Hotcams shim problem

I've used Hotcams shims in all my bikes with no problems, until now, when my Husky was new I set the valves and adjusted only the right exhaust, I checked them tonite and all were perfect except the right exhaust, it was .26mm (specs .15 to .20mm), I pulled the .230mm out and put in a .240, then I had .08mm, pulled the .240 and put in a .235, got .13mm, put in a new .230mm and was right back to the original .18mm I had when bike was new, (8200mi ago) Long story short the shim wore. I'm very happy with no movement of my valves, but don't trust my shims anymore, you can see where the shim is worn where it contacts the valve stem, checked all other shims and are perfect, along with the cams, followers, etc. I guess I'm just asking if anybody else has seen this? This is also on the valve that is used for the decompressor. Mike

I've noticed it also, but it only becomes measurable after a long period of time (my case 2 seasons). Just think of it this way, would you rather the shim wore down, or the stem of your valve? Shims now seem dirt cheap and simple to replace. I still use them in all my 4-strokes.

I've noticed it also, but it only becomes measurable after a long period of time (my case 2 seasons). Just think of it this way, would you rather the shim wore down, or the stem of your valve? Shims now seem dirt cheap and simple to replace. I still use them in all my 4-strokes.

I'm very happy with no valve wear in 3yrs and 8200 miles, just wondering why only 1 shim wore. I'm actually amazed that I've not had to adjust the valves.

Hmmm

I wonder if type of oil has anything to do with it.

Of a stiff valve guide.

Possibly the top of my valve is cupped or dished slightly, causing the shim to wear, if I put the shim in upside down the measurement is ok, I can catch my finger nail in the groove, here's a picture.

shim.jpg

Could be you got a bad shim in the kit.

The engines are designed so that the cam lobe hits the bucket off center, causing the bucket to spin as the enigne runs. This way the cam is contacting the bucket in a different spot all the time and slows down wear to the bucket. The problem is, now your shim will most likely spin with the bucket and grind on the top of the valve stem. Since it is easier and cheaper to change a shim than to change a valve, you want the shim to be softer than the valve. There really isn't any way to solve it. If you make the shim harder than you will wear down the stem of the valve, which would be worse. You can flip the shim over and get twice the life out of it, or just replace it. This wear should take a long time, so it shouldn't be something you have to worry about all the time.

Flipping the shim is not advisable. I don't know about a Husky, but the underside of YZF lifters has a "button" on it that is slightly smaller than the shim diameter so it will not touch the spring retainer, even if the shim is quite thin, or missing entirely. Using a shim with a pocket worn in the center of it against the lifter surface will increase the load borne by that surface, and possibly spread the damage. Shims are cheap. Throw it away and use a new one.

Another question is whether the top of the valve stem is oiling correctly, and whether there is something wrong with the surface of the tip of the valve stem to have lead to so much abrasion of the shim. Hopefully, the shim was just a dud.

Flipping the shim is not advisable. I don't know about a Husky, but the underside of YZF lifters has a "button" on it that is slightly smaller than the shim diameter so it will not touch the spring retainer, even if the shim is quite thin, or missing entirely. Using a shim with a pocket worn in the center of it against the lifter surface will increase the load borne by that surface, and possibly spread the damage. Shims are cheap. Throw it away and use a new one.

Another question is whether the top of the valve stem is oiling correctly, and whether there is something wrong with the surface of the tip of the valve stem to have lead to so much abrasion of the shim. Hopefully, the shim was just a dud.

Yea I used a new shim, I just flipped it to see if the whole shim was thinner. The husky doesn't have a bucket, a rocker arm rides directly on top of the shim which sits directly on top of the valve, so flipping the shim would wear the rocker arm, its a very simple design and valves can be adjusted with experience in 15 min. Mike

The husky doesn't have a bucket, a rocker arm rides directly on top of the shim which sits directly on top of the valve, so flipping the shim would wear the rocker arm, its a very simple design and valves can be adjusted with experience in 15 min. Mike
Something like an earlier KTM, then. I would guess, given that, that the trouble is either that the particular shim was loose in the spring retainer, allowing it to shuffle around on the valve stem, (because Husky uses shims larger than 9.48mm in diameter, the shim was undersize, or the retainer pocket is worn open), or the motion is normal, and Hot Cams shims just aren't hard enough to be used in that configuration.

Rockers "wipe" across the top of the valve at right angles to the rocker pivot as they swing, and this lateral thrust/movement causes more wear to the rocker noses, valve guides, and shims than an OHC/bucket tappet arrangement.

Maybe the stock shims are harder, since the only shim that wore was the Hotcams, and maybe most bikes don't go that far before being replaced. Mike

You need to check your lifter to verify that it has not cupped. Everytime I have seen a shim wear as shown here the lifter had gone bad and "cocked" the shim on the valve. You also might want to check the spring, especially if it is an exhaust. Exhaust springs are exposed to much more heat and tend to loose there "pressure". When this happens the the lifter looses contact with the cam and it beats the hell out of the lifter. In my experience a worn shim is a sign of another problem.

You need to check your lifter to verify that it has not cupped. Everytime I have seen a shim wear as shown here the lifter had gone bad and "cocked" the shim on the valve. You also might want to check the spring, especially if it is an exhaust. Exhaust springs are exposed to much more heat and tend to loose there "pressure". When this happens the the lifter looses contact with the cam and it beats the hell out of the lifter. In my experience a worn shim is a sign of another problem.

This bike does not have lifters, the rocker arm rides directly on the shim which rides directly on the valve, and the only shim that has gone bad is the Hotcams shim, the stock Husky shims are still in the other valves and are perfect, and they are all 9.48 shims. Mike

This bike does not have lifters...
That's a matter of nomenclature only. Either name is accurate where an OHC engine uses rocking cam followers.
That's a matter of nomenclature only. Either name is accurate where an OHC engine uses rocking cam followers.

Sorry I'm used to working on cars, many overhead cam cars have lifters and cam followers (rocker arms), if I go to my parts department and ask for a lifter I will not get a cam follower. The "lifter" is not worn and the shim would be almost impossible to cock without some major clearance as it slides into the valve spring retainer and fits flat on top of the valve, and there is no wear on those parts, I get the same valve clearance on both sides of the cam lobe.

I'm going to just check the valves next summer after some more miles, if all OK I'll assume a bad shim. Mike

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