Shims ... What's the Most Common from the Factory

[Mr.humbucker]

I am restoring another GS650G 1982, It was my parts bike from my original restoration ... couldn't stand seeing it sit there and not on the road. So ... I bought another parts bike for it. I was "harvesting the shims" from my part's bike part's bike .... and 7 out of 8 were 2.70, and the last was 2.75. I found it interesting that they were all almost the same and wondered whether this was an indicator that these were all the factory-set shims.

I've set the shims a half dozen times or so and find that I am using thinner shims, 2.40 to 2.65. Does the size of the shims tell us anything about whether there's increasing wear in any of the components?

Thanks to all those out there who are more familiar with these bikes and share their knowledge here for those of us on the shallow side of the learning curve!

 

[Suzukian]

If the valves seat it a lot, the shims would get thinner, if the cam wears a lot, the shims would get fatter. So they do tell you, but they do last a long time and can be reused, unless visible marred. A good Micrometer will tell you if they are truly flat.

 

[bwringer]

Valve clearances always get narrower on these engines; over the miles, the valves wear where they contact the seat. The outer rim of a GS valve gets skinnier, and when it gets below a certain point at very high mileage, you're out of room and need to replace the valves.

Shims are much harder than the cam lobes and run in oil, so they do not wear.

Factory shims have a distinctive style of stamping and type in the sizes, and shims marked with an "X" are "fat" shims, which were only installed at the factory (for example, a 2.70x would normally measure 2.72 or 2.73). I've accumulated a small stash of "X" shims, and they can be handy. Factory shims are shiny, and you can often see a circular pattern from the heat treating. Most or all aftermarket shims are a uniform gray color and have sharper edges.

 

[unfocused]

It's called valve recession. This is when the valve face and valve seat wear, then the valve starts to travel up into the valve seat causing the valve stem to move higher thus reducing the valve clearence. This is normal wear and is the reason for valve adjustments early in the engine life but less frequent as the miles add on. This doesn't mean something is going wrong at all. However, enough valve recession could lead to very tight clearences or none at all resulting in, low compression/poor run-ability, valve tip filing or replacement, or worse, catastrophioc failure when the valve face and valve stem become 2 pieces (valves are originally 2 peaces and friction welded together.) In my industry, we run alternative fuels requiring valve recesion checks every so many hours. Yes, we do see valves come apart taking out cylinders. Thankfully we can rebuild the cylinder with a power pack and get the engine up and going quickly although expensive ($15k+ per power pack)

 

[Nessism]

Shims in the 2.70 range were common on new bikes. When stocking shims, it's advised to have a couple of steps available, so you don't need to stop in the middle of the job and wait for parts. So in this instance, I'd order a handful of 2.65's and a few 2.60's, which you will use eventually.

And be sure to follow the factory cam positioning method. Some people simply point the cam lobe away from the bucket, then measure this way. Doing so, though, will show more clearance than when using the factory method, thus fooling you into a false sense of confidence.

 

[Suzukian]

If shim wears, or gets galled, you have an oil feed problem, they are extremely hard. I've seen shims reused so many times. unfocused​ , you're right, it's almost always the valves seating deeper into the valve seat, or them wearing away wearing.

When I rebuilt my M.G. 1275 engine for my '73 MG Midget, MG Hardened the cast iron head valve seats anticipating the coming of unleaded fuel. They hardened the valve seat area by applying large amounts of heat, and quenching. It was a really bad way to do it. I had a machinist mill out and press in new valve seats that made the head up to modern standards, I also had valve guides installed for unleaded fuel, they run a little wider as unleaded fuel did not have the lead as a lubricant to run tighter valve stems. I can safely run the M.G. with unleaded fuel without any problems.

 

[Mr.humbucker]

Lots of helpful information here that has confirmed my beliefs of what is occurring with the valves. I went to a fellow "Suzukian" across town today to borrow his stash of shims. He is 79, rides every chance he has, has had 40 bikes over the years, mostly Suzukis. The thinnest shim he had of 12 or so was was factory stamped 265 and it actually measured 270. This stash confirms that as bikes age the shims needed are thinner. I am now going through the shims on my latest 650 parts bike hoping to find a few sub 270's otherwise I will have buy some.​

Thanks again to all who have replied.

 

[Mr.humbucker]

Shims in the 2.70 range were common on new bikes. When stocking shims, it's advised to have a couple of steps available, so you don't need to stop in the middle of the job and wait for parts. So in this instance, I'd order a handful of 2.65's and a few 2.60's, which you will use eventually.

And be sure to follow the factory cam positioning method. Some people simply point the cam lobe away from the bucket, then measure this way. Doing so, though, will show more clearance than when using the factory method, thus fooling you into a false sense of confidence.

Great plan ... Ill be ordering a half dozen or so to keep on hand so I am ready.

 

[salty_monk]

2.6-2.75 seems to be the factory range in anything I've played with.

 

[LAB3]

Great plan ... Ill be ordering a half dozen or so to keep on hand so I am ready.

You'll often see sellers on eBay with offers for three or five in one batch at a much better price than buying them individually.

 

[Mr.humbucker]

Instead of resorting to eBay I went to the Suzuki dealership in town, which I rarely visit, figuring they probably charge me an arm and a leg for the two shims I needed ... Nope, they gave them to me for free ... needless to say I was pretty happy and as such I will likely pop by there from time to time to browse .... hope I don't end up buying another bike as a result

 

[93Bandit]

Instead of resorting to eBay I went to the Suzuki dealership in town, which I rarely visit, figuring they probably charge me an arm and a leg for the two shims I needed ... Nope, they gave them to me for free ... needless to say I was pretty happy and as such I will likely pop by there from time to time to browse .... hope I don't end up buying another bike as a result

Wow that's a good deal!

Do any modern suzukis use the same shims that our GSs do? I'm surprised the dealer even had the shims.

 

[Mr.humbucker]

Wow that's a good deal!

Do any modern suzukis use the same shims that our GSs do? I'm surprised the dealer even had the shims.

I wouldn't think that modern bikes use the old 29mm shims. One fellow in town that has been working on bikes for 40 Yeats that I visited in search of the correct sizes had a nice Suzuki factory box of shims. Many of them mid sizes were gone but there were
​​​​​ probably 40 to 50 others. He offered me the box of shims for $200 Canadian dollars great deal IF you do a lot of valve clearances ... I passed as I have around 15 or more already.

 

[rphillips]

Don't know if anybody uses the big shims any more, I was so thankful when the bike mkt. started going away from them and going towards the rocker arms and screw adjusters. Very surprised when they went back and started using shims again, but made them worse by installing them under the buckets... They do work, as good as the big shims or rockers, but, for me, sure are aggravating .