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YZ444 Review

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Posted by: endosports---------------------

First off let me tell you that I was very happy with the performance of the stock 426. But after having my connecting rod bearing fail and needing to freshen the motor I calculated the cost difference of a stock rebuild and big-bore kit. What I found was the cost of this mod is little more than that of a stock rebuild.(I also want my bike to compete with the new breed 450s)

Parts and services included:
ProX connecting rod kit.
Wiesco 97.00mm piston kit. (Sleeveing done by LA Sleeve. 5 day turnover)
Cometic Gaskets
Stock Valve springs
Powernow valve, Bk mod.

The power increase is very impressive. From the bottom all the way to the rev limiter the bike has increased power. The front wheel does not like to stay on the ground and rideablity is lowered for the novice rider. I haven't gotten to get the bike on the dyno so I will have numbers coming soon.

First test: Spazdick Olympics BPMC Jawbone Canyon.
Private race last weekend 45 entrys in the big bore class. Start of the race, dead engine start, sand wash 1 mile. My competition consisted of every class bike from 250-650s. I got a one kick start out of gear and blew the field away by 10 bike lengths. I finished 6th after some simple mistakes I got passed.

Overall rating of mod. for a novice engine builder as myself. I give the the bike a 9.5.

More testing of M0S2 coating on gears and shafts to come. Noticeable difference in shifting.


Posted by: Thump---------------------

That is cool man. Did you do the large center valve? I had the pleasure of riding Zoomers 444 at DirtWeek... It was similar to my CRF in power but his had no flat spot. Off idle to the limiter it had power. I look forward to hearing your impressions as you get used to it.

Also, do you have a cost breakdown of the parts for those that may want to try this at home? I think Eric Gorr is doing the mod for $375 so it is not terribly expensive for the performance gain you are getting.


Posted by: endosports---------------------

All valves are stock size.

I am not sure if the oversize ti valves are available.

Wiesco TE kit: 169.95
Prox rod kit: 139.95
Cometic Gaskets: 29.95
LA Sleeve: 210.00 labor/sleeve(turn around Endosports order)less than one week.
Seals, orings, washers: 70.00
Crank rebuild: 60.00

Note: this quote is for reference only, please do not take this as advertisement of any services or parts for sale. Build your motor at your own risk.

Porting, coatings and all other services are experimental and there are more reviews to come. I have only 3 hours on this motor and need to do more testing with the dyno and at the track.

I have a YZ450 in the shop and we will have to see how the two line up!

Ohh and thanks To Zoomer for helping me get to the race on time w/ those gaskets on B/0!!


Posted by: Camstyn---------------------

Did you notice any extra decompression braking, or lack of, after the big bore kit?


Posted by: endosports---------------------

Quote:
Originally posted by Cam Mitchell
Did you notice any extra decompression braking, or lack of, after the big bore kit?



I couldn't tell much difference between the two. I also had some very tall gearing(14/45) on for the race so it made it harder to tell.

The steep sand hills had no chance with the power of this thing. I was shifting up to fourth while climbing them.

Uh Cam? Can I have my stabilizer back because my bike is too fast now?J/K


Posted by: SFO---------------------

Quote:
Originally posted by endosports



I couldn't tell much difference between the two. I also had some very tall gearing(14/45) on for the race so it made it harder to tell.

The steep sand hills had no chance with the power of this thing. I was shifting up to fourth while climbing them.




Good to hear about another happy 97mm transformation.
I ran 15/42 in baja with a wr trans and could still pull it up in 4th just on the throttle. It would also pull the revlimiter in fifth.
I am working on a batch of lightened wisecos right now for Eric.
I lightened my original 97 to within 5 grams of the stock piston and am now working on the cad/cam for a better 3d machined backside than I was able to produce with manual means, and solid works has a FEA built in now so I can try to keep the longevity as well.

I look forward to your dyno runs, here is what I got...

http://www.four-stroke.com/Dyno_runs/SFO_index.htm

and here is an unofficial before and after 426 to 444...

http://www.four-stroke.com/Dyno_run...ne_yzf_+444.htm


BTW< Zoomer is the man :flame:


Posted by: bclapham---------------------

brian, did you ge it bored and then a sleeve fitted, or just bored and then nikasil plated?


Posted by: endosports---------------------

Quote:
Originally posted by bclapham
brian, did you ge it bored and then a sleeve fitted, or just bored and then nikasil plated?


Sleeve fitted. :flame:


Posted by: MotoGreg---------------------

Those dyno charts from SFO look like a good advertisement for Vortec ignitions. How does the stock 426 ignition curve look? Is it somewhere between the Vorec's power and traction modes?


Posted by: MotoGreg---------------------

Nevermind, I went back and looked at the charts and the stock curve is pretty close the Vortec's power setting. I guess they just add the traction mode as an alternative and the power mode isn't too far off of stock.


Posted by: SFO---------------------

actually both vortex modes made less hp everywhere than the stock wr box.


Posted by: pursang262---------------------

Thanks for the report. My 444 is still in the parts gathering stage.Got the top end back from Eric, just sent out the crank to get balanced to the new piston,and welded.How much of a jetting change is needed from stock? I realise every bike is different, I've got a practice day before my first race weekend and I'm wondering how much brass to bring.Thanks again.


Posted by: SFO---------------------

I use the ekp needle 3rd clip and have gone down to a 155~158main for the 0 to 5000ft riding I do.


Posted by: JYD---------------------

what kind of power are you guys getting with the 444 kits? the dyno sheet links arent working for me.

thanks.


Posted by: SFO---------------------

MR RR needs to scope the old links out.
My best run with the old 97 was right at 54rwhp on nutec.
Stock valve sizes on a dynojet 150 with NO corrections and maximum smoothing.



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