444 big bore


22 replies to this topic
  • 2001YZF426Rider

Posted February 17, 2009 - 07:41 PM

#1

To everyone that has the 444 bigbore in their 426, is it worth it? I didnt find much on it searching.. My 426 is converted to street legal, and it seems i am looking for more power.. Is the 444 kit that much better? Worth it? Can i run pump fuel through it? Is it as reliable as my 426 is? If anyone can give me some input i would appreciate it!

  • 642MX

Posted February 17, 2009 - 07:58 PM

#2

Yes, the 444 kits are worth the money. The 444 is like a 426 on steriods, more power everywhere. The 444 kits come with either a 12.5:1 or a 13.5:1 piston, if you want to run pump gas then go with the lower compression. I've got 50 hours on mine, and so far so good. :lol:

  • Zaj 243

Posted February 17, 2009 - 08:12 PM

#3

I'm dying to set my 426 up with one, I just built a '06 450 for flattrack to replace my 426, but i love the old girl so much i wanna do the 444 and run it still!

  • s14 2510s

Posted February 18, 2009 - 07:23 AM

#4

My 444 rips. I would never go back to stock.

  • 2001YZF426Rider

Posted February 18, 2009 - 11:33 AM

#5

Hmm so i guess it is a good option then!! My bike gets ridden every day so i need the reliability of stock..

  • 642MX

Posted February 18, 2009 - 06:16 PM

#6

Hmm so i guess it is a good option then!! My bike gets ridden every day so i need the reliability of stock..


I don't see any reason why it would be less reliable.

  • 2001YZF426Rider

Posted February 18, 2009 - 07:36 PM

#7

I just wasnt sure.. My buddy has an athena big bore on his wr450, and on the dyno all he gained was 1 ft.lb of torque!! This was on a reputable dyno, at a reputable shop, and my buddy knows his shit too!! So i want to make sure the 444 kit is worth the money power wise, and i also want the reliability ive been accustomed to from my 426 for the past five years! I probably wont do the BB until this coming fall, just trying to gather as much info as i can now.

  • Birdy426

Posted February 18, 2009 - 10:18 PM

#8

If you have to replace your cylinder or get it replated, the big bore kit is a no-brainer cost wise. Made a huge improvement on my WR.

  • 642MX

Posted February 19, 2009 - 06:45 AM

#9

Birdy is the one who talked me into the 444. Besides the suspension revalve and the Rekluse, its been one of the best mods I've done. :lol:

  • 2001YZF426Rider

Posted February 19, 2009 - 10:09 AM

#10

What are you guys seeing for speeds from the kit do you know? Anyone put one on a dyno?

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  • grayracer513

Posted February 19, 2009 - 11:28 AM

#11

Speeds are determined by the gearing. A big bore kit by itself won't change that.

  • Birdy426

Posted February 19, 2009 - 11:51 PM

#12

Speeds are determined by the gearing. A big bore kit by itself won't change that.


True...

When I got my 444 put together, I found that it had so much off the bottom that first gear was pretty useless. I went up one tooth on the countershaft sprocket, and the bike pulls it (along with my fat butt) just fine.

  • s14 2510s

Posted February 20, 2009 - 07:54 AM

#13

I bet i gained 10+ hp off my 444 kit. But the olney thing stock in my 426 engine is the cases,timing chain, and few other things he he. I told eric gorr to do everything he could to make this a stump puller. Eric even asked me if I just wanted to crap the rebuild becuse of how much i spent on rebuilding the old girl. I made My 426 run 110 because my smoker was alredy built for 110. Both my bikes get broke down atlest twice a year. I never have any problem starting to 426 unless its below-10 out. We rode once this year when it was colder than that. I had to put my 426 in a van with a fishhouse heater to warm it back up. With all the stuff i have done I still run stock main and one size fatter pj.

  • jonova

Posted February 21, 2009 - 10:22 AM

#14

10+ hp is a bit much..... That is a more than a 22% gain with only a 4% increase in displacement. I think 5 hp is more like it. And don’t forget about the added torque!!

I put in a 444 kit on my 01 426 along with some head work and it had a noticeable gain every where especially the bottom and mid range. I broke it in with stock cams and then replaced both with hot cams and the bike became even more powerful, but I lost a bit of low-end. That didn’t matter as I’m a Southern Cal desert rider.

One thing I did notice was that the added stress on the motor was evident over time. My rings went bad ad seized the wrist pin the piston, cracking it. New crank, piston and main bearings…. I stopped racing the bike and put it all back to stock and it still felt like a strong motor. Not quite the mid range hit, but still ripped with the hot cams and head work.

I would not put a 444 kit in my bike if I rode tails only. But for desert and dunes it is worth the risk of reliability.

  • grayracer513

Posted February 21, 2009 - 11:55 AM

#15

I think 5 hp is more like it.

I'd be surprised if it was more than 2.

  • FinchFan194

Posted February 21, 2009 - 08:46 PM

#16

I'd be surprised if it was more than 2.


This is true the 426 I had was not that different in HP than my 04 YZ450

  • s14 2510s

Posted February 21, 2009 - 09:17 PM

#17

5 angle port and polish with 1mm+ kibble white valves. Somebody else had a gorr built 426 like this one they rip. SFO had a 444 built from eric they are picky to what kind of 110 they run. Ive got 18 hours on mine and have tryed just about everything in jetting im happy how it pulls now. Ive got a R&d bowl and flexjet. The adjustable leak jet is nice. powerbomb header with a yosh pipe i run in the winter. No spark for the yosh. Ask SFO he will vouch or look up old threads about his old 426.

  • grayracer513

Posted February 21, 2009 - 10:13 PM

#18

5 angle port and polish with 1mm+ kibble white valves. Somebody else had a gorr built 426 like this one they rip. SFO had a 444 built from eric they are picky to what kind of 110 they run. Ive got 18 hours on mine and have tryed just about everything in jetting im happy how it pulls now. Ive got a R&d bowl and flexjet. The adjustable leak jet is nice. powerbomb header with a yosh pipe i run in the winter. No spark for the yosh. Ask SFO he will vouch or look up old threads about his old 426.

We aren't trying to decide how much power you can build out of a 426 if you do everything possible. The question was what the 444 kit was worth, and the answer is about 4%.

  • s14 2510s

Posted February 22, 2009 - 05:55 AM

#19

I'd be surprised if it was more than 2.


We aren't trying to decide how much power you can build out of a 426 if you do everything possible. The question was what the 444 kit was worth, and the answer is about 4%.


A 444 is worth it if you do it right. Its just you had to chime in and say a 444 kit wont give you that much hp. Thats were it got off topic. I was just stating if you add the dispalecment and dont change the port design you probly will olney yield a 1hp gain. I bet I make it to 150+ hours on my 444 piston and head work without a problem. The extra power is nice in the dunes and flattrack racing. It smoothed out the power too and made the bike ez to ride compared to how I remember it with stock displacement. I dont run a flywheel weight and i never stall my bike out. my 444 runs strong. Ive picked the bike up multiple times this winter off its side and its always running.

  • 2001YZF426Rider

Posted February 22, 2009 - 01:49 PM

#20

I meant to say what are people running for gearing with this kit. I ride mine on the street, so higher speeds are very common. I would only do the kit, probably not any other engine/valve work to it. So if its not worth it just doing the 444 kit then i wont do it. I love the reliability i have had.





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