Freshening an 01 YZ426F Engine. Suggestions?


23 replies to this topic
  • SCORPiON5150

Posted December 13, 2007 - 06:53 AM

#1

Planning on doing a little "freshening" of my 426 engine. I estimate I have put probably way OVER 200 hours on my bike. I have never had any sorts of problems or abnormal noises or anything, lots of compression still, and I have kept up on my basic engine maintenence (valve adjustments, oil changes, clean filters, etc) religiously since the bike was almost new. I am simply planning on doing this for peace of mind, rather than to correct any specific issues. I was planning on a piston & rings, cam chain, and possibly valve springs. Anything I am leaving out that should be addressed? Anything I am planning on replacing that is probably not necessary? The bike has been so stinkin' reliable for me I just wanna make sure she stays that way!

  • grayracer513

Posted December 13, 2007 - 07:15 AM

#2

Valve guide seals, of course. Don't, whatever you do, lap the valves. That little bit of service advice is left over from the stainless steel days.

  • rein

Posted December 13, 2007 - 07:29 AM

#3

valves,springs,cams get the 03 cam if you can i hear thats makes a HUGE difference have the valve seats on your head recut and you should be good to go.

  • tnl

Posted December 13, 2007 - 12:12 PM

#4

Don't, whatever you do, lap the valves.


What's that mean?

  • SCORPiON5150

Posted December 13, 2007 - 12:23 PM

#5

Valve guide seals, of course. Don't, whatever you do, lap the valves. That little bit of service advice is left over from the stainless steel days.


Good advice, the valve guide seals slipped my mind completely. I'll add those to the list for sure.

valves,springs,cams get the 03 cam if you can i hear thats makes a HUGE difference have the valve seats on your head recut and you should be good to go.


I was considering dropping in a pair of hotcams at the same time. I honestly don't mind the stock 426 "starting drill" at all, as the bike will almost ALWAYS start with 1 kick hot or cold. However, I was considering the hotcams for their power characteristics anyway, so why not upgrade to auto decomp. at the same time, eh?

Aside from the valve guide seals which I will be replacing, would anyone consider it an ignorant move to leave the valve assembly alone, other than doing a quick dissassembly and visual inspection? I have no hesitation whatsoever dropping the $ into my bike but I don't wanna go overboard or anything either. Reason I am even asking is I have read tons about how nearly bulletproof our yamaha valve setups are. Along with that, my valve clearances have not changed basically at all since the first 3 valve adjustments. I have checked the valves religiously and I haven't needed to swap out a shim for the last 100 or more hours, which to me is really saying something for the reliability yamaha has. However, I don't want to be asking for trouble either. My 426 has kept me very happy over the years so I wanna do the same for her!

  • rein

Posted December 13, 2007 - 01:04 PM

#6

Well I have been down bout 2 monthes yz250f 03 due to a bent valve and broken teeth on crank total nightmare. My girlfriend was happy. I dumped about 1700 into the top & bottom so if you are going to refresh it you might as well do it right before it costs you a boat load. check this site out http://www.mxtime.co...eat Cutting.htm but then again mabye you will be ok with just doing what you said...how often do you do oil changes?

  • grayracer513

Posted December 13, 2007 - 01:54 PM

#7

What's that mean?

Lapping is the process of wear matching two parts with each other by applying an abrasive paste to the wear surface and rubbing them together. In the case of valves, the paste is applied to the seat, the valve placed in the guide, and rotated against the seat. The problem in the case of Ti valves is that this runs the risk of damage to the hard coating on the valve, and for that reason, caoted Ti valvbes should never be lapped.

Should you do the valves at all? Read posts 11, 15, and 18:

http://www.thumperta...321#post5611321

426 owners have the option of using the SS valves, springs, retainers, and keepers (cotters) from the 2000 model as a way to save money big time on a head rebuild.

