Grime in Valve Cover

[stossboss_gaming_and_news]

So, going through my GS750T methodically this year because I never got it running well in the last.

Had carbs and tank off (cleaning them) so figured I should check the valves. Opened it up and every valve was out of the 0.004-0.005" range - what it says in the book for TSCC. (they were all nearly impassable, especially the exhaust ones). The valve gasket was leaky to begin with and fell apart when I took the cover off. Now, adjusted the valves in the correct order, everything is close to spec. Would tight valves contribute to terrible starting/idling? Unless I'm measuring it terribly (I haven't done it before) it would seem the valves were seriously neglected, the valve cover doesn't seem to have been removed in a decade, the PO definitely mentioned he rebuilt carbs, but I don't recall anything about the valves and it has always had serious trouble starting cold, always had to give it some gas as I slowed down too or else it stalled (even with a little choke).

- BUT, as I am cleaning the old gasket off the head, dust/gasket and bits of plastic, possibly metals (noticed my credit card has some soft metal in it) are falling into the head, I'm trying to limit it as much as possible but this gasket feels like it was glued on and now it's all stuck. How serious is this? Fine if I just change oil right away and frequently for the next few changes?


Also---- halfmoons... Do I really need to replace them?

[Rich82GS750TZ]

Yes, tight valves can and does cause hard cold starting. You should not feed gas while starting. Get the valves in spec and get it running before trying to diagnose possible carbs issues. As for the gasket, yes they go brittle when on there for a on long time. Stuff rags down the cam chain tunnel to keep bits from going down there. Bits that do fall in will end up in the sump, could get recirculated and clog oil passages. I would definitely to an oil/filter change before too long. You could remove the oil pan and clean it out and the oil pickup strainer screen. But if you think the valve cover gasket scraping is a chore, I assure you it’s nothing compared to the oil pan gasket that’s been on there for 42 years. It’s a much worse job done on tour back, looking up. Soften gasket with WD 40, I use a razor blade, very carefully. Once the big bits are off, I use a green scotchbrite and more WD 40. Others have other methods. This works for me.

yes, replace the half moons. They’re old and brittle. Use a thin shmeer of the recommended RTV (I don’t remember what the book says or what I used) on the half round dips in the head. I did not replace the half moons on subsequent valve clearance checks, just the first time I did it, which was likely the first time it was ever done, when the bike was 30 years old.

[oldGSfan]

Yes, tight valves can and does cause hard cold starting. You should not feed gas while starting. Get the valves in spec and get it running before trying to diagnose possible carbs issues. As for the gasket, yes they go brittle when on there for a on long time. Stuff rags down the cam chain tunnel to keep bits from going down there. Bits that do fall in will end up in the sump, could get recirculated and clog oil passages. I would definitely to an oil/filter change before too long. You could remove the oil pan and clean it out and the oil pickup strainer screen. But if you think the valve cover gasket scraping is a chore, I assure you it’s nothing compared to the oil pan gasket that’s been on there for 42 years. It’s a much worse job done on tour back, looking up. Soften gasket with WD 40, I use a razor blade, very carefully. Once the big bits are off, I use a green scotchbrite and more WD 40. Others have other methods. This works for me.

yes, replace the half moons. They’re old and brittle. Use a shmeer of the recommended RTV (I don’t remember what the book says or what I used) on the half round dips in the head. I did not replace the half moons on subsequent valve clearance checks, just the first time I did it, which was likely the first time it was ever done, when the bike was 30 years old.

Great tips from Rich - I use the strongest paint remover I can find on gaskets. Usually, it's called Aircraft grade, at least in California. I use a cotton swab to apply the stuff. It can take a couple of applications, but it works. Just give each coat 20 minutes. It can help to slice the existing gasket cross-wise with a razor to enable that nasty stuff to get in there.

As far as I can tell, it's the same as gasket remover. I got a set of wood-handled small woodworking chisels, and wow, they are great on gaskets, just the right size, super sharp, and plenty of strength and leverage. Beats using a single-sided razor, even with a holder. Never trust a PO's maintenance claims. Go by the book and do it right.

[stossboss_gaming_and_news]

I'll try the rag and scotchbrite tomorrow, I'm about 1/2 finished clearing it today using a credit card and diesel for big stuff.

Get the valves in spec and get it running before trying to diagnose possible carbs issues.

So I already took apart the carbs since the master carb was visibly flooding, float was completely stuck and rusted, that carb wasn't recoverable so I ordered a 1981 GS750 assembly off ebay, which I think runs the exact same carb specs and was just gonna try to just swap that master carb in (rest of them are in great shape). Still waiting on it so I jumped ahead and worked on valves without functioning carbs. I guess I'm stupid but I just cant stand waiting around doing nothing.

[stossboss_gaming_and_news]

Great tips from Rich - I use the strongest paint remover I can find on gaskets. Usually, it's called Aircraft grade, at least in California. I use a cotton swab to apply the stuff. It can take a couple of applications, but it works. Just give each coat 20 minutes. It can help to slice the existing gasket cross-wise with a razor to enable that nasty stuff to get in there.

As far as I can tell, it's the same as gasket remover. I got a set of wood-handled small woodworking chisels, and wow, they are great on gaskets, just the right size, super sharp, and plenty of strength and leverage. Beats using a single-sided razor, even with a holder. Never trust a PO's maintenance claims. Go by the book and do it right.

Gasket remover. Of course that exists.... It just didn't even cross my mind because I was thinking "Gaskets are made for the specific purpose of not reacting to chemicals, just takes muscle I guess". I should go back to elementary school...

[oldGSfan]

Gasket remover. Of course that exists.... It just didn't even cross my mind because I was thinking "Gaskets are made for the specific purpose of not reacting to chemicals, just takes muscle I guess". I should go back to elementary school...

You can buy it, but I am a certified cheapskate Suzuki GS owner. so I look on the shelf to see which, among the hundreds of cans of caustic goo I have may do the job!

[KiwiAlfa156]

Its really important that you measure the clearance between the tappet screws and valve stems with the cams in the correct position as per the workshop manual. There is clearance between the cam journals and the bearing beds and caps and correct positioning stops inaccurate measurement caused by the camshaft being unevenly loaded by the valve springs.

[stossboss_gaming_and_news]

Its really important that you measure the clearance between the tappet screws and valve stems with the cams in the correct position as per the workshop manual. There is clearance between the cam journals and the bearing beds and caps and correct positioning stops inaccurate measurement caused by the camshaft being unevenly loaded by the valve springs.

I definitely did the order/position properly. I just haven't done it before so I'm still a little uncertain if I measured properly. Hard for me to believe they were off by as much as they were.

[Grimly]

I definitely did the order/position properly. I just haven't done it before so I'm still a little uncertain if I measured properly. Hard for me to believe they were off by as much as they were.

Oh, believe it. Some folks have no idea the gaps exist, thinking they might be hydraulic lifters or something.
Others are put off by the cost of workshop time and eventually the bike doesn't start or runs like a pig so gets laid up as a 'someday' project.

[stossboss_gaming_and_news]

So... Anyone have a gasket templates for valve covers?

[Rich82GS750TZ]

Gaskets are still available from dealer or online sources. Buy OEM.
part # 11173-49224-H17 -$31.32 plus shipping. Shipping isn't that bad if your getting a bunch of things at the same time: half-moons, etc.

https://www.partshark.com/oemparts/a/suz/50d400abf8700230d8b4e32d/cylinder-head-cover-model-d