL, which in effect advances the timing about 20 degrees because thats how long the magnet is. If it is properly wired in, then the spark/fire will happen at the END OF THE MAGNET ON THE FLYWHEEL, which in the case of the LT250R Quadracer is correct.

 

Good show man! Glad you found your problem. The thread really turned out well didn't it? And coincidently, while welding on my swingarm, POOF! Gas fumes lit and burned up my CDI box, it should be here by the weekend. Some of my coil wires melted and need spliced also along with the throttle cable and a bunch of soot on my plastics. (note to self--Shut off gas and drain carb BEFORE upending quad to weld!) Will keep this tip in mind while fixing my ride. Excellent!