Yoshimura RS 4 Full System Review Installed on CRF250L

An aftermarket exhaust system was easily last on my wish list. I had modified the stock CRF250L exhaust to perform extremely well, so I didn't think I needed it, and I liked the quieter sound.
But... I couldn't resist the urge to explore the capabilities of what I think is the best aftermarket system for this motorcycle -- the Yoshimura RS-4 Competition Series Full System (Yoshi # 123500D521).
And so I did it. I purchased the full Yoshi RS-4 System, plus the optional spark arrestor, to be legal off-road, here in the Central Okanagan, B.C. (aka: forest fire territory).
Wow, is all I can say. That fat header and well-designed mid pipe and muffler, has really opened up the bike. I spent two or three days tuning the system to make the most of the new exhaust, and now it is performing just the way I want; strong acceleration, good torque, and increased top speed. The bike now easily accelerates to RPM's that were unattainable or painfully slow to achieve before.
There were however, a couple problems with the Yoshi RS-4 that I detail in the video.

[@azdesertdog]

Yoshimura is about the best quality stuff out there. I used to run them on my street bikes. Great choice. Sounds awesome!

[@Scoottoots]

+azdesertdog Yeah, I'm quite liking it. Still got to get used to the sound level though :-)

[@dennismcelroy5914]

Great Review! Well documented! The exhaust note when you open it up really BARKS!

[@Scoottoots]

+Dennis McElroy Thanks Dennis, the spark arrestor has made it louder . I've finally got it tuned to match the system without being overly rich.

[@ev3rlastingfaith]

Great info! Another thing I noticed is that because of the reduced weight at a higher center of gravity, the bike is less eager to lean into corners compared to the time the OEM mufler was installed. Just like you, also installed the spark arrestor. I like the free-revving, quicker acceleration. There are times when i do like the sound, but in general I wish I found a way to attenuate it. Overall, on my bike, the 13 tooth gear, full sustem Yoshimura and Takegawa 305cc kit have changed the bike significantly. (Next i will want anbigger gas tank like yours and in the more ditant future a race tech suspension and then I will be broke). Thank you for the very useful post.

[@Scoottoots]

+ev3rlastingfaith Yeah, it performs well with the Yoshi, and I also wish it were a little less loud, but can't have everything :-). You'll really appreciate the larger tank. One of the best mods I've done.

[@WOODZMAN]

Nice review . Your bike sounds great !

[@Scoottoots]

+WOODZMAN Thanks. Just fine-tuning now. pretty happy with the system :-)

[@timgerein9731]

Fantastic video and review. The bike sounds great.

[@Scoottoots]

+Tim Gerein Thanks Tim, The bike awesome as well :-)

[@SantaridesaKTM]

Excellent video. Don't you just love it when you have to modify something thats really expensive, and 12% on the top end is fantastic. Good job.

[@Scoottoots]

+Mr Wobbleknocker I think I was the exception with the flange bolt issue, as I've not heard of anyone else with this problem. But yeah, very happy with the system.

[@SantaridesaKTM]

I have an excellent tip for any one thats interested in making there bike a little quieter that has a nearly straight through pipe on it. Up until recently i had a CCM 600 r30 (big thumping rotax 4-stroke single) with a race silencer that was made by CCM, the bike was also jetted for the race silencer. All i did was doubled up a piece of chicken wire and sculptured it nicely just inside the end of the rear silencer and drilled 2 holes for stainless steel bolts to go through. The end result was a noise half way between the standard pipe and the straight through pipe and because of the slight increase in back pressure this improved the acceleration (not that it didn't have enough anyway). This mod far outweighed my expectations of what i thought it would do. Hope it helps anyone out there.

[@Scoottoots]

+Mr Wobbleknocker That sounds (no pun intended) interesting, but it is difficult to visualize. Are you saying that you attached a wire mesh at the tailpipe end? My exhaust with the low volume insert is perfect on performance and sound. A spark arrestor at the tailpipe end would be cool.

[@SantaridesaKTM]

If you go to my youtube channel and click on videos (i only have 1 video because i'm not very good at this sought of thing so my daughter keeps telling me lol) you'll see my bike just before i sold it. you can just make out the chicken wire on the end of the silencer.

[@Scoottoots]

+Mr Wobbleknocker Hey, cheers; I watched carefully and saw your wire addition to the tailpipe. That's pretty much what I was considering for a spark arrestor, except the wire mesh would be spark arrestor gauge. I'd have to experiment to test the performance affect, of course.

[@SKarlsson]

Sweet! Sounds right proper now :)

[@Scoottoots]

+Scott Carlson Cool. Thanks Scott :-)

[@SKarlsson]

Talk about LOUD - my buddy used to run the Supertrapps on his XR's. I could hear him from a mile off easy.

[@Scoottoots]

+Scott Carlson Gives the moose and bears plenty of time to vacate the trail :-)

[@SKarlsson]

+BlastsFromTheSaddle no kidding lol.

[@amselc1]

Nicely Done! I run the same mods (more or less) except that I installed K&N filter since I think the main air flow restriction into the engine is mainly due to the filter itself. I also installed AFR gauge (wideband sensor and a gauge) since I felt I am blind with respect to the A/F ratio and I did not want to run it too lean. Too lean A/F ratio is not healthy to the engine and also results in higher running temperatures. Anyway, my EJK settings are 2, 3, 4 for the first 3 and I did not changed the 3 others and I am really satisfied with it

[@Scoottoots]

+Daniel Mitlansky Yeah, too lean is dangerous when under load or high rpm esp. My ejk settings currently are 1.5, 3, 6, 4, 2.5, 2.5. That gives me a good economical cruise mixture, with power when I want it. The advanced cut in points help with throttle response, making it possible to run leaner at cruise, as the Yellow setting will kick in sooner, avoiding any lean-under-load condition.

