GS850 Valve Shim Sizes?

[Nessism]

Recently purchased a 1982 GS850 with 3500 miles. Checked the valves and pulled two shims that were too tight. Was surprised to have to go down to a 2.60 on one valve and 2.55 on another to get the clearance in spec. Shims on both my low mileage 550’s are in the 2.70 – 2.80 range.

So my question is whether or not this sounds right for a bike with 3500 miles? Engine certainly appears to be original for the bike and bike in general matches the mileage – even has original tires.

Please chime in if you own an 850, or have adjusted the valves on one, and give me a sanity check.

Thanks.

[BassCliff]

You're not crazy

Mr. Nessism,

I'd have to check Steve's spreadsheet when I get home, but it seems I'm down to a couple of 2.60s on my bike too. That was at about 18,500 miles. I'm due another valve check soon.

Thank you for your indulgence,

BassCliff

[TheCafeKid]

Recently purchased a 1982 GS850 with 3500 miles. Checked the valves and pulled two shims that were too tight. Was surprised to have to go down to a 2.60 on one valve and 2.55 on another to get the clearance in spec. Shims on both my low mileage 550’s are in the 2.70 – 2.80 range.

So my question is whether or not this sounds right for a bike with 3500 miles? Engine certainly appears to be original for the bike and bike in general matches the mileage – even has original tires.

Please chime in if you own an 850, or have adjusted the valves on one, and give me a sanity check.

Thanks.

Im down to a 2.50 on one of my intakes on a 750 motor with 22k on it. All my exhaust are 2.7 or over tho. Intakes are 2.65 to 2.50. For some reason they seem to get smaller faster, as my other 750 motor had smaller intake shims than exhaust.

[Steve]

There must be SOME reason that stock shims go down to 2.30. :shock:

Do you know the history of the valve adjustments on this bike? (On second look, it's still basically a new engine.) It is entirely possible that when the bike was new, that the valve seat was cut just a bit deeper or the valve stem was on the long side of 'normal', either one of which would require a thinner shim.

The actual number on the shim does not mean much. You need to know how it has changed.


.

[tconroy]

There must be SOME reason that stock shims go down to 2.30. :shock:

Do you know the history of the valve adjustments on this bike? (On second look, it's still basically a new engine.) It is entirely possible that when the bike was new, that the valve seat was cut just a bit deeper or the valve stem was on the long side of 'normal', either one of which would require a thinner shim.

The actual number on the shim does not mean much. You need to know how it has changed.


.

I have a couple down to 2.45 on my last valve check.Most were 2.50 to 2.60. as long as the clearance is within range I dont think it matters much but I could be wrong.

[salty_monk]

Stock goes down to 2.15. I would imagine what you are seeing is just down to manufacturing tolerance. My 1000 has some 2.55's in it...

Dan

[catbed]

on mine, most were at 2.65. i had one 2.70 and one 2.55. 8k miles

[49er]

After the cam cleanup, my shims ranged from 270 to 285.
The inlets will reduce quicker than the exhausts because of their larger size/mass. They hammer the seats a little harder at higher rpms.

[Roostabunny]

At about 37k miles mine ranged from 250 to 265 - no significant difference between intake side and exhaust side.

[Nessism]

Thanks for the input everyone.

Steve sent me his latest shim spreadsheet so I'm going to pull them all and catalog the sizes. 2.55 and 2.60 shims on an engine with only 3500 miles still doesn't seem right to me. Wondering if the engine has more miles than first thought. Cams look super clean with no signs of wear. The backside of the intake valves, as visible with the boots off, have carbon buildup on them - should there be build up after only 3500 miles? Head pipes have some gold color to them on the right two cylinders so maybe the bike was running lean which caused some damage?

Not a whole lot I can do at this point but can't help but wonder. Paid a medium high price for the bike under the assumption it's in near new condition, don't like surprises.

Ed

[49er]

[quote=Nessism;754850]Thanks for the input everyone.

Steve sent me his latest shim spreadsheet so I'm going to pull them all and catalog the sizes. 2.55 and 2.60 shims on an engine with only 3500 miles still doesn't seem right to me. Wondering if the engine has more miles than first thought. Cams look super clean with no signs of wear. The backside of the intake valves, as visible with the boots off, have carbon buildup on them - should there be build up after only 3500 miles? Head pipes have some gold color to them on the right two cylinders so maybe the bike was running lean which caused some damage?

