OEM 426 Kit



16 replies to this topic
  • Brad

Posted July 04, 2000 - 01:13 PM

#1

Thanks to the online fiche at www.hlsm.com I was suprised to discover that the 2000 WR400 and 2000 YZ426 share almost every bottom end part with the exception of the following:

5JG-11651-00-00 Rod $38.08
5JG-11631-00-00 Piston $134.82
5JG-11603-00-00 Rings $20.57
5JG-11633-00-00 Wrist Pin $8.66
93420-19084-00 Circlip $0.30 (2)
5JG-11181-00-00 Gasket $25.23
5JG-11311-00-00 Cylinder $222.03

Total $449.69

So for a mere $450 bucks (+ other gaskets) you can have the stock 426 motor, with no fears of broken rods, cranks, etc. I'm doing this as soon as I need to replace my rings!

Brad



[This message has been edited by Brad (edited 07-04-2000).]

  • Mitch_from_Oz

Posted July 04, 2000 - 04:14 PM

#2

Well done Brad,

You have done the home work that most of us wished we did... :)

But, as you know, the YZ426's have problems with clutch and gearboxes... That is the feedback from the dealers in Australia. AS such, will the added ooomph pose a problem to the 400's clutches and gear boxes?????

  • Brad

Posted July 04, 2000 - 05:48 PM

#3

Good question about the clutch, maybe some guys with 420 kits can give us an update on how their bikes are holding together.

Brad

  • Matt_Porritt

Posted July 04, 2000 - 06:52 PM

#4

Remember the 426 got a 1mm oversize wristpin AND crank pin

The weak link in the 420/426/450 kits is the bottom end.

Seems like you'd have to remove the crank and either get a 426 crank or get the crankpin hole in the crank halves machined and a new pin pressed and welded.

Also the CDI ignition is different and the carb.. but the carb should be no prob to jet for a 426 conversion
Gear ratios and primary ratios also differnt but in my opinion the YZ400 has a better gearbox spread than the 426.
The other thing is as Mitch mentioned the clutches... but a Hinson and HD kit 'should' be ok.. the 426 does have an extra plate though

Unfortunately its not as easy as parts to get the same motor!! :)

------------------
--
**Ride it like you Stole it!**
Matt Porritt
99 YZ400F
Vist the Rubber Chicken Racing Online Shop
Discounts for ThumperTalk members.

  • Brad

Posted July 04, 2000 - 08:00 PM

#5

Matt,

My point is that the 2000 WR crank and the YZ 426 crank are identical. I was suprised to see this, but discovered it while comparing part numbers for the two bikes. The wrist pin is larger on the 426, and that is why the part number for the rod is also listed above, but the crank pin and bearing are the same part as the YZ426. Yes, crank disassembly is obviously required for the rod change, but not a huge deal. So yes, it as actually as easy as parts to get the same motor, although somewhat labor intensive. As far as the ignition is concerned, some 426 owners actually prefer the old YZ (and some the WR)ignition timing to the 426 (remember recent vortex ignition discussion). Based on James Dean's recent jetting experimentation, I plan on giving the 426 needle a try as well. The good news here for us Y2K owners is that for $450 dollars in parts, we can bring our bikes up to 2001 engine specs(minus titanium valves of course). If and when I attempt this, I'll let you know how it works.

Brad

[This message has been edited by Brad (edited 07-05-2000).]

  • Taffy

Posted July 04, 2000 - 11:26 PM

#6

as i understood it , only the little end size had changed (agreeing with brad) or has the big end gone up as well? as matt says?

  • Matt_Porritt

Posted July 05, 2000 - 12:49 AM

#7

Originally posted by Brad:
Matt,

My point is that the 2000 WR crank and the YZ 426 crank are identical. I was suprised to see this, but discovered it while comparing part numbers for the two bikes. The wrist pin is larger on the 426, and that is why the part number for the rod is also listed above, but the crank pin and bearing are the same part as the YZ426.
As far as the ignition is concerned, some 426 owners actually prefer the old YZ (and some the WR)ignition timing to the 426 (remember recent vortex ignition discussion).


Hmmm.. to my knowledge they didn't change the WR crank pin.

According to the www.hlsm.com fiches:

The 99WR pin is #5BE-11681-00-00
The 00WR pin is #5BE-11681-00-00 (same number)

The 99YZ pin is #5BE-11681-00-00
The 00YZ pin is #5BE-11681-00-00 (same number again)

The 426 lists the part as '...PIN, CRANK 1 (5JG1)' while all the others list the pin without the 5JG1.

There is obviously something not right here as its saying that the pins are the same for both YZ/WR from 98-00 while we KNOW the 00YZ has a 19mm pin and the others have a 18mm pin.

The 99 YR & WR have the same crankshaft assembly #s while the 00 WR & YZ have different assembly numbers but according to the fiches the webs and pin are the same.
They say the 00WR uses a #5BE-11651-10-00 rod
while the 00 426 use a #5JG-11651-00-00 rod.
Also says the 99Wr uses the same rod as the 00WR.

