1984 GS1000G valve clearances?

[Finn]

Right.

I'm in a middle of valve adjustment and after adjusting three valves my clearances are now as follows:

cylinder	intake / mm	exhaust / mm
1	0.06	0.06
2	0.05	0.06
3	0.06	0.05
4	0.05	0.05

Factory clearances are 0.03...0.08 mm for intake and exhaust.


Before adjustments intake valve on # 1 was very tight, perhaps 0.01 but now it is OK.

The exhaust valves on # 3 and # 4 are a bit of a problem or something I'm not quite happy with.

The 0.05 clearance on both is something I get when I slide the feeler gauge in from the center. 0.06 goes in halfway if I slide it in from the side. Once it comes closer to center it gets tight on both # 3 and # 4 I believe 0.05 is correct result.

If I put in one size thinner shim (0.005) the clearence increases up to around 0.14...0.15 ie. more than what the thickness difference should bring.

How do you guys see my clearances? Should I leave them like this or should I increase exhaust clearances with one step?

[Buffalo Bill]

Interesting, tell you what, bring it over to the 2023 Brown County, Indiana GS Rally - June 8-11

an some of our best experts will take a close look.

[srsupertrap]

cylinder	intake / mm	exhaust / mm
1	0.06	0.06
2	0.05	0.06
3	0.06	0.05
4	0.05	0.05

Factory clearances are 0.03...0.08 mm for intake and exhaust

Leave them as is. You're valve clearances are in spec.

[Nessism]

Did you position the cams per the factory standard method? Or did you point the lobe away from the bucket and measure that way? If the latter, then you should go back and double check, because the "point the lobe away" method results in more clearance than is normally the case when measuring correctly.

[Suzukian]

Nessism could you please explain why? Just curious.

[Nessism]

Nessism could you please explain why? Just curious.

The factory method puts two adjacent lobes on the base circle, then the valves are checked/adjusted in pairs. When pointing the lobe away, the adjacent lobe will be depressing the valve spring, which causes the spring to push up in the cam, skewing it in the journal clearance. This will cause the clearance to measure about .02-.03mm more than there actually is when measuring properly.

That said, using the "point the lobe away" method can work, but increase the minimum clearance up to at least .05mm.

[Finn]

The factory method puts two adjacent lobes on the base circle, then the valves are checked/adjusted in pairs. When pointing the lobe away, the adjacent lobe will be depressing the valve spring, which causes the spring to push up in the cam, skewing it in the journal clearance. This will cause the clearance to measure about .02-.03mm more than there actually is when measuring properly.

That said, using the "point the lobe away" method can work, but increase the minimum clearance up to at least .05mm.

Thanks. I will check the clearances again with this method.

[Finn]

Out of curiosity:

How is the GS valve train in general - do the clearances tend to close because of wear or do they tend to stay within spec?

[Nessism]

BTW, Suzuki copied Kawasaki when designing the GS 2V engine cam/valve/bucket design, and Kawasaki uses valve clearances from .05 - .15mm. Bottom line, you can safely run clearances up to at least .12mm on a GS engine without concern.

[Nessism]

Out of curiosity:

How is the GS valve train in general - do the clearances tend to close because of wear or do they tend to stay within spec?

The clearance will close up. Almost never increase. The valve train is VERY durable for the most part. Some idiots don't check clearance regularly, though, and when that happens the valves tighten and can hang open. At that point, the valves/seats carbon up, and/or, overheat, which can shorten life quite a bit.

[Finn]

Thanks. Kawasakis were in my mind as IIRC the 80's Kawasakis over here had a lot of problems with valve trains.

So, the measurements should be taken at positions A or B.

[Nessism]

Rotate the engine until # 1E (exhaust) lobe points forward at the gasket surface, then measure/adjust # 1E & # 2E
Rotate the engine until # 4E (exhaust) lobe points forward at the gasket surface, then measure/adjust # 3E & # 4E
Rotate the engine until # 1I (intake) lobe points at 90 degrees to the gasket surface, then measure/adjust # 1I & # 2I
Rotate the engine until # 4I (intake) lobe points at 90 degrees to the gasket surface, then measure/adjust # 3I and # 4I

[Suzukian]

My '8e GS750ES has the valve set up in a cam follower set up. I adjust one valve at a time, adjusting the two followers for each valve(4 valves per cylinder), turning the crank, then going for the next. Do you think I would experience the same issue. The vales are so small, it's very easy to over tighten them, so I tighten them on the mean (.004"). The bikes runs great, right up to 120 mph.

[salty_monk]

In my experience the 8v valves close up VERY slowly on a well running bike... Set to maximum tolerance I think you could easily go 30,000 before you'd need to change shims. I check about every 12k.
As per Nessism if the next size up is "slightly wide" I run that rather than run one close to low end.

[KiwiAlfa156]

My 2 cents. I agree with Salty Monk, valve clearance closes up with wear very slowly (it can only come from either cam/shim wear or valve/valve seat erosion). And shim swaps are a relative rare occurrence on a well settled-in GS engine.

Valve clearance on alloy head engines (especially hotter running air-cooled heads) increases with engine temperature, because the coefficient of expansion of the alloy is about 3 times that of steel and the camshaft and valve seat is separated by a lot of alloy. So when the engine is at operating temperature the expansion lifts the cam shaft off the shim more that the swelling of the warm steel parts. A qualified Suzuki technician -who prepped the dealer's race bikes at the time, once told me that their quick and dirty valve clearance check for too tight, was that if you could rotate the shim under the cam base circle on a cold engine, you have no worries. When you think about it, hydraulic lifters maintain 'zero lash' in a running engine which is the ideal, as it provides continuous 'cam following' of the profile and a more consistent oil film thickness during rotation. Valve clearance on manually adjusted valve trains is a compromise for wear and expansion.

On the GS the bottom limit of 0.03 mm is there to set a 'safety buffer' to 'catch' the gradual wear between clearance measurement intervals in normal use. At 0.03 mm, the clearance will never get tighter than this in a running engine due to thermal expansion. Same thing if it drops below 0.03 mm between services. The upper limit in the case of the GS of 0.08 mm is the lower limit plus one shim size (0.03 mm + 0.05 mm shim size graduation) - which to me suggests that you really don't have do a shim swap unless you are at or under 0.03mm. While it appears you could run above spec clearances as with the Kwaka 0.05 -0.15 mm clearance range discussed above possibly without mechanical issue (which given Kawasaki's wider lower limit of 0.05 mm corresponds to an upper GS limit of 0.13mm), it does begs the question is of whether there is an advantage in doing so?

Wider clearance increases mechanical noise. This is due to the extra clearance effectively shortening the ramp section of the cam profile. The ramp (or flank) is the section of the cam profile between the base circle and the cam lobe that gently takes up any clearance lash and eases the valve off its seat before the cam lobe really accelerates and decelerates the valve. Importantly the ramp gently eases the valve back on to the valve seat, eliminating any valve seat hammering action. The wider the clearance, more of the ramp section is used just taking up the slack, and less ramp there is to do the gentle lifting and easing back on the valve seat. Remember this clearance gets wider on a hot engine, and in my experience, all GS/GSX are noisier when hot.

The wider clearance also affects valve timing. Just as the extra clearance causes the valve movement to occur later on the ramp, the lobe acts later to open later and close the valve later relative to crankshaft position. There will also be a corresponding small reduction in overlap, valve lift and valve curtain area. All of which doesn't mean much in normal real world terms, but does explain why the race guys run valve clearances at the tight end.