Its that time!!


15 replies to this topic
  • ISBB

Posted June 18, 2007 - 02:18 PM

#1

This post is mainly towards grayracer and those with far more motor knowledge than me. :thumbsup:

My bike is spooging more and more out of the crank case breather... The bike is 4 years old and never given me a lick of worries however i think its gettin time for the dreaded top end rebuild... A few questions for you in particular. I have read numerous debates on high comp + overbore, high comp standard bore and so on and so forth... What is the best setup in your opinion. If im going to tear this apart and do it i want to do it right and get more power out of it (RELIABLY). Getting parts is of no issue for me so im just looking for the best combination.

Bike is a bone stock (engine wise) 02 wr426. Only thing i did to the motor was oil changes and a extended fuel screw. What i was THINKING was High Comp Piston, probably go with new valves springs and associated hardware, i have acquired a 06 YZ Cam with auto decomp which thru a previous post was determined i should be OK as long as i time it correctly. And possibly getting my flywheel ground to give me a little more snap off the bottom.

What are your thoughts and opionons on the high comp stuff?

Will a YZ flywheel fit and still retain the lighting stator or am i better off getting some milled out of mine to make it lighter?

What is a good recomendation on valves that will last. I have had Ti Valves this long so i dont see a problem going with some oem replacements or another brand of the such but are kibble whites all they are made out to be for being stainless? I also plan on getting the head ported while i have it apart and am getting the valve job done will that be a factor in choosing my parts?

Thanks for any tips or help you could provide in advance.

  • TeamScream

Posted June 18, 2007 - 05:54 PM

#2

I have 2 426's now, both of them have high comp big bores.
Both of the engines are beasts now, the best mods you can do to thise engines is up the compression and go with the big bore.
I built both of them myself.

If you go with an after market piston (no choice if you go with the big bore) then DISOBEY the recommended piston to cylinder wall clearance which is roughly .0035" (three and 1/2 thousandths) which is printed on the piston manufacturers box.
Instead do what I did and what Yoshimura does and have the cylinder honed to .0015 (one and 1/2 thousandths) and you will be a MUCH happier guy.

The JE, Wiseco and other pistons actually shrink slightly after a hour or so of use and you will get NOTICEABLE piston slap noise, which is exactly what happened to mine back in 2001 when I did my first big bore.

Both of the engines I have run so strong and are so reliable and silent that is is mind boggling. Both have .0015" clearance.

If you are not going to do a big bore then use an OEM piston and run the clearance that is stated in the manual.

Either way send your cylinder to Millennium plating in Wisconsin WITH your new piston and be VERY CLEAR on how much clearance you want.

New valves, new springs, new seals and a top end set of gaskets from Cometic, you might want to consider getting mild head porting done which is all these heads need while it is apart, that alone really wakes them up.

  • ISBB

Posted June 18, 2007 - 06:16 PM

#3

so when i send the Piston, and Cylinder off to get bored and plated tell them i want .0015 piston clearance after the +2mm over bore?

What about valves what is a good combo for valves? Kibble whites or OEM?

What about the Flywheel? any signifigance by lightening it?

How reliable have your bikes been with the big bore and high comp?

  • ISBB

Posted June 19, 2007 - 01:38 PM

#4

welp waiting to hear from the TT OEM store what replacement hardware for the head will cost me... i hope its cheaper than kibble white cuz that number scared me a lil!!!

  • TeamScream

Posted June 19, 2007 - 08:11 PM

#5

so when i send the Piston, and Cylinder off to get bored and plated tell them i want .0015 piston clearance after the +2mm over bore?

What about valves what is a good combo for valves? Kibble whites or OEM?

What about the Flywheel? any signifigance by lightening it?

How reliable have your bikes been with the big bore and high comp?


Hey ISBB,
Yes I recommend staying with the OEM valves, that is what I have always done,

OEM valves, springs, seals
Wiseco or JE piston (I have used both and both work just fine as long as you follow the .0015 rule)

I have never lightened the flywheel so cannot comment.

HOWEVER alot of the race bikes from back in 01-02 actually removed the counter balancer for quicker revving snappier response, mine are both still in.

Mine have been really reliable so far, that last time I took my #1 bike apart to rebuild it was mainly to bling it up a bunch, everything looked brand new still inside after over 7000 miles.

I have always and continue to use Maxima 0W-30 Fully Synthetic race oil in my bikes from the initial break in to where they are now.

Trust me, port the head instead of spending it on a lightened flywheel, you will be reaaaaaaaaaaally glad you did.

Heres my A-Bike:

Posted Image

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  • mcflzwr450f

Posted June 19, 2007 - 08:36 PM

#6

that bike is sweeeettt....:thumbsup: :thumbsup: :busted:

  • Snakko88

Posted June 20, 2007 - 02:33 AM

#7

Hey ISBB,
Yes I recommend staying with the OEM valves, that is what I have always done,

OEM valves, springs, seals
Wiseco or JE piston (I have used both and both work just fine as long as you follow the .0015 rule)

I have never lightened the flywheel so cannot comment.

