NEED HELP WITH MY 86 R, Please!

[Domingo]

I need help with my R. I just got a new cylinder. It came off a TRX 250r. I got everything installed. I started it up, ran kinda rough. Took it out...made it about 50 ft, then it shut off. I have been able to start it about 3 times since then, but then it shuts off. I have checked my gas...good. I have decent compression, around 125 psi( fresh bore and piston and rings) I have decent spark. I have no diea why it wont start. My fear is that this jug is from an 87 TRX. Which has the bridged intake. How can I tell if this is the case. I dont know what one looks like. Any suggestions will be appreicated. Please help me out here. I dont know why it wont start anymore. Thanks for the help.

[Lots_Of_Nothing]

what is it doing when it shuts off? can you describe better? like noises? smoke? smell?, also, when you try to start it back up what does it do? nothing? backfire? what?

[Billy Golightly]

I need help with my R. I just got a new cylinder. It came off a TRX 250r. I got everything installed. I started it up, ran kinda rough. Took it out...made it about 50 ft, then it shut off. I have been able to start it about 3 times since then, but then it shuts off. I have checked my gas...good. I have decent compression, around 125 psi( fresh bore and piston and rings) I have decent spark. I have no diea why it wont start. My fear is that this jug is from an 87 TRX. Which has the bridged intake. How can I tell if this is the case. I dont know what one looks like. Any suggestions will be appreicated. Please help me out here. I dont know why it wont start anymore. Thanks for the help.

125 is no wheres near enough for a 250R. Especially for one that has a fresh rebuild. It should atleast be in the high 140's range.

[smokinwrench]

My top end is over a year old now and has about 185 psi.

Sounds to me like maybe you got a piston ring wedged in the cylinder.

[C W.]

pul the jug inspect the rings check ring gap it goes over that in your book.and also 87trx rod length could be different than86atc.i dont know if rod length efects cyinder height on these things but it could.maby they just change the wrist pin location.always order the piston for the year and model jug you have.for the best r motor info on the web check out http://macdizzy.com/2stroke.htm its a must read. i ride the same bike ass you

[firebird13601]

if i remember corectly the 87-88 trx's had a longer rod

[sandrooster]

Domingo,
Have you disassembled the carb to clean and check operation?
Is the plug fouled black and wet?

[Domingo]

Thanks to all who replied. I took off the jug, I did have a piston ring stuck. I fixed that problem and have better compression now. But now, I have no spark. I had spark before, but now I dont have any. I have changed plugs and still nothing. I am going to try and get a DMM tommorow so I can get some readings on my coils and CDi and try and figure out what is wrong. Any other ideas would be helpful as why I am not getting any spark anymore.

[sandrooster]

Since you had spark before.
Check the plug boot. Sometimes the line from the coil isn't making good contact with the boots contact.

So whats the new compression reading?

[Domingo]

I hopefully have the problem figured out. After testing stuff with my DMM I reliezed that my ignition coil is not OEM or after market. It isnt't even Honda. It looks like something that would come from a lawn tractor. It had close to 4 times the amout of resistance a normal 250r ciol would have. My theroy is, that it would work only under low pressure. Outside the jug...and before my rebuild. Under high pressure, my current compression is 150, it doesnt spark. So I need a new coil, that will hopefully solve most of my problems with not starting. Thanks to all who replied