LT80 won't start
 

New to the forum. Read a lot figured you guys could help. Bought an 87 Suzuki LT80 for our twin daughters BDay coming up in April. Doesn't run. Check it out and had no spark. CDI/Coil unit is outrageously expensive so pulled a couple wiring diagrams and robbed a CDI Box and Coil off a wrecked Chinese wheeler that my buddy has. Got fire. Nothing. Checked compression. 30psi. Rebuilt top end. Rings are correct. Tried some oil in the cylinder gained about 5-8psi. When starter is spinning it acts like it wants to fire and actually is its just so weak it won't run alone. New plug correct gap. New jug, piston arrow to the rear, rings right side up. This thing puffs smoke and coughs but just won't do it. Compression after rebuild 30-38psi with a little oil. I'm at a loss. Reeds are good. Stator 170ohms. Same results with pull starting. Spark never seemed super strong but it fires off somewhat. It fires enough that the head heated up pretty good but that's while spinning the starter and its puffing smoke. Ok so I'm not a 2 stroke dude at all but could tru fuel 50:1 be a problem? had in in my shop so I used it. Carb is clean and working getting fuel to the cylinder. I'm lost.

If you have spark and it seems to fire incorrectly, there may be a chance the key sheared on the flywheel, so you are firing at the wrong time. I don't think the 50:1 mix is critical, it would run, just smoke more, around 34:1 is a good mix for general use. You seemed to have covered the other bases pretty good, just make sure the kill switch is not giving you a problem either.

[QUOTE=95wolv;3317605]If you have spark and it seems to fire incorrectly, there may be a chance the key sheared on the flywheel, so you are firing at the wrong time. I don't think the 50:1 mix is critical, it would run, just smoke more, around 34:1 is a good mix for general use. You seemed to have covered the other bases pretty good, just make sure the kill switch is not giving you a problem either.

Thanks for the response. I was thinking timing. I will check that this afternoon and get back to you. The 30-38 psi compression after rebuild is throwing me off but the rings may not have seated good yet.

Is there anything else aside from head gasket and rings that would cause low compression. Should I pull the engine and go do new case and crank seals? I know if their leaking it's not good but doesn't seem like it would be a low compression issue. I checked the head to make sure no warp. Checking that timing this afternoon. Are there marks?

timing is correct

I have to apologize, I misread your first post, I thought you said it had 30 psi so you rebuilt it, but I see you still have 30 psi after the rebuild, there is no way it will start with that low of compression, there must be a problem with the rings, or the piston is mismatched to the cylinder and is allowing blowby. you will need to get the compression above 70 or 80 psi to run at all, it should be about 110 with a fresh rebuild. I would say you are going to be taking it apart again to check out ring clearance and piston fit.

I agree. I tore it back down. This is a kit off eBay. So who knows to what spec their made to. But I'm going to be returning it and getting a decent kit. Crazy thing is. I put the original jug and piston back on and get exact same compression. Older fellow down the street used to work on them a bit. He told me to pull the engine split the case and change all gaskets and seal in the crank case. How would that help compression and should I try that?

If the crank seal is shot, it would leak badly and not build compression, you would find that seal behind the primary (front) clutch where the crank drives the output shaft to the clutch. If it looks worn, or there is slop in it, it will not seal and suck air and leak compression. unless you see a lot of oil leakage all over the motor, replacing the crank seal should do it, unless you already have it pretty much torn down, then replacing the case gaskets would not be a bad idea either, to eliminate all sources of leaking.

Thanks for the info sir. I'm ordering seals tomorrow. I'll keep posted on the results but I hope that gets it fixed. I'll let you know. Thanks agin for your help

This post said more....
95Wolv..I'm heading to your garage. You obviously got some chinese stuff since the last time I was there and I need a anchor. :p
OK, why would a seal effect comp?