HOWEVER alot of the race bikes from back in 01-02 actually removed the counter balancer for quicker revving snappier response, mine are both still in.

Mine have been really reliable so far, that last time I took my #1 bike apart to rebuild it was mainly to bling it up a bunch, everything looked brand new still inside after over 7000 miles.

I have always and continue to use Maxima 0W-30 Fully Synthetic race oil in my bikes from the initial break in to where they are now.

Trust me, port the head instead of spending it on a lightened flywheel, you will be reaaaaaaaaaaally glad you did.

Heres my A-Bike:

Posted Image

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Hey Scream, what is the cylinder attached to your clutch cable near the cylinder base on the pic of the WR 426 ?? .........Steve

  • jbrooks26

Posted June 20, 2007 - 04:18 AM

#8

That is a hydraulic clutch slave cylinder I believe. Postive on the hyd clutch, not so sure about it being a slave.

Josh

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

Posted June 20, 2007 - 09:38 AM

#9

That bike looks freakin AWESOME dude.. you werent kidding with the bling.. I got a quote from the TT OEM store for EVERY little part needed to rebuild the head and its about the same as Kibble White so i think im just going to stick with OEM.. I also talked to Eddie aka Burned and he is going to do the head for me and the cylinder will go off to millenium :thumbsup: I Will probabbly go JE since they are Cast and not forged but im sure either one will be fine plus JE is just a tad cheaper.

I do appreciate all the help you guys have given.. I cant wait to ride this bike when im done... Dune season is gonna rock next year.. :thumbsup: time to start savin a few paychecks...

  • grateece

Posted June 20, 2007 - 01:54 PM

#10

Just have to say that is the best looking yam I've ever seen.

  • TeamScream

Posted June 20, 2007 - 07:25 PM

#11

Just have to say that is the best looking yam I've ever seen.


Hey thank you very much brother, I do appreciate that a bunch.



I Will probabbly go JE since they are Cast and not forged but im sure either one will be fine plus JE is just a tad cheaper.


Negative on that one ISBB, you definitely want a forged piston, I don't think JE even makes a cast piston.

You will want to use the Wiseco style wrist pin (retaining) circlips with ANY piston you use, I had a stock Yamaha circlip break after about 20 hours on one of my builds, scarred the cylinder, piston and required a new bore/plate and hone plus a new piston, AND a total tear down of the bottom end to get the broken bits,

I heard a light knocking and shut it down, tore apart the top end and noticed the wrist pin was displaced, couldn't find the circlip so pulled the bottom end to discover the rest of the little tiny fragments of circlip in the bottom end.

That is a hydraulic clutch slave cylinder I believe. Postive on the hyd clutch, not so sure about it being a slave. Josh


Yes, that is the business end of a Magura Jack clutch.
I love them by the way, but if you get one make sure you order the 9.5mm master cylinder and NOT the (Yamaha version) 10.5mm as the pull will be just as hard as the stock clutch, The 9.5mm (Honda CRF version) makes the pull a whole lot easier than stock, but you have to mix and match parts to make it work...in other words CRF master cylinder, YZF slave.

  • ISBB

Posted June 20, 2007 - 08:02 PM

#12

so would it be safe to say a JE pistion and buy a Wiseco wrist pin and clips? or just get the whole wiseco setup and call it done? there is about a 30-40 dollar diffrence between the 2?

  • TeamScream

Posted June 20, 2007 - 10:41 PM

#13

so would it be safe to say a JE pistion and buy a Wiseco wrist pin and clips? or just get the whole wiseco setup and call it done? there is about a 30-40 dollar diffrence between the 2?


It is 6 to one half dozen the other as far as I am concerned, I have had good luck with both of them running tighter tolerance bores, go with the JE spend the savings on other stuff.

BUT if you want to be trick, get the JE piston, the stock (OE) Wrist Pin which is like 4 grams lighter than the JE or Wiseco and get Wiseco circlips.

However to be brutally honest, the lighter wrist pin is not going to make that much difference unless you bounce the thing off the rev limiter all the time like RC or Bubba., and would really only be worthy of serious consideration if you were balancing the entire engine.

As far as I can remember the JE circlips will be fine, when you buy a piston set from JE you get rings, wrist pin, circlips and piston in the package so to save money just run the stuff that comes with the kit, that will be totally fine.
What you WILL ABSOLUTELY have to do is order a big bore head gasket from Cometic.

Since the bore is bigger, the OE gasket will not work so I would order a base gasket and big bore head gasket from Cometic, you will also need the rubber o-rings that go around the water tube between the cylinder and case, you will also need new copper crush washers for the oil lines between the case and head and you should replace the o-ring for the water pipe that goes from the head to the left radiator.

