YZ 426 Performance Pipes

Just bought a new 426. What performance exhaust seems to work the best?

Run the stock mufler and use a fmf high flow header. That works best all around for me.

Depends on where you want the power. If I remember correctly, I read some test results that said the stock system makes just about the most power throughout the entire rpm range but the aftermarket setups can give you a boost in the low range with a little sacrifice on top or vise-versa. I did hear good things about Doug Dubachs systems, I remember Dirtdad was looking into one. Maybe he'll comment.


[This message has been edited by flyinguitars (edited 08-02-2001).]

what do you think of the fmf q pipe?

Yes, I can comment that to date the Dubach 426 pipe is still not available. I just received an e-mail from them stating that the head-pipes are finished and it'll be about 2-4 more weeks before they have the complete system to market. I ended up installing an FMF "Q" muffler on my bike so I could ride this season because of the occasional ride on national forest trails as a break from mx. I'm still very interested in the Dubach system as I've heard so many good things about their 250F system and the fact that the guy should know more about the 426 than just about anyone else on earth except maybe the engineers that he helped develope the thing!


00 YZ426F

01 TT-R125L (my son's)

74 Hodaka Super Combat(gone but not forgotten!)

I just got the FMF IV Q muffler yesterday, and I installed it with the stock header for now, but I may add the power bomb later.

The bike has lost some power off idle (I haven't messed with the jetting yet), and it almost seems more 2 stroke like now. When you really twist it from idle, the bike slowly builds for about 2 seconds, then really takes off, and seems to have more on top.

Definitely quieter though, which is the reason I got it, so maybe I won't piss off the neighbors now.


'01 YZ426

'00 Harley Police Special(Got it for free, and I get paid to ride it!)

I'm very satisfied with it's performance. I have changed the jetting slightly to go along with it. I've installed an 01 needle, 165 main and a 48 pilot. I'm still not quite sure if this is where I want the jetting. It's a little better low to mid and smooths the transition between the two. I can't really comment about the top-end as I don't ride the limiter much. It seems to pull strong all over though. What it really did for me was add a spark arrestor and DID quiet it down quite a bit. I mostly mx with about 30 percent of my riding in the woods and it suits me just fine. I haven't added a flywheel weight and I have no problems with stalling in the tight stuff either. I remember Hick commenting recently that he has one on his bike too. I think he rides mostly desert though. He can problably describe the performance characteristics better than I can. Hope this helps.


00 YZ426F

01 TT-R125L (my son's)

74 Hodaka Super Combat(gone but not forgotten!)

[This message has been edited by dirtdad (edited 08-03-2001).]

The stock pipe works real well. I use the Procircuit T4. It has different end caps for tuning per track. I have been completely happy with this system

Pro-Circuit t-4 works great for me, the 2" end cap gave it great top end power but stalled too easy at slow speeds. I use the 1.75" end cap with out a spark arrester screen, it is a little loud but has the best mid to top power of the 426 pipes I've seen. Also very high quality and clears the oil filter. mike

Anyone have any experience with the Yoshimura TI pipe and header?

Any jetting suggestions would be appreciated.

I'm @ sea-level.

[This message has been edited by IBWFO (edited 08-03-2001).]

has anyone used the pro circuit t4 with the quiet core...if so does it help much?

I've got the DSP Titanium w/spark arrestor and the jetting they recommended made my life miserable for weeks!! I think the Yosh is about the same,they make it for DSP.Heres where I am ,now back to a 162 MJ,a 42 PJ,and I raised the needle or dropped the clip one to richen it up and I'm 2-1/2 out on the fuel screw,no blubbering ,starts easy,pulls hard,no fouled plugs!!Still blows black when you wick it on--BK mod must be the next step!!!

Thanks. I put it on tonight and the fit seemed to be pretty good. One question though, the connection of the silencer to the headpipe came with no clamp and doesn't look to need one? I'm hoping the pipe is pretty close to the DSP, so I am going to start with your specs.

I just picked up a pro circut T-4 setup with a spark arrestor endcap and a quiet core cap. I have noticed a loss of bottom end with this pipe, gearing is 14/48. I have flywheel wieght, I weigh 190lbs and say I'm riding moto and corner a bit lazy in 3rd I usually can make a very powerful exit by using minimal clutch. I now find myself sorta down on juice and this is the only thing i can attest it to.My jetting seems spot on, runs good still mid to top but bottom is slacking, especially in loam or soft sand. Anyone else noticed this?

I run a White Bros. E-Series on my 00'. The bike is ridden exclusively in the woods of S.Indiana and N. Kentucky (re: tight). The bike runs really well down low and has plenty of top end charge. Just remember, I don't scream the bike alot. It is the Randy Hawkins series. This pipe was the only one in the Dirt Rider test that hung with the stock pipe through the entire range and was a little better on the bottom. It is definitely quieter and now I have a spark arrestor too.


Somebody's gotta win; Somebody's gotta lose!!

Larry Roeseler's Stroker Fourstroke Speed Equipment has both torque and rev systems.


I raced my bike (01 426) for the first time since installing the TI Yoshimura pipe and was really happy with the performance.

It was close to the stock pipe but seemed to have a bit more in every gear. As far as jetting goes, I just raised the needle one position and the bike seemed to run great.

Have you checked your plug yet WFO? I still get the black,sooty look to mine.I'm thinking about doing the BK mod as soon as I get time and thay may change the stock jetting because of the decrease in fuel being shot in at throttle openings.Did Yosh also recommend a 168MJ and a 48 PJ ,I'm was so pissed after the first couple fouled plugs and I was running a 165/42 . Stock has been the best so far.


I checked the plug and it looked good.

I felt like it was running pretty good and I also tried some of that new unleaded VP 103 octane gas last night too.

The track is SX style, so I didn't get much of a chance to put it in 5th gear.

I really need some more time on it since I'm heading to Millville next week.

Oh, and I was kinda bummed that Yosh didn't even mention jetting.

[This message has been edited by IBWFO (edited 08-05-2001).]

Well I rode again yesterday and after all the fear I had about my junk not running right all it turned out to be was a bad jug of fuel. I am really shocked that was it but it was, new plug new gas and pro circut t-4 is okay. However the quiet core s/a endcap thoroughly blows. That is a power bandit like you cant believe! If anybody buys this setup stay away from the quiet cap unless you gotta pass db test to ride somewhere.

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