Please Help Fine Tune My Cr250, Im Stumped

[SIKSPAK777]

Ok i have a 02 CR250, V-Force 3 reeds, FMF fatty with shorty silencer. Heres my problem. It runs great but under load like a hill climb it would ping. Just your normal riding it would never do it , track , ramp, ect, just under heavy load. FMF calls for a 380 main jet with needle clip at 3rd position and 1.5 turn out on fuel/mix screw. So i did that and like i said it would ping under engine load. So i got it to stop pinging with these changes, 390 main, 4th clip position(2nd from point) and 2 turns on fuel/mix screw. BUt it seems to smoke alot. Not so much ideling just wide open. I MIX IT 40:1 with Klotz super which is supposed to be a very clean burn. I dont know if its just my oil im using now or what. Should i go back to the 380 main and play with the needle clip position more? Im goin nuts. It runs great, no hesitation or anything just more than usual smoke at full throttle. O and i just put new piston and ring in it not long ago. And it doesnt foul plugs or anything.

thanks

 

[Matt90GT]

Ping is from lack of octane. Sounds like you need to run premium. If you are, then you need to run like a 50/50 mix of race gas.

You may want to check into a JD jet kit. They work really good for most all bikes. They use a special taper needle, may help out a bit. But you need more octane for starters. Those reedcase CR250s are known to ping a bit.

 

[SIKSPAK777]

ok Matt90GT, so should i go back to the FMF's jetting suggestions with the 380 main and 1.5 turns and 3rd clip postion and mix 50/50 and see where i am then?

 

[whenfoxforks-ruled]

You would do good to start with the original oil ratio. Then jet it. How old is the silencer packing?

 

[zrxrider]

What type of fuel are you using? Super 93? Maybe try Sunoco 94? That was enough to stop my modded kz1000 from pinging.

 

[whenfoxforks-ruled]

Got a ping? An easy method of ruling out detonation? Look at the plug, some real time investing work for sure, but, it could be a 4t?

 

[jsantapau]

when you are heading up the hill and it is pinging at you actually holding the throttle wide open? if the the throttle is only 1/4 to 1/2 I would try needle clip position or possibley different slide cutaway if it is1/2 to 3/4 I would try needle position or a different needle taper.

If you are going to change the fuel and or ratio then probably all jetting will get askewed

 

[SIKSPAK777]

The silencer packing is new, i just put all the these parts on the bike, exhause and v-force ect. Yeah the pinging happens at like 1/2 to 3/4 throttle. Like i said i have the clip at the 2nd position from the bottom and it seemed to stop but smokes alittle more than average. o and i run 93 no less, i could mix 50/50 if that will help!

thanks for the feedback

 

[Matt90GT]

Here is what MXA used for jetting specs on the 03 bike, might help you get into the ballgame better:

HONDA CR250


Main: 420 (400)
Pilot: 30 (40)
Needle: 6BHY38-73 (GBHY38-70)
Clip: 2nd (1st)
Air screw: 1.5


here is what they say about the 06, but applies to 02-07 motors:

Q: WHAT ABOUT THE CR250’S JETTING?


A: We always felt that the CR250 was on the verge of detonating. Going up one main made it burble. Going down one made it ping.

So you might want to try their jetting, if that does not help then maybe a JD jetting kit (dont spend the money on the OEM needle, just get the JD kit), and then run some race gas mixed in there.

http://www.jdjetting.com/xcart/product.php?productid=87&cat=6&page=1

 

[SIKSPAK777]

Wow a 420 main that is alot bigger than im running now. I will have to look into the JD kit.

 

[2strokerfun]

Good thing you listen to your engine.
I've had this problem on my old elsinore after I replaced the carb. Thought it was jetted perfectly from tests around my house, but after I got about 2 miles from my truck, on a tough one-way track (of course) got detonation bad when putting it under load, about 1/4-1/2 throttle. Needle was at the richest point, but I managed to stop and raise the float a bit and ride it back like an old four stroke, in a taller gear with a whole lot of throttle. I learned to test my carb changes on more demanding track than the very flat street that runs near my house.
I've heard a lot of people say they had no idea their bike was detonating after they destroyed their piston, but I always try to listen to how my bike sounds while I'm riding it.

 

[ZOMBIE666]

i have an 02 as well, could never get the thing jetted spot on; the 02 cr250 are known for finicky jetting. I tried the JD kit and while it did help a lot it still wasnt perfect. I ended up picking up a PWK air stryker carb and it was a good deal less of a PITA to jet

 

[whenfoxforks-ruled]

Do not mistake a rich condition for a leaky right crank seal. Then jetting is a pain and confusing!

 

[SIKSPAK777]

thanks

 

[RACER557]

maybe you could retard the timing just a little bit?