Valve guide O,D,

[Guest]

Ok so here's the story I broke off the end of one of my exhaust guides pulling off my oil seals, so I ordered one from Boulevard Suzuki. After 3 weeks it finally arrived; it measures .4874"- .013" larger on the O.D. than my stock guide! I called Boulevard, the numbers are correct, his solution is for me to put it in the freezer first, obviously he knows nothing about fits. No way that's going in that hole. My question is this my: stock guide od was .4748" is that what I should make the replacement to or should I make it to .475" I see that after market sells a .0002" larger guide. The hole in the head measures at .4745". What is the correct fit/ interference in the head supposed to be? Thanks for your help it's been a long haul to get this bitch on the road again. Oh yea 1980 GS1000G

[GregT]

Make it to .475.

I assume you're doing it in cast iron ? I usually ream to finished size in the lathe before installing - then hand ream to finished size again once installed. Usually there's only about 2 -3 tenths of a thou to take out.
Make yourself a brass driver which bears on a shoulder of the guide to install. Heat the head to around 200 - 250 deg C and put the guide in a glass with ice in your freezer.

The valve seat wll need recutting too.

Edit - if the replacement guide is satisfactory in everything except OD, put it between centers in the lathe to reduce the OD. I assumed perhaps wrongly, you were making another from scratch.

[WShie]

Thanks, Ill turn it to .475.

[Nessism]

Suzuki's service replacement valve guides are oversize because they are afraid of the hole becoming oversize after they are removed, then the guide subsequently falling out. Suzuki sells the appropriate reamer, or at least they used to. I suppose you could turn the guides down, or just get the reamer.

[WShie]

That's good to know. My concern is getting the correct interference between the guide and the hole it fits into. Suzuki in their shop manual says to ream to 12.2 mm which is .4803". I figured that the new guide would be to fit this size hole and as such could measure and determine the correct fit. Alas that is not the case as the replacement guide measures .4874, still .007 over the reamed size. I can make the guide any size I want so the real question is How much interference is needed in the head? My guess is somewhere between .0002" and .0003" using a rule of thumb of .001 per inch of od. Don't want to end up with a guide that loosens as the motor warms up, but don't want to smash the snot out of it trying to force it in the head. Thanks.