Valve clearance check on GS850

[Chris G]

I'm on call this weekend, so no opportunity to ride being house bound I've decided to check the valve clearances, I have the shim tool but this will be my first attempt.
What I would like to know is is the method shown in my Haynes manual the acceptable method for working out the shim sizes required. It stares to select the correct size shim thickness required, subtract 0.03mm from the measured clearance on the fitted shim then add this figure to the size of the shim fitted to the bike, then select the largest available shim whose thickness is slightly smaller than the final figure hope it's easier in practise.

I don't have any spare shims at the moment, but if after measuring all inlet/exhaust I find I can swap a few existing ones around what can be used to act as a shim while rotating the engine, read on here someone had used a coin as a substitute shim, appreciate any information.

 

[Steve]

The EASIEST way to do the figuring is to take advantage of the offer in my sig.

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[tkent02]

What I would like to know is is the method shown in my Haynes manual the acceptable method

The Haynes method isn't right at all, the way it puts the cam lobes up away from the valves gives bogus readings. The valve spring of the next valve over pushes the cam up away from the valve increasing the clearance reading. Use the method shown in the Suzuki service manual, checking two valves at a time.

 

[Chris G]

Thanks Steve, will send an email thank you.

 

[Chris G]

The Haynes method isn't right at all, the way it puts the cam lobes up away from the valves gives bogus readings. The valve spring of the next valve over pushes the cam up away from the valve increasing the clearance reading. Use the method shown in the Suzuki service manual, checking two valves at a time.

I have both the Haynes and Suzuki service manual, both state the same thing that the clearence scan be measured in either of two positionswhat is my best means of attack.

 

[tkent02]

Use the Suzuki technique, check two valves at a time and then rotate the crank 180, do two more.

 

[Chris G]

I may be way off here, rather than removing the side case to rotate the engine, when checking clearances can I remove the plugs put it in gear and just rotate the rear wheel, or is this a no no due to it being shaft driven

 

[Steve]

You could do that, but removing the side cover is SO much easier, not to mention more accurate.

.

 

[Chris G]

Started checking my clearances today, either I'm doing something wrong or these are very tight, when using the gauges should it physical pass between the cam and the shim when you find the relevant gauge size, as even my smallest of 0.05mm does not slide between the two faces.

Been looking through the paper I got with the bike, it's done just over 3k miles since the last time they were done by a shop, it's quite a few years ago, but the previous owner paid ?180 for it doing

 

[tkent02]

Probably the shop didn't do anything but take his money. Possibly they were all at or slightly above the minumum clearance and they just left them there instead of fixing them. They shouldn't have moved much in the last 3,000 miles.

See if you can spin the shim in the bucket with the cam in the correct position for checking. If you can, there is at least some clearance, go down one size on the shim. This will put you somewhere above .05mm.

If it won't spin, it's stuck, there is zero or less clearance. Go two sizes smaller than the existing shim. This will leave you somewhere less than .10mm clearance. .10mm is what a lot of us use as the upper limit, anything less than .10mm is OK.
Still check them again once all of the new shims are installed, but this should get you close to the right size.

If you had some with zero or less clearance, check the compression after you are finished to see if you have any burnt valves.

 

[Nessism]

I have both the Haynes and Suzuki service manual, both state the same thing that the clearence scan be measured in either of two positionswhat is my best means of attack.

You are misreading the Suzuki procedure. The OEM cam positioning method is specific and doesn't offer optional positions. Valves are to be checked in pairs, with both adjacent valves positioned on the cam base circle at the same time. The clearance decreases with time, so people that don't adjust their valves are damaging their engine because when the clearance is gone the valves will burn.

 

[Chris G]

Probably the shop didn't do anything but take his money. Possibly they were all at or slightly above the minumum clearance and they just left them there instead of fixing them. They shouldn't have moved much in the last 3,000 miles.

See if you can spin the shim in the bucket with the cam in the correct position for checking. If you can, there is at least some clearance, go down one size on the shim. This will put you somewhere above .05mm.

