question about my new valve guide

[DEmily]

Hey all,

Just got my valve guide in. As some of you may recall I had oil running out my exhaust pipe. We determinied it was a valve guide. The valve guide number they sent my is 1j7-11134-10-00. Can anyone with the original microfische tell me if this is the original sized guide? Does Yamaha produce oversized valve guides? Just looking at it it seems a bit larger than the original. I have had my share of issues with this bike and wanted to double check.

Thanks

Dan

[Ken Talbot]

The number looks right:

The description field describes it as a first oversize exhaust valve guide. Do you have a way to check the inner diameter of the guiude to compare it to the outer diameter of your valve stem? You could then verify it the clearance will be what is should.

[DEmily]

Ken,

I noticed the fische shows ( 1st O/S) next to the number. Could it be they only sell the 1st over sized?

[DEmily]

Sorry Ken,

I did not read the bottom part of your message. I will have to barrow a digital mic and check them.

Thanks

[DEmily]

So an oversized valve guide would be oversized inside diameter or outside diameter?

[Ken Talbot]

I'm not quite sure how that would work, and the service manual doesn't seem to explain this in much detail. Here are a few paragraphs that might help make some sense of it all:

C. Valve, valve guide and valve seat
1. Valve stem wear must be measured and then combined with valve guide measurements to guide clearance. This clearance must be within tolerances. If it exceds the maximum limit, then replace either or both valve and guide, as necessary.

(It then lists valve stem clearance for intake as 0.020mm to 0.041mm and exhaust as 0.035mm - 0.059mm. It also lists maximum clearance as 0.10mm for intake and 0.12mm for exhaust)

<snip>

4. Valve guide and valve oil seal replacement
If oil leaks into the cylinder through a valve due to a worn guide, or if a valve is replaced, the valve guide should also be replaced.
Note: The valve oil seal should be replaced whenever a valve is removed or replaced.

a. Measure valve guide inside diameter with a small bore gauge. If it exceeds the limit, replace it with an oversize valve guide.

[Guide diameter (I.D.):
Limit: 7.10 mm (0.280 in)

b. To ease guide removal and reinstallation, and to maintain the correct interference fit, heat the head to 100 degrees C (212 degrees F). Use an oven to avoid any possibility of head warpage due to eneven heating.

c. Use the appropriate shouldered punch (special tool) to drive the old guide out and drive the new guide in.

Note:
When a valve guide is replaced, the o-ring should also be replaced.

d. After installing the valve guide, use the 7mm reamer (special tool) to obtain the proper valve guide to valve stem clearance.

[DEmily]

Well, I have checked the old valve guide and the new valvel guide and here is what I got.

Old guide: 12.55 MM (.4940 in)
New guide: 12.58 MM (.4955 in)

It appears the 1st oversized refers to the ourside diameter.

Now heres my problem. So far non of the machine shops around here will touch it. They would if it were a Harley. The bike shops are not so sure they want to mess with it because of it's age. I can't believe they are making such a big deal abou it. It is just a matter of boring the hole to new specs. Why should it matter that it is a 25 year old bike? What now?

[Ken Talbot]

Are you able to measure the inner diameter of the new guide to compare it to the outer diameter of the valve? This is where you want to ideally have anywhere from .035mm to .059mm, with a maximum of .010mm

[DEmily]

Ken, '
The vaiance between the new valve stem and the id of the guide is .037. It fact the new and the old valve guide are almost the exact same size on the ID.

[Ken Talbot]

IMHO, .037mm is within the specified range, even if it is towards the tighter end of the range. As long as the valve stem is not a bit thicker at another part, and assuming that the id of the valve guide should not vary much, I would be inclined to put it back together as is. Do you think there would be any chance of you borrowing a 7mm reamer from an independent shop and doing that part yourself? I wonder if this may be one of those specialty tools that might even cost less than the "half hour minimum shop time" equivalent....

[DEmily]

I am not sure I would be comfortable trying to make such a small increase on the head. The variance between the od of the old valve guide and the new valve guide is .03mm. Thats not much. Infact it is less than the thickness of a peice of notebook paper. Cut it to much and the valve guide would be loss in the head.

[Ken Talbot]

No, you would leave the OD alone. You rely on the interference fit of the cold guide into a warmed up head to get it in, then it locks in when everything goes to one temperature.

[Geezer]

Originally posted by Ken Talbot
No, you would leave the OD alone. You rely on the interference fit of the cold guide into a warmed up head to get it in, then it locks in when everything goes to one temperature.

I concure. The oversized guide it to restore lost material from a forced removal of the guide.

Put it back in the same way you go the old one out. There is a possibility that the inside hole will have to be reamed to size but that is normal even with a standard size guide. Make sure that new guide is really frozen not just cold and it’ll drop into the hot head pretty as you please.

Geezer

[DEmily]

OK, I just finished putting the valve guide in. I heated the head for an hour and half at 400 deg. I frooze the guide for two days in my deep freeze and than 3 hours in dry ice. It did not just drop in like the originals. I tapped it in about 2/3s way and it began to sound like I was hitting solid aluminuim. Of course I began to SH@#.

Using a 3/8 in, cooper water pipe I started tapping it even harder. I was at the point that I was concerned I was going to break off the flang on the guide. It got about an 1/8 of an inch from the bottom and once again it began to sound like I was hitting solid aluminum. I tapped even herder and the sound changed and the guide began to move again until it bottomed out and the sound of solid aluminum was back again. It is in!!!!

I think I took 5 years off my life with those few seconds, but it is in. I will continue the assembly in the morning. Why was it so hard to drive it in? I kind of thought that the old guide may have been that size before it wwas dropped in to the head and it compressed a bit, so that is why I decided to go with it. Well, at least it's in and hopefully by the close of the day SAT. I will be able to let you all know how it turned out.

I'll tell you this, with the tightness of this valvle guide, if I ever have to take it out I may have a problem. Well, I probably won't have to deal with that. The old girl will probably out last me.

[Geezer]

That sounds like the first time I changed guides. Way to go it's in and now you can get it back together in time for all the good riding weather.

Geezer