Raptor project

[Mongrel714]

I've posted this on some of the cart forums but now that I'm working on it this will be the "official" build site
A friend of mine sold me a 660 Yamaha Raptor for $150, he was sick of fooling with it, he threw a rod after rebuilding the engine, he put a 250 yamaha two stroke on it now which is having some problems.
The top end of the 660 looks good as you can see from the pics, also in the pics you can see the crank that is gouged as well as the piston and rod which are deystroyed, so I'm thinking it shouldnt take to much to get the 660 back together.
For the time being I'll see if I can get the 250 in shape, it will run, but won't rev up to a high RPM untill it starts to run out of fuel then the RPMs will climb, any ideas on this??
I lk forward to any help anyone can give me, thanks in advance!

[DocHemi]

Sounds like a fuel delivery problem.

And that you basic air/fuel mixture is way to rich.

As you indicated, as it runs out of fuel it begins to be able to rev higher....this is due to the mixture leaning out and for a brief period, the mixture has enough air to burn the fuel.

Check and clean the carb real well, make sure float is ok and adjusted correctly.

Make sure the needle and seat are good and functioning.

Might check the Reeds as well.

I dont know if you running it with the air cleaner on or off.....if its on try taking it off and see the result...may be a dirty air element.

[Mongrel714]

Sounds like a fuel delivery problem.

And that you basic air/fuel mixture is way to rich.

As you indicated, as it runs out of fuel it begins to be able to rev higher....this is due to the mixture leaning out and for a brief period, the mixture has enough air to burn the fuel.

Check and clean the carb real well, make sure float is ok and adjusted correctly.

Make sure the needle and seat are good and functioning.

Might check the Reeds as well.

I dont know if you running it with the air cleaner on or off.....if its on try taking it off and see the result...may be a dirty air element.

Thanks for the info!, I myself have yet to run the engine, I believe te prior owner was running without a filter, he said they were running this engine on a three wheeler and it was way to fast for that setup, we'll see, , oh ya, it is a 89 Yamaha Tri V Y2F 250 2 cycle water cooled engine, your advice sounds dead on, I'll try this this weekend.

[nvmyengine]

my lawn mower does this...took the air cleaner off and it runs fine.....no i am not dumb it turned it off after a minute and will fix it and not run it w/out an aircleaner