If it won't spin, it's stuck, there is zero or less clearance. Go two sizes smaller than the existing shim. This will leave you somewhere less than .10mm clearance. .10mm is what a lot of us use as the upper limit, anything less than .10mm is OK.
Still check them again once all of the new shims are installed, but this should get you close to the right size.

If you had some with zero or less clearance, check the compression after you are finished to see if you have any burnt valves.

Thanks for the reply, all the shims rotate in the buckets I've taken them out and made a record of there sizes, what threw me was my gauges don't no why I got confused by the smallest I have being 0.05, for all I know there all at 0.03, would it be better to get a set of gauges that read lower to get a true reading.

 

[GSX1000E]

Thanks for the reply, all the shims rotate in the buckets I've taken them out and made a record of there sizes, what threw me was my gauges don't no why I got confused by the smallest I have being 0.05, for all I know there all at 0.03, would it be better to get a set of gauges that read lower to get a true reading.

Yes and it would be a good bet to just do as tkent suggested and replace each of those, apparently on the tight side, shims with one size smaller and measure again after rotating the engine a couple of times by hand
to allow the new replacement shims to seat into the buckets.

 

[Grimly]

I have both the Haynes and Suzuki service manual, both state the same thing that the clearence scan be measured in either of two positionswhat is my best means of attack.

Yep; for years I was simply turning the heel of the cam to be against the shim and measuring like that, using the same method I'd used on hundreds of OHC engines in cars and bikes over the years. This most recent time I actually paid attention to the manual and rotated the cam to either of the two positions shown there. Turns out the real clearance there is a couple of thou greater than on the optical heel. Who would have guessed that?
So, the real cam heel is not quite where you think it is, but as it turns out, it's a relatively safe error, because you'd simply give it a couple of thou more clearance than it really needs. In these lumps, that might make a bit of difference to service longevity and cater for a delayed check.
What I've found on the GS 850 engines (at least the three or four I've owned) is that checking them every book interval is oftentimes unrewarding, as nothing needs doing, and I put that down to steady-state running, in that the engines never revved much, topping out at 7000 rpm or so and never thrashed through the gears - these were working bikes and had to stay reliable day after day.
Otoh, in non-working use, where the bikes are given a bit of welly around the back roads, the clearances DO alter and I nearly got caught out by leaving things too long.

 

[Chris G]

You are misreading the Suzuki procedure. The OEM cam positioning method is specific and doesn't offer optional positions. Valves are to be checked in pairs, with both adjacent valves positioned on the cam base circle at the same time. The clearance decreases with time, so people that don't adjust their valves are damaging their engine because when the clearance is gone the valves will burn.

I agree, reading the Haynes manual is very vague / misleading after reading the work shop manual I realised it made more sense, as you check in pairs on either intake or exhaust, the Haynes manual makes it look as though you can simply rotate the cam and check the clearance in either the vertical or horizontal position to any shim, which is not the case.

 

[850 Combat]

I may be way off here, rather than removing the side case to rotate the engine, when checking clearances can I remove the plugs put it in gear and just rotate the rear wheel, or is this a no no due to it being shaft driven

I do it that way. I'm just used to it from old bikes I used to own.

 

[Chris G]

After a bit of head scratching, and moving various shims around on paper, I think i'll be needing to get hold of four shims, as tkent02 mentioned they all appear to drop by one shim size, though No4 exhaust is in tolerance.
I have one shim marked with a X making it 2.62mm the suggested replacement is a 2.57mm are these intermediate size easily obtainable from a Suzuki main dealer?

I will put up my measurements and suggested replacement shim sizes later, for folk to confirm or not if I am heading in the right direction.

 

[Steve]

You might be able to get that 2.55x (2.57) shim from a member or the Shim Club, but you can not order them from any Suzuki vendor.

What you can do, though, is to evaluate the clearance it will leave you. If it will be near the tight side, just go with a 2.55 for the extra half-shim's worth of clearance. If it will leave you on the loose side, feel free to use a 2.60, as long as it still leaves you within the range.

.

 

[Chris G]

Thanks Steve, that's just answered what was on the agenda if I could not obtain the specific shim.

 

[Steve]

Just get them as close as you can to spec. If you have to "fudge" it a little, go LOOSER.

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