Kiwi piston dimensions

[Mike Ginn]

Guys. I have completed the machining of the piston for the Kiwi MK2 from solid. All is well and I have left the length as 1 1/8inch which is longer than needed.

My question is "how far from the top of the cylinder should the top of the piston be". This obviously affects the compression and Westbury makes a reference to this for the cylinder machining. The engine is only intended for occasional use and will not be used to drive anything.

I would appreciate any guidance

Many thanks

Mike

 

[Vietti]

If it were me I'd leave it full height and shorten if need be. Leave ring grooves lower on the piston in case it needs lowering. I tend to think slightly higher compression ratios are good in a model as they seem to make idling lower and more consistent, there are limits of course.

 

[Mike Ginn]

Thanks for that reply. As an update I found I had the GA which shows the top of the piston flush with the cylinder liner top so I guess that is what I will do.

I cut up my drawings and scan each part and print on A4 (letter) size. During this process I "lost" the GA but now found!

Thanks

Mike

 

[jrslogs52]

Hello Mike,
My drawings are in inch and the piston top is flush with the top of cylinder liner.
Hope this helps,
John

 

[Mike Ginn]

Guys
Some advice please. I have finished (well almost) my KIWI and need to get it running. Using an electric drill it will fire but it is not sustained. I am using Coleman fuel. I have removed the float and valve and am using the float chamber as the fuel tank (I have blocked the normal fuel inlet at the base). I notice that the engine usually fires when the fuel is about level with the outlet to the carb and that maybe is a clue. I could rig up a fuel tank and set-up the float to keep the fuel level with the outlet if that is the solution.
I have a general lack of experience of running this type of engine so any thoughts would be appreciated.
Many thanks
Mike