bike hard to restart, have spark (can CDI still be bad) (flooding)????

[soccer2963]

Hi, i have a 1987 YZ250, and it is giving me a heck of a time. I checked the PSI and the higest it goes is about 150psi. That is good i think. I just replaced the bottom cylinder gasket because it was poping out the back and wouldnt start (thats why the guy sold it to me). The bearing seem all good ( the rod had no up and down play. Now, it will start for a little while then die out. And wont start again. I thought that it was the Spark, but while in my dark garage the spark came out good. Can the CDI be bad but still spark? Or how do i know if the timinig is correct? ( you dont really have to adjust timming right?)

And on the carb, it leaks gas from the bottom port. This one seems to be an overfill for the bowl? I took out the needle and seat and they look good, i push the nipple and i cannt blow through it. Someone said that the floats may not be right, how do i set these, or does that not even sound like its the problem?


Thanks for any help!

[soccer2963]

Ok, update: Checked for spark again tonight, and it comes out a bright blue/white spark. So thats not the problem. And the carb is good (I think). What gives? I think tomorrow i will take the carb off and spray some starter fluid in and see if it will start up.

[SirFallsALot243]

Compression should be around 180. A bike needs 120ish just to run. 150 is a bit low, you might consider putting a new ring on it.

[twoofeach]

That does sound like you are not getting any gas because of the floats. Check Faded's post here...

How To Set Your Motorcycle Carburetor Float Level

[soccer2963]

Sirfallsalot, ya it does seem like my compression is a little low then, but it should be good enough to run right? I checked the floats, and they were off a little, but i got them within specs now +- .5mm, AND nothing still. If i pour a little gas into the intake while the carb is off, it will fire up. DO you think that i should do a leak down test on the engine? (then i would have to build a tester, but no biggie, i saw some ways on google)

[BlazinLdub]

How does it run? Does it bog or run erratic? Check the actual spark plug and see what color it is and tell us. Also, what number is the spark plug?

[soccer2963]

the plug is a b9eg, and it is new. I have gotten the bike to start up twice since i had it, and ride it around the back yard before it would die. It seemed to run good, smooth too. What do you think about the leak down thing, or should i not worry about that?

[BlazinLdub]

A leak down test would be a very smart idea because for your bike you have very low compression and should definetely have more. This is probably the problem and you should definetely do the test.

[ossagp]

Let me get this straight.....it will start if you put a little bit of gas in the cylinder, you think the carb is "right", and should you do a leakdown test.

My friend, if you are getting it to start by priming it and then it dies, I am betting that it is not getting fuel. Entertain yourself with a "leakdown" test if you want, but I am thinking that like TwoOf you need to address the fuel delivery. Try taking the carburetor out and throughly cleaning it, including the removal of the needle jet and it's passage. If it is still dripping fuel out of the vents your float system still needs help. Inspecting the reeds while you are there is a good idea, but it doesnt sound like the reason yours is not staying "lit".

As for timing, this is always a good thing to check when you get something that is new to you, usually checking the alignment marks on the stator is all that is required.

Good luck, I buy a project like that every so often.