97 cr250 wont start

[Perk_zk]

Hey everybody, first post but this forum has helped me out here lately with my kx125 rebuild so thanks and maybe i can get some feedback on this problem

A friend of mine bought a 97 cr250 from a guy a few years ago, had a new top end when he bought it, rode it a while and heard some noise from the crank case, he ended up tearing it all apart and replacing the crank bearings and seals, put it all back together, started turning it over and said he could get it to sputter but never really ran, then noticed gas pouring out of the carb so drained the tank, set it up, and ordered a carb kit, this prolly a year ago. NOW the bike has changed owners to another friend of mine and we started working on it yesterday. We put the carb kit in the bike and tried cranking it. NOTHING. Spark plug was dry, but firing. Did some more lookin on it today. Took the carb off. Adjusted the air screw back to 1-1/2 turns out. Blew some air through the carb and gas flowed out like you would expect. So we started looking a little deeper. The intake boot seemed to have some pessure coming back when we turned it over and not as much vaccum as i would have thought. We pulled the reed block out and could see some daylight under one side of the reeds. Flipped that set of reeds over and not quite as much daylight now. Also noticed 2 dif types of reeds. Reinstalled the reed block with gasket sealer. Put the carb back on and started giving it a try. We did finaly get a few coughs out of it but it never took off. Compression is at 120 after reeds were re installed. Tried it with choke on and off. expansion chamber on and off(cuz it had been in the way we removed it)dosent seem to have as much air coming back through the reeds. Hard to say its completly gone but it def better.

Sorry for the long post but wanted to tell the story. Any ideas or help would be greatly appreciated. Hate to start pouring more money it b4 we ever hear it run. Thanks in advance

[turbo dan]

120 psi is very low compression. 

[Perk_zk]

Do 250s run higher that 125s?

[Perk_zk]

I just read about opening the throttle for a compression test. Never heard of that before. How much difference would that make?

[Excitable]

I just read about opening the throttle for a compression test. Never heard of that before. How much difference would that make?

tons.

 

throttle wide open , 10 good kicks.

[Perk_zk]

Aright thanks. Ill give that a try next time im messin with it and see what i get. Any other suggestions anybody?

[Sam097]

Is your plug still dry?  I would put the pipe back on it before you try anything else. It sounds like your not getting fuel into the cylinder.  First thing I would do is lean the bike on its side for a few secs then stand it up and make sure you get fuel out of the overflow tube.  If you get fuel out of the tube try starting it full choke no throttle.  If it doesn't fire pull the plug and if its not wet put a little fuel in the plug hole.  A straw works good for this.  Just put enough in to get it to fire...about an inch on a straw should do it.  If air and spark are ok then it should at least bark.  I know your down south but what temp are you trying to start it in???  If its below 50 pull the plug and heat it up with a torch or lighter...warm enough that you need a glove but not cherry red.  Full choke no throttle.  My 98 will not start cold with ANY throttle.  Make sure your choke stays in the detent cause ive heard of some of them wearing out and it might be falling back down.  Since its been torn down reach up in and make sure your power valve isn't stuck up before you put the pipe back on.  I don't know if that would prevent it from starting but its worth a look and prob adds back pressure.  Good luck and hope you get it going.   

[Perk_zk]

I havent pulled the plug i dont think since i started getting it to cough cuz i assumed it was getting gas. Ive done some other reading and i think we are on the same page. As of right now im thinkin probably not enough gas and or weak spark. Hoping i get to work on it tuesday and see if we can get somewhere. Im in arkansas. Temp the day i was working on it last was probably pushing 60 or so. I will check the powervalve thing. I had my hand in there the other day but didnt pay attendtion to anything but the cylinder movement. I have dropped some gas in the cylinder and it will cough, after pullin the reed cage and all we started getting an occasional cough. And it seemed to happen after choke open and throttle cracked one or 2 kicks then close and kick it would cough. Thanks for the input well see what happens

[Sam097]

Your heading in the right direction.  Once you get it fixed you should be able to pull the choke up, start the bike, and not have to touch the throttle for about 30sec.  Choke up, kick it, let it do its thing! 

