Yamaha LT2 not starting

[racerxnico]

Hello,
I am new to this forum and joined hoping that I might find someone to help me. A couple years ago a friend bought a house and there was a small motorcycle in rough shape buried in the weeds of his back yard. Much to his surprise, I told him I'd give it a good home. I stripped it down to the frame and cleaned, painted, and restored everything I could.

Last week I got it to start for the first time. I had to bump start it the first couple times, but it didn't want to stay running. I took the carb off and checked a couple things and put it back together. I got it to start off the kick start once. Since then I have only been able to bump start it. The carb is completely clean and clear (checked and cleaned about 4 or 5 times).

Once running, it will gradually want to run down and die. This seems to be getting worse and it seems less willing to start. I don't have a dial guage, but I know the timing is very close if not right on. During the rebuild, I had the cylinder off. The bore looked good and measurements with a hand micrometer showed it round so I reused the piston and ring (single ring piston). I don't remember measuring the ring gap, but think I must have.

I'm looking for theories as to why it isn't starting and staying running. The only things I can think of are the timing and poor compression.

I don't have a compression tester or leak down tester, but could get ahold of one if anyone can tell me what sort of numbers I should be looking for.

If I don't recieve any wisdom I'm going to pull the cylinder off, check the ring gap, but if that's not it, I'm stumped.

 

[julien_d]

That bike probably has points. Have you cleaned them?

 

[dirt bike dave]

Worn out reeds can make a two stroke nearly impossible to cold start.

When they wear out, the cold starting problem gradually gets worse and worse.

 

[julien_d]

yes, it does have reeds. Neat. I expected piston port intake. Definitely check those. Like Dave said, if they're worn, chipped or not sealing you'll have problems starting.

 

[Someone]

I was checking out this old bike and found the manual in case you're needing one:
http://www.pitstop.net.au/view/bikes-yamaha-wsm/page/query/plu/14760/

 

[racerxnico]

Hey all,
thanks for the replys. The points look great. No pitting and appear almost new. I do have a new set, but opted not to put them in when I saw the condition of these. Intake reeds are new. While doing restore some NOS come across ebay at a good price and I figured, why not.

In spite of the visual description of the points is it possible that they are still the problem? I would think that they would effect the spark and spark seems very strong.

I do have a manual too, but I haven't found anything to help me figure this out in it.

 

[helio lucas]

the most likely is a fuel problem. since is a old bike the inside of fuel tank may have rusted an blocked the fuel line.
make sure the carb receives enough fuel.

i would not think it´s the points since the bike starts and gradually dies.
have you clean the internal passages of the carb? jets? or just the fuel bowl? make sure all the lines are properly clean with blown air and maybe carb cleaner.

 

[racerxnico]

Carbs are completely cleaned. I stripped and dipped them. All jets and air ways are clean and clear. The gas tank was cleaned (muriatic acid and ball bearings) and coated so that's good. The fuel lines are all new and I put an extra filter in line from the petcock to the carb. I don't think fuel is the issue or it wouldn't rev up the RPM's when it is running. Also, Dirt Bike Dave, the starting issue isn't just when cold. It will stay running at higher RPMs and I've let it do so until it was pretty hot. Then I let it die and tried to start it again without success.

 

[rmc_olderthandirt]

What kind of engine rebuilding have you done? Bottom end seals?

If the crankshaft seals have dried out after sitting for years they could be totally ineffective and be leaking badly. Such a leak would be the most significant to starting and low RPM.

Compression and leak down tests would be my recommendation on how to proceed.

Rod