I need MORE POWER!!!!!!!

9 replies to this topic
  • G-Man

Posted September 28, 2001 - 09:03 PM


Just kidding.... anyway I had a FMF certificate I won from the Prescott race that was ready to expire. With my discount I already get and the 35% off (certificate) I can get a PowerBomb FMF header pipe for a smokin price!!! I ordered it.
Anyone done the BK Mod and JUST HAVE THE POWERBOMB combo? I already went to a 165 main. Any other jetting tips?

I'm in AZ, 1500 ft.

btw anyone need a 01 header pipe?


Moto to Live
Live to Moto



  • dirtdad

Posted September 29, 2001 - 03:47 AM


G-man, how much do you want for the 01 header? I've been thinking about getting one for my 00. Is it banged up at all?

00 YZ426F
01 TT-R125L (my son's)
74 Hodaka Super Combat(gone but not forgotten!)

[This message has been edited by dirtdad (edited September 29, 2001).]

  • F-Pilot

Posted September 30, 2001 - 07:39 PM


G, I want that header!
I know you are getting alot of buyers but maybe I can get the AZOTMX inside line on it. :)
E mail me or call 602-432-3836.

'00 YZ426F

  • Boit

Posted October 02, 2001 - 04:15 PM


There is a guy over at www.dirtrider.net who installed a 444cc kit that was developed by Rich Rohrich and Eric Gorr. Check out what he has to say in the "Thumper Central Forum" and check out the post by SFO entitled "Gorr/Rohrich big bore kit Breathes fire". Rohrich is well known for his fuel expertise and sometimes pops in here for a post or two. Gorr is a well respected 2-stroke engine builder who is moving into the 4-stroke high performance market. Also, Jeremy Wilkey of MX-Tech suspension has a Q&A forum.

Surprisingly, Thumpertalk is a much more laid-back site than dirtrider.net. That site is heavily moderated and there is constant bickering going on. Go figure. Thumpertalk is still my most favorite site on the web.

  • MX_Tuner

Posted October 02, 2001 - 04:32 PM


Sorry, Boit. I beat them to it. Rich and I ordered the 97mm piston at the same time and I got it. I built mine over a year ago. Eric did my cylinder (boring and decking) and Rich clued me in as to which fuel to run. Both are great guys who know their stuff better than anyone else I know. Thumper Racing were the first ones that had Wiseco make the 97mm piston. Some of you may remember the yellow YZ the mags tested a few years ago. Thumper had reliability problems from trying to do a steel sleeve in a 400 cylinder (this was before the '00 426 was in production). The best way to go is bore a 426 cylinder 2mm over. Nice and reliable. Just seems you're saying it like it's ground breaking news. 450's (444 cc's actual displacement) have been around for a while.

Wanna ride it? It's like driving a V8 Pinto.

MX Tuner

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  • motojunkie

Posted October 03, 2001 - 01:12 AM


G- you need more power because you rode my 520, and your 426 feels like a moped in comparison. :) Just kidding, you left yourself open for that. Later.....Tom

  • Boit

Posted October 04, 2001 - 05:57 PM


Sorry. Just noticed your post Tuner. Did I make it sound like ground breaking news? It was simply a post that was fresh on my mind so I made a link for anyone who would like to check it out. It must have gotten by me that you had posted info about this kit. Hey, lots of stuff gets by me.

  • Hick

Posted October 05, 2001 - 01:03 PM


Originally posted by Boit:
Sorry. Just noticed your post Tuner. Did I make it sound like ground breaking news?

I had Eric bore my ’00 for the 97mm Wiseco about a year ago, and posted about it here, I went with the 13.5:1 version. I plan on putting that same barrel on my ’01 at some point, but I think I will try the 12.5:1 piston this time.

At the time Eric recommended against any head work, saying the cost/benefit just wasn’t there, apparently that opinion has changed a bit.

I love the extra ooomph it gave me but I had a problem blowing head gaskets (3). I also had some unrelated cooling system problems though so it is hard to say if the overbore is at all to blame. But I noted that one of the DRN guys blew a (97mm) head gasket (at their “spodefest,” I think) also. I think that was in the same post Boit refers to…

After I lost the second gasket Eric lapped the head and barrel for me. The third gasket didn’t really “blow” but I discovered that the coolant was disappearing, and it wasn’t in the oil (but it still ran). Walks like a duck, quacks like a duck…

I was ordering (another) gasket from White Brothers and, on a lark, asked to be transferred to someone who could help me with my problem. I got a guy named Gary Jones from their R&D dept. on the phone as their resident YZF expert. THE Gary Jones? Not sure, didn’t occur to me until later…

Anywho, I mentioned that I had the high compression piston and he said he thought the std. made better power. He also seemed to think warping anything significantly (due to it getting too hot for various reasons) wasn’t a real possibility, and said that in his experience though the head tended to “soften” and advised I just try torquing the four main bolts a bit tighter. Apparently Dubach’s (or Spud’s, I forget which guy) race bike lost all the coolant in a moto and seized (i.e. it got real, real, hot). He subsequently blew a gasket at some point after they fixed everything but tighter bolts seemed to prevent a recurrence.

Boit, Tuner, anybody have any comments on this? I have yet to try the big bore again on either bike.

  • MX_Tuner

Posted October 05, 2001 - 02:40 PM


I'm still on my original head gasket. I don't have a million hours on it but I do ride it extremely agressively (I mean, what the heck do you get a big bore kit for anyways?). Eric didn't do any head work for me, he decked the top of the cylinder .020". I knew that there wasn't much power to be had for a lot of time consuming porting. Head work normally gives peak rpm gains- nothing I'm interested in.

I've built one 450, about 6 420s and two 263's (2mm over 250F's) and haven't had any blown headgaskets yet. I put the gaskets on dry and torque to factory specs with used head bolts.

And yes, Gary Jones is "the" Gary Jones.

MX Tuner

  • Boit

Posted October 06, 2001 - 03:07 PM


Hick, I think I've finally reached the point where I accept that my 426 is where I want it to be power wise. I'm far too old and cautious now to take advantage of any more power. I'd rather spend my time doing fine tuning of the suspension since it took me a while to dial in the carburetion. I had a thread "over there" where I asked about doing some head work. From the answers, I decided to not touch it. And then from what you just described, I'm even more inclined to just ride the bike and enjoy what it has to offer. With my Stroker built KLX, I have all the performance mods to play around with that I could want.

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