[RamboEinar]

Hello, greeting from Norway
I bought a 07 CRF 250R secondhand from a friend in December and the bike was in really good condition. Engine completely rebuild 13 hours ago, top to bottom. I ran the bike earlier in winter and it preformed good, no "sputter" from the exhaust or stalling.

But now when it's a bit warmer outside the bike runs great for 2-3min, then it begins to "sputter" and stall and gets hard to start. If i let it cool down a bit it will start and run until it get hot again.

I have done following, but no luck yet:

- Cleaned and checked the carb and fuel line (Main Jet *175 and Slow Jet *42, Pilot screw = 2 1/4)
- Fresh air filter and stock exhaust
- Fresh fuel (98oct)
- Checked spark plug (Almost new)

I checked the valves and the intake looks good (0.12 and 0.15mm), but the exhaust valves i got 0.40 and 0.45mm, i think it's a bit too much as i should be 0.28mm? I don't have shims, so i bought some on ebay.
I was told the stator could have a weak spot somewhere, and when it gets warm it expands and won't deliver charge.

Anyone got some ideas?
I think the problem is in a place where something expands and change when it gets hot, like the valves or stator..

[GB555]

Maybe check the exhaust to see if it is clogged with something.
GB555

[crfsonly]

Welcome to CRF's Only. Definitely get your valve clearance set correctly. If it set with fuel in the carb for a long time without be run then check your float and float needle. If the float is stuck it may not let fuel in quickly enough to run longer than a couple of minutes.

Ken

[RamboEinar]

Maybe check the exhaust to see if it is clogged with something.
GB555

The exhaust is not clogged and should perform "as new". But thanks nonetheless
Another thing i haven't mention yet is that the header gets glowing red after 1-2min when it stands and gets warmed up, with or without choke. Talked to a friend who got a Yamaha and the same thing happens to his bike, but that bike runs great. Also googled it and seems to be "normal" for these bikes.

Welcome to CRF's Only. Definitely get your valve clearance set correctly. If it set with fuel in the carb for a long time without be run then check your float and float needle. If the float is stuck it may not let fuel in quickly enough to run longer than a couple of minutes.

Ken

Thanks!
Yep, i will get my valves clearance correct when my shims arrive
The bike stood with fuel probably 2 months before i bought it, after i got it i maybe got 1-2 hours riding and i have started it now and then, 2-3 times a week until today. Earlier in winter i ran it 30-40min nonstop with no problems. I didn't measure the float level when i opened my carb, but the float blow seemed to operate freely and the carb was very clean from the beginning.

[redrider250r]

To me it sounds like your bike is over heating and that's why it stops running. Another thing is if your header is glowing red after 1-2 minutes then your jetting is probably pretty lean. This could be why your bike is over heating fast while idling and then dieing. These bikes need to be moving for air to flow through the radiators to keep them cool.

[CRF25]

Definitely a lean condition. Like what was mentioned above, check the header temp.

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2008 CRF450X

[Aussiecrf230]

Check jetting here to see if your setup makes sense.

http://crfsonly.com/forum/viewtopic.php?t=13470

You already have pilot screw a fair way open it might be better to go up a size anyway.

If it only last 2-3 mins, then could be running out of fuel in the bowl of the carby.
Check float needle and seat as well.

[staffy24]

check that your intake boot is on right and your fuel filter is clean and try ruining it with the fuel cap of it may not be breathing ?

[RamboEinar]

Hello again!
Got my shims couple of days ago, and got the valve clearance set correct. The bike now runs great even when hot! And starts almost instantly if i kill the engine. Ran it for about 20min without any trouble
It's still a bit tricky to start when cold, but once it starts and get warmed up with the choke for 1min it runs much better on idle than before.
The header will still glow if i start and leave the bike on a stand for 1-2min as before, but that's normal for these kind of bikes. The engine don't even get hot before it glows.
My jetting and pilot-screw is set as stock for the 07 250R bike, and should be fine (Main Jet *175, slow Jet *42 and pilot screw 2 1/4 out ). (Adjusted from the manual from cyclepedia.com, highly recommended manual!)

Thanks for the help

Edit: Here are 2007 CRF250R Jetting Chart
Maybe a 178 Main Jet wouldn't hurt though.


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[crfsonly]

sounds like you are making good progress! continue to work on the jetting or get the jd jetting kit we offer. you should be able to start it easily when cold if the carb is well jetted and motor are functioning correctly.

ken

[RamboEinar]

I replaced the *175 Main Jet with a *178, and it made a huge difference! The bike runs far easier on idle, don't need choke after i get it started. It still needs at few kicks but i think it's normal.

Thinks it's ready to run now!

[crfsonly]

excellent news! good job!