cracked valve guide????


8 replies to this topic
  • thriller

Posted November 16, 2004 - 05:06 PM

#1

I just bought a project bike. A 98 wr 400. It has a cracked valve guide and I was wondering how you would take it out, and if anybody else had this happen before? :cry: The story I am told is the bike would not kick over and the guy went to jump-start it and it jammed. It bent the valve a bit so I will have to get another. Any input would be great. thanks in advance. :cry:

  • bushy

Posted November 16, 2004 - 06:50 PM

#2

Heat the head up to around 300 degrees, and hammer it out. With all the valves out that is.. :cry:

  • Oasis_Flame

Posted November 16, 2004 - 07:50 PM

#3

Nows is a great time to get the head re-worked, new guides, seals and a valve or two. You do not want to wait until it smokes it's self. A new head is 600.00 bones. Useing a drift punch will remove the old guide, put some new parts in it and have lash adjusted. Pull the old valves and put them in a drill press chuck, spin them, to see if their bent.

  • thriller

Posted November 16, 2004 - 09:15 PM

#4

ok I got the old guide out. Now when I go put the new one in do I just freeze it and heat up the head? :cry:

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  • thriller

Posted January 26, 2005 - 04:10 PM

#5

ok I ended up cracking the 1st valve guide trying to install it. Now I need HELP. I waited for about a month to get another one in. I measured the guide and get 10.06mm or .3960 in inches. I measured the bore and get 10.03mm or .3945 inches.

So I heat the head to 250f and freeze the guide and measure again but get the same measurement on both parts. I don't want to try to put this thing in again and break another one. I know Yamaha has a special tool to tap these things in and was wondering if any of you have seen it and can tell me what it is shaped like? Or does anybody have any tricks as to putting these things in?? PLEASE post any info you might have. thanks in advance.

  • Frostbite

Posted January 26, 2005 - 04:17 PM

#6

ok I ended up cracking the 1st valve guide trying to install it. Now I need HELP. I waited for about a month to get another one in. I measured the guide and get 10.06mm or .3960 in inches. I measured the bore and get 10.03mm or .3945 inches.

So I heat the head to 250f and freeze the guide and measure again but get the same measurement on both parts. I don't want to try to put this thing in again and break another one. I know Yamaha has a special tool to tap these things in and was wondering if any of you have seen it and can tell me what it is shaped like? Or does anybody have any tricks as to putting these things in?? PLEASE post any info you might have. thanks in advance.


You don't have enough difference in temperature. Send me the parts. I can usually push the guides in with my thumb if I leave them outside for an hour. :cry: :cry:

  • thriller

Posted January 26, 2005 - 04:25 PM

#7

I have a small problem with my deep freeze. It does not want to stop working and is very cold. like -20f or -29C. I would think that would be cold enough. Do you heat up the head?

  • Frostbite

Posted January 26, 2005 - 05:29 PM

#8

Yes, definitely heat the head. The guides are an interference fit. When you heat the head, the hole gets bigger. You've gotta be quick because as soon as the guide touches the head it starts to heat up and expand. It's been a while since I installed a guide and I did use a factory tool. They look like punches but with the end machined down to fit perfectly into the guide to hold it aligned and then the larger shoulder of the tool sits against the face of the guide to push it in. You tap it in with a hammer, light taps, not hay-makers.
You could probably make something up with an old valve. I'm assuming you have the old bent one. The shaft of the valve would be the same size as the small end of the special tool, so all you need is a collar to slip over it that will sit against the face of the valve seat.
You may come up with something more sophisticated but maybe simply slipping an old socket onto the valve will work. Find an old socket (maybe a deep would be better to keep you out of the port)a bit bigger than the face of the guide. Maybe a 1/4 drive and drill out the square drive end so the valve shaft slides through. If you slip it over the end of the valve the open end should seat up against the back of the valve face. Slip the guide on after the socket, line the guide up with the hole in the head and tap on the face of the valve which should transfer through the socket to the guide and seat it in place.
You should probably use a metal collar instead of a socket.Cold sockets can break easily. An old mechanics trick to replace worn Snap on sockets was to freeze them and then put a bolt in a vice and wrench on it until the socket cracked. Snap on will replace any broken tool but not worn out tools, and if they see that you crushed a socket in a vice you're not getting a new one. The cold break trick works.
The best solution would be to buy the tool. The second best solution would be to use a metal collar instead of a socket, but if it was me all I'd have here would be the old valve and a socket so that's what I'd use. :cry:
If you are going to do this you have to freeze you home made tool along with the guide. Put the tool and guide together and toss it into your Arctic freezer and let everything freeze and shrink together. That way the tool will help the guide stay cold longer. Heat the head and when you are ready tap it in quickly and with confidence. If it takes more than 30 seconds I'd start completely over with the heating and freezing since you interference clearance will be gone. Good luck! :cry:

  • Gadsen

Posted January 26, 2005 - 06:54 PM

#9

Bent valves will usually crack the guide in the port area. I have never done this to a bike, but at work, we drive the guides out from the spring end, instead of the other way. This prevents the tight fit you get fromt he carbon build up and in your case, the bent/broken guide. Toyota guides have a snap ring groove in the guide wheich determines depth. We just hit the guide sideways with a hammer, it breaks right at this ring, the ring falls off and I have a bit for my air hammer made just for driving in/out guide and push it right out. We drive the new ones in from the top. Many guides are designed so they dont need to be fitted. Not sure about the Yammie ones.




 
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