shims

[lee8040]

can anyone tell me how you tell if the shims need replacing on my zx6r j1 ninja? its coming up to 28000 miles but i dont think they have been done but when i phoned one service shop they said they'd replace only if they needed to be but they were to far out for me to use but others are saying they will do them anyway.

how can i tell if i still have life in them?

thanks

[Kickstart]

Hi

You need to measure the valve clearances. Based on those you can tell if the shims need changing (the shims don't wear, they are just there to adjust the valve clearances).

The cheap skate way of doing it is a compression check, and then only go near them if compression is down on 1 or more cylinders. However a bit dodgy really.

Most bikes with shimmed valves will have the clearances get tighter with wear and so have the engine get quieter (ie, don't just wait until it rattles).

All the best

Keith
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[lee8040]

so there not an item that needs replacing after so many miles they could need replacing after 10k or 30k depending on bike?

[Kickstart]

Hi

Yes. The shims are just small pieces of very accurately machined hard metal.

This is a car one:-

https://www.alfa-pages.co.uk/TempPicture/shim.jpg

You measure the clearance, and if it is out of spec take out the existing shim. From the size of the existing shim and the clearance you can calculate the size of the required shim, which you then put in.

While you have 16 valves each with a shim, even if all required replacement there is a good chance that many could just be swapped into another position to minimise the number you need to buy.

The shims themselves shouldn't wear to change dimensions (although be dubious of believing the size marked on them, some people grind them down to change their size rather than using a replacement.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing