ok, i took out several baffels in the muffler of my 500i. i aslo had a snorkel made. now when i let off the gas it will backfire some. sometimes its loud sometimes it not as bad. mostly when i am going faster and let off the gas to decelerate. i have turned out the air screw adj but it has not helped very much. i have read where this is a lean condition, and some say its a rich condition. do i need to go up one size on the pilot jet. now when i removed some of the baffels the packing came out as well. there was this big tube the had all the baffels inside. i put this tube back in to keep the noise down. i have not checked my plug yet. any help would be great

 

Max- removing the baffel is less back pressure will result in a lean condition that should be corrected be backing off on the air mixture screw. Combined with more air from the snorkle will require rejetting or a restrictor on the snorkle. I cut out 2 baffles in my pipe but I welded the inner pipe back in so no air could go past it. I did not have to adjust the carb.

 

max,
on motorcycles, the airscrew, or primary mix screw can be adjusted quite a bit, I have adjusted them out to 4 turns or more on a mikuni carb, the backfire is a lean condition in the pilot circut, if you can't get anough adjustment out of the mix screws, yes, going up 1 size on the pilots will help.

 

on the snorkel it was the exhaust not the air intake. should have explained futher on that. took the plug out and it looked a little black around the threads. the center part was between grey and light brown. i took it out and put the choke on full and i could not get it to backfire at all. as soon as i took the choke off it would start right back to backfiring. i could not get it do do anthing different by turning out the air screw so what do i need to do. now it will pop and backfire in all the gears as soon as i let of the throttle.

 

Did you notice any power increase by messing with the muffler? I was thinking about doing something with mine but don't know what. I don't like em too loud.

 

yes it made a big difference in power,and it does not die out when you go in deep water anymore. i am taking it in the morning to get the jetting checked out.

 

I'm already running an exhaust snorkel on the stock pipe. I just had them weld it to the factory outlet.

Is it really worth it power wise to go back and have the baffels cut out?

I kind of like the stealth approach. Everyone I ride with said they can't even hear it running.

But, I do need some more grunt.

Just added the 28X10.50X12 Laws on the front.

 

it did make a big difference in power of the stock pipe. everyone that has tried it said it works. i am just trying to get it jetted right. the plug does not look bad though it just backfires when you let off the gas. i ran it with the choke on and it would quite backfireing as soon as i took the choke off it would start back backfiring. it has a 148 main and a 90 starter jet. i think i am going to try a 152.5 main and a 95 starter jet. maybe lower the clip a notch as well. this should make it a little richer in all the throtle ranges. hope this will work

 

How do you takeout baffels on the stock muffler?Is it difficult?My 250 has a new primary jetting from the dealer because off cold weather sputtering.Would this take care of any lean condition that would occur from removing the baffels?

 

I have no idea why i am responding to this old topic but for future reference,if your bike runs better with the choke on then you were getting to much air. When your choke is on it cutts off the air to your carb!

also if you are ever out on the trail and flip your bike and you break your choke switch, just take off your seat a cover the air intake snorkel with your hand and hit the starter if you need to choke it. Its the same thing!

I would have went with a bigger size in the main and such!
bigger size means less air! "I think"

But you have to do a test at each rev range! to see what each jet is doing,
clean your plug, run it a 1/4 throttle for about 5-10 mins. check the plug, then adjust the pilot
clean plug run it 5-10 min at half or little ablove half and check your plug. adjust the needle
cean your plug run it at full and adjust your main

I believe that is the rule of thumb