The fiches are a good indication but don't take them as gospel.. (as the above has shown)
There are too many errors for my liking to be able to accurately order engine internals from it.

As far as igntition curves go, the fact of a larger displacement, carb, flywheel weight (426 got a lighter crank/flywheel) etc all come into play.
A 99 with a 426 kit and ignition will perform differently to a stock 426 setup.
The vortex ignitions are also different for a 400 and 426.
The main difference is the ignition timing/mapping between the 2.. the 400 has more advance than the 426.

I'm not trying to say that a 426 upgrade won't work but there are quite a few differences in the piston/crank area before you head back to primary ratios and clutch etc.


------------------
--
**Ride it like you Stole it!**
Matt Porritt
99 YZ400F
Vist the Rubber Chicken Racing Online Shop
Discounts for ThumperTalk members.

  • Brad

Posted July 05, 2000 - 06:21 AM

#8

I spent quite a while going over the parts list. The change between 99 and 2000 in regards to the crank appear to only be with the crank web and the bearing, not the crank pin itself. The 19mm you are referring to is the wrist pin diameter, these part numbers are different between the WR and YZ. The assembly between the WR and YZ is different due to the different rod (bigger small end) on the crank assembly. Rich from the other forum may have the definite answer to this. If I find out more I'll post it here. I'm still pretty excited about this possibility. It seems like a much better option than spending $450 on an aftermarket 420 or 426 kit.


Brad

[This message has been edited by Brad (edited 07-05-2000).]

[This message has been edited by Brad (edited 07-05-2000).]

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Rich_Rohrich

Posted July 05, 2000 - 06:01 PM

#9

We just did the 426 rod for my 444 and the crank pin is the same size. I didn't really pay close attention to see if there were any other differences in the big end, but upgrading the rod on a YZ400 crank is doable. It's just a big crank and doesn't easily fit in standard crank jigs for two-strokes. As for the clutch. I'm pretty hard on the clutch but have had no issues running for 2 years on OEM parts. Running 1 year as a 400, and 1 year as a 417 I changed fibers once in that time more out of anal behaviour than need. Seems like the early YZ/WR clutches have gotten an undeserved bad rap.

I might go to a Hinson setup on the new engine only becuase I plan on pushing it REALLY hard to make horsepower.

Rich Rohrich

  • Mitch_from_Oz

Posted July 05, 2000 - 06:20 PM

#10

Hey Rich,

After I installed the DSP Airbox with velocity stack I do not see the need for extra power. I am putting out about 50HP right now and dont need anymore. Afterall, you cant finish the race if your engine grenades.. :)

Mitch

  • Matt_Porritt

Posted July 05, 2000 - 06:39 PM

#11

Originally posted by Brad:
The change between 99 and 2000 in regards to the crank appear to only be with the crank web and the bearing, not the crank pin itself. The 19mm you are referring to is the wrist pin diameter, these part numbers are different between the WR and YZ.


Bugga.. typed wrong numbers.. yes 19 is the wristpin.. I'll have to find the bottom end spec again.
My point is then reinforced.. the pin is the same for the 99 and 00 WR and so is the rod.. therefore the WR didn't get the large pin.
According to the list, the 98&99 YZ have the same pin and rod as the 98,99,00 WR.

------------------
--
**Ride it like you Stole it!**
Matt Porritt
99 YZ400F
Vist the Rubber Chicken Racing Online Shop
Discounts for ThumperTalk members.

  • MotoGreg

Posted July 05, 2000 - 08:12 PM

#12

My point is then reinforced.. the pin is the same for the 99 and 00 WR and so is the rod.. therefore the WR didn't get the large pin.
According to the list, the 98&99 YZ have the same pin and rod as the 98,99,00 WR


Of course they do. The '98-'99 yz and the '98-'00 wr are all 400cc. Only the '00 yz426 is a 426 so only it has the new rod with bigger small end for the bigger wrist pin. Is there something I'm missing here??

------------------
'99 WR400
'92 GSXR 7/11
Visit my photo album AT YOUR OWN RISK!! My photo album
Anyone here a sportbike fan also? Then visit us here at www.insanespeed.com

  • Matt_Porritt

Posted July 05, 2000 - 09:31 PM

#13

Originally posted by MotoGreg:
Of course they do. The '98-'99 yz and the '98-'00 wr are all 400cc. Only the '00 yz426 is a 426 so only it has the new rod with bigger small end for the bigger wrist pin. Is there something I'm missing here??


We're talking about bottom end pins! :)
The fiche says that all the pins in all WR/YX 98-00 are the same.. which they're not as the 426 is 1mm larger.
All rods except 426 are the same.
A straight purchase and fitment of 426 parts mentioned in the 1st post in this thread will not work due to the bottom end pin on all YZ/WRs 98-99 and including the 00WR.
This was confirmed with my local dealer when I gave him the list of parts to price.

It can be done.. just a little machining of the webs to fit the larger pin.


------------------
--
**Ride it like you Stole it!**
Matt Porritt
99 YZ400F
Vist the Rubber Chicken Racing Online Shop
Discounts for ThumperTalk members.

