2006 CRF250x Carburetor Jetting Questions - pictures!
Posted March 17, 2010 - 04:42 PM
I've been reading up, and getting the facts about what jets to use. However i'm having trouble identifying What's What!
Posted March 17, 2010 - 05:30 PM
The other jet (i don't know what it call) you will likely never touch it. The leak jet is in the fuel bowl.
I dont know what mods have been done to it but im running a 165 main and and my buddys bike is running a 168 main. Both bike are on the lean side at sea level. Both bike have all the ccc mods, 05 r cams, and the exhaust has been changed.
That main jet may not be as lean as you think.
Posted March 17, 2010 - 05:42 PM
My bike has the 'r' cams as well as an aftermarket exhaust and K&N air filter.
The needle is definitely stock, as for the other jets, i'm not sure what size they are. Will post those when i get home.
Could my bike be running lean? I know it is possible to get the "pop" if the jetting is too lean or too rich.
When i pulled the spark plug, it was black and dirty which is why i think it's running rich.
Am i right? What would you suggest for jetting at sea level?
I looked into a dynojet kit and the largest main jet they provided in the kit was a 132, and 48 pilot jet. Are you sure 160-170 is normal for the main?
Posted March 17, 2010 - 07:30 PM
Figured i should jet it down a little too and went to a 165 main
The bike would start to sputter at 3/4 and above throttle. Switch main to a 162 and it got worse. Went back to a 168 and its back to pulling hard.
I would think the 140 size jets would be fine for stock exhaust, cam and/or air box not cut. I think i was running a 145 main back with the air box cut, stock cam, r head pipe, and stock pipe.
Look up what dyno jet is running for r bikes.
Easy way to find out is get a 165 main and a 155. See witch one it like the best. Should be obvious.
Both bikes also run a 45 pilot. Main reason is so my t handle mixture screw doesn't want to vibrate out at only 1/2 a turn.
Posted March 17, 2010 - 07:36 PM
Some of the main sizing you'll find posted here is from the JD jet kit, which also uses thier (generic) red or blue needle which has a fat tip, so uses a bigger jet. Same with the R needle spec'd in the CCC mod calibration. If your jetting with the stock X needle you might find you'll be a little smaller on the main.
Suggest jetting in steps of 5.
Posted March 17, 2010 - 07:52 PM
the jets provided with the 2006 'r' kit range from 150 to 170.
I know the dynojet needles are tapered differently than the stock needle, which could be why the jets are smaller. but i'm not sure, my bike is modded enough from stock that i'll probably have to play around with the jetting a little bit to find out what works.
Does a dark spark plug mean you're running too rich, or too lean?
Posted March 17, 2010 - 07:59 PM
Posted March 17, 2010 - 08:01 PM
does it run rich on the main? popping on closed throttle decel has nothing to do with the main jet.
Posted March 17, 2010 - 08:56 PM
Your dark plug may only be telling you your bike is idleing rich if the bike is idleing when your shut it off.
dark sooty plug is too rich, bright white is too lean.
Pulling the plug is a pain. use your seat of the pants dyno.
Posted March 21, 2010 - 08:06 AM
162 main jet.
68 (other jet) slow jet?
fuel mixture screw is 1 1/2 - 2 turns out.
k&n air filter
opened air box
From what i've been reading, this seems to be an okay setup.
I think the problem is with the pilot circut.
Those of you who have more experience with this... Please comment.
My carb seems to be a little dirty, which might be a contributer to why i'm experiencing some of the obnoxious popping when i roll off the throttle. I'm going to clean it up today, but before i put it back together, i'd like some comments on the jetting.
Dynojet kits are usually a good call.. however the 'x' kit has 118-132 main jets and a 48 pilot jet, which seems really small to me. 'r' kits have 150-170 main jets, no change in pilot jet.
If i were to rejet it would be to get a better needle, and use the dynojet recommendations as a starting point to tweak the jets. Should i consider getting the 'r' kit instead of the 'x' kit?
Pulling the spark plug was actually alot easier on this bike than on my WR450, or DRZ400. all you have to do is take off the seat... and it's right there! Dont have to work around the frame at all.
Edited by drob720, March 21, 2010 - 08:39 AM.
Posted March 21, 2010 - 07:21 PM
Posted March 21, 2010 - 08:51 PM
Will that help with the decel pop at all?
sounds to me like that will make my bike much more punchy when i hit the throttle.
Dont get me wrong..
I'm Definitely gonna switch that out so the bike rips harder when i want it to.
But, Any suggestions for the decel pop?
I was reading some of Eddie's recommendations about tweaking the fuel mixture screw until the pop decreases to a normal amount and - a few on the pilot if the mixture screw is less than 1 turn out, or + if it's greater than 2.5 turns out.
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