2005 450F Jetting

So... I tore the carb off my bike last night to clean it and re-jet, and found that it had been ported/polished. I bought it from a semi-pro racer and had not realized it was ported. So now im stuck with trying to re-jet it. It has a yoshimura TRC pro series titanium exhaust. The jets that were in it were, 165main, 45 pilot. It pops and backfires under deceleration, so i figure it needs a bigger pilot. It would seem that it should have a larger main jet due to the port and polish and the exhaust. The plug seems to be a darker chocolate so should i lean it out? Elevation is around sea level. Any help would be great, and whats the gain of unplugging the TPS?

Decel backfiring is also caused by air leaks in the exhaust. Yoshimura exhausts can be more prone to this kind of thing because of their spring and slip fit construction. Bumping the jetting up beyond the point where the engine runs right in order to stop a decel backfire that's caused by an air leak will just give you an engine that's too rich.

In any case, IMO, a YZF that never pops on decel is jetted too fat.

Ignore the porting and jet to make the bike run correctly.

I also put the stock exhaust back on it to see if there was a problem with the Yoshimura exhaust, but it does it just as bad with the stock exhaust. My bike kinda sounds like a semi-truck with the jake brake on when i decel.

Decel backfiring is also caused by air leaks in the exhaust. Yoshimura exhausts can be more prone to this kind of thing because of their spring and slip fit construction.

Some red rtv (just a teeny bit) around the slip joint edge will cure that.

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