Jump to content
Sign in to follow this  

Lean Slow Air Jet??

Recommended Posts

Max rpm 3rd gear.. On decel, (closed throttle) backfires, with blue flames

KOZO PZ28 (PWK clone) MJ:110 PJ:42 2.5 turns out

(Engines Only - TM24/manifold in photo)

Was thinking to try a #35...

PRC built - XR150 stroker

14.3 HP - Dynojet 250i

The bike is set up to run on an indoor gokart track.. www.allsportsgp.com

using only 2nd/3rd gear..

JYPipe.jpg

Pic from AllsportsGP...

(see below link)

http://nobalance.com/gallery/v/motorcycles/allsport_030710/DSC_0549.JPG.html

Share this post


Link to post
Share on other sites
you mean pilot jet? what is the currect air screw setting?

Yes.. as mentioned above: PJ #42.... 2.5 turns out

KOZO PZ28 (PWK clone) MJ:110 PJ:42 2.5 turns out

Share this post


Link to post
Share on other sites

That does not make sense , if you have a #42 and you feel its lean then why would you want to go to a #35 ? , that would be even leaner !

also check your header gasket and the connection where the header attaches to the muffler , if there is any leak it will backfire as well , so make sure that neither are loose !

Share this post


Link to post
Share on other sites
That does not make sense , if you have a #42 and you feel its lean then why would you want to go to a #35 ? , that would be even leaner !

also check your header gasket and the connection where the header attaches to the muffler , if there is any leak it will backfire as well , so make sure that neither are loose !

I just installed this NEW carb.. so still trying to dial-it-in.

That's what I thought..smaller is leaner, till I read this thread from William1

http://www.thumpertalk.com/forum/showthread.php?t=595711

post #5 "Slow Air Jet.. Richen with smaller jet" looks to be from SUDCO.

Edited by millwoodva

Share this post


Link to post
Share on other sites
its gonna pop on decel no matter what.thats just life with a pipe that short.

It did not pop with the TM24...

I just installed the PZ28 carb.. pulls much harder now, so it likes the larger bore carb.

Share this post


Link to post
Share on other sites

Slow air jet works in conjunction with the pilot jet. The idea being is you size the slow air jet to put the pilot jet in a mid range point.

As Eddie says, a pipe that open and short is going to backfire more. The shorter and more open, the more pronounced it will be.

If you richen the pilot circuit a bunch or reduce the straight diameter of the needle to reduce it, your low speed jetting will be too rich. On top of that, hot starts will be tough.

Set your pilot circuit up right, realize the popping is a matter of fact and ignore it.

Share this post


Link to post
Share on other sites
It did not pop with the TM24...

I just installed the PZ28 carb.. pulls much harder now, so it likes the larger bore carb.

With a smaller carb, the increase in vacuum on decel does reduce popping some at top end expense.

Share this post


Link to post
Share on other sites
Slow air jet works in conjunction with the pilot jet. The idea being is you size the slow air jet to put the pilot jet in a mid range point.

As Eddie says, a pipe that open and short is going to backfire more. The shorter and more open, the more pronounced it will be.

If you richen the pilot circuit a bunch or reduce the straight diameter of the needle to reduce it, your low speed jetting will be too rich. On top of that, hot starts will be tough.

Set your pilot circuit up right, realize the popping is a matter of fact and ignore it.

The intake port is "blacken" from.. I'm assuming, the backfiring as well...

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×