FMF Ti Slip-on

Hey, like the thread says, on a 07 450, I have the little more than normal pop on decel. Should there be high temp silicone put on the connection, put on dry or is there some kind of muffler clamp missing? Seems like silicone might be a bit of a pain in the ass when you do a repair or something cleaning it all off and re-caulking. What do you guys do?

The popping on decel is typical when a non stock exhaust system is installed. It usually means that the jetting is a little too lean. Try turning your fuel screw out 1/4 to 1/2 a turn.

As for installing the slip on, I just slip it into the header (using the proper FMF supplied insert) and head on out.

BTW, I have an 07 YZ450F with a FMF TiPowercore slip on exhaust.

If you feel feel exhaust coming out at the midpipe joint then you can put some high temp silicone on the header and then slip the midpipe on while it is still wet. Let it dry before riding it. If you haven't adjusted your jetting at all then that is likely the issue, try turning your fuel screw out and changing the pilot jet if necessary.

try turning your fuel screw out and changing the pilot jet if necessary.

I will do that, thanks

The slip on has more flow than the stock muff ,more flow = more fuel needed so I would jet the main up one size and I always use motoseal silicone between the pipe joint.

Ok, I'm having the same problem with my new exhaust. Stupid question, but is the fuel screw the one that came stock with the finger screw? Or the one that requires a small flat head and is difficult to get to?

Ok, I'm having the same problem with my new exhaust. Stupid question, but is the fuel screw the one that came stock with the finger screw? Or the one that requires a small flat head and is difficult to get to?

It's the one on the bottom up in a hole that requires the small flat head screw driver. Do yourself a favor and buy an extended one so you can turn it by hand, you should be adjusting it every time you start the bike.

fine tune with the fuel screw but the poping is a lean situation that can be cleaned up with a simple needle adjustment. Raise the needle (drop the clip) one position. This will clear up the pop more than going bigger on the main. The main has little effect when you chop the throttle closed.

Neither the needle or the main jet has anything to do with decel popping. That is an idle circuit issue.

my bad... apparently my clip adjustment was not what cleared up my decel pop??... Please explain.

With the throttle closed, no fuel flows through the main circuit, so only in the case that the main side is grossly rich, or the idle set so high that the throttle allows airflow over the main nozzle sufficient to pull fuel through it will the main or needle have any effect on it.

Jetted correctly, a YZ450 should be so nearly on the verge of decel backfire that a ten degree drop in temperature can "cure" it.

Got it. So my clip change just helped the first 1/4 throttle. It was the only change I made and the pop has been gone. Just thought it was too lean on the bottom and I never touched the fuel or pilot.

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