engine problem

[89250rhonda]

put my new kehien 38mm a/s carb on kicked it up on second kick, let it tick over for 5 minites then got on it, tuck my time for a minite or two, then fully opend the throtle in 4th and it took off i changed to 5th and it just cut out, now there is no comprestion.
what do you think i have done?

[1promodfan]

We need a little more info, but it sounds like your piston let go. Same thing happened to me, and it was the piston. Have you pulled the head and looked at the piston?

[Honda 250r 001]

What jets did you have in your new carb? What cylinder and exhaust are you running?

[fearlessfred]

is there aluminum on the spark plug

[wilkin250r]

Honestly, this is one of those "Open her up and see" kinda problems.

You may have blown a ring, melted your piston, or just blew out a head gasket (but you'd almost ALWAYS see coolant if you did that). Unless the spark plug blew out of it's threads, those are the only things that can cause loss of compression.

The fix is the same for any of them, a top end rebuild. So regardless of the actual reason, the first step is the same, tear apart the top end.

It's also entirely possibly that it's just coincidence, that your top end was worn out and it finally gave, and had nothing really to do with your new carb.

[89250rhonda]

pulled the barrel 2 day and found i had melted the piston i hav also scratched the sleve so i am going to get it bored out to next size.

[fearlessfred]

Originally posted by 89250rhonda
pulled the barrel 2 day and found i had melted the piston i hav also scratched the sleve so i am going to get it bored out to next size. it may sound dumb to say this but make sure u fix any air leaks or what ever lean condition caused the melt down . i have seen people repeat the melt down on the fresh top end. i would suspect the carb was the culprit but would ck. everthing

[wilkin250r]

And just in case nobody has told you yet, melted piston mean's you're running lean. And since it happened just after you opened it up WOT, it means the damage was occuring before that (pistons don't melt in a couple seconds).

Move the needle clip down (raises the needle up, richer jetting) and maybe go up on the main as well.

[89250rhonda]

how do you i move the needel? and how many sizes should i go up on the main jet?

[wilkin250r]

Moving the needle isn't difficult, but first, tell us what you ARE running.

Are you running the stock cylinder, or a bigger aftermarket (like a 310cc, 330cc ect).

Any porting done on the cylinder?

What kind of pipe are you running?

What kind of airbox and filter setup do you have?

What jets are you running right now?