[Perk_zk]

UPDATE: Set timing based on the marks in case and on stator. Checked compression WOT 10-15 hard kicks 125psi. Replaced plug. Checked/set gap .022- .024. Choke on. 35-40 degrees here today. Air adjustment set 1.5 turns out from seated. Kick kick kick....nothing. Crack the throttle kick kick cough. Kick kick kick. Crack throttle kick kick close throttle kick cough. Started adjustin air screw some more basicaly same results. Pulled carb went back through it. Reset the float. I havent found anything that real clear how to set it. I had it b4 where without a doubt it had enough but was closing the valve. I picked it up a little more to close the valve sooner. Set it where float is parallel to carb when upside down (kx125, yamaha outboard, old evinrude outboard, bout every float ive ever messed with is set). Pulled choke assembly and cleaned it. Ran cleaner through choke channel. Checked all cent hoses for kinks. Checked idle jet and high speed jet for trash. Put all back together. Boots on carb are sealed up tight and in place. Again...choke on. Air screw 1.5 turns out from full seat. Kick kick kick cough. The only thing dif after pulling the carb is i dont seem to have to crack the throttle ALWAYS to get it to cough. Only sometimes. Adjusted air screw in and out 1/4-1/2 turn at a time. That did make a dif but a no setting would it hit everytime and farther i got away from the 1.5 it never got anymore consistant. It will cough anywhere from 1-2 turns from seated again further from the 1.5 seems like i have to crack the throttle. Ive had enough of it today. My leg tired haha. I REAAAALY starting to lean more on compression. The guy that put it back together did tell me it was a new top end when he got it b4 he tore it down. When he put it back together he put a new ring on the piston. So idk if the new ring may be messed up, just not seated right for some reason, idk. Then i also keep going back to the reeds. And maybe they have something to do with it. Some other reading ive done suggest it should still start with a reed that isnt perfect just run bad. Any comments, help? Thanks yall

[Excitable]

125 psi is low, you need to open her up, sounds like he put a ring in when it needed a piston also.

[chanlarius]

Check the top end or check the float level

[Perk_zk]

Is there a possibility that the timing is off? Thats really what it seems like is going on. What have read (without a manual) its VERY unlikely. But i havent read much on the subject

[chanlarius]

If the floats are even a little off it wont start, it will either be starved of gas or not enough gas at all, happened with my cr250, it started after 10 minutes of gas flowing because it was barly getting any

[ByronK]

new top end with 120psi something is wrong with it, disassemble the top end and inspect every component to be within spec, you never know if previous guy has done a good job.

 

also inspect the reed flaps must "seal" onto the cage and gasket surfaces (base, head and reed cage) in good condition to seal properly!

[Fenmore]

sounds like a new top end is needed and then I'd put reeds in it too.  The reeds will def cause starting issues, but your 120 compression is really low too so you have a double whammy.  

after that if it doesn't start, take that carb and throw it as far as you can in a field.  those carbs are horrible 

[Excitable]

sounds like a new top end is needed and then I'd put reeds in it too.  The reeds will def cause starting issues, but your 120 compression is really low too so you have a double whammy.  

after that if it doesn't start, take that carb and throw it as far as you can in a field.  those carbs are horrible 

those carbs are fine if tuned properly, haven't had a problem with mine yet.

[Perk_zk]

How much conpression would u think could be lost from reeds not sealing conpletly?

[Perk_zk]

Just had another idea. We pulled the expansion chamber off today and was lookin in the cylinder. It is WET in there. And quite a bit of it looks oily. Put ur finger in there and get back an oily sludgy residue. First i was thinkin the case was loaded wifh fuel. Then i had the idea what if there is trans fluid in the crank case. What yall think? Whats the odds? How would it act?.... Thanks

[chanlarius]

Very slight chance that'd happen. There could be seals thatre gone to shit, and that could be why, or thats just pure 2 stroke oil