yz426f help blown engine


62 replies to this topic
  • bakeyz426f

Posted August 12, 2009 - 06:54 PM

#41

do i need the inch/pound torque wrench? in the manual the cam caps say 7.2 ft/lbs of torque

  • bakeyz426f

Posted August 13, 2009 - 01:40 AM

#42

aslo do i need the beam torque wrench to get torques under 5 ft/lbs?

  • matt4x4

Posted August 13, 2009 - 03:39 AM

#43

Although it's a good idea to replace the cam chain, the motor has never been prone to the chain stretching - it's just always recommended to replace it since it is cheap insurance against otherwise costly repairs (for all makes). Maybe too many people have recommended to replace the cam chain and it's turned into an urban myth that the motor supposedly has issues...

Hotrod cranks should be available most places for 230 to 270 - just order the one for your year/model bike.

Kibblewhite valves do NOT create any more resistance on the cams than any other SS valve - and yes - going the stock route is way cheaper over kibblewhites. I like to use things that don't let me down though - and kibblewhites are pretty bullet proof (they even keep hondas running well beyond the holeshot corner) - but then again - stock Yamaha SS valves are pretty tough too.
You might as well get Millenium to install your valves, they will cut your seats properly and make sure the valves all seal good and everything is good with the head - they aren't going to soak you for the valves or install either it might be another 30-60 minutes labor plus the cost of the parts which you would incur anyways - if you do want to go with SS valves make sure you let them know before hand.

  • bakeyz426f

Posted August 13, 2009 - 07:36 AM

#44

i tought the valves where titanium in a 02 426? is there a ratcheting torque wrench that can get the torques 0-5 ft/lb or can beam types only get those torques?

  • grayracer513

Posted August 13, 2009 - 08:06 AM

#45

Although it's a good idea to replace the cam chain, the motor has never been prone to the chain stretching - it's just always recommended to replace it since it is cheap insurance against otherwise costly repairs (for all makes). Maybe too many people have recommended to replace the cam chain and it's turned into an urban myth that the motor supposedly has issues...

What has happened is first that too many people never replaced them (they are oddly left off the list of maintenance items in the manual), which allowed some of the older ones to get worn really long and damage the crank sprocket, and/or slip time and destroy an entire engine in an engine that just about nothing else ever goes wrong with. The second thing is that from the '06 on up, and most commonly with the '08's, it seems, there has been an increase in the number of cam chains that develop binding links, start kinking up, and lead to the engine jumping time, all at fairly low hours. Whether this is an problem with the chains used in those engines, the oils used by some owners, or a combination, is unclear. Either way, when it happens 3 times, it's an epidemic. You know how that works.


Kibblewhite valves do NOT create any more resistance on the cams than any other SS valve - ...

True, of course, but SS valves do require heavier springs because of their greater weight, and that adds load to the entire valve train, including the chain. It isn't enough to cause any service problems, however, so it's a red herring anyway.

  • matt4x4

Posted August 13, 2009 - 08:23 AM

#46

i tought the valves where titanium in a 02 426? is there a ratcheting torque wrench that can get the torques 0-5 ft/lb or can beam types only get those torques?


Yes, the 02 has Ti Valves, but you can change to SS if you prefer.

If you buy a good 1/4" torque wrench, they usually go in inch/lb increments and are accurate from about 30-40 in/lb onwards - usually - you don't need lower torque settings on a bike, 12in/lb = 1 ft/lb.

  • mxmaddman

Posted August 13, 2009 - 01:24 PM

#47

Although it's a good idea to replace the cam chain, the motor has never been prone to the chain stretching - it's just always recommended to replace it since it is cheap insurance against otherwise costly repairs (for all makes). Maybe too many people have recommended to replace the cam chain and it's turned into an urban myth that the motor supposedly has issues...

Hotrod cranks should be available most places for 230 to 270 - just order the one for your year/model bike.

Kibblewhite valves do NOT create any more resistance on the cams than any other SS valve - and yes - going the stock route is way cheaper over kibblewhites. I like to use things that don't let me down though - and kibblewhites are pretty bullet proof (they even keep hondas running well beyond the holeshot corner) - but then again - stock Yamaha SS valves are pretty tough too.
You might as well get Millenium to install your valves, they will cut your seats properly and make sure the valves all seal good and everything is good with the head - they aren't going to soak you for the valves or install either it might be another 30-60 minutes labor plus the cost of the parts which you would incur anyways - if you do want to go with SS valves make sure you let them know before hand.


my guess is 90% of yzf failures are caused by the cam chains. I would say thats fairly a close estimate. Every yzxxxf I had rebuilt that was blown up, was from the chain jumping. I have an 07 apart right now that the chain is so stiff i can hold it straight out. Thats a problem. Why you would want to add more unneeded tension to the chain and higher seat pressures to the valve seats is beyond me especialy when the stock ti valves last a very long time in yamis and they are cheaper.