  • Rich_Rohrich

Posted July 06, 2000 - 06:02 AM

#14

I guess I should probably clarify some.
On the US spec YZ426 rod kit, no machining is needed to fit the bigend pin to the US spec 98 YZ crank. The difference in the rod's dimensions are limited to the 1mm increase in the small end to accomodate the bigger 426 wrist pin. I'm not sure if this info holds true for the Euro, or Aussie spec bikes though.
It's standard crank build up but it takes a fairly specific jig setup to do it right. I didn't have the capability to do it, so I had Jim Nupert do the work because he uses the RCE crank tool, and he has the adapter to handle the YZ crank correctly. Be careful who you have do the crank, it's fairly tough to do right.

For those who want to try the upcoming Wiseco 97mm (444cc) kit on their YZ400 or WR400 you'll need to use the 426 barrel (bored and plated to 97mm) and the 426 rod as well. Wiseco will only be making these pistons for the 426 rod. They have dicontinued the 97mm pistons to fit the YZ400 (18mm wrist pin) rod. The new 97mm pistons are scheduled to start shipping in August .

For anyone who is interested
Jim Neupert - 2-Fast Racing
twofastracing@yahoo.com
1701 S.Stoughton Rd.
Madison, WI 53716
( 608 )345-5278


------------------
Rich Rohrich
==

If you're not sliding you aren't going fast enough.

- Kenny Roberts

  • Rich_Rohrich

Posted July 06, 2000 - 06:06 AM

#15

Mitch - I'm just interested in seeing what the engine is capable of. I'll actually be running it at lower rpm than I would be with a 92mm bore. If my math is accurate I believe the combination I'm working on will be just as reliable as the stocker, just more interesting. Frankly if I did a skill/hp need ratio, my TTR125 makes more power than I'll ever need =)

Rich Rohrich

  • Matt_Porritt

Posted July 06, 2000 - 06:10 PM

#16

Originally posted by Rich Rohrich:
I guess I should probably clarify some.
On the US spec YZ426 rod kit, no machining is needed to fit the bigend pin to the US spec 98 YZ crank. The difference in the rod's dimensions are limited to the 1mm increase in the small end to accomodate the bigger 426 wrist pin. I'm not sure if this info holds true for the Euro, or Aussie spec bikes though.


Hmmm.. now I'm confused!!
Why would they make different crank webs and pins for US and 'Others'??
Are you saying in 100% certainty Rich, that the US Yamahas use the same size crankpin from 98-00 including the 426?
Hopefully! As I may find a rebuild coming up REAl soon! :)

Here is it.. MXA Sept 99:
4:Connecting Rod
While the stroke is unchanged, Yamaha beefed up the width of the rod at the bottom end and increased the size of the rods top end to accomodate the large wrist pin.
-This to me sounds like its the same size but wider (uses thinner thrust washers??)

Australiasian Dirt Bike Jan 2000
Connecting rod wristpin is 1mm bigger in diameter for increased strenth. Bottom end is 1mm bigger for incresed strength (diameter or width??)

BUT in April-May 2000 Sidetrack
The gudgeon has gained a millimeter in diameter so naturally the conrod has a bigger hole- except it has a bigger ne at both ends.

I've always thought it got a 1mm bigger pin.. but from all the differnces between the above tests it could be a:
-bigger pin and conrod hole
-same pin with bigger conrod hole and a larger(thicker bearing)
-same diameter bottom end with a wider rod

There was a mag that has ALL the MX bike with ALL the differences between the 99s and 00s in a table under a pic of each bike.. but I can't find it.

I thought the problem with the early bigbore was the bottom ends faling and head gaskets blowing.. whats been changes to prevent this in the new kits and with the 426??


------------------
--
**Ride it like you Stole it!**
Matt Porritt
99 YZ400F
Vist the Rubber Chicken Racing Online Shop
Discounts for ThumperTalk members.

  • Rich_Rohrich

Posted July 06, 2000 - 07:06 PM

#17

Yes I'm 100% sure. The big end is the same diameter at the crank journal press point and the small end diameter is 1mm larger, with a 1mm larger pin. The rod IS the bearing surface on this engine, there is no seperate bearing like a two-stroke. I didn't remember to measure the actual bearing surface on the big end , but whether they changed it or not it will still fit the US crank halves.


Keep in mind the magazines guys are the same lunkheads who tried to convince us Yamaha retarded the exhaust cam timing on the US WR400 and added 23 degrees to the overlap. :)

My my plated 420 has been stone reliable, as have all the kits Eric Gorr has done. I've heard there were some problems with some of the sleeved 94mm engines, but that probably has more to do with the installer than sleeves in general.

The 426 barrel is reinforced in a number of areas. Eric did some BIG test barrels for Yamaha on the original 400 barrel, and when i saw them I just shook my head and reached for the bucket of Hard Block. The 426 barrel is really a nice piece.

Rich Rohrich



[This message has been edited by Rich Rohrich (edited 07-06-2000).]




 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.