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Yoshimura RS4 insert

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Hi have a 2010 CRF250R

I wanted a little more bottom so I order a RS4 competition system. I plan to remove the spark arrestor insert and we don't have sound limitation here. I want the more power possible but Yoshimura said I gonna loose power without any insert and in their website they seen to only have the 94db insert for my bike. I can't believe this option is the best one.

Someone can help me ?

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They doesn't make the RS4D for my bike. And I compare dyno sheet. The difference is really small. Also they only sell the RS4D in the professional version. So I bought the SS/AL system for 500$. I didn't plan to go with a 900$ Titanium setup.

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I have the Yosh SS system on my 2010 CRF250.

I had it re-mapped for the new exhaust, by Eddie Sisneros , and he recommended running open ( no insert ) for best performance.

Bike runs strong , and is not too loud

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Took out the set screw and removed the whole thing . It was a bitch to get out though. If it does not stay lined up while removing , it binds. Then try shooting in a little WD-40 in the edge, between the silencer and the insert. The lubrication will help.

Even still , I pretty much destroyed the insert while removing , but will never use any way

Good Luck

When I get home from work today I could send you a photo or two

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No , did not get a dyno sheet from Eddie. But I trust his word.

Only other engine mods are TUF throttle body insert, and Twin Air power flow filter and cage, and Eddie's remapping

Bike runs better all around. More bottom and top:banana:

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I can't remenber off hand the price of the throttle body insert , but I think it was around $ 90

I did this mod first , before I bought the pipe. Definitly worth it. If you do a search , you will find some good reports on it.

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The Yosh without the insert is crazy loud.

Call Yosh they sell a 99DB insert that runs well and is not to loud. Its the same one all the Pros ran outdoors last year because the AMA didn't do any sound checks.

Eddies map gives a nice boost, yes its noticeable.

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I emailed Yoshimura about the exact same question a year ago. This was their response.

The RS4 system is designed to use an insert; you will see better

performance if you replace your spark arrestor with the optional insert

rather than running it wide open.

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Yosh is corect im always experimenting with diferent lengths and diameter inserts usuall a large short insert will boost bottom end power from 5000 rpm to around 7000 rpm but it will sacrifice some paek and over rev .Im waiting for some new parts from fmf that they made to my specs to see if i can gain some bootom and keep the bike quiet yet.

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I'm suposed to receive 2 insert with my SS/AL full system ?

Unless thats something new? you only get one insert that the muffler comes with. Should be a 96DB spark arrestor.

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This is the specification

The next evolution in Yoshimura exhaust, the RS-4 delivers huge power at a very light weight

Offers better handling thanks to a lower centralized mass coefficient

Uniquely-styled pentagonal muffler body with a carbon fiber cone end cap

Front cap design functions as a polyresonant chamber to lower dB output while improving mid- to top-end power

Two-staged, stepped baffle

Tapered head pipe delivers optimal flow and performance

Pro Series features a titanium header construction; Competition Series features stainless steel header construction

Competition series mufflers include spark-arrested 96 dB insert

Pro Series mufflers include non-spark-arrested 99 dB motocross insert

Mufflers available with glossy carbon fiber, satin titanium or brushed aluminum sleeve

99 dB and 94 dB muffler inserts available separately

The SS/AL is the competition series

The carbon and titanium is the pro series

They said the 99 db inserts is available separately, but Yoshimura himself didn't talk about it

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Yoshi only offer a 94db insert for the Honda

Yosh is corect im always experimenting with diferent lengths and diameter inserts usuall a large short insert will boost bottom end power from 5000 rpm to around 7000 rpm but it will sacrifice some paek and over rev .Im waiting for some new parts from fmf that they made to my specs to see if i can gain some bootom and keep the bike quiet yet.

I ordered a new insert to replace the original 94db insert with a spark arrestor. The new one has the same diameter as the original, but it's about two inches longer. If I remove the spark arrestor mesh from the original one, will there be any difference will be between the two? i.e. same diameter long insert Vs short insert.

BTW, if anyone wants to sell me an RS4 99 or 96 db insert (2010 CRF250), let me know! Yosh only sell 94db inserts as a replacement part, which sux!

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