[@crfadventures]

Excellent review John. Thanks for posting! I'm amazed at the top speed increase. Have you done any longer highway trips yet? How's the noise level and long trips or WOT? Does it get to be to much or is it just right?! :)

[@Scoottoots]

+CRFAdventures.com Thanks Deven, I'm really pleased with the system. The noise level? I'm getting used to it. Most of the time it's just throaty and growly. It gets real 'brappy' and loud when you put it under load. Just cruising along, it is quite pleasant. I have carefully adjusted the air and fuel to make the most of the system without wasting silly amounts of fuel and depositing carbon heavily. I have it perfect now. Excellent throttle response, good low end grunt, fast acceleration, and descent economy. Understanding how the switch points work in the Fuel Controller really adds a fine level of control to tuning the throttle response. Just returned from an off road ride with a buddy. Some fairly aggressive riding at times, and I gotta say, I'm really liking the difference. It wasn't annoying loud on the trails. It seemed in keeping with the power and throttle response. I'm happy with it :-)

[@crfadventures]

Thanks for the update! I will likely be adding one to the future mod list :)

[@Scoottoots]

+CRFAdventures.com You should come over one day and hear it in person before you decide. take it for a spin around the block; see what you think before investing. There is no question that it is loud when under load.

[@crfadventures]

I would love to, thank you for the offer!

[@RAW-db3uh]

Great vid man, thinking about getting the yoshi myself. Where did you get the handguards? Been looking for those!

[@Scoottoots]

Thanks. It's been so long I can't recall. Could have been from CRF's Only.

[@lewistacey6407]

Great video

[@Scoottoots]

+Lewi N Cheers :-)

[@hillbillydualsport]

Nice review.

[@Scoottoots]

+hillbillydualsport Cool, thanks!

[@lexotic2421]

Nice vid :-) I just bought a Yoshi, did you buy the spark arrestor from yoshi?

[@Scoottoots]

Yes, it is specially made for the RS4 with the turned out end.

[@gnath9]

great video !!!

[@Scoottoots]

+Gary Nath (gnath9) Cheers, Gary :-)

[@69adrummer]

I love that coat. Have you done a review on it? I might have missed it. I need something with armor in it; that would be nice any how! :)

[@Scoottoots]

+69adrummer Stay tuned! Reviews on the newly acquired jacket and pants are coming SOON.

[@Cormos8]

How were you able to keep your license plate attached? My understanding was that with the Yoshi system there was no way to reattach the license plate assembly. Is this incorrect or do you have a different mod for the license plate assembly? Thanks in advance.

[@Scoottoots]

+Dustin Overby That may have been before the introduction of the RS-4 with the turned out end cap. I modified my tail section last year to get rid of the excess, but I can't see how this Yoshi would interfere with anything.

[@hillbillydualsport]

Sounds good to me.

[@Scoottoots]

+hillbillydualsport Cheers :-)

[@DucatiNiederlande]

Please tell me, what the cost of the complete Exhaust ?

[@Scoottoots]

Can't recall, but it isn't cheap for sure. The Yoshi more expensive than the FMF. Sometimes there are good deals. I think I paid about $600 all in.

[@johnnymurrow7325]

great videos! what are your final ejk settings?

[@Scoottoots]

+Johnny murrow Thanks :-) My final settings -- so far -- are: 1.5, 3, 6, 4, 2.5, 2.5 with the O2 Sensor connected, and the air box opened out to 2.5" i.d. custom snorkel, and stock air filter with backfire screen removed, and PAIR system completely removed.

[@RobAshMotoVlogs]

WOW! Sure does look the part. Very nice. How would you even go about repacking something like? Looks like a nice jump in power, even for quite a small engine size. It sounds nice too, not too loud.

[@Scoottoots]

+Rob Ash To repack it you have to drill out the rivets at the tail end, remove the carbon fibre cap and repack, then rivet it back up. Yoshi produces a kit for it that comes with everything. I asked them, why not use screws. They said they did that in earlier days, but they constantly seized, etc. It's interesting to get people's take on the sound volume. To me it is very loud, but then I am used to a fairly quiet bike.

[@hetfield_75]

Is it ABSOLUTELY necessary to install an EJK?...or is it doing fine without one?

[@Scoottoots]

If you install a full system it is always best to be able to adjust the mixture, especially if you also free up the intake. You get more power that way, and you protect your engine. A fuel controller is highly advised. You risk running too lean which can damage your engine from excess heat on the valves and such.

[@bradb9146]

Nice : )

[@Scoottoots]

+brad b Thanks :-)

[@mr.conner636]

Where did you get the system from?

[@Scoottoots]

Oh man, I forget now. It was 7 years ago.

[@mr.conner636]

@@Scoottoots understandable lol didn’t even see that at first. Thanks for the response.

[@senilefoolidge2777]

Is it louder with spark arrestor?

[@Scoottoots]

Yes it is.

[@Mr.BlueOfficial]

117 that in MPH? if so wow,

[@Scoottoots]

No, that was KPH on the stock exhaust system. Since then, as shown here, I have achieved over 130 KPH from the same gearing, using the new exhaust and corresponding fueling tweaks.

[@I_Am_Michael]

your hot rod honda.

[@Scoottoots]

+michael adams Woo hoo... braaap braaap rumble rumble :-)