You will also need a new exhaust header gasket (the copper multi layer one), and you should send your head pipe and that new gasket to Eddie when he ports your head so he can match the exhaust port to the gasket AND head pipe for ultra smooth exhaust flow.

A proper Top End rebuild with a big bore modification should consist of the following parts:


94591-50120-00 - Cam Chain
4KG-1111G-00-00 - valve cover seals (you need 2)
5BE-11193-10-00 - valve cover gasket
3VD-14613-00-00 - GASKET, EXHAUST PIPE
93210-16500-00 - O-RING (water pipe to cylinder head)
33M-12119-00-00 - SEAL, VALVE STEM (exhaust valves) you need 2
4SV-12119-00-00 - SEAL, VALVE STEM (intake valves) you need 3
90430-10188-00 - GASKET (copper, oil line) you need 2
90430-08119-00 - GASKET (copper, oil line) you need 4
93210-19758-00 - O-RING (water pipe between cyl & case) you need 1
C7470 - COMETIC - (I think this is the top end gasket kit for big bore 97mm)
175001 - JE - 13.5:1 Big Bore Piston
5JG-12111-00-00 - VALVE, INTAKE (center intake valve) you need 1
5JG-12112-00-00 - VALVE, INTAKE 2 (outside intakes) you need 2
5JG-12121-00-00 - VALVE, EXHAUST you need 2
5BE-15451-00-00 - GASKET, CRANKCASE COVER 1 (stator cover gasket)

If you are being really smart about the rebuild then you should replace this:

5TA-12210-00-00 - TENSIONER ASSY, CAM CHAIN
4FM-12213-00-00 - GASKET, TENSIONER CASE

If you are going to do the 03 Exhaust Cam mod while it is apart then
:
5TA-12180-00-00 - CAMSHAFT ASSY 2 2003 Exhaust Cam
http://shop.thumpert...p/qmr-03dpb.htm Decomp lever plug.
http://shop.thumpert...p/qmr-03pls.htm New decomp lever plug seal.
This is almost a MUST do to these engines, smartest money I spent I think.
[COLOR="Red"]
And finally make sure your dealer stocks various sizes of valve shims.
New valves means new tolerances generally, it is a real bummer to wait for 3 days while they order these things, however Eddie probably has dozens laying around and he should send you the head back complete (clearances already done) so all you have to do it bolt it (the top end) all back together correctly right?[/COLOR]


I cannot comment on the 2006 Exhaust cam as opposed to the 2003 exhaust cam, the heads are different I think and the cams may be different enough to cause an issue, why re invent the wheel when dozens of people have used the 2003 cam with ZERO issues and fantastic results?

One last thing...and pretty darned important!
Since you have the top end apart, wouldn't it make good smart sense to take the bottom end to a machine shop somewhere and have them mic the small end of the connecting rod to make sure it is still within tolerance, and more importantly still ROUND ??????
This requires a pretty small bore guage so call around before you go riding into the sunset with your bottom half in the back of the truck.
And never trust ANYONE who would measure a hole with a set of calipers and try to tell you if it was round or not.

  • ISBB

Posted June 21, 2007 - 02:20 PM

#14

Damn now thats a list... But i didnt see base gasket in there? or is that part of the Cometic kit?

Thanks for the list bud.. All of my stuff will be purchased thru TT so i dont have to worry about going to the damn dealer.. :thumbsup:

Gray had mentioned that the Exhaust cam should be perfectly fine in the head and the reason for attempting to re-invent the wheel.. It was FREE :thumbsup: a buddy of mine had to have hotcams in his new bike so he gave me his stockers with nothing but breakin time on them.. I have both intake and exhaust but wont use the intake as that was frowned upon unless i have a degree wheel and no hw to use it which i dont.

Why do the oil lines need to be removed? was that the recomendation per yanking the bottom end out and taking it to get it mic'd ? IM assuming they would need to be removed to get the engine out?

  • TeamScream

Posted June 21, 2007 - 10:29 PM

#15

The oil lines that go from the clutch side case to the cylinder head have to be removed, it is the silver colored hard steel line right next to the intake.
Have you torn the top end apart yet on your bike? are you going to leave the bottom end in the frame when you do this work?
If so you should pressure wash the whole engine area first, get all the little tiny pebbles that lodge themselves in the strangest places.

  • ISBB

Posted June 22, 2007 - 09:31 AM

#16

Nothing is apart. I planned on doing it IN frame.. but if its recommended to get the little end on the crank checked out then i will probably yank the whole thing out and just do it on the shop work bench unless i can find a buddy w/ a mic that travels.. I forgot about that little oil line.. my bad..

So when you wanna come to vegas and lend a hand drinkin my beer and supervising lol




 
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