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Need some help guys...

Two weeks ago my buddy and I head out riding. A minute into the ride his 04 250X backfires and shuts down. The battery drains attempting to restart and we both kicked our guts out trying to get it to run again. It will try running just slightly, or idle very low but not accept the slightest amount of throttle and would soon die again. Finally I get it running and keep it running by staying on the throttle slightly. I ripped on his bike for about 3 miles never going less than 1/4 throttle. When I came to a stop, it idled roughly for a few seconds then shut off again. We give up on the ride, get it running again and back to our starting point.

I pulled the carb and removed the bowl. (BTW is removing the rear shock the best way to do this? Looked like the easiest way to me.) There where 3 small flakes of something in bowl. I completely cleanedi it, cleared all passages, dissassembled the accelerator pump and made sure it and all its passages were clear, pulled the pilot, main, and bleed screws and made sure they were all clear. The carb was impecable inside except for these 3 flakes. I put it all back together and it ran flawlessly.

A few days later we ran a 45 mile loop of extemely varied terrain. Rough rocky stuff, smooth fire roads, tight mountain biking trails... a little bit of everything and the bike ran flawlessly.

Today, he and another buddy of mine were headed for a ride and it pulled the exact same stunt as our previous ride. He brought it back to my shop and dropped it off. Tonight I pulled the hose from the carb and drained every drop of gas from the tank through a fine strainer cloth into a can and didn't get the slightest spec of dirt.

Guess I'll pull the carb again and hope to find dirt in bowl again, otherwise I'm going to be very puzzled. The petcock stems are screened are they not? Any chance of them jumping out of location?

My questions: Has anybody had a similar experience or know what might be going on? And what's the easiest way you guys have found to get to bowl enough to be able to remove it? Last time I lifed the subframe and pulled the rear shock since I just couldn't seem to get enough rotation to do this from the side.

Have you checked the valve clearence?

Yep, just did that in Feb while adding the dual sport kit... less than 100 miles ago.

On that note, the previous owner had an R cam installed in it. If the R cam has one, could the automatic decompressor be fouling up?

The fact that it runs fine above 1/4 throttle, tells me that the pilot jet is the issue. Try an inline fuel filter.

Change the float bowl screws to Stainless steel Allen head Screws.

These are the sizes:

Idle-adjust bracket - replace stock screw with M4x10 and M4 lock washer.
Float bowl - replace four stock M4x14 screws with M4x16 screws (no one seems to stock the M4x14 in stainless) plus M4 lock washers. If you don't use lock washers, one of the M4x16s will not fit; use an M4x12 instead.


I use a tool that is the most awesome tool for doing work on these bikes.

Husky Pro #66604 Available in a set from Home Depot.

http://www.homedepot.com/prel80/HDUS/EN ... 76&pos=n01

It's a racheting double box end wrench. 1/4 on one end, 5/16 on the other. In the 1/4 end I use a flat screwdriver bit about 1 1/2" long for pilots and leak jets. Then get a 3mm allen head bit for the new float bowl screws.

On the 5/16" end, I use a 1/4" socket drive with a 6 mm six point socket for mains. The wrench is so flat with just the perfect angles for doing carb work.

Get one, you'll thank me.

You have some tainted fuel. Completely drain it and fill it with a little clean gas and swish it around and drain again. The in-line fuel filter is a good idea too. Your jets are clogging up. Let us know how it turns out.

OK guys, I spent some time with this bike yesterday without resolution...

I pulled and completely drain the fresh tank of Sunoco 94 though a fine white cloth - not a spec of dirt.

I pulled the petcock out of the tank and verified that the strainer is in place. It is in perfect condition and did not have a spec of dirt on it.

I pulled the fuel bowl and all jets - not a spec of dirt anywhere.

I pulled the valve cover and re-checked valve clearances. Intakes are .005 and .006. Exhaust are .010 and .011. The auto decompressor spring is in perfect shape and the auto decompressor moves freely.

Put the bike all back together. It started on the first kick with choke on. Warmed for 20 seconds before shutting the choke off. Wicked the throttle a few times and it took it perfectly. Then it sat and idled perfectly for almost 2 minutes before just shutting off. No low idle or anything abnormal - just bam shuts off.

Trying to restart it was a bear, but I could get it running. If I let it idle it was very rough and would only do so for a few seconds before shutting off again. If I kept it up in the rpm's and took it out to attempt riding it, it would boc with just about any amount of throttle given, but when it would take throttle I could tell the bike lacked its usual power.

After letting the bike cool for several hours. It starts perfectly and runs 100% for just a few minutes - both at idle and ripping on it, then goes into it's fit of rage once again.

It really seems heat related in that it has to start coming up in temperature before the problem presents itself again.

How we got our 40 mile ride in the other night without an ouce of trouble is beyond me... but it is consistent in its behavior at this point.

Anyone have any ideas?

I'm thinking of removing the auto decopressor for additional testing although it moves so freely that I'm not sure how it could be a problem.

My only other thought is that I have a valve binding in a valve guide and it takes just a bit of heat to make it stick. Am I off base with this thought, or has anyone else had a similar problem?

One thing that will cause what you are seeing is lack of proper venting on the fuel tank. If you have changed the vent line to a dandy little cap, then remove the cap and try it. Its best to put the old vent line back on if your tank is very full to prevent sloshing gas all over you.
Joe

Thanks Joe, I'm still using the stock vent hose.

The first time this problem presented itself I pulled the gas hose at the carb and ran about a pint out in 15 seconds - flowing very freely.

Yesterday I pulled the hose from the carb and drained the entire tank in about 3 minutes with the cap tight and vent hose in its normal position so I'm pretty sure it is flowing free, but good thought and I will double check it.

Certainly sounds like it is venting well! I suppose everything is OK with the float? Weird!
Joe

Get the bike warmed up and start ringing out the electrical system. Do you have manual? Check all electrical components against spec. Especially the ECM.

Sometimes electrical issues only show up when temps increase. Just thinking out loud....

124, I've been wondering the same thing. I have a service manual for my 450X, but only the owners manual for the 250X. I wonder if the coil, cdi, and ecm might test the same.

I might get some time to work on it later tonight... Wish me luck!

Following on down the electrical path - have you checked for spark when it has died ?

I had an old XR 250 which did similar things - great when cold - warmed up and then died - turned out to be the stator - took a while to find ...

I think it might be fixed!

The first thing I decided to try last night was a new $22 spark plug. Popped it in there and it fired first kick as normal. 30 seconds with choke, then a minute of warm up without. 2 minutes, 3 minutes. Hey, it's not doing it. So I jumped on it and ripped on it for about 20 minutes and it performed flawlessly.

This problem started out somewhat intermittent so I'm hesitant to say with certainty that this is resolved, but it looks good so far. Yea!

I'll keep you all updated.

Thta's great news! What did the old plug look like when you pulled it?
Joe