Piston 650 to high? - Page 2

Taffy · July 8th, 2020, 12:45 AM

Originally Posted by SandurRx

Thanks for your help Taffy.
Bought a new chain off you that needs to be fitted.
Don’t think the Engine is machined though.

I will check how the piston sticks out when then engine is out off the frame.
Little time to spend on the bike at the moment.
You mean left and right when standing on the left side of the bike right?

They did not put a new rod or crank in the engine when the new piston was placed.
Could the piston just be to high? The previous owner did tell me the new one was higher.
I then just thought it would be a high compression one.

About the case id. I think it’s a rebought 2004 one

I think you'll be fine with that piston if you machine a little off the rim to make sure the engine is safe. it will give a very good boost in performance too!

But I would want to know how it came to this.

one thing just occured to me; try measuring the stroke please? it should be 80mm.

there is a possibility this engine is a strange one, as said above, the serial numbers don't seem right.

Taffy

SandurRx · July 11th, 2020, 08:42 AM

What a bummer! Measured the stroke and it turned out to be a 550 engine.

70mm stroke 100mm piston

Whats the difference between a 550 and 650 piston?
Hope im good with the headgasket i bought...

The piston is 1.1mm over on the left and 1.2mm on the right.
Taffy can you help me calculate how many needs to be machined off?

Im going to put new main bearing in the engine so wil get to crank float later.

Taffy · July 11th, 2020, 10:31 AM

I nearly said; "i wonder if it is a 550?" but then just left it as; "there is a possibility this engine is a strange one, as said above, the serial numbers don't seem right."

Take off 0.8mm nothing over 0.3mm should be over the top of the crankcases.

the piston will be down 1mm in the middle. hardly worth counting. its 5cc so a drop of 0.3 to 1 perhaps? but with a proper squish you'll probably gain performance.

Taffy