Time to replace valves


11 replies to this topic
  • foreverblue

Posted December 27, 2005 - 05:47 PM

#1

I have a 2001 yz426f with approximately 300 hrs on it. I regularly check the valve clearance and two months ago the clearance dropped to .001 on all the intake valves. I shimmed the valves back to spec and put about 25 hrs on the bike before checking the clearance again. I checked the clearance last night and all the intake valves are back to .001-.002 . I know, I need new valves, now the questions. Can you replace the valves without re-cutting the valve seats? What type of valves do you recommend, OEM or aftermarket. I was contemplating sending the head to Eric Gorr for a complete rebuild but, I plan on selling the bike this spring and hate to put a lot of money into it. This bike has been bullet-proof and I plan on buying a 2006 yz450f this spring. I appreciate any recommendations.

  • BC3

Posted December 27, 2005 - 06:31 PM

#2

If your going to remove the head and go through the hassle of replacing the valves
take an extra couple minutes and have a good three angle seat cut at your local bike shop....or hot rod bike shop....It will make the bike run much better than just throwing
in new valves by themselves...

  • Matty05

Posted December 27, 2005 - 06:52 PM

#3

It is also a good opportune time to get the head ported too!

  • Matty05

Posted December 27, 2005 - 06:53 PM

#4

Sorry, just seen the planning on selling part..............

  • jvann13

Posted December 27, 2005 - 07:29 PM

#5

Yes, you should get the seats re-cut, definitely. If you don't you will mess up the new vales (the new vales will not mate up to the old seats). Go with OEM. You got 300 hours out of them. That is not bad.

  • grayracer513

Posted December 27, 2005 - 07:29 PM

#6

As hard a pill as it is to swallow, the only right way to replace a valve is to recut or grind the seat. Otherwise, it's like putting a new piston and rings in the old, scored up cylinder. The intakes have definitely gone through the hard coating, but you might get by on the existing exhaust valves just to get it ready to sell. The problem is that you can't tell when the hard coat will wear through on those. Could be 2 years, could be the week after you reassemble it. :applause: You can see what a local machine shop will charge to patch it up. Someone in your area is doing the heads for the Yamaha dealer near you.

Whatever, just don't pawn off a pile of trouble on someone else. Do a minimum repair if you have to, but do it right.

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  • foreverblue

Posted December 30, 2005 - 11:36 AM

#7

Thanks for the input, you told me what thought, but I needed a push.Well I tore the bike apart and sent the head to Forward Motion for a complete rebuild. Cylinder checks to spec with bore gage and piston Mic's up good also but it was replaced last year. I did not replace the timing chain last year so I will do it this time. I will let you know how it runs in the end. Thanks for the help.

  • 642MX

Posted December 30, 2005 - 05:25 PM

#8

Thanks for the input, you told me what thought, but I needed a push.Well I tore the bike apart and sent the head to Forward Motion for a complete rebuild. Cylinder checks to spec with bore gage and piston Mic's up good also but it was replaced last year. I did not replace the timing chain last year so I will do it this time. I will let you know how it runs in the end. Thanks for the help.



How much is the head work costing?

  • falshh

Posted December 30, 2005 - 08:01 PM

#9

according to dirt bike magazine you should be able to do the valves about 3 times before the valve seats need to be redone, they did say that if you waited to long to do the valves you would likely have to do the seats.

one interesting point they made was the yamaha 450 can only have the seats done maybe once and sometimes, not even that, I cant remember why I dont think there is much to cut on the yz's but I cant remember for sure,I just know it made me think Its better to install new valves more often and dont worry about the seats.

They also reccomended switching to kibblewhite stainless valves and matching springs and said you would get seven times more life out of the engine before rebuild.

anyway this is just info I am passing on from dirt bike mag.

If you catch the valves before they have hurt the seats you can buy the valve tool and put a new set of valves and springs in yourself at home.

  • JSanfilippo

Posted December 31, 2005 - 02:14 AM

#10

according to dirt bike magazine you should be able to do the valves about 3 times before the valve seats need to be redone, they did say that if you waited to long to do the valves you would likely have to do the seats.

one interesting point they made was the yamaha 450 can only have the seats done maybe once and sometimes, not even that, I cant remember why I dont think there is much to cut on the yz's but I cant remember for sure,I just know it made me think Its better to install new valves more often and dont worry about the seats.

They also reccomended switching to kibblewhite stainless valves and matching springs and said you would get seven times more life out of the engine before rebuild.

anyway this is just info I am passing on from dirt bike mag.

If you catch the valves before they have hurt the seats you can buy the valve tool and put a new set of valves and springs in yourself at home.



Very interesting!!

  • foreverblue

Posted December 31, 2005 - 07:53 AM

#11

The head rebuild cost $545, includes re cutting seats, porting, new seals, retainers, springs, gasket kit and black diamond stainless steel valves. The head was sent to Eric Gorr's Forward Motion.

  • 642MX

Posted December 31, 2005 - 01:22 PM

#12

The head rebuild cost $545, includes re cutting seats, porting, new seals, retainers, springs, gasket kit and black diamond stainless steel valves. The head was sent to Eric Gorr's Forward Motion.



That actually sounds like a deal. Most of that is probably parts isn't it?





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