CRF250R 2008 jetting

10 replies to this topic
  • sandman1111

Posted June 10, 2013 - 07:42 AM


I know it has been asked many times, but I rly can´t figure out whats wrong with mine.

The problem is that if I stall her, she often does not want to start (flooded). Then I can only push start or just wait for a long time and she fires. Opening throttle and kicking it 5-20 times does not work!!!! If I just kill it or start cold there is no problem at all.
I also noticed that my plug was black when the needle was in 3rd clip, so i changed it to 2nd and then it was dark brown, now I put it in 1st and I´m concerned that it is way too lean. What you guys think? It was trail ride, so not much full throttle.
Also I have noticed that i cannot get bike to idle real low! What can cause that?. (Yes I know how to set the idle and fuel screw)
Carb is clean, valves in spec, air filter clean and not over oiled. Did not find any air leaks. I have not tried new plug. Actually all stuff in engine has been rebuild 15 hours ago. And plug breather hole is not plugged.

Mods: Aftermarket fuel screw, Decompression mod, TwinAir airfilter.

I´m riding at sea level
Temp around 70
Main jet: 175
Slow jet: 45
Fuel screw: 2 1/2 Also bike is rly sensitive, when I turn it 1/4 turns out, it wants to bog and 1/4 turn in and I get hanging idle and popping.
Needle: NMTT (EURO STOCK) Clip 2
Leak jet: 50
Fuel: 98
Oil: Motorex 4t top speed 10w/40

Would be very happy If someone could help me to find a way how to get rid of flooding or some trick how to start her when she is flooded. And I´m a bit concerned that she does not want to idle low, like I would like to.

Edited by sandman1111, June 10, 2013 - 02:17 PM.

  • sandman1111

Posted June 10, 2013 - 02:16 PM



Strange thing is that if I flood her, I can only get her fired when I jump start (Gotta push very hard). Clearing does not work (holding throttle wide open and kicking). Ofc she will fire after some time, but that is not an option. What would cause that? Plug change would be easy, but those things cost 50 EUR here. Maybe that+s why I can´t get her to idle low also?

  • Fistfullofthrotl718

Posted June 11, 2013 - 05:57 PM


Same bike, same issue. Or at least used to have the same issue. It's sucks man but here is a pain in the ass way to get her going. Cut the fuel off. Lay her over to drain the bowl as low as it will go just on its side. Pick it up, gas still off, hot start and give it a good kick or two. Mine used to fire right back up with that. Instead of the half million kicks. Don't forget to turn the fuel back on after she busts off. The plug is a good indicator or your mixture. Tan is ideal. Spot on jetting with the decompression mod made me forget I had starting issues.

Edited by Fistfullofthrotl718, June 11, 2013 - 05:58 PM.

  • sandman1111

Posted June 11, 2013 - 11:19 PM


Thanks for reply

I changed the plug, and it seems a bit different. I did not get a chances to ride, but I noticed that if I start her, she now picks idle rpm up instantly, I remember there was small hesitation. Also repaired my cam chain tensioner, it was broken!!! Really happy that it did not happen while riding. I´ll go riding on Friday, will inspect my plug (trying to get medium brown) and see If she´s still hard to start when hot. BTW the Idle did not go any lower after plug change. Yesterday I also visited Honda mechanics, and they told me If my plug and jetting changes do not work, there is something wrong and should bring her for inspection.

Edit: Got video, where my bike idles!!!

Edited by sandman1111, June 12, 2013 - 09:21 AM.

  • Fistfullofthrotl718

Posted June 13, 2013 - 08:24 PM


Could be the audio but doesn't sound like an excessively high idle to me. Your jetting is a bit different then mine. I'm sea level at around 85F now with a 178 main, 42 pilot, stock needle at 2nd clip. I'm also running my intakes a smig on the tighter side(004"). Also trying to clear it out on an engine that's already flooded is already hard enough on our bikes. Hitting the throttle wide open is just putting more gas in a cylinder with to much fuel already. Check your hot start plunger has a good seal and not stuck partially open. Make sure there is a little slack in the hot start cable too. Good luck achieving what your searching for. Keep me informed if you find something

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  • sandman1111

Posted June 13, 2013 - 11:06 PM


Hot start is all good, but yes if it was a bit open It would have higher idle effect.
Well yesterday I tried everything again. Very frustrated because now the bike is in the hands of Honda mechanic :D. I will be very embarrassed if it turns out to be something as simple as jetting or for example bad hot start plunger, because I swore to him that I have checked everything :D. Anyway I hope I get her back soon, because friends are hitting track today. Will definitely post here what was wrong!!!

  • adam8781

Posted June 14, 2013 - 10:17 PM


sounds like air leak, hot start would have been my first guess.

  • essex426

Posted June 15, 2013 - 10:46 AM


Try using the original fuel screw, i used 2 different aftermarket ones, and had trouble starting.
I even replaced the piston and fitted new valves,was still hard to start.
Refitted the original fuel screw set at just under 2 turns out, and it started first kick!, and it starts first or second kick hot or cold now.
Same year as yours by the way, 08.
That is with a 42 pilot jet, and 175 main jet, in the uk.

Edited by essex426, June 15, 2013 - 10:49 AM.

  • sandman1111

Posted June 18, 2013 - 07:53 AM


So she´s back at home. Still does not idle as low as should, but lower then earilier, mechanics said that they could not get it better. Turned out cam chain was stretched (18 hours), and the accelerator pump was a bit dirty. They did some jetting changes. SJ is now 42, They changed pilot air jet (no idea about that one), Also put in 178 MJ, and needle in 3rd clip. Said it is stock jetting. So i guess I had wrong air jet in cause I could not run 42. They did not mention leak jet. I haven´t had a chance to ride, but they did and said that it performs good except on idle it is not perfect. Problem solved or not, but it is better now. Aah fuel screw is 1,75 out if im right.

Edit: First ride report. Well the fuel screw 1.75 out was kinda wrong I don´t know where I ended up somewhere near 2.5 or even more (I adjusted while riding so don´t know). Anyway everything worked nicely. Started easily. Would be cool if idle was a bit lower but its okay. It was like 17 C out there so 3rd clip and 178 worked nicely, if it was warmer I would go 2nd clip and 175.

Edited by sandman1111, June 18, 2013 - 12:20 PM.

  • adam8781

Posted June 19, 2013 - 01:34 PM


Had a thought, add some slack to the throttle cable, if your throttle tube is bottomed out, but the cable doesn't have enough slack, no matter what you do the idle will never drop because the throttle slide wont be able to sit low enough.

Pull the plastic cap off the carb where the cables go in, you will see how to add slack. Im betting you don't have enough free play to even drop the idle lower than where you seem tobe hung up. Ive seen this happen with bikes, sleds, cars, you name it.

  • sandman1111

Posted June 20, 2013 - 01:51 PM


Got slack in there. Put my 45 slow jet back. Bike still runs fine. Haven´t had any trouble with starting anymore. Can´t say if it was new spark plug or new cam chain, cause I think timing was a little bit off. I guess It is normal for my bike that it idles a bit higher. Well I gotta adjust my throttle cables a bit cause I like more slack then atm, and it is not moving as freely as it was before. Why I know it is not cables? Because it dies when I try to adjust idle screw lower :).

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