did it blow up??? HELP!!!!

[outlawgrafyx]

i just put my bike back together, starts up on the 1st kick, i rode it when it was really lean, and so i messed with the air mixture, it seems to be running better but as soon as i get it up to like 4000 rpms it falls on its face and almost dies!!!

is my mixture still too lean???

or did i blow up the engine???

I NEED HELP

its a 1973 yamaha dt250 :bang:

 

[YZracer021]

It doesnt sound like a blow up. If it starts on the first kick that means it still has decent compression. an easy check would be to pull your exhuast off and look and see if the piston or cylinder walls are scored. To me it sounds like the engine is just starving for fuel. if your cylinder looks fine just set you carb. settings back to stock.

 

[YZracer021]

Another thought would be the reed valves, see if they're curled up or chipped. if they're curled just flip 'em over.

 

[outlawgrafyx]

the reeds are good, i think its my fuel lines, some times it gets pinched, but i tried to unpinch it and then try it, but i guess it didnt get unpinched all the way...i really hope it didnt blow

 

[Isobareng]

1973 yes indeed we are back in my hayday.
OK first take the carb apart and ensure every jet is clean and each passage way thur the carb is free of gunk. if that is all good 1973 used points and condenser are they new fresh and set correctly. did you put the piston on backwards? short side of the skirt faceing the carb. next is the exhaust clogged with carbon? there used to be a restriction near the silencer that easily clogged,and last is the gas new and fresh?

hope this helps

D

 

[outlawgrafyx]

ok, carbs clean...poitns and condensers??? never messed with them, dont know how. piston hasnt been touched, bikes never been "opened" i took the restricter off and pulled out the old packing and made sure that the restrictor wasnt clogged....anything else???

 

[Patman]

Check the plug and see what it looks like it can tell you a lot about what is happening inside.

 

[2strokerfun]

Also, make sure the gas cap vents properly. I've had this happen with a clogged vent.

 

[outlawgrafyx]

where does it vent from??? my bike is old and doesnt have a vent tube like on the new biikes.

my plug isnt dry and white, but i think its a normal color, medium brown...


should i adjust points??? if so i have no clue how to do it

 

[2strokerfun]

If your gas cap has no visible vent on top, they usually vent underneath, just outside the cork or rubber gasket. To test, try running it with no gas cap on it and see if it makes a difference.

 

[outlawgrafyx]

i did that and it made no difference. i have no clue whats going on!

Isobareng, i need your help!!

 

[outlawgrafyx]

ok, so i still have the same problem... i have really good gas flow now, i cleaned out the petcock... the plug doesnt indicate a lean condition. but a normal one, but it still falls on its face up around 4000 rpm... is it my cylinder/piston?? is it the carburetor???

i just cleaned out my carburetor and blew out all the passages. my main jet is a #160...

the only thing that i can think of is that i got a new needle jet setter, it has an oring on it. my old one didnt. i guess with out the o ring it makes it richer. now i have one with an oring in, it seems like its not running good. i might take apart the top end tomorrow to see whats up.


i need help!!!!!!!

 

[JunkmanDT250]

Let me know if you need some help.