86 250r dies after running 2-3 minutes!!! HELP!

[Taiser]

Posted this in another forum but this one has more traffic and hopefully more ideas!

Here's my original post and the follow up from the other forum...

Post #1

OK. Finally got my rebuild of an 86 250r going. All the parts are from e-bay...I mean every nut, bolt, plastic and part was bought there because these machines are IMPOSSIBLE to find up here. The engine is new (less than 10 hours), carb is BRAND NEW and so is the intake boot. Had a few problems at first (resolved) now a new one has cropped up...

The carb is a BRAND NEW 39mm Keihin striker carb. The bike fired up on the first few kicks and I was able to ride it for about 10-15 minutes with no problems. The idle finally works good (1400 rpm) but I have to screw in the idle screw almost all the way in for it to run smooth but I'm assuming all I need is a bigger jet, which I will look into later on. I'm at 800 feet ASL so I'd assume the stock jet would have been fine. She's also a bit harder to start than I like...takes 6-7 kicks, jet problem again (too small) I'm guessing?

Any hoo the last few times I've started it up to adust the idle it runs fine for about 3-4 minutes then just DIES like it's out of gas. Hitting the throttle does nothing just before it dies but when I first start it and hit the gas it reves fine. It's like somebody turned off the fuel and once the gas in the carb is gone it just quits!!! Remember the carb is BRAND NEW. I checked the spark after it dies and it's fires fine.

Trying to start it after it dies is useless but wait an hour and it's ok. Fuel is new too. I'm figuring this has to be fuel related but why would it run ok the first day I got it going (except for the idle)? I'm going to pop the fuel line off and check the fuel flow later today but it does the same thing if it's on main or reserve. Anything in the carb that might cause this? Thinking a stuck float needle but again IT'S BRAND #$%^&* NEW!!!! I really don't want to tear a new carb apart unless I have to!!

Any comments or ideas on what else might have been missed?



Thanks guys.


#2

OK I'm ready to SNAP!!!!

Came home from work and took another boo at it...again if fired up then just stopped running after about 3 minutes...while it's running everything is fine, throttle response etc all fine. I checked the gas cap and vent tube...no problem, checked the fuel flow on both main and reserve that's fine, checked all the vent lines to the carb (2 of them, one on each side) and air goes through no problem. Can't check the overflow because it's on the muffler side, but when I calm down a bit, I will, but again THIS IS A NEW CARB!!! WTF??? The whole reason I got a new carb was to avoid these #$%^&* problems! I KNOW it's running out of gas just by the sound of it when it dies. I'm thinking of popping off the carb and checking to see if the overflow works then even opening it up, but there should be no reason... especially when it ran fine when I first put it on!!!

Any ideas??? Getting desperate and pissed here!!!

[factoryX]

I had the same problem, ran fine but as soon as got warmed up it died, it was the spark plug for me, try buying a new spark plug brushing it does not always work.

You may have just burnt the plug thats all...

[factoryX]

also it was fine on idle but if I gave it gas it did the same thing.

[Taiser]

Plug is new, spark is good and strong It's not getting time to warm up, 2-3 minutes and dies, that's from a cold start

[factoryX]

what color is it?... running an airfilter? try running it with out? could be just to much air getting in there. idk at this point.

[factoryX]

http://3wheelerworldforums.com/showt...r+fuel+problem This as close as I could find....

[smvorndran]

Sometimes the exciter/pickup coil on the stator plate will go bad. It's essentially a crank position sensor that tells it when to fire. They sometimes crack, and will only work while they're cool. You may still have spark, but it may give an incorrect reading, and it could be firing out of time. Just a thought. I had a Hodaka dirt bike that did that.

smvorndran

[Erics350x]

Pull the fuel line and let the gas run in a can for a few seconds to see if the petcock or tank cap is clogged. If not pull the carb and check out the float and needle.

[Macs]

Have you tried flipping on the choke when it tries to die? It sounds like your float level might be too low or a problem with the needle valve. Right when it dies open up the float overflow and see what you get out of it. If everything is right there then i would look for a clog downstream. If you find nothing there then it will be on to plan B.


New parts can still have problems. Especially a carb that might have been sitting on a shelf for the last 20 years.

[Taiser]

Electronincs are new, stator is original but the motor has less than 10 hours on it, never been opened. I just ordered a complete new harness (wires, coils, rectifier etc) just in case though.

Already pulled the fuel llines and checked the flow to the carb, all was fine. Air filter is new and clean (why would it run fine for a few minutes then die due to the air filter???), choke does nothing when I pull it. I'm 99.9% sure the float bowl is running dry, but why did it work fine at first? I'm gonna pull the carb tonight and take a peak inside because that's gotta be it. I may try leaving the carb all attached and just poping it off the intake and hopefully the overflow has a screw, I'll check and see if the gas starts gurgling. Maybe a piece of crud got in there, but I don't see how, I took out the petcock when I got the tank and cleaned everything...this is just weird. I'll let you guys know, and maybe post pictures. Anybody got the specs on a Kiehin 39mm striker carb?

[Macs]

That is what i am betting. Maybe a piece of shipping material got caught up in it.

[johnny's X]

I had the same problem with my X. I tried everything. After alot of frustrating hours I looked at the fuel line and it was a bit to long and it was holding in a pocket of air. The air was holding back the fuel from entering the carb. I cut the hose shorter and the problem was solved. Try it out and see if it works

[Blown 331]

I had the same problem with my X. I tried everything. After alot of frustrating hours I looked at the fuel line and it was a bit to long and it was holding in a pocket of air. The air was holding back the fuel from entering the carb. I cut the hose shorter and the problem was solved. Try it out and see if it works

Damn, I never thought of that, I think I might have that problem on my first ATC70.

[Taiser]

Damn, I never thought of that, I think I might have that problem on my first ATC70.

Thought of that already, the original line went down a bit in front of the carb (kinda like a smooth drain trap), nothing excessive cut it shorter anyways, now it's straight to the carb...no joy!

Gotta be the carb bowl running dry!!!! I remember my old honda 200 would go quite a ways with the gas cap vent turned off, and I remember it would go a bit as well with the petcock left accidently off, any idea how long a 250r will run with just the fuel in the carb bowl?? It's dying on me in about 2-3 minutes just idling with a few revs added in...sound about right? When it dies it's not a clean kill like turning off the ignition, it sounds just like it runs out of gas!!! #$%^&*

[DeePa]

you fuel bowl isnt filling back up. it sits for a while, fills up, runs, dies, and then takes a while to fill back up.

pull the carb apart, try a different carb, all that jazz

if fuel does in fact run out nice from the petcock, it has to be your float needle