  • 642MX

Posted December 13, 2007 - 04:41 PM

#8

Planning on doing a little "freshening" of my 426 engine. I estimate I have put probably way OVER 200 hours on my bike. I have never had any sorts of problems or abnormal noises or anything, lots of compression still, and I have kept up on my basic engine maintenence (valve adjustments, oil changes, clean filters, etc) religiously since the bike was almost new. I am simply planning on doing this for peace of mind, rather than to correct any specific issues. I was planning on a piston & rings, cam chain, and possibly valve springs. Anything I am leaving out that should be addressed? Anything I am planning on replacing that is probably not necessary? The bike has been so stinkin' reliable for me I just wanna make sure she stays that way!


For a yearly rebuild I do the following: Replace the rings, cam chain, valve springs, valve seals, and spark plug.

Every other year I replace the piston.

I have also replaced the valves once (2 years ago). They where far from shot, but I felt guilty about not replacing them.

This year, I'm replacing the whole lower end. I just ordered my crank, main bearings, and all the tranny bearings today. I also am doing the yearly maintenance too.

Do I replace too many parts? Probably, but I don't want it to lock up and end a riding trip. Sometimes I drive 3-5 hours to go riding and failure is not an option.

On a side note, I just replaced the whole lower end, valves, tranny bearings, shift forks and installed a 290cc kit in my wifes bike. I was surprised to find the big end bearing on the crank was loose and all the tranny bearings where shot. I'm not sure how long the motor would have ran without blowing up and I'm glad I did the rebuild.

  • SCORPiON5150

Posted December 13, 2007 - 05:50 PM

#9

Should you do the valves at all? Read posts 11, 15, and 18:

http://www.thumperta...321#post5611321


Thanks alot grayracer, your tips and knowledge have been very helpfull to me here on the board. I haven't posted much until recently, but I have been lurking here for quite a few years now. You have been a great help to all our fellow yz riders!

  • SCORPiON5150

Posted December 13, 2007 - 06:03 PM

#10

Do I replace too many parts? Probably, but I don't want it to lock up and end a riding trip. Sometimes I drive 3-5 hours to go riding and failure is not an option.

On a side note, I just replaced the whole lower end, valves, tranny bearings, shift forks and installed a 290cc kit in my wifes bike. I was surprised to find the big end bearing on the crank was loose and all the tranny bearings where shot. I'm not sure how long the motor would have ran without blowing up and I'm glad I did the rebuild.


I work as an automotive tech and am all about PREVENTIVE MAINTENENCE. Something most never even consider. To me, failure is not an option as well (far as my engine goes!). I am just not nearly as familiar with 4 strokes as I am with 2 stroke or automotive - so I turn to TT. You all have been a great help and my YZ and I thank you all for the advice!

I am going to plan on inspecting the valves very closely, and go from there but sounds like I will be doing a replacement with the number of hours I am pushing.

Any negative side to using the SS 426 valves instead of my 01 Ti? How do they wear in comparison? I'd never count on this with any bike but I'd love to be able to get a couple more hundred hours out of the next set. By that time I will likely be eyeing new fuel injected bikes which I have been sorta holding out for...

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • 642MX

Posted December 13, 2007 - 06:30 PM

#11

I work as an automotive tech and am all about PREVENTIVE MAINTENENCE. Something most never even consider. To me, failure is not an option as well (far as my engine goes!). I am just not nearly as familiar with 4 strokes as I am with 2 stroke or automotive - so I turn to TT. You all have been a great help and my YZ and I thank you all for the advice!

I am going to plan on inspecting the valves very closely, and go from there but sounds like I will be doing a replacement with the number of hours I am pushing.

Any negative side to using the SS 426 valves instead of my 01 Ti? How do they wear in comparison? I'd never count on this with any bike but I'd love to be able to get a couple more hundred hours out of the next set. By that time I will likely be eyeing new fuel injected bikes which I have been sorta holding out for...



No negatives with SS. I had a set of Faction SS valves put in my wifes 290. If you choose to go with the 2000 model SS valves, make sure you replace the springs, keepers, and cotters like Grayracer mentioned.

The SS valves should last forever. They are a bit heavier and some may say that the motor could rev slower, but I haven't been able to tell.

If you choose to replace the valves, be sure to have the seats touched up by a machine shop. If you don't, the valves will last 1/2 as long as the originals.

