05 yz450f popping spitting flames !

[slothman]

hey guys...need your thoughts...I put a Lexx pipe on my bike, and it also has a Bills header pipe (full exhaust now). It starts and idles fine, but she is popping on a little on decel, and I have seen flames come out of the exhaust ! The flames did not start until I added the pipe. This is with a 52 pilot (stock was 45). The main is 165 stock, I am bumping it to a 170. I have not checked the pilot screw, so I may start out at 1.5 turns out. Any suggestions ?

[grayracer513]

What the hell are you doing with pilot jet that fat, for crying out loud?  Riding in the snow at sea level?

 

The popping is probably due to an air leak at one end or other of the header.  IMO, you should drop back to at least a 48.  I'm amazed it will start at all in the heat of summer with a 52 in it.

 

https://www.thumpertalk.com/topic/340570-popping-on-stock-06-yz450f-exhaust/#entry2983539

 

https://www.thumpertalk.com/topic/271735-how-to-confirm-your-pilot-circuit-setting/

[slothman]

I ride 0 up to 5000ft, usually between 40-70 degrees. So you think I should run 48 pilot /170 main with full exhaust and uni filter ? Do you think it's running so rich the extra fuel is causing the popping/exhaust flame ?

[grayracer513]

I ride 0 up to 5000ft, usually between 40-70 degrees. So you think I should run 48 pilot /170 main with full exhaust and uni filter ?

 

More like a 45/165.  48/170 should be too fat at 3500+.  Could be popping because of richness, but if it started with the pipe, or even if it didn't, you have to chase down the air leaks first.  Otherwise, it's like shoving a dead cat under the rug to get rid of the problem.

[slothman]

More like a 45/165.  48/170 should be too fat at 3500+.  Could be popping because of richness, but if it started with the pipe, or even if it didn't, you have to chase down the air leaks first.  Otherwise, it's like shoving a dead cat under the rug to get rid of the problem.

stock jets are 45/165, why not bump up to 48/170 with full exhaust ? I hear they came lean from the factory.

[grayracer513]

The bike came with a full exhaust, and not a bad one at that.  If you were to hang an old White Bros R4 on it, it could well make the bike richer, not leaner. 

[slothman]

I'll check the plug and see what she looks like...

[grayracer513]

The plug won't tell you anything.  Reading plugs only works for checking main jets, only when the engine is chopped and shut off right at the end of a full throttle run, and only when using leaded gas.

 

https://www.thumpertalk.com/topic/272073-burner-how-do-you-confirm-the-mainneedleneedle-clip-for-a-fcr-carb/#entry2289879

 

https://www.thumpertalk.com/topic/604124-yz400426450-user-jetting-database/

[slothman]

The plug won't tell you anything.  Reading plugs only works for checking main jets, only when the engine is chopped and shut off right at the end of a full throttle run, and only when using leaded gas.

 

https://www.thumpertalk.com/topic/272073-burner-how-do-you-confirm-the-mainneedleneedle-clip-for-a-fcr-carb/#entry2289879

 

https://www.thumpertalk.com/topic/604124-yz400426450-user-jetting-database/

yes I know that....thanks .

 

I'm going to bump down to a 48, adjust the pilot screw, and also check for air leaks.