I have a 350L 2*4 that smokes when revved. I got it dumped on me and it sat for over 2 years. Just did a carb rebuild and new battery, fresh plug, oil and gas and starts right up but smokes when revving. Any help appreciated.

 

bad rings or stuck from sitting?

 

Run it and watch it , it may clear up , may not.

 

OK, piston has some scoring on it and will need a bore job, new piston and rings. About $200 I think in parts and boring. How can U tell if the oil injector pump is working to make sure that is not what caused this?

 

i think everybody just keeps an eye(measure) on the oil tank to see if it's using any. you could take the oil pump out ,hook the hoses back up ,open up the the valve and spin the shaft with a drill and see if any oil comes out the oil tube. i think it rotates counterclockwise. on breakins they want you to premix 40 to 1 plus use the injection. while you have the motor down you may want to check the crankshaft end-play and up& down as well just in case the bearings are loose, you might want to think about new crank seals as well(just the 2 outers). with your carburator not working quite right, it had a vacuum leak,whether the rings were the cause?? fix it while you got it apart that way next week when you get it back together you can let us now how great it runs instead of "hey it still don't idle right"

 

had the same problem with my 350L and just tore it down today. I was losing a bit of coolant (like a 1/2 cup a week and I ride every other day), so I thought it might be blowing into the combustion chamber causing the massive smoke I was getting...it's a 2stroke of course it'll have some, but wow it was excessive! I found a section of the case was missing a small chunk of aluminum between the oil pump section and the actual crank case on the oil pump section of the case itself. It's a non-stress area, meant only to hold vacuum, so I'm going to repair it and smooth it back out. Should work fine.
I do have a question-I've done dozens of the 250cc's but this is the first 350 I've done-the cases came apart quicker than I expected so I wasn't able to mark out where the counter-balance/oil pump shaft rides in relation to the crank...does anybody know if that matters? I would think it would, but my Clymer manual doesn't mention it at all....

 

there should be dots on the crankshaft and the counterbalancer,line them up when you're putting it back together and you'll be fine. easier if you put the outer crank seals in after you get the two cases back together.

 

Thanks a BUNCH!! You're right, I found them. Again, can't tell you how much I appreciate the help from you guys :-)

 

OK, Got the TopEnd rebuild complte, piston, rings, bored the intake to clean it up. New plug, plug wire, fresh gas. No it won't fire, compression is at about 90-100, no apparant leaking anywhere, it cranks all day but no fire.

Repulled the carb and it was all good, still no fire? Any ideas?

 

Well, if there's no fire, then it's probably the stator/magneto. Believe it or not, even just the position of the stator (as it is mounted) can make a difference :-) I'd be glad to send a pic of proper alignment if you need)
Have you tried pulling the plug out (leaving the coil wire hooked up to it and still touching the block) and cranking it? If it's not in direct sunlight, you should be able to see the spark. If you're not seeing spark, it's got to be (1) of (3) things, or even a combination of all. Was it running before you pulled it apart?
If you're not getting spark, it's either the CDI unit, the stator/magneto (inside the motor, behind the pull starter and flywheel), or the coil itself...
We'll figure this out :-)