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yz125 stock vs aftermarket pipe

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the yz125 i purchased last year came with a full pro circuit exhaust system and came with the stock system. i have noticed that alot of the top guys riding yz's in my area seem to be running a shorty or r304 tail pipe but are running the stock pipe over an aftermarket one. one of the guys claimed that the stock pipe goes better than his pro circuit pipe. does any one have any info regarding performance of aftermarket vs stock pipes?

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When I see guys running the stock pipe and shorty silencer I always get a good laugh. In my expierence on my YZ125's that set-up kills the over-rev/top end power. It's a 125 so that is where you should be riding. It might be a good woods set-up but not a good one for MX tracks. 

 

You will take a bike that has a short, narrow power band and make it smaller. Not good for me. 

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Pipe shootout in "Sticky". Your personal riding area may very opinion. I run a stock with FMF TCII now, but my bike is YZ250 modified. 

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On 5/11/2017 at 11:53 AM, Rocket416 said:

When I see guys running the stock pipe and shorty silencer I always get a good laugh. In my expierence on my YZ125's that set-up kills the over-rev/top end power. It's a 125 so that is where you should be riding. It might be a good woods set-up but not a good one for MX tracks. 

 

You will take a bike that has a short, narrow power band and make it smaller. Not good for me. 

Word.  I thought a stock with a Powercore killed the overrev too.  I think over rev in the woods is as important in the woods as the track.  It tight woods even more so.

 

i added a Fatty and it brought the over rev back.  

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You can put as many pipes on you want.  They won't give you much more but the mental part you think it's faster. Use to race highly modified yz's with stock pipes they work good. Until I smashed them then I'd get GYTR. But really couldn't tell a difference. would never run a shorty silencer they just fall apart and make louder. Yamaha has great stock pipes :thumbsup: that's why you see them still on bikes at track 

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2010 YZ125 here,

I experimented cutting down a spare stock silencer to the same length as a FMF/PC shorty,

as described in an eariler post by Rocket416, what little extra 'hit' it gave when it came on the pipe

was negated by falling off the pipe sooner and killing the overrev.

Despite new packing, it was also annoyingly louder.

 

One track day was convincing enough, switched back to the stock silencer.

just dissapointed I cut down a perfectly good silencer for such an experiment.

 

Yamaha engineers have years of experience in designing and building 2-stroke engines & pipes,

the late model 05-17 YZ125 pipe is very good, giving it a broad power spread for a 125.

Aftermarket pipes may move the power around and make it 'feel' faster

but IMO, having broader 'usable' power is way more beneficial to most non-pro racers.

Edited by mlatour
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What mlatour said. What the hell? This is a racing bike from the factory. Yamaha does not cork it up. 

I personally feel that for a spark arrestor (where required), Pro Circuit makes better looking and more durable options than FMF. JMO. 

Edited by shrubitup
because

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Yamahas Oem setup was designed for strong power delivery throughout. I've actually bought new oem expansion chambers off eBay over going with aftermarket, but I prefer power delivery across the spectrum over Gains in a specific area. I read that Dr. D's 2t exhaust (made only for yz's) delivers some gains over stock but unlike most other pipe companies the dyno didn't seem to indicate that the small gains came at the expense of performance in other rpm ranges .. pipe combo was noted as being ideal for riders who let her eat in the meat aka working best for those not overly reliant on torque to grunt through corners or those who prefer tapped out hauls over clicking up a gear.

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One thing that should not be overlooked is that stock bikes to mod bikes make a big difference on exhaust systems. If you are porting the cylinder you need to see what exhaust the tuner doing the work recommends. If that tuner has done his homework he should have tailored his work around a particular exhaust to get the biggest gains. 

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