Cruise Control Dirt Bike

I have a 2004 Honda CRF250F with 30mm tusk  bar risers, JD Jetting kit, FMF powerbomb, FMF Q4 exhaust and a 2 inch longer throttle cable and my dirt bike wants to go 3-5mph in first gear without giving it any gas. I checked the throttle cable multiple times, fuel/air screw is good and i cant figure out why it just wants to go. 

 

Where do i go next? 

 

Thanks for any input!

I have a 2004 Honda CRF250F with 30mm tusk bar risers, JD Jetting kit, FMF powerbomb, FMF Q4 exhaust and a 2 inch longer throttle cable and my dirt bike wants to go 3-5mph in first gear without giving it any gas. I checked the throttle cable multiple times, fuel/air screw is good and i cant figure out why it just wants to go.

Where do i go next?

Thanks for any input!

You're talking about putting it in gear and letting the clutch out coasting? I'm confused, what is it you were expecting?

Is the idle high?

That sounds normal to me?

Uhhh, so what is the problem here?

Turn the idle down?

How do you know the as is good.? The set to the highest idle many claim here is horribly wrong.

When im riding a tighter trail and i come around a corner and the bike starts deciding it wants to just go all i can do is pull in the clutch and feather it. Ive never had a dirt bike that i can ride in circles without my hand on the throttle. 

You're talking about putting it in gear and letting the clutch out coasting? I'm confused, what is it you were expecting?

Is the idle high?

Yes the idle is higher. It is set with the recommendation from the JD jetting kit though. 

When im riding a tighter trail and i come around a corner and the bike starts deciding it wants to just go all i can do is pull in the clutch and feather it. Ive never had a dirt bike that i can ride in circles without my hand on the throttle. 

 

that sounds like a vacuum leak, and/or very lean jetting. the idle should be (look in your service manual) set, and forget. 

Sounds like your jetting is good. Most bike will not idle and stall in this situation. You can try turning the idle down. But really with the clutch out the bike is suppose to move. My FI yz450 does this. It runs clean enough at idle to roll along at a couple mph without stalling on flat ground.

How do you know the as is good.? The set to the highest idle many claim here is horribly wrong.

I may be wrong but its my understanding to adjust the air screw for highest idle then adjust idle screw till rpm is at desired level, low without faultering. But as all have said if your bike is in gear and the clutch is out the wheel will turn if the engine turns. I have to use clutch in places that slow me down to 2mph, seems normal. If you have your idle screw turned all the way in thats your problem. The idle screw pushes the slide open in the carb effectively opening the throttle slightly same as twisting the grip a little.

I may be wrong but its my understanding to adjust the air screw for highest idle then adjust idle screw till rpm is at desired level, low without faultering. But as all have said if your bike is in gear and the clutch is out the wheel will turn if the engine turns. I have to use clutch in places that slow me down to 2mph, seems normal. If you have your idle screw turned all the way in thats your problem. The idle screw pushes the slide open in the carb effectively opening the throttle slightly same as twisting the grip a little.

If you adjust the air, or fuel, screw for the highest idle it will be lean.

Thought about it.

Your mixture may not be lean by definition looking at air fuel ratios at a steady throttle. Here steady idle. Acceleration is best with a richer than perfect ratio. Most of us are after power over economy.

Try turning your air screw in a 1/4 turn then try roll ones from idle. Now 1/2. A turn. Big difference on a two stroke.

Most bike's will be lean enough to surge at 1/16 throttle with the highest idle air or. Fuel screw setting. I see a lot of 4 stroke bike's that can't maitain low speed steady throttle because of this.

When im riding a tighter trail and i come around a corner and the bike starts deciding it wants to just go all i can do is pull in the clutch and feather it. Ive never had a dirt bike that i can ride in circles without my hand on the throttle. 

I'm guessing you used to ride small bore two strokes?

 a 2 inch longer throttle cable. I checked the throttle cable multiple times.

Since you are using aftermarket cables you may have to adjust the cables both at the carb and at the throttle a little better in order to get it dialed in?

CRF450_880.jpg

My fcr doesnt idle high the further I go in with the screw. While that would be making it more lean, it isn't like an air leak lean. It just sputters and dies eventually. 

Edited by J_YZ2fittyF

Well my FCR doesnt idle high when i turn the screw in lol. It dies.

I gotcha. It doesn't idle up like a 2 stroke.

I'll stand by my statement many 4 t riders go to lean. The pump shot covers it up on roll on. It won't at steady throttle. I tended to set mine where it was easiest to start. That was always a little rich.

that sounds like a vacuum leak, and/or very lean jetting. the idle should be (look in your service manual) set, and forget.

Four strokes creep forward when idling… As long as they are moving before you just let the clutch out to stall. Two strokes do not have engine braking, do not creep, and are thus better. But a smoker and you'll be happy!!

Four strokes creep forward when idling… As long as they are moving before you just let the clutch out to stall. Two strokes do not have engine braking, do not creep, and are thus better. But a smoker and you'll be happy!!

This is no place to get on your damn 2T soapbox  :lol:  :lol:

Edited by J_YZ2fittyF

Thought about it.

Your mixture may not be lean by definition looking at air fuel ratios at a steady throttle. Here steady idle. Acceleration is best with a richer than perfect ratio. Most of us are after power over economy.

Try turning your air screw in a 1/4 turn then try roll ones from idle. Now 1/2. A turn. Big difference on a two stroke.

Most bike's will be lean enough to surge at 1/16 throttle with the highest idle air or. Fuel screw setting. I see a lot of 4 stroke bike's that can't maitain low speed steady throttle because of this.

Hmm makes sense to me, I am not a super carb tech, I can half ass and make sure its rich enough to not lock up but I dont think ive ever had one just perfect. I say this because I dont change jets out very much and on an extra crisp morning I get more oomph out of it. I do foul a plug every few weeks but meh whats 4 bucks.

As far as the 1/16 throttle goes, honestly no smartass dead derious, didnt know that position existed. Im not a racer, never try too keep up with anyone, dont have a clue about proper mx technique. I just open it up and eat a tire. Seems to run best wide open anyway. Probably the wrong method but Im just riding for fun and its fun to lean up open it wide open then weight the rear till it starts coming up in the front, shift and repeat. On occasion I will give it half through a sweeping curve but mostly its just open it up and hang on. I dont ride on mx tracks so most of my corners are either flat or a 30 foot tall burm from a levee around a reservoir or tall road where we dug a 20 foot wide ditch and threw the dirt on the road, or some other trail through the woods hunters use. I have never actually ridden on terrain intended to ride on other than gravel roads which I try to avoid because they are slick as snot zero traction. I live in the middle of nowhere and just go all over for miles around my house, through anything I see and just play. Dirtbikes are a toy for me. I work on a farm and we are forever digging huge reataining ponds ditches and the like for irrigation. I have fun getting in a big flat field thats been plowed and leveled smooth then left sit through a few rains. Real loose dirt with a crust on top. I will just head across hold it wide open in 5th and lean for all its got. Theres nothing to hit so the turn can go anywhere and you can really lean in and see just how hard it will cut without worrying about hitting a tree. It cuts into the crust and grabs, almost wont slide out. I guess what Im sayin I never ride with anyone else never seen another person on a dirtbike so Im probably doin it wrong but it sure is fun, and I only know 3 throttle positions none half and all.

Few pics to go with the rambling.

Dirtpans and dozer in the first and my office in the second and third.

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