New owner maintenance: 77 GS750

[hannibal]

Hello,
I got a 77 GS750B about a month ago. I've been going through each system on the bike. I have threads in the fuel, electrical, and brake forums but thought I should start a new post here for all the other random things.

I checked valve clearances last week. I was pretty intimidated by the process, but it turned out to be quite straight forward. Here are my clearances:
Cyl 1 EX .102mm, shim=265; IN less than .038mm, shim=250

Cyl 2 EX .076, 275; IN .102 270

Cyl 3 EX .051, 275; IN .127 270

Cyl 4 EX .127, 270; IN .051 (couldn't read the number on this shim. will try again when i change shims)

My feeler gauge sizes are .038mm, 051, 063, 076, 102, 127, 152. The size listed above is the largest that fits. Is it odd to have so many clearances on the "too big" side? I thought clearances typically decrease over time (still not sure why that is). I'm also concerned about Cyl 1 IN. My smallest feeler (.038mm) didn't fit so this valve is very tight and it already has a 255 shim. All other shims are 265-275.

Two other concerns: On cyl 1 exhaust valve, when I dropped the shim back in the bucket and lightly centered it with my finger, lots of oil came up from below the bucket and there was a bit of a puddle of oil in the cylinder head next to the cam. Any ideas what caused this? Hope it's not a bad valve seal.

On the cyl 4 side of the head, I found this blue gunk behind the cam shaft "cap". I also noticed some blue gunk on the cyl 3 header right where it goes under the bike. Is this just a bad sealing job with some kinda of liquid gasket?

[tkent02]

The valves normally wear into the seat, or recede into the head, the valve stem seems to get longer, the clearance goes away. Not always, but usually they get tighter. You must fix the tight one.

It is unusual to have so many loose ones, who worked on it last? Might have measured things wrong, or used the spec off his Chevy or something. Maybe he set the clearances with a hot engine. Maybe he didn't know what he was doing and just tossed a shim in each bucket without measuring. Who knows?

There is supposed to be oil sitting in the head. It seems to drain from some of the areas better than others. No oil in any of them is a bad thing.

Some engines have all nearly the same shim sizes, some are varied all over the place. No idea why. Super high mileage maybe? New guy machining the heads back at the factory? Poor batch of valves from the company that makes the valves? Dunno.

I don't know what that blue stuff is.

[hannibal]

Thanks! The PO had a few Kawasaki's and a Honda CB in his garage and knew plenty about the bike. But a lot of what he said turned out to be lies, so I'm guessing that he hadn't adjusted valves as he said he did. If the last adjustment (by whoever) was done on a hot engine, that would explain the big clearances. I guess watching how the clearances change over time is more important than all valves starting from the same shims and clearances.

[hannibal]

I know a lot of members suggest running larger than the factory 0.03-0.08mm clearances. Ray from the shim club thought my .127mm clearances were OK. What do you guys think?

I expect that the gaps should close as the bike gets used. I really don't know the usage history of the bike or whether it's been sitting for awhile. Do you guys think I'll be OK with the larger clearances? I'm definitely going to get a new shim to fix the tight valve. Just wondering if I should increase the shim sizes on the .127mm valves.

[JJ]

I have always kept mine within the tolerance called for in the factory manual. I'm not so sure about .127mm clearance. I'll let other members chime in on that. I definitely wouldn't go any higher. If you check and adjust every 6K miles, you won't have to worry about them closing up.

[tkent02]

I would not go that loose. Prefer .05mm to .08mm, .10mm is my limit.

[hannibal]

Thanks. I'll close up the 127 valves and just check them at the end of the season. If I have to go back down, I'll have the correct shims waiting on the shelf.

[Nessism]

Did you position the cams per the factory Suzuki service manual procedure and check the valves in adjacent pairs? The reason I mention this is because if you use the Clymer instructions, which have you point the cam lobe away from the bucket and then check the clearance, it will result in more measured clearance than the Suzuki method.

[John Park]

Thanks! The PO had a few Kawasaki's and a Honda CB in his garage and knew plenty about the bike. But a lot of what he said turned out to be lies, so I'm guessing that he hadn't adjusted valves as he said he did. If the last adjustment (by whoever) was done on a hot engine, that would explain the big clearances. I guess watching how the clearances change over time is more important than all valves starting from the same shims and clearances.

