My 640 lump - under Master Surgeon Minter

[ellrider]

Could I get a CCM rotax engine and fit that?

[ZIP TIE]

Could I get a CCM rotax engine and fit that?

No because 350 owners have already bought all the available ones

[Bunker]

Thing is, you'd still end up with the shorter stroke so I presume less gas to compress thus a low comp 500 - this is true even if we found a taller 89mm piston. Just to complicate the maths further, doesnt the 500 have a 2mm cylinder head gasket - so does 'one' assume the barrel is 2mm shorter? Or is that just because the MilSpec is valve safe - I think the 504s piston comes right up to the top of the cylinder....just a mix of facts there.

So which part of the crank is different to get the stroke if its not a longer con rod. And can it be swapped out onto a 350 crank shaft...obviously we dont want to start rebuilding crank shaft assemblies willy nilly but it would be interesting...

I think I need to separate this onto a new/ revived thread.

[ZIP TIE]

Thing is, you'd still end up with the shorter stroke so I presume less gas to compress thus a low comp 500 - this is true even if we found a taller 89mm piston.

No, it would be down to piston design and the shape of it's crown and the size/shape/volume of the combustion chamber and has very little to do with the barrel.

Just to complicate the maths further, doesnt the 500 have a 2mm cylinder head gasket - so does 'one' assume the barrel is 2mm shorter? Or is that just because the MilSpec is valve safe - I think the 504s piston comes right up to the top of the cylinder

The head gasket is due to the use of different metal between head and cylinder and it is possible to do away with it with some careful lapping

So which part of the crank is different to get the stroke if its not a longer con rod. And can it be swapped out onto a 350 crank shaft..

A longer con rod would give the same stroke but would just smash the piston into the head or increase compression. The position of the hole machined for the big end pin is moved closer or further away from the centre of the crank web to give different stroke so you could weld the hole and remachine for a different stroke

obviously we dont want to start rebuilding crank shaft assemblies willy nilly

I don't know sounds like a good start to me

[ZIP TIE]

I think I need to separate this onto a new/ revived thread.

Yes agreed

[Minter]

Back to the rebuild!

Its getting there slowly but surely..



Thats this side finished...



And this side is nearly done...

[Minter]

New rings on the 100mm Omega Piston..

[namtip]

Sorry to hijack the thread a little, but when you look at the engine from this side, which way are the wires supposed to be routed? To the left or to the right?

[ZIP TIE]

Sorry to hijack the thread a little, but when you look at the engine from this side, which way are the wires supposed to be routed? To the left or to the right?

On the 500 they were routed up the front ie to the right but this causes problems due to the heat from the exhaust and spray etc from the front wheel and general weather/water crossings.It's a much better idea to route them to the left up the back of the engine following the oil pipe.

[Minter]

Sorry to hijack the thread a little, but when you look at the engine from this side, which way are the wires supposed to be routed? To the left or to the right?

On the 500 they were routed up the front ie to the right but this causes problems due to the heat from the exhaust and spray etc from the front wheel and general weather/water crossings.It's a much better idea to route them to the left up the back of the engine following the oil pipe.

Yep exactly as Zip says, I always wrap them in spiral wrap to keep them neat and always up around the back of the cylinder even on 500's