2004 Gas Gas 250 MC Cutting out.

[Nekocopter]

Hey guys, new to the forum here, been browsing around a bit and haven't really found an answer to my specific issue.

I'm new to Gas Gas's, and i'm a bit rusty when it comes to 2-strokes in general, my last 2-Stroke was an 88' Honda CR250r, which I purchased in 95'.

Just bought this Gas Gas a week or so ago, and hadn't really had any problems with it at all until my last ride.

It seems to be a carb problem, but at this point i'm still unsure.

The motor has been completely gone thru and redone, which is evident by the new gaskets throughout the motor.

My problem is, it's cutting out/sputtering on me in the mid/upper revs, my first thought was bad gas, so I drained the old fuel, mixed a new batch, and the problem remains. Checked the plug, looks great, cleaned the air filter, had the pipe off to have a peek at the exhaust side of the piston, everything looks excellent in there. Pulled the tank to check for any contaminants, everything looks great there, fuel flows freely from the petcock.

The bike still idles/revs fine when there isn't a load on the motor.

My first couple rides on the bike went great, plenty of power, no cutting out anywhere in the rev band.

And suddenly it's sputtering on me in the mid-high revs and i'm kinda stumped as to why.

Any ideas would be much appreciated.

My next idea is to pull the carb off and have a look at it, but it's been so long since i've worked on a 2-stroke, and these gas gas's are completely new to me.

But I thought i'd ask around here first to see if there's anything I may have over looked.

Thanks in advance guys, and I look forward to getting to know you guys, and these Gas Gas's.

Sincerely,

Anthony

 

[eff]

You didn't mention if you pulled the carb and jets and cleaned everything real well. If not, that is where I would start.

 

[Dude]

Check all connectors and grounds

 

[Nekocopter]

You didn't mention if you pulled the carb and jets and cleaned everything real well. If not, that is where I would start.

Haven't done that yet, but that was definitely my next idea.

Is there a write-up anywhere on the site that could guide me along?

The bike did sit for a while, so i'm guessing the carb could be a bit gummed up.

Just strange how well it ran, then all of the sudden i'm sputtering and cutting out.

Will let everyone know how that carb cleaning goes.

As far as I can see, the only aftermarket on the bike is the Doma pipe, and the LTR Powervalve cover.

The previous owner had no idea what all had been done to the bike, other than he had the motor gone thru and rebuilt at a local shop.

 

[Nekocopter]

Just had the carb off and had a look at the float/jets etc.

Everything seems to be great there.

So i'm guessing it's probably time to move on to the ignition system.

Can anyone recommend a good place to start looking for issues?

 

[gasgasman]

There have been issues with ignition coils getting contaminated with water and shorting out.
Symptoms are like you described.

 

[Dude]

same with bad grounds.

 

[Nekocopter]

Thanks for the input fellas. Gonna do a once over on all the electrical a little later on tonight and see what I can find.

Also ran a compression check earlier and its ~180psi, so i'm guessing that's a good sign.

Will keep everyone updated on what I find.

So far I love the bike, when it was running strong it was a hell of a lot stronger than my old CR250 and could probably keep up with my YZF450

Glad I found a site full of knowledgeable people, because the bit of google research I did, didn't come up with a whole lot of information.

Thanks again,

Anthony

 

[eff]

Sorry went home from work at 5:00. I recommend removing the jets and spraying them and the orifices in the carb with carb cleaner. While you are doing that write down what jets and needle you have in the bike.

Although the other guys have good advice too, starting with simple carb cleaning is always my first step.

 

[Nekocopter]

Sorry went home from work at 5:00. I recommend removing the jets and spraying them and the orifices in the carb with carb cleaner. While you are doing that write down what jets and needle you have in the bike.

Although the other guys have good advice too, starting with simple carb cleaning is always my first step.

Looks like a 180 Main, 40 Pilot with a #7 slide, stock needle in position 3.

Float height is between 15-16mm

I'm still kind of an amateur when it comes to dialing in these carbs, but it seems that it's jetted correctly, and the carb is very clean.

Bike starts up/runs/idles great, but it's still breaking up in the mid/high rpm range, and the way it does it leads me to believe it's spark related, it'll completely quit pulling, then come back, then break up again.

I just took the coil off and had a look, there's some rust protruding from the post where the power/ground connects, and it's entirely possible that water has made it's way into the coil from the looks of it.

Scrap the coil and get a new one?

Any way to test these coils to make sure that it's the culprit?

I don't have a multimeter handy at the moment.

Thanks again for the help, and bare with me.

I'm a Marine Diesel mechanic by trade, and I know them like the back of my hand, but these 2strokes are not exactly my strong point .

 

[eff]

Well if you have cleaned it all out and it is still doing it, then I guess you will need to look on the electrical side as referenced above. I can't help you with testing the coil. Good luck.

The needle has the number stamped on it and you should write that down too. You will need all that info if you plan to tweak your jetting in the future. What needle you have will will require different main and pilot jets.

 

[lonetree]

my 04 ec did exacly this....
i cleaned, re cleaned and re cleaned the carb again , nothing, no change.
change 3 plugs, nothing, took air cleaner off, nothing. on and on this went, had spark and everything,
started fine, but no mid to top end, sounded like the exhust bung was in it or somthing.....
finally, i checked the ignition lead, where they connect onto the coil, it seems to be just a push on type connector, it had come off just a little, pushed it good and hard, bike has run fine since....
have a look there first.... good luck

 

[GMP]

Its NOT a push on connection. The coil has a recessed stud terminal like a wood screw, and threads into the HV lead wire. The sealing fails over time and lets water in. You need to remove the wire and cut it back about 10mm, clean the coil/stud as best as possible. Use some Honda grip glue as an adhesive sealant on the HV wire insulation and small boot, and thread the wire back on the coil. Check the plug cap also.

 

[Nekocopter]

Thanks a ton for all the help guys, gonna work on it a bit tomorrow and see what I can do.

Will post back results tomorrow, and some pictures of the ol' girl

 

[Nekocopter]

Well, she's still cutting out.

Cut a little off the plug wire, cleaned the post on the coil, reassembled, still having the same issue .

Anywhere else I should start looking before I break down and bring it to a shop?

I'm hoping it isn't CDI related.

 

[jhendr3702]

for grins... i would lean the clip on the needle and see if it is any better..
my 01 has run beautifully for 3 years, but with the climate here this year, i had to change and it is fine now..
easy and cheap..

 

[GMP]

Put a timing light on the HV wire and see if the misfire correlates with what you see.

 

[MJC]

Have you checked the reeds ? When they are chipped or cracked it will cause the bike to sputter on the topend as you are describing alot of times.

I also had a bike that I pinched the coil wire on. I pinched it between the frame and the radiator in a fall ,and it didn't look that damaged , but it was and it caused the bike to run like crap as the rpms went up. What a nightmare that was to diagnose.

 

[Silver]

sounds like yet another cdi but no one ever listens chase your tail . Listen to them tell you its this its that . Good luck . Been there done it twice both times cdi. I hope its something simple as cdi's are not cheap.

 

[bossmans kid]

Did you clean your power valve? make sure it is not sticking, also check your reeds. Just a thought.