Stacking valve shims

[corksil]

During a valve lash adjustment, is it possible to stack valve shims to attain required measurements?

Example ---- 1.75mm shim required to set proper lash. All 1.75mm shims used during previous un-related valve lash adjustment procedures.

1.00mm and 0.75mm shims remaining.

OKAY to stack 1.00mm and 0.75mm shim on top of each other under bucket to attain required height?

Thanks!

[Linkin]

Sounds dodgy, I personally would not do it my bikes, even where a dodgy workaround would get it going again. No sir.

What's the diameter of the shims? You can get a hot cams valve shim kit or even just the little refill packets with 3x each size shim. Amazon or ebay.

[corksil]

7.48mm OD.

I purchased the hotcams kit, which has 1.20-3.50mm shims in 0.05mm increments.

Only problem is that the kit only comes with three shims in each size -- so if you have 4 valves requiring the same shim height, you're forced to stack shims of different sizes on top of each other to attain required height -- or -- buy more individual shims.

[rc racer]

Buy more individual shims. Also check the shims you removed from the engine. The marks are probably worn off but you could measure them with calipers. One of those from the other cylinder might be the 1.75mm you need.

[Racer x]

Don't stack the shims.

[corksil]

Here's the technical part.

I installed "race" cams from DCR, and after some research -- I determined that the more aggressive camshaft profile is not from welding material to the cams and re-grinding them -- but actually from removing material from the rest of the camshaft, excluding the lobe.

The result being -- camshafts that have an aggressive profile, which are then shimmed more excessively to regain the appropriate clearances when the valves are closed.

Learning from experience -- stacking shims is not a good practice. My shim kit included shims up to 3.50mm. Some of the valves required 3.55mm and 3.60mm to be shimmed back to kawasaki spec.

I used all of the 3.50mm shims in the kit (3) -- and attempted to stack two smaller incrementations to achieve the 3.60mm required. (1.80mm + 1.80mm = 3.60mm OR 1.75mm + 1.85mm = 3.60mm respectively.)

Stacking valve shims involved a successful test ride until 4k RPM, at which point a clattering sound occurred. The bike was promptly shut down and tore down for inspection.

Inspection revealed that two valves (each containing stacked shims) -- had thrown the shims out of proper placement under the bucket, and gone so far as to eject the two half-moon-shaped keepers from within the valve spring retainer; also found under the bucket with the displaced [stacked] shims.

No valvetrain damage occurred, the bike was reassembled with 3.50mm shims and all but two valves remained close to ideal valve lash specification. The remaining two valves were on the loose end of the tolerance range.

Bike was reassembled, taken for very aggressive test ride. After 40 miles, the drive chain master link sheared under hard acceleration and the drive chain was ejected from the rear sprocket causing no mechanical damage to engine, albeit cracking the rear tail fairing and shattering the chain cover safety guide.

Engine starts/idles/runs fine with no drive chain connecting front and rear sprockets and after a 13 mile walk, I am home. Will recover bike from secret location tomorrow morning and bring it back to the shop for replacement drive chain installation and more thorough inspection.















I tell myself that I will only make these types of mistakes once, and it is good to learn these things on such a small and forgiving machine.








With all that said, these new cams are significantly more powerful in the upper RPM range and I suspect that the added power was what caused an old and fatigued drive chain to fail. Non-O-ring race chain, here I come.
@Racer x --- I believe that your 'world fastest ninja 250' record may some day be contested, if I decide to record/publish any of this redneck engineering. However, publicity has and never will be in my plans. With that said, any help/advice/guidance is welcomed.

[Linkin]

What about the shims in the bike that you're removing? Are any of them 1.75mm? You can also use 1.72mm, 1.74mm, 1.76mm etc

Here's a pic of a few swaps I did in my FZR

[subxero]

kinda surprised you actually tried stacking them. As soon as I read the topic of the thread, my thought was they would never stay seated as was your result.

If I was that desperate I would have at least tried mating the 2 together with jb weld or something IDFK?

either way seems like you didn't mess anything up so that is good.

How much were the cam shafts if you don't mind?

[corksil]

I'm not one for speaking poorly about an individual and their business practices unless it's absolutely true -- but my impression was that these are the cheapest camshafts on the market, and they do NOT come with any technical support or installation guidance.

The one or two times I got him on the phone, he was very hurried to end the call. These are one or two minute phone calls, not discussions about personal life or any superfluous BS.

Advertised on the website -- 259 if you mail in your cams as core. Also advertised on website was free shipping orders over 50. I paypal'd 259, mailed my cams -- waited for a call. Two weeks later, called in and they were indeed received. After that call, new cams were mailed -- but the free shipping was not honored and the excuse of "new website, and the designer must have put that up without my permission because I would NEVVVVER offer free shipping.

55 later, cams were mailed. So 259 and 55 shipping. After a few phone calls and package tracking which confirmed that my cams DID arrive quite some time ago and that I had not received anything back.

As far as stacking shims -- this is the first valve adjustment I've done on a motorcycle, so yes it was an idiot mistake.

DC also mentioned that a suzuki dealer may have shims thicker than the 3.50mm largest size in the hotcams shim kit. Also mentioned that if a suzuki dealer didn't have them, he could "make" them. I'm skeptical.

I'll also add that I got a bit dyslexic in adding shims to remove lash, removing shims to add lash, metric conversions, discussions with thousands and ten thousands... it was a learning experience. Took me a couple tries but I'd like to think the bike is fixed and will provide another 25k miles before needing anything other than chains and sprockets and tires.

About that.... time to order new chain/sprockets.