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2007 RM-Z Yoshimura RS-2 Jetting

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I have just ordered a yoshi RS-2 full system for my stock rm-z 250...

any suggestion for jetting?

I ride at sea level and only ride motocross. usually 20min motos and practice.

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check out www.dynojet.com, they have jet kits for it, probably a 155 or 160 main would do the trick and a different needle, but check out the web site they should have what you're looking for, let me know how you like the yoshi exhaust, looking at it for my 08, it sounds like its about the best one you can get

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the yoshi RS-2 works great... it has a little bit more on the bottom-mid like i noticed that coming out of sandy or loamy corners was a breeze now... the first thing i noticed though was that it now pulls all the way to the top, where previously the power tended to die off, comparably it pulls like a YZ in the top now.

I haven't changed the jetting at all yet... gonna play around with the jetting when i get back the the track.

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Hey guys. I was searching through some jetting topics and I noticed that you said your RS-2 gave you a bunch more bottom. On my bike it seemed to completely take it away. In fact I was making a lot of mistakes because I had to be greater than 1/4th throttle or else my bike would be really slow. I was thinking about putting the stock pipe back on because it pulls so much more down low. The RS-2 RIPS in the mid and through top, but for me there is practically no bottom.

Could it be my jetting? I have hot cams stage two. My main is around between a 195-205 (Because when I put the hot cams in it it still was popping with a 190 main.) My pilot jet is one or two sizes richer than a 42. I'm pretty sure the jetting was "good" BEFORE I put the pipe on. But now there is practically no bottom. One day I switched back to the stock pipe and was very surprised because it seems to pull twice as long, yet seemingly a lot less powerful.

Also, I installed the hotcams and the ~~200 main jet and the size richer pilot jet when it was about 40 degrees. Not its around 80 degrees.

And after I installed the RS-2 I HAD to use the hot start when it's hot. Before the pipe I NEVER had to use it.

Edited by Tha Breeze

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IMO..if I remember correctly with my 07 best pipe setup was the fmf mega bomb header, this enhanced bottom and gave much needed top end. My 08 was best with stock header and slip-on. Either way your jetting shouldnt change to far from stock, maybe one size MJ. 07-09 rmz's were jetted pretty spot on. With your popping and hot start issues check and dial in your fuel screw.

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The stage 2 tends to have less torque at low rev's and it sounds like that and the pipe was too much, your jetting sounds close to what I ran with a fmf slip on and a stage 2 cam, mine had decent bottom, you sure your rings are not worn? They loose a lot of bottom end power, 25 hours is not unusual on rings to get to the Max limit

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Okay that may be it. I'll look into doing a piston/cylinder. Thanks!

EDIT: But if it was the rings that was causing the loss of the bottom end why does the stock pipe help so much? Or do worn rings exaggerate the effect of all the mods?

Edited by Tha Breeze

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It doesn't sound like the rings if it works well with another pipe, sounds like that cam and pipe just don't like each other

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Hey guys. I was searching through some jetting topics and I noticed that you said your RS-2 gave you a bunch more bottom. On my bike it seemed to completely take it away.

Your not the only one who thought this Breeze. When I swapped my DEP S7 system on my 08 for a Yosh rs2 I immediately noticed the bike was harder to start and it had no bottom end. But it did have loads of topend which is where a 250f lives really so I liked it. For enduros I preferred the DEP. Dep said standard jetting was fine but I'm sure a jet change would help with the RS-2. The other thing I liked with the Yosh is that floating rear mount, which stops the vibration being felt through the frame. For the life of me I can't find it but I used to have a link saved somewhere that took you to a full 08-09Rmz exhaust dyno test shootout for a standard and tuned 08-09 rmz with the standard exhaust pipe on both bikes as a base setting. By far and away the big hitters were Akrapovic, HGS and the Yosh probably had the best spread with a good top end. FMF and PC were nowhere. The Akrapovic had stonking low end, something in the region of 3hp over standard. I've ridden an rmz with that pipe and a ported head, the power was really impressive.

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I may try and lean out the pilot and or main and mess with the needle and also ride some more with the stock pipe. With all the power up top it's harder to ride, but faster. I noticed in my last race I was making a lot of mistakes in some slower corners since i was expecting the bottom end to be there. I may try and sell my RS-2 after I get a chance to mess with jetting and the two pipes.

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