Not a whole lot I can do at this point but can't help but wonder. Paid a medium high price for the bike under the assumption it's in near new condition, don't like surprises.


Ed, a 26 year old bike with low miles (3500) does not necessarily equate to a great buy. Having said that, if the bike is complete, you will eventually have a nice machine.
When bikes sit unused for extended periods of time, they need thorough maintenance on the brakes, carbs/inlet system, electrcal, ignition (especially points) and the engine internals. Bores, camshafts and valves and airbox crankcase breather ports are particularly susepitable to rusting.

Your inlet valves with excessive carbon buildup are probably the ones that had the tight shims fitted. When the valves don't fully close, some of the deposits that form naturally on the piston crowns and valve heads also appear on the seating areas.
Once you've re-set the valve clearances, they are likely to change slightly on those valves as the carbon disappears with use. You should re-check your clearances after a short period, as these ones will need adjustment earlier than the rest.
Don't be pedantic about the shim variations. Suzuki's machining isn't perfect. Slight variations in valve insert depths and cuts, cam bucket head thicknesses, valve stem lengths,valve head seat cuts and cam lobe profiles all contribute to the shim thickness require for each valve.
I guess that you have cleaned the carbs. Probably time for a balance check and plug chop sessions.

[robertob]

Thanks for the input everyone.

Steve sent me his latest shim spreadsheet so I'm going to pull them all and catalog the sizes. 2.55 and 2.60 shims on an engine with only 3500 miles still doesn't seem right to me. Wondering if the engine has more miles than first thought. Cams look super clean with no signs of wear. The backside of the intake valves, as visible with the boots off, have carbon buildup on them - should there be build up after only 3500 miles? Head pipes have some gold color to them on the right two cylinders so maybe the bike was running lean which caused some damage?

Not a whole lot I can do at this point but can't help but wonder. Paid a medium high price for the bike under the assumption it's in near new condition, don't like surprises.

Ed

What color is the inside of the valve cover? Clean shiny silver aluminum or a little yellow/brown?

[Nessism]

The inside of the engine looks clean other than somewhat dirty oil. Most of the clues so far point to the mileage being true, it's just those shims and carbon on the intake valves seems strange to me. And speaking of carbon, it is present on all the valves, not just the ones with the tight clearance.

Regarding low mileage bikes, I tend to agree with your comments 49er after experience with my two 550's. Both of those bikes are in great shape but it took a fair bit of work to bring their roadworthiness back up to speed. I enjoy working on the bikes, and don't consider it a chore. So far haven't been burned by internal engine damage due to storage. Once bought a brand new transmission for my car though and one of the bearings had rusted, so I know how that goes.

Thanks for the comments.

Ed

[bwringer]

It doesn't take long for carbon to build up if the bike was run on choke quite a bit. This is common on low-mileage bikes that were started and run in the garage every once in a while on the theory that this was somehow good for the bike.

I wouldn't worry too much about it -- an "Italian tune-up" will do a world of good. (Get it running right and then go ride the snot out of it for a while.)

As far as valve wear, the critical dimension is the width of the margin at the edge of the valve. In other words, how blunt or sharp are the edges of the valves?

If you have or can borrow a borescope of some sort, or find a way to illuminate and look in the combustion chambers via the spark plug holes, you could turn the engine slowly until the valves open and look at the edges of the valves for yourself.

[Nessism]

Used Steve's spreadsheet to catalog all the valve clearances this weekend; they are pretty consistently at 2.60 with one valve at 2.65 and one at 2.55. Have some 2.60X shims which are damn handy at getting the clearance just right so to speak. I feel better to see the clearances so consistent.

Checking the valves was child's play compared to getting the old gasket off. The damn thing was hard as a rock. Had to chip it off in chunks before even attempting to scrape off the excess. Tried some of that Permatex gasket removal compound, applied with a brush. Worked to loosen the last bit of gasket but the stuff is very harsh and takes off paint despite my being careful. In the end I got the surface clean but it must have taken me at least 2 hours of work. Huge pain. Using a Real Gasket from now on, no way I'm going through this headache again.