Jetting question!

[Rick Lee]

So i installed the hindle on the crf450r last night and i have a jetting issue. The pipe off the engine is getting cherry hot in about 5 minutes at idle and when i let off the throttle i'm getting a good flame out of the the can. I'm assuming too much fuel. What is the best way to adjust this without getting it on a dyno with a sniffer?

Thanks ~ Rick

[rebelpacket]

Running hot and flames out of your exhaust is usually a sign your running too lean. With a pipe, I'd go with the next size up main jet, or just buy the JD Jetting kit and be done with it. (easy fix). My KTM was burning my legs and the header was turning all sorts of pretty colors after a ride. I went from a 160 to a 170 main jet, and it went away....

Honestly, the JD jet kits are kinda pricey for a bunch of needles, jets and a few o-rings. But so far, every one I've used has worked great on every bike I've put it on.

[Manny]

Shouldnt the header turn blue? Is the color on the header a sign of an incorrect mixture?

[rebelpacket]

I could definitely be wrong, but getting "rainbow" colors on your headers is usually a sign of your pipe getting "cherry hot" as Rick put it. From what I've come to understand its a sign that your bike is running lean on one of the circuits.

[Degsy]

Shouldnt the header turn blue? Is the color on the header a sign of an incorrect mixture?

Manny, he's talking about while running.

If the pipe turns red while running, it's a sure sign of a lean condition (too much heat,mixture close to detonating etc)


derek

[Degsy]

Just my $0.02c. DONT run it until you richen it up. You're risking meltdown.

Try unscrewing the mixture screw a half turn to start with.

derek

[Manny]

I think it depends on the type of material the pipe is made of....here is a thread on TT that I started that talks about it...

Header Color/fuel mixture - ThumperTalk

[rebelpacket]

I'm sorry for any confusion Manny!

[Manny]

I'm sorry for any confusion Manny!

No confusion at all man.

[Tricky Mike]

Try unscrewing the mixture screw a half turn to start with.

Yep...
If it's lean at idle changing the main isn't gonna help it.
Remember the different "circuits"
Idle-low rpm = Mixture screw/Pilot jet
Low RPM (full-throttle) = Float level
Mid RPM (full-throttle) = Needle/clip
High RPM (full-throttle) = Main jet

I start by figuring out the main and then work down since the main affects more than just high RPM/full throttle. If the main is wrong, you'll be running in circles.

If you "blip" the throttle at idle in neutral does it hang for a minute and then drop down to idle? Does it get better when it warms up? If yes to both it may be lean. If it's lean I agree with Degs... I wouldn't run it much until you get it sorted. Detonation is a very bad thing.

[Rick Lee]

Yeah im not gonna run it till i get this sorted thats for sure. I'll richen it up with the stock needles to see if that helps. Other wise it looks like i have to get a needle kit.

Thanks yall ~ any other thoughts are welcome as well