Clearances increase as the engine warms. This is because the head is aluminum and the valves are steel so the valve seat expands AWAY from the cam. Or the cam expands up from the valve seat.

The exhaust valve does get pretty hot and will expand and reduce some of the clearance, but the intakes are in fresh air and pretty well cooled. The stock clearances are the ones to use, but I'd prefer to run on the looser side of the tolerance on the exhaust side.

It's not the same as a cast iron car head where the metals expand at the same rate. Aluminum expands something like twice as much as steel.

[hannibal]

I used the Suzuki factory method of pointing the #4 EX lobe parallel to the head and the #4 IN lobe pointing straight up.

Makes sense to run looser on the EX since the clearances change more when the engine is running.

Thanks for the explanation John. I guess I had it backwards. Clearances would be on the tight side if they had been set with the engine warm.

[John Park]

I had a '77 750 and really loved it. It may be my imagination, but the spoke wheels always seem to dance better for me than the cast wheels. I think they're lighter; maybe not?, but they have a springiness that just feels better to me than the cast wheels that followed. Of course, you can't run tubeless, but that's no disappointment to me.

It never had any of the stator problems with it that seemed to plague the GS line. The '77s had that funny regulator can and a headlight switch that added another leg of the stator when you switched it on. I'm not sure if that was a good idea or not, but mine always worked fine.

The '77 was the first four cylinder GS and a definite classic so take good care of it while you enjoy it. I now wish I'd kept mine.

[hannibal]

It took me about 9 months to find this bike. I love the wire wheels but was not aware that I couldn't run tubeless tires. This is my first bike and I hope to keep it forever. Haven't been able to enjoy to yet as I'm still going through it. But that day is cimung soon.

Thanks for your advice and comments.

[John Park]

It took me about 9 months to find this bike. I love the wire wheels but was not aware that I couldn't run tubeless tires. This is my first bike and I hope to keep it forever. Haven't been able to enjoy to yet as I'm still going through it. But that day is cimung soon.

Thanks for your advice and comments.

You can certainly run tubeless tires, but you'll have to put a tube in them anyway. There aren't that many tube type tires being made anymore, and there's no particular point in preferring them, other than that the bead is more flexible and easier to pry on.

One thing to watch for is the rim strip. This is the rubber band that keeps the heads of the spoke nipples from abrading or poking holes through the tube. The ones I can get these days are pathetically flimsy and barely do the job; I guess nobody really cares about tubes anymore. You want to grind any roughness off the nipples [ I like to put a layer of tape or two over them after] and then make sure the strip is in good condition and straight; otherwise you can get a 'no reason' flat. Same goes for loose flaky rust from the rim floating about in there.

One good reason to do your own tire mounting with tubes is that it's reasonably straightforward and you know it's done right. It's often the lowest flunky in a shop doing things like mounting funny old tube type tires and anything can happen. Just because it's holding air leaving the shop doesn't mean it will keep doing so.

[hannibal]

Makes sense. The spokes on wire wheels go through the rim, so the rim can't hold air and therefore requires a tube.

When I was measuring valve clearances a few weeks ago, it started to rain. I quickly threw the valve cover back on and left the bike for the day. I opened the valve cover recently and saw some rust on the cam lobes. I can't believe something could rust so fast, but I guess it did. I freaked out thinking I had just destroyed the cams, but surface rust seems to be a common occurrence. I was able to wipe off some rust with a paper towel, but I need to remove the cams to clean them correctly with brillo pads and PB blaster. The factory service manual outlines the procedure fairly well: remove tach drive, clamp down the cam, and remove caps. To reinstall, coat journals with moly paste (I was planning to use motor oil), clamp down the cam, and torque down caps. There must be bearings under the caps, so I'll take care to keep those in order. Is there anything else I should be aware of? Any tips/tricks I should know about?

I plan to install the new shims while the cams are out. This will save me from having to turn the motor and use the valve shim tool.

[chuck hahn]

And a rim strip to protect the tube itself from spokes wearing a hole.

I have seen a few tutorials about sealing the ends of the spokes with thin gs such as gas tank liner and some various industrail adhesive sealants. Anyone here ever done it? reviews???