  • grayracer513

Posted December 13, 2007 - 08:18 PM

#12

Any negative side to using the SS 426 valves instead of my 01 Ti? How do they wear in comparison? I'd never count on this with any bike but I'd love to be able to get a couple more hundred hours out of the next set. By that time I will likely be eyeing new fuel injected bikes which I have been sorta holding out for...

Theoretically, yes. From a practical standpoint, none. The '00 YZ426 runs fine with them, and they may be the only thing that lasts longer than Yamaha's OEM Ti valves. If it were my bike, that's what I'd most likely do.

  • GCannon

Posted December 14, 2007 - 11:44 AM

#13

I have a question about valve guides. I understand about checking for wear during the rebuild. Do you replace the guides every time you replace the valves?
If and when you replace the guides do new valves fit well or do you need to ream the guides to fit the new valves.

What is the perfered method of reaming the guides?

  • 642MX

Posted December 14, 2007 - 12:05 PM

#14

I have a question about valve guides. I understand about checking for wear during the rebuild. Do you replace the guides every time you replace the valves?
If and when you replace the guides do new valves fit well or do you need to ream the guides to fit the new valves.

What is the perfered method of reaming the guides?


I've never seen or read about worn YZF valve guides. :banghead:

  • GCannon

Posted December 14, 2007 - 01:36 PM

#15

Really? new valves old guides?

No need for me to stress? This will make things alot eaisier.:banghead:

Thanks! everybody else have the same experience?:busted:

  • grayracer513

Posted December 14, 2007 - 03:22 PM

#16

You can check them for wear by using a dial indicator and checking the lateral movement. Because of the design, there is almost no side loading of the valve stem (unlike engines that use rocker arms of any type), and as a result, there is normally little if any wear.

That they do fit properly is very important, however, so it is worthwhile to check.

  • GCannon

Posted December 14, 2007 - 03:29 PM

#17

Thanks Guy's:worthy: :banghead:

  • Terrain Rider 4z

Posted December 14, 2007 - 11:33 PM

#18

Wow, this thread is just in time. I wrote this spring about issues I was having with my 426 this past March. At the time I thought it was fuel or electrical issues, valves checked out OK, well the story has changed.

I called the mechanic tonight and he found two tuliped intake valves on my 2001 YZ426 with GOBS of hours on it. He said I could go cheap and replace two valves for $411, or fix the bike right by replacing all valves for $738. I hung up and thought about it, then considered the need for a piston and rings along with a cam chain. I called him back and he agreed that a top end was a good idea if I was going to keep the bike.

Next, I got on here and saw you could use 2000 426 stainless valve components and save a ton of $$$$ :banghead: I also want the 03 style cam, now possible with the TT store parts prices. So, I have made a list of parts to buy and was wondering if you could look it over and give me any suggestions.

Here is the list:
Part # Quantity
Cometic Gasket Set 1009120111 1
Exhaust Cam 1095700002 1
Intake Valve 5BE-12111-10-00 1
Intake Valve 5BE-12112-10-00 2
Intake Valve Spring 5BE-12113-00-00 3
Cotter Valve 1WG-12188-00-00 3
Intake Valve Retainer 5BE-12117-00-00 3
Intake Valve Seal 4SV-12119-00-00 3
Valve Seat 3GM-12126-00-00 5
Exhaust Valve 5BE-12121-10-00 2
Exhaust Valve Spring 5GR-12114-00-00 2
Cotter Valve 1AA-12188-00-00 2
Exhaust Valve Retainer 4GY-12117-00-00 2
Exhaust Valve Seal 33M-12119-00-00 2
Cam Chain 94591-50120-00 1
Piston 5NG-11631-10-00 1
Rings 5JG-11603-00-00 1
Wrist Pin 5JG-11633-00-00 1
Circlip 93420-19084-00 2


Total Parts Cost: $485.72

  • rein

Posted December 15, 2007 - 08:20 AM

#19

what brand are the valves your getting?

  • Terrain Rider 4z

Posted December 15, 2007 - 09:40 AM

#20

The Yamaha 2000 YZ426F valves, switching from titanium to stainless.





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