shortened muffler. rejet?

[system32]

i have all stock, 2 month ago i shortened stock muffler http://gstwins.com/gsboard/index.php?topic=65659
now it is only strait can. when i'm going at high revs and releasing throttle muffler have popping noise.
does i need to rejet carbs? which size i should buy? and where i can buy them?
need help, thanks

[JAS6377]

It's possible you may need a slight rejet to compensate for the added air flow. It certainly wouldn't hurt. These bikes run lean from the factory anyway. I would start with a conservative rejet. Maybe one size up on each jet.

I'm sure Buddha will chime in soon with all sorts of carb knowledge.

[The Buddha]

If it was rejetted before it was cut you dont need a rejet, cos you would have got to be rich, and now you're less rich.
However if it was stock, it would be lean to start with, and you're now more lean.
Cool.
Buddha.

[system32]

short muffler  =  less resistance and less vacuum created by burn gas leaving cylinder. is it right?
so less resistance = more air and less gas goes to cylinder. is it?
i do make rejet before. i dont know if its pre-owner made it before

[comradeiggy]

When you aggressively release the throttle from high-rpm riding to low-rpms you will temporarily get a high vaccuum, leading to a richer mixture than needed and incomplete combustion in the engine and also you can temporarily have air also being sucked in from the exhaust. So you have lots of hot air and unburned fuel in the exhaust, which then combusts and leads to popping. It's not a big deal though, it can happen to any 4 stroke. Even my POS Ford Contour has done it a time or two.

[JAS6377]

And there's Buddha, right on cue lol. Yes, shorter muffler = less resistance = more air flow, which means the motor needs more fuel to compensate. You said you rejetted before. What are your current jet sizes? You may just need to adjust the mixture screws.

[system32]

i don't now jet's size. tomorrow i will disassemble my carbs to view.
how many jets gs carbs have, 2 or 3?

[JAS6377]

If it's 01+ (I believe) it should have 3 circuit carbs. The older ones only have 2.

[The Buddha]

He he, shorter muffler automaticallys doesn't mean better flow ... If you cut the 1/2 that is closest to the header out and put the 1/2 with the end cap in its place, you would have nearly choked off much of the flow.

You cut the 1/2 with the end cap. You removed all the baffles ... I'd suggest you run a perforated sleeve from the end cap and pack around it ... but that's just me ...

3 jet carbs - you have 17.5, 60 and 130. You need 20 and 132.5 1 washer and 3 turns if all you did was muffler mod. You swap filter for K&N lunch box you need 147/5 mains.

Cool.
Buddha.