Hello i have a Yamaha DT50MX from 1987 (Twostroke). And i recently changed the piston. Then i started it and let it run on idle.

But after 2 minutes it just died. And i do not know why. I have looked in the Carburetor in details. And i have really good spark on the sparkplug.

I have both tried to roll start it and spraying in starting fluid. Please help if you can Thanks.

Does it actually turn over?

4 hours ago, Snakebite68 said:

Does it actually turn over?

Yes and no unusual sounds. 

Ok, start at the beginning...

All the stupid answers in order of simplicity:

1/ Did you remember to turn the fuel tap back on (trust me, I've done it...)?

2/ Is there actually any fuel in the tank (not personally done this one)?

3/ Are all your fuses ok (done this one too)?

4/ Does it have a fuel pump?

5/ You'll need a compression gauge, check the compression (if you've just put a new piston in it, the rings may be bad).

 

Well, that's pretty much most of my experience..!

2 minutes ago, Snakebite68 said:

Ok, start at the beginning...

All the stupid answers in order of simplicity:

1/ Did you remember to turn the fuel tap back on (trust me, I've done it...)?

2/ Is there actually any fuel in the tank (not personally done this one)?

3/ Are all your fuses ok (done this one too)?

4/ Does it have a fuel pump?

5/ You'll need a compression gauge, check the compression (if you've just put a new piston in it, the rings may be bad).

 

Well, that's pretty much most of my experience..!

Sorry. But i have checked everything. even opened the cyliner and looked at the piston and rings in detail.

And still wont run i smell gas after a couple of tries to start it. And the filter sucks in air. So i dont really know what else to do. 😕 Thanks for the help still.

Why did you change the piston. I'm not taking the piss, if the piston failed. How can tell you about other issues. 

For now. Try squirting some oil behind the generator rotor. 

Some wd on the leak points is also worthwhile. Running for 2 min is enough heat to get any weak gaskets seals to leak. Several small leaks can be worse than 1 biggy.