  • grayracer513

Posted August 13, 2009 - 01:59 PM

#48

... the stock ti valves last a very long time in yamis and they are cheaper.

They do last a long time, at least as long as KW's, but they are not cheaper. At least not very much. The set is around $400 plus $40 or so for new springs. The KW's are about $200 for the valves and another $240 for the spring kit, so it's about the same, really.

In earlier 426/400 engines, however, it's a much situation, and the OEM springs and valves for a 2000 426 will fit everything from '02 back for a third the cost.

I also think that the concern over SS valves leading to early cam chain problems are poorly founded. history doesn't support it.

  • bakeyz426f

Posted August 13, 2009 - 02:02 PM

#49

do they make a yz426f hot rod crank still? couldnt find one. do oem last longer than hot rod. the price sounds nice 250 instead of 450 oem but i dont want to buy something that has lesser quality and doesnt hold up

  • RPB

Posted August 13, 2009 - 03:11 PM

#50

If it hasn't already been said, as someone who has rebuilt a 02 YZ250f and is in the process of rebuilding a 00 YZ426, I recommend using all OEM parts. Especially the valves and valve springs. You should be able to get all the parts you need from the thumpertalk store. The only thing I would replace would be the exhaust cam with an OEM 03 YZ450F cam. There is really no need for hot cams or any of those other 'performance upgrades' for a 426.

Here is alittle pic of what I am dealing with. Virtually the entire engine, top and bottom end, trans, clutch basket, everything has some sort of damage done to it. There are parts that are completely missing or only partially there. Alot of damage.

Posted Image

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted August 13, 2009 - 03:30 PM

#51

... The only thing I would replace would be the exhaust cam with an OEM 03 YZ450F cam. There is really no need for hot cams ... for a 426.

I'll differ with you on this point. At one time, when the Hot Cams product was priced $40 higher than the OEM 450 cam, and they were having problems getting the decomp pins right, I would not have, but things have changed.

The Hot Cams product has improved, and Yamaha has raised its prices. The stage one Hot Cams exhaust cam is functionally identical to the gring of an '04 YZ450 cam, and offers the following advantages:

  • Lower cost
  • The chain fits the sprocket correctly
  • Timing marks are made for the 426, so it requires no special timing procedure.


  • bakeyz426f

Posted August 13, 2009 - 04:01 PM

#52

will it cost over 500 bucks to have millenium repair my head and put valves in

  • USED YZ426F

Posted August 13, 2009 - 04:05 PM

#53

will it cost over 500 bucks to have millenium repair my head and put valves in


Only way to know that is to contact them and see. No one here will be able to tell you how much they will charge.

  • mxmaddman

Posted August 13, 2009 - 04:27 PM

#54

I cant locate my 426 parts prices because i haven't priced any in ages, but I get 250/450 valve kits for $300-325 off ebay from central Florida powersports. Its a heck of a deal it comes with every piece needed. springs, keepers, locks, retainers and seals. It might be a good idea to ask the power sellers for and estimate on the OE parts.

  • bakeyz426f

Posted August 13, 2009 - 04:29 PM

#55

anybody ever had there crank repaired by mr crankshaft?

  • mxmaddman

Posted August 13, 2009 - 04:43 PM

#56

anybody ever had there crank repaired by mr crankshaft?


No, but i have used crank works and was happy. I have a local shop here who's real good at truing the cranks I send him as well.

  • bakeyz426f

Posted August 13, 2009 - 06:03 PM

#57

i think hot rod and wiesco stopped making yz426f cranks

  • bakeyz426f

Posted August 13, 2009 - 08:19 PM

#58

can i use oem valves on my head when its repaired? i fond some for 330 bucks is that a good price for titanium valves and springs?

  • USED YZ426F

Posted August 14, 2009 - 04:44 AM

#59

If you want, you can get OEM stainless steel valves and springs for a 2000 YZ426 and use them. You have to use the springs and valves for a 2000 YZ426 though, but you should be able to save some $$ going that route.

  • grayracer513

Posted August 14, 2009 - 06:36 AM

#60

can i use oem valves on my head when its repaired? i fond some for 330 bucks is that a good price for titanium valves and springs?

Yes, and yes.





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