1984 yamaha 125 tri moto issues

[jdhallmark1994]

got a 1984 Yamaha 125 tri moto from a buddy, he said it needs piston and rings replaced. i took the top head off and piston moves good, cylinder is not scratched or anything, looks good and feels smooth,i took the bottom 4 nuts off the studs holding down bottom cylinder and was not able to take bottom cylinder off, is that all holding bottom cylinder down??? i put it all back together and pulled the pull rope and it started first pull. idled really high,and blew out a lot of white smoke. if i could describe it it was screaming. so i killed it and took carb off figured it was stuck, and it was. the slide cylinder was inserted wrong. i cleaned carb, put it back together and put it back on, and now i cant get it to start. any ideas on what i should start with? asked previous owners what problems they had with it and they said same as what it did to me and that they just didn't have time to mess with it.



also, can i upgrade the motor? make it to 175 or anything like that? and where is good place to order parts?

[RubberSalt]

You've got a few problems. It sounds like you've got a blown clutch seal. Your jugs is probably worn past the service limit and will need a bigger piston + bore job. You'll also need gaskets. Only the 4 bolts are holding the cylinder down. The gasket will stick the cylinder and the cases together. Once the 4 bolts are removed, use a mallet to knock the jug loose (tap upwards). What ever you do, do not pry on the gasket surfaces. The aluminum is soft and will get damaged. You'll develop air leaks if you do. Airleak+ 2 stroke = toasted motor.

You've got an air leak, probably the clutch seal. It'll make things hard to start, and when they do start, rev high. It'll pull oil in from the transmission and cause it to smoke bad. You should always been smoking some, these are 2 strokes. If your not premixing, then you'll need to make sure your oil tank has oil and the line going to the oil pump doesn't have any dirt/air bubbles in it.
The carb settings are in the manual, and will tell you how to set it. Theres a website you can download this from (i forget where).

After all the work you do, you'll need to do a leak down test on the motor. Look up 2 stroke leak down test. If your motor passes the test, then you'll have a good running motor for a long time.