Posts
2789
Joined
4/5/2017
Location
Monett, MO, USA
Edited Date/Time
6/17/2025 12:55pm
My 07 CR 250 won’t clean out from midrange on up unless I load it up with the rear brake. Then it sounds fine, take the load off and it sputters again.
I’ve cleaned the carb and swapped the plug and it’s still the same.
I’m guessing something to do with the electronics hooked to the carb.
Any suggestions?
Jet block gasket.
You can get from JD Jetting
Thanks!
Powervalve cables adjusted? Inspect the electric powervalve motor”s plastic gear…my buddies bike had broken teeth on plastic gear which affected overrev…
I checked the cables, they are good. It looked like it was operating properly. I have the gasket ordered, I’ll give that a shot.
Thanks!
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Free shipping: VITALMX
There was a Magic nozzle to crispen the jetting on those mikunis
Depending on altitude the trick was to run an S8 nozzle at sea level and the S7 nozzle at elevation.
Does it smoke excessively until it cleans up?
It doesn’t smoke, and it runs crisp until it’s close to wide open. Then as said above, if I load up the engine with the rear brake, it runs perfect. As soon as I take away the load it sputters again.
Also, it was fine, then it set for a few months,( no gas in it) and the next time I started it, it did this. I thought it was just a little crap in the carb, but it was good. With it sitting dry, I’m thinking the gasket mentioned above may have dried out and cracked and this might be the fix.
Still open to and appreciate all feedback, though.
Also, I know a lot of guys swapped carbs on these, but I can’t remember what they were putting on it. That may be what happens in the long run.
On my mx CR250 I have an old school Keihin air stryker. I got it from JD Jetting. I ordered their jet kit with it. On my woods CR250 I have a Lectron carb. Both work well.
Thanks, do you have to do anything special with the electrical connections? Just seal them up?
Just unplug it and tape it up real well. Secure it so it doesn’t flop around
The Keihin PWK 38 is available with TPS and Powerjet, replace the Powerjet with a grub screw, and connect the TPS wiring to the existing CR250 wiring.
Get the cylinder head squish band corrected and it will run fine with the Mikuni forever.
If it clears up under a load, that would be an indication that it’s rich, right? I would be thinking main jet is too big?
But nothing has been changed. It has always ran great. This just started recently.
Ah I missed that part. I think I’d go towards jet block gasket also in that case
If you get a wild hare up your ass you could check the clutch side main seal. Mine had pushed out and would suck oil and smoke like crazy and in left turns would suck air and run super lean, like throttle was stuck. I know, different symptoms but it never hurts to check.
I had the JD Jetting Keihin on mine too.
If the jet block gasket doesn’t fix it, I’ll check that out for sure.
Thanks!
Pit Row
How recently have you inspected your reeds?
They were one of the first things I looked at. They looked good.
As a follow up, I took out the jet block, and there is a small split in the gasket radiating from the large hole. There was also a small piece of what looked like the gasket material partially blocking the small hole.
I used a pick and removed that and put it back together ( my new gasket hasn’t arrived yet ) and it was actually a lot better. It still wasn’t 100 percent consistently clean, but better.
I’m pretty convinced the new gasket will solve the problem.
I bought the JD jet kit as well and will get the jetting dialed with it.
Had a 2011 YZ125/big bore that ran fine but later would not rev out. JD bloke gasket returned to normal. The JD gasket looks like it will last longer ??
Only use use the HRC method for 02-07 cr250. I use a 13mm socket with a couple wraps of electrical tape in the exhaust port to hold the pv flaps up & even with the top of the port. On my 04 cr125. I just changed my needle to 1 that’s a 1/2 leaner needle. If it runs flat yet I,m going with a fulll needle leaner. 93 today with 78% dew point. It runs super crisp at 60 degrees . Not now tho. Older bike check fuel screen on tank.
The stock gasket is like thin, rubbery junk and you can see how it's basically impossible to install it without distorting it. The JD one is like coated thin sheet metal or something that holds it's shape much better.
FGR01 described it spot on. I smeared some tacky BelRay grease on gasket to help hold in place for assembly. Hopefully this cures Gworm 's problem.
Well, I got the gasket and a JD jet kit yesterday. Put it in just now as well as swapped the jets, and it fixed it. Runs great, and crisper with the new jets.
Thanks for all of the replies!
Post a reply to: 07 CR 250 2stroke carb issue?