Back Fire Problem w/ New Muffler - Need Assistance!

[twenty34]

I took out the Spark Arestor of my new GTR muffler and now the bike sounds real good, but man it sure has a loud backfire sound now when you blip the throttle closed. Is this because I took out the Arrestor? It also has a dead spot now off idle if you blip open the throttle quickly.

For the fuel screw, I have an easy access aftermarket installed, but someone suggested it's now too lean.

Do I go counter-clockwise (closing) or clockwise (opening) to richen it? How many turns/adjustments do I make and do I just keep adjusting until the backfire goes away or is that due to the lack of a Spark Arrestor.

[byggd]

Removing the spark arrestor in itself will not cause a back fire but removing it may have caused the bike to run lean. Start turning the air/fuel screw in until the RPMs start to drop, then back it out until it smooths out again. If you back it out past where you achieve max RPM you have gone too far and if you can turn it all the way in without a change in the RPM you need a richer PJ or you have an air leak.

[dbailey223]

Richer PJ is a larger numbered PJ?

[byggd]

Richer PJ is a larger numbered PJ?

Exactly ?

[dbailey223]

Glad I asked. My bike runs great after doing the JD kit and re-jetting per Indy's chart. But, I noticed that no matter I did with the fuel screw, it had no real effect. So, I thought that I read that I was to go leaner on the PJ and MJ.

I just re-jetted because I was also replacing the rear shock spring, so it was easy to get to the card. Time to go home and re-jet again!

Should I go richer on the MJ and PJ, or just the PJ, so the fuel screw will have some effect?

[twenty34]

I'm in the same boat. The only effect turning the fuel screw had was when I turning it all the way in and then the idle started to come down. I backed it off just a bit after this and it seems a lot better. I had it out 2 full turns so this was quite a bit to turn it in with no effect.

Glad I asked. My bike runs great after doing the JD kit and re-jetting per Indy's chart. But, I noticed that no matter I did with the fuel screw, it had no real effect. So, I thought that I read that I was to go leaner on the PJ and MJ.

I just re-jetted because I was also replacing the rear shock spring, so it was easy to get to the card. Time to go home and re-jet again!

Should I go richer on the MJ and PJ, or just the PJ, so the fuel screw will have some effect?

[kkameny]

It is probably backfireing because of the A.I.S. Either remove it or just plug the hose from the air box. Same system as my R1.