Remember seeing someone say that one can modify the stock exhaust on the DS90, but can't remember who said it. If anyone has any info on this please give a shout. Don't want to spend a wad of cash if i can make the stocker more effective. Thanks in advance!

 

You have to spilt it open to modify it, get in there and you'll see the problem. Stingers extending into the belly.

 

Thanks,
Are the stingers the only problem? No wadding to have to remove?

 

You could do what I did to my daughter's Kasea Skyhawk 50. I took an FMF from my dirt bike that I sold and cut it down. I had the core welded to the stock pipe (after cutting off the stock silencer). The silencer was too big so I cut the baffle and the aluminum housing down. I reinstalled it and made a nice bracket and bushing to mount it in the stock location.

I started it up and my daughter said, "It sounds like a real bike!".

You could use just about any stock silencer or check out Ebay for a cheap aftermarket one.

Look at the pic "Mini FMF"

 

Let me try to clear this up. If you are wanting this thing to run good, then spend your money on other mods because the pipe is OK. If you want to make a rip snorting machine then the pipe has to go. The pipe is a good stock pipe. The machine will run like h3!! if you do some changes to the airbox and carb. No matter what you do, the pipe will not compete with a real race pipe, but it will run laps around a stock thing on the other machines out there.

 

And certainly don't go to big on the opening of the muffler replacement . Tons of bottom end has been lost doing that.

 

Thanks guys,
Info is extremely useful. My only problem is making sure I don't brake any of the AMA ATVA rules in regards to modifications. At this time he is running in the stock class with the DS90. Mods can be made as far as Jetting,sprockets and minor clutch mods. Exhaust is a gray area because rules only state that the original exhaust must be used ( no aftermarket )but doesn't say anything about modifying it![img]i/expressions/face-icon-small-wink.gif[/img] Guys, your opinion please, bike runs Mikuni Vm16mm carb. We re-jetted from stock to a 102 main and complimenting pilot, drilled needle seat two steps ( had too, kept draining the da*% float bowl after two laps ) and dropped to a 4-28 rear sprocket. Also did some changes to airbox, ( why Bombardier put the silly thing under the seat right on top of the expansion chambers still baffles me!! ), by mounting it like the Polaris scrambler.These Mods have given us 20 bike lenghts in 90 ft. over a bone stock DS90. My Q's now are, if i shave every other blade on fan, remove 2 maybe even 3 variator weights and install stiffer torq spring will I gain or lose performance!?