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Valve clearance - Super out of spec but on the 'loose' end?

Started by VroomVrooom, September 27, 2021, 11:34:26 AM

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VroomVrooom

Hi guys,

I've scrawled through some old posts for various questions I've had & have luckily always seen an answer of sorts, till now (so I made an account)!

A little background - Im from the UK & have been riding for around 4/5 years, with this GS500EY being my 4th bike (I still have 3/4 of those as projects lol). Ive bought it as a commuter & courier bike, & being the cheapest GS on ebay at the time, the condition is as you would expect. It functions fine, revs up with no hangups, just a bit noisy from the engine...

Anyway, I gave it its first service under my ownership, oil, filters, spark plugs and have finally got around to doing the valves. If im correct the measured spec should be between 0.03 - 0.08mm for Ex & Intake, but the measured specs are;

Exhaust valve left: 0.23mm
Exhaust valve right: 0.31mm
Intake valve left: 0.13mm
Intake valve right: 0.16mm

My question is, clearly they are all out of spec, but from my knowledge valves typically tighten up with wear. Does anyone have any explanation as to why almost every valve is almost double the tolerance or 'looser'?? Guess this explains the noise  :dunno_black:

Just a weird one, Im going to be removing all the shims and probably buy replacements to get them around ~0.10mm as I've heard this is ideal.

(Ive been following the Haynes manual & also BaltimoreGS's How To video on YT)

Edit -> The numbers seem so off to me that im triple checking that Ive followed the manual correctly








Bluesmudge

#1
Assuming you are measuring everything correctly it sounds like you already know the answer. Those clearances are too large!

I aim for .05 - .10 clearance for intake and .08 - .13 for exhaust. I try to never go larger than .13 but I think I've run .14 and .15 before without issue.
Suzuki's .03 - .08 spec is probably more correct if you actually check your valves every 4,000 miles as Suzuki suggests, but .03 clearance doesn't give you much margin of error if you put off the valve clearance check for a few thousand miles.

As to the "why?" No way to know...could be valve seat wearing faster than the valve seat for some reason. Or just a previous owner setting to the wrong spec. All you can do it set them to the correct clearances and then monitor them to see how they wear over time.

VroomVrooom

Thanks for the reply,

I had my doubts that I measured the tolerances correctly, so I slept on it & measured them again today. Measuring them again I get;

Exhaust valve left: 0.21mm
Exhaust valve right: 0.30mm
Intake valve left: 0.10mm
Intake valve right: 0.16mm

This is slightly better as this time I was basically laying on my back making sure that the R.T mark lines up with the left-hand pulse generator coil. Then having the cam shaft notches facing inwards, I measured both intakes & the right exhaust. Then rotated the crank another 360 degrees to measure the last exhaust valve on the left.

Ive decided to leave the left intake shim as is, 0.10mm is good for me & matches your helpful tips  :)

as for the Shims, Ive measured them all and they're either 2.50mm measured with a micrometer, or 2.45 with a Vernier caliper... I wonder what I should go with  :hithead:


Bluesmudge

#3
That's a big range between measurements. I always measure mine with a digital caliper and 99% of the time they match up with the size written on the shim. Very occasionally they will be .01 off from what the shim says. Do yours not have the size written on them? If so, the last person to do the valves must have put them in with the numbers facing the cam instead of the bucket.

The fact that they are all the same size is also pretty weird. Maybe whoever did the valves last didn't really understand what they were doing.

Have you tried calling your local Suzuki dealer? Some of them have a shim kit and do a shim exchange for a small fee (like $2 per shim). That's cheaper than stocking up on shims at $6 aftermarket or $16 OEM each.

VroomVrooom

They unfortunately we're all blank from wear, probably had the numbers facing up like you said. I've just gone with the micrometer in this case and have treated them as 2.5mm shims.

I've calculated them so that the tolerances are still on the looser side, Ex valves would be around 0.11/0.12 & my Intake valves would be around 0.10/0.11... or maybe the original shims will turn out to be 2.45mm after all, in which case they'll fall inline with Suzuki's spec lol.

I bought replacement shims from Wemoto - I didn't know about shim exchanges but I'll definitely consider that for a future valve check. It sounds like a good way to save money, especially if you have a 4 cylinder, 16 valve engine (only did a valve check once for a NC23 and what a pain that was...).

The Buddha

There was a bunch of cast chinese crap shims a few yrs back (god, near 10 yrs now)
Those I believe were K&L supply. Make sure these are not cast. They need to be made of cut from steel stock and heat treated after being machined and micropolished to spec.
Cool.
Buddha.
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I run a business based on other people's junk.
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VroomVrooom

Shims do seem like the kind of thing that a chinese factory can make some quick money on, I wouldn't be suprised if the same company made coins or something.

Wemoto doesn't list the manufacturer on their site, so i'll make a point to check the invoice or at least the quality & thickness of the shims with a tool. I'd hate to use dodgy parts at this point.  :nono:

Bluesmudge

#7
I wouldn't worry about the K&L shims anymore. I have recently used K&L shims in both my GS500 and GS1000 without issues. I think K&L issued a statement years ago that the shim issues were from a single production run. Like you said, it was like 10 years ago...think about all the thousands (maybe millions?) of bikes using the shims since then. The K&L shims are like $6 each vs $16 for Suzuki shims. That adds up, especially on the GS1000 that uses 8 shims. I just had to change 5 of them so that would have been $50 extra for the OEM shims. If the peace of mind is worth that much to you, go for it.

I find that the K&L shims are just cheap enough that I can make myself a kit of shim sizes I'm likely to need for my bikes since I keep a record of what is in there and the clearances. That way I can do the valve checks in one day without waiting for shims in the mail or having to drive across town to the Suzuki dealer.

Since shims don't really wear out, you can also buy them on eBay. That's one way to get the real Suzuki shims for around the K&L prices. You can also get the in-between sizes that only come inside bikes from the factory. They will either be stamped with the size like 2.62 or with an X like 2.70x with the X meaning "a little bigger than." So 2.70x might be 2.71 or something. Those can be helpful when you don't want to make a full .05 clearance jump.

The Buddha

I thought the K&L issue was supplier related - not from 1 run - anyway those had lettering that you could see as different from the rest.
Anyway I contacted a few local shim manufacturers - but well never made through the process of making them.
Cool.
Buddha.
-----------------------------------------------------------------
I run a business based on other people's junk.
-----------------------------------------------------------------

VroomVrooom

As an update,

The shims came - I then measured them with both my micrometer & vernier calipers and found that the vernier calipers showed the exact measurements, whereas the micrometer inflated the size by 0.05mm. Not a big deal, but I had to order 2 more shims and wait a little longer. now my tolerances are measured at;

Exhaust valve left: 0.13mm
Exhaust valve right: 0.11mm
Intake valve left: 0.10mm
Intake valve right: 0.10mm

Much better than my previous spec and some wiggle room added to the hotter exhaust side.

The shims that arrived from Wemoto were in their own packaging, except for one that has the manufacturer mark & product name 'JMP - VENTIL SHIM 29.50 MM' on the packet, incase someone wonders what shim supplier they might have.

Now the only downside is that the breather gasket tore, so Im currently making one out of gasket paper, then finally I can get the bike back together  :icon_mrgreen:

Bluesmudge

Nice! Glad you got it sorted! Those clearances look perfect. You shouldn't have to change another shim for many miles.

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