Can a GS run without valve clearance?

[MrKaizer]

I've had my sidecar GS1000G for a few hundred kilometers and finally got around to checking the valve clearances. I couldn't even get the 0.03 mm feeler gauge between 6 of the 8 shims/cams

I was able to get some of the valves to within spec with shims I salvaged from a donor motor. But the math suggests that there was no clearance at all! For example, I went from a 2.50 to a 2.40 shim and got a clearance of 0.05. So there was 0.05 mm "non clearance" before?

Am I measuring wrong? I'm using the guide from BikeCliff's website. I'm wondering because I could not imagine an engine running like that...

[gorbys]

I bought a neglected kawasaki kx250 once where I couldn't get the feeler blade between the cam and shim bucket. I assumed 0 valve clearance and bought a shim to put me on the looser end of the scale but after fitting it it ended up being just over the minimum, which would suggest a negative valve clearance to start with. I don't know if that's how it works but that's what it was. And yes it ran. 

I just did a vfr800 where two of the intake valves where 0.05 (supposed to be 0.13-0.19) and it also ran fine 

[BigT]

To answer your question, yes, a GS motor will run with zero valve clearance

Then, it gets harder and harder to start and gets parked for a long time

Since you are following the factory method, be sure and rotate the motor several time and recheck the clearance

You can go to a 2.35 shim in that example, many people run .1 mm clearance

The clearances diminish over time

 

[gs7_11]

If you only check the clearances at one point in the cams rotation (as when doing it by the manual) you nay find there's a viable clearance at another point.

I've found GS cam base circles have some variation, so you can find a clearance at different points.

I usually follow the method in the manual for speed  and simplicity, as well as erring on the safe side. There's an argument, often had, that it's the only "safe" way as it accounts for the leverage of adjacent cams, oil films etc. Personally I'm not convinced, but I'm happy to play it safe now as the clearance on a GS is quite small, and going bigger doesn't seem to have any detriment.

[Rijko]

they run with zero clearance or less but then you have a high probability of burned valves.
Good practice is to see if you can rotate the bucket before changing shims if you can't get a feeler in there,
so you know if they are really without clearance.
I would do at least a compression check but even better a leakdown test in this case.

Best thing is ofcourse to remove the head and inspect and grind the valves.

Edited August 11, 2023 by Rijko

[MrKaizer]

3 hours ago, Rijko said:

Good practice is to see if you can rotate the bucket before changing shims if you can't get a feeler in there,
so you know if they are really without clearance.

This is a really good idea, I'll try that.

3 hours ago, Rijko said:

I would do at least a compression check but even better a leakdown test in this case.

Best thing is ofcourse to remove the head and inspect and grind the valves.

I did a compression check before checking the valves. The result was 9 - 10 - 9 - 9,75.

I will do the head eventually but was hoping to be able to ride a few more kilometers before I have to take the lid off.

[Reinhoud]

Just don't!!

Do it right, no excuses! Valve clearence is there for a reason!

[Gixer1460]

13 minutes ago, Reinhoud said:

Just don't!!

Do it right, no excuses! Valve clearence is there for a reason!

Deffo concur ! A correct clearance will, a) ensure the valves are closed and not leaking and b) provide sufficient time when seated, to transfer heat from the valve into the seat and head to prevent overheating / burning valves or pre-ignition / detonation. Even reduced clearances when cold are not sufficient as heat expansion closes the gap and you will be back to square one. Unlike tappet style valve operation where the gap grows with use and gets noisy, buckets close the gap so you don't get the audible warning - everything just gets FUBAR'd

[TonyGee]

1 hour ago, Reinhoud said:

Just don't!!

Do it right, no excuses! Valve clearence is there for a reason!

yep, as the factory designed it. 

[MrKaizer]

1 hour ago, Reinhoud said:

Just don't!!

Do it right, no excuses! Valve clearence is there for a reason!

I didn't write this clearly, sorry.

I'll definitely do the valve clearances before I ride any more! But I'm hoping I won't have to do a full head rebuild, valve seats and all, yet. 

[Reinhoud]

10 hours ago, MrKaizer said:

I didn't write this clearly, sorry.

I'll definitely do the valve clearances before I ride any more! But I'm hoping I won't have to do a full head rebuild, valve seats and all, yet. 

I think I didn't read properly.. Sorry..

In theory you're right, but experience tells me it's not always like that.

 

[gsx]

I had a gs 1000 custom from the USA a few years back , all were tight ,look at shim sizes after you've tried to measure them to see if any can be swapped around but you will need to pop the cams out to do this , gs 500 shims are the same 

[Rijko]

9 hours ago, gsx said:

you will need to pop the cams out to do this

That is true if it has an aftermarket shim under bucket setup, but a standard GS1000 has shims that can be removed without removing the cams.

[Swiss Toni]

2 hours ago, Rijko said:

That is true if it has an aftermarket shim under bucket setup, but a standard GS1000 has shims that can be removed without removing the cams.

Fact! There's an OE tool, much like a C spanner, that goes under the cam and locates on the edge of the follower. on rotating the handle of the too towards the head surface, the follower is depressed enough to remove, measure and replace the shim. 

[DAZ]

8 minutes ago, Swiss Toni said:

Fact! There's an OE tool, much like a C spanner, that goes under the cam and locates on the edge of the follower. on rotating the handle of the too towards the head surface, the follower is depressed enough to remove, measure and replace the shim. 

Best using a magnet on a stick pick up tool to remove the shim if you got one to save your fingers ...

[gs7_11]

I have a 79 GS425, which as you'll know is the same sort of engine, just half of one! One of the receipts I got with it when I bought it was for repair of a starting problem.

The cause was that the shims hadn't been done for too long, so it must have been holding valves open. The fix was to reshim the valves.

Since then, the bike's done maybe 10,000 miles with no problems and runs really well. I'm planning an engine strip to replace the valve guide oil seals, but wouldn't be bothering otherwise, as the compression is fine.

[BigT]

On 8/13/2023 at 2:15 PM, gsx said:

I had a gs 1000 custom from the USA a few years back , all were tight ,look at shim sizes after you've tried to measure them to see if any can be swapped around but you will need to pop the cams out to do this , gs 500 shims are the same 

Uh, no, just no