77 GS750 Valve Replacement

[Guest]

So I pulled apart my top end and spent today soda blasting. The valves cleaned up a bit, but still seem to be pretty burned. Part of me wants to replace them all, but the other part doesn't want to spend $300 on valves. I was going to get some chem-dip and let them soak and then maybe try cleaning them again. Any thoughts on this? If I were to buy new valves, where is the best place to get them, and what size do I need?

[chuck hahn]

By burnt you mean they are all crusty with carbon or real black in the metal looking? The carbon will brush off with a wire wheel on a bench grinder..then you can see the surfaces better. On the 78 750E we just did for the rally auction last October, we went with OEM replacements.

Do the stem seals too while your at it. Got anyone you trust to cut the seats and lap the valves properly, or you gonna do that?

[Nessism]

You might want to find a machine shop to face the valves for you. They will look like new again, assuming you still have enough margin. Check out the Suzuki service manual for the appropriate specs. I had some valves done and it only cost something like $3 each.

[Havoc1231]

I just found a machine shop in town that looks like it does total header rebuilds and the like. I'll be giving them a call this week to see if they can handle my valves. I'll also see if they can do the valve lapping as well. I must admit, I've done some bike work in the past, but never nearly as comprehensive as I'm trying now. I have the engine completely apart and figure I might as well do everything on the up and up while I put her back together to make sure she actually starts when the last bolt is torqued.

[Steve]

So I pulled apart my top end and spent today soda blasting.

Sorry, but it appears that your first sentence is missing and your post started with the second sentence.

Apparently, something happened, "so I pulled apart my top end ..." What happened that made you pull the top end apart?

The valves cleaned up a bit, but still seem to be pretty burned.

What appears to be "burned" on them? There are only two areas that really matter on the valves. 1. The sealing area around the edge and 2. The stem at the seal area.

Inspect the edge of the valve, if it's still smooth and clean, the valves are not "burned". Check the stem to ensure it is smooth and will not tear up the seal.

I was going to get some chem-dip and let them soak and then maybe try cleaning them again. Any thoughts on this?

Before soaking the valves, be sure to label them so you can put them back in the same hole they came out of.

Personally, I just stick them in my electric drill and run them up against the wire wheel in the bench grinder.
Anything that is still stuck to the valve after that won't really matter.

.

[Havoc1231]

Steve, when I got the bike the engine was caked in road grime, the exhaust was leaking at the connection to the engine, when I removed the carbs one was completely dry etc. etc. etc. I had pulled the bike apart completeley and figured the best course of action was a complete tear down and rebuild the engine as well. Hence the heads torn down. Everything came out clean after some soda blasting and I think I'm going to have the crank cases powder coated.

I took my head to the local shop to pull my valves as I didn't want to pay for the tool for a single use and didn't want to cob them off. Unfortunately when I got them back, there were 8 valves sitting in a box unlabeled...so there's that. I know wear patterns will have an influence on performance and the valves should be put back in their original spots, but it seems that won't happen here. Is this a critical issue?

I'll try the wire brush and see how they come out. Maybe burned was the wrong term, just have a lot of buildup on them. I'll give them another once over when I get home and report back. This is why I come on here, thanks or the help.

After a little more reading it doesn't seem like lapping the valves is all that difficult, just need the tool (stick and suction cup) the compound and a bit of elbow grease? I'm still going to contact the machine shop and if it's not ridiculously expensive I may just have a pro do it to ensure a proper job.

[Steve]

If you are going to re-face the valves or at least have them lapped, the importance of keeping them in the correct hole is minimized.

Good luck with the powder coating, make sure it will withstand engine heat.

.

[cowboyup3371]

Look on basscliff's site for instructions on lapping the valves. Steve, my eldest daughter and I all worked together on putting it together for folks and it should help you immensely.