GS850 Valve Guides

[Guest]

I intend on replacing the valve stem seals on my '80 GS850 (after all, they are 30 years old), as I've noted a few puffs of smoke after riding downhill. While I was poking around on parts fiches, I noticed that the valve guides themselves had o-rings on them. I assume that these o-rings would also require replacing.

Somewhere, I read that if the valve guides are removed from the head, they have to be replaced with new ones. For the life of me, I cannot re-find that reference. I did a search on GSR, but couldn't find anything like that.

My question is, then, do the guides actually require replacement, or can they just be supplied with new o-rings?

As the base gasket will require replacing, once the head is loosened (again, 30-year old disposable parts), I'll also get the jugs honed and new rings, and get the head itself cleaned up and valves lapped, etc. All the machine-type work will be done by a local specialist. I hoping that I don't encounter out-of-round or scored cylinders, warped head, cracked head, or any other unscheduled issues.

Everything I want to do is textbook stuff, except for this question about guides.....input welcome.

[Nessism]

The guides do not have an O-ring, they do have a metal ring though but you don't need to worry about them unless the guides are worn and need to be replaced. And speaking about wear, it's best to measure the various parts before assuming too much. Cylinders, valves, valve guides, head/cylinder flatness, etc, are all easily measured by a machine shop. Once you have the information you can make an informed decision about what needs to be done.

[hampshirehog]

No O ring on the guide - the valve stem oil seals are usually all that need replacing but check the valve stem to guide clearance against the manual specs while you've got the head apart.

[TeamDar]

If you do replace the guides, the valve seats WILL have to be re-cut to keep the guides and seats concentric.

[Runningdog]

Thanks for the quick responses...they were even along the line of what I was hoping for.

I'll let the wizard in the head shop (no water-pipes, sorry) sort out what needs addressing.....

Updates/conclusions as they come along, but it may be a few weeks.....

[Nessism]

Thanks for the quick responses...they were even along the line of what I was hoping for.

I'll let the wizard in the head shop (no water-pipes, sorry) sort out what needs addressing.....

Updates/conclusions as they come along, but it may be a few weeks.....

You might want to copy the pertinent service manual specifications from the factory service manual and give them to your machine shop. If they come back with a long laundry list of what's wrong, question them before plunking down big bucks to have the parts refurbished. 850 heads/cylinders/pistons are plentiful, so you might want to consider purchasing some low mileage used parts vs. paying your machinist to bore the cylinder and/or perform a valve job. Ebay or the Parts Wanted forum here is a good place to find the parts - you can purchase several sets of used parts for less than referbing your existing parts should the measurements dictate they are not useable.

[Runningdog]

Oh, Fer Sher, Nessism, after all, this is winter, so I have the time to source out parts for the best deal/necessity. Plus, I have a 1000 engine sitting under the bench (carbs, as well, but no exhaust)....if too much is hinky with the 850, may as well put the same money into the 1000...ah, winter, dream time.....

[SqDancerLynn1]

If the 1000 is a shaft drive motor put it in, don't spend money on the 850. On the other hand a few puffs of smoke is nothing to worry about. Now if it is fogging for mosquitoes that's another story

[Runningdog]

Update: I took Nessisms advice and supplied specs to the head shop.
Head bits look OK, and barrels are not oval.....whoopee....
he's going to just ball hone the barrels to cross-hatch, and says that standard rings will do fine.
I ordered OEM head and base gaskets, and rings, plus an Athena gasket set...I already had OEM valve seals....I know, I'll have lots of extra parts, but it was still the easiest route.
The head has been glass blasted, and he'll do the jugs, as well, so it'll look nice and fresh for a while. Has anybody applied silver/grey engine enamel to head and jugs during a refit and been satisfied with the result?
Spraying a clear coat and baking in Momma's oven may not be acceptable to all in the house....

[Nessism]

VHT rattle can silver engine paint is a reasonable OE color match. One other thing to check is the surface of the head and cylinder for flatness. It's not cheap to cut them but better than dealing with a leak.

[Runningdog]

Thanks, Ed, that's exactly what I had in mind...I wire-wheeled the exhaust collars this summer and sprayed them with high heat silver....they look OK, but they're also hidden a bit, just concerned about having the whole top-end out in the breeze for all to see what a crappy look it became. Likely bite it and go for it.

[Runningdog]

Well, after quite a long time (I think almost 4 months), the head shop finally got to my little project.....one-man operation, lots of bigger regular customers...I know, I know.....Charged me $125, new bronze exhaust guides, lapped the valves in, bead blasted the cam cover, head, and cylinders, honed the barrels.

The paint I chose is flat aluminum VHT, deadly match for the colour of the blasted parts. After a pre-paint cleanup with some acetone, I placed the parts in a little heated cabinet for a couple of hours, along with the paint, at about 65 degrees, then applied three thin coats......dried to the touch in about 20 minutes, and I'll leave them in the cabinet o'nite. I may make use of the drying oven in our soils lab for the curing, or do an on-engine routine later after assembly.

Now to find the time to put it all back together, spring is here, and so is construction season......