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View Full Version : 250R fatty vs stock pipe RPM differences


lynitup82
05-09-2011, 01:21 PM
Hello,
Even though im 36yrs old, ive never owned or ridden a two stroke trike. I bought an 86 atc 250r last fall. I was not familar with the different hits and powerbands of a two stroke.
It had a fmf fatty and silencer (aware of not the best)when i bought it, it comes on hard and quik and revs forever, without ever falling off. It also pulls-spins hard in sixth
I bought a like new stock pipe and muffler just to try it out. Although now it has more bottom end, it revs good and falls off very quik at the top of each gear, and i feel i have to short shift it to stay in the powerband. The FMF seemed to never fall off .

So is the stock pipe that bad for mid to upper RPMs, or are the aftermarket pipes just that much better?

Thanks
fabiodriven
05-09-2011, 01:31 PM
So is the stock pipe that bad for mid to upper RPMs, or are the aftermarket pipes just that much better?

Thanks

I'm pretty sure you've already answered your own questions.

They came from the factory with a broad range of uses in mind, from trail riding to racing and everything in between. The stock pipe was a good compromise for a bike that could do all kinds of riding and still run good. It provides good low and mid range grunt (as you said) and delivers a much more "user friendly" power band. They sell these machines to the masses and have to keep John Q. Public in mind when marketing them.
rdlsz24
05-09-2011, 01:42 PM
It's also possible you were jetted for the aftermarket pipe and when you put the stocker back on there it threw everything off. Or did you rejet when putting the stock pipe back on?

Rob
lynitup82
05-09-2011, 02:03 PM
Jetting was the same for both, on the rich side from the previous owner. I havnt really played with this ATC much. I think jetting was in the low 160s main. Ill get around to tuning this one sometime.

BTW Fabiodriven, My first trike was a 85 KLT160. Never had one problem with it in the 12 yrs i had it. I would shift everygear at WOT and hold the shifter in between gears as if i had a manual clutch. I never had a tranny problem.