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July 2017 Club News

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Finding the Compression Stroke

by Arthur

I had some spare time the other day as I was getting ready to change the timing belts and do the valve clearances on the Monster. I'd made the engine-turning tool, a closing rocker depressor and a strut to hold the fuel tank out of the way.

As I turned the motor to get to TDC to change the first belt, I realised that I could put that rush of air out of the plug hole to good use. To my surprise, the whistleplug actually worked!

Compression whistler parts.
It's no big deal on the Monster because the plug holes are right where you can see them but on other bikes it can be difficult to turn the motor and watch for flywheel marks or rocker movement - especially if you are turning the motor by turning the back wheel.

Who knows what will emerge from the shed?

If you have some spare time in the shed and would like to make finding that compression stroke into party time, try modifying some bits to create an AUDIBLE indicator.

1. Rip the guts out of an old spark plug.
2. Get hold of a party whistle.
3. Add heatshrink tubing to strengthen the whistle bit.
4. Hot glue the whistle bit into the now empty spark plug body.
5. Dig into the box under the bench and find a bit of hose: cut and fit.
6. Lightly screw the whistleplug into the chosen plug hole.
7. Turn the motor over slowly.
8. Listen. When the whistle whistles, that’s your compression stroke.
9. Ease up onto Top Dead Centre.

Or you could just put your thumb over the plug hole and wait for the rush of air. But where’s the fun in that?

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