Piston 650 to high?

SandurRx · Jun 28, 2020

Hello guys.

Got a 650 from 2002 with a later model engine.
The previous owner did put a new piston in but could not get it running.
I did by cleaning carb but under throttle cooling fluid came out.
So retorq the headbolts and then piston started hitting The head.

Is this piston to long? Can anyone help me?

https://ibb.co/C71NRp1
https://ibb.co/r32nLxt
https://ibb.co/7RYnZf6

Also there is goo on the drainplug. What could that be.
Planning on opening the engine anyway.

https://ibb.co/y0BgBm7

Thanks in advance
Sander from the Netherlands

canolman · Jun 28, 2020

How do you know the piston is hitting the head?
The goo on the drain plug if you rub it between your finger tips can you feel anything bigger than a grain of salt?

husabutt · Jun 28, 2020

It looks like the piston is too long to me. I would venture a guess and say the goo is probably fiber clutch plate material and that the oil was not changed and proper intervals. Even if not worn out the fiber clutch plates tend to lose their friction material with age. I think your fiber clutch plates are either very old, very worn or of low quality.

Taffy · Jun 30, 2020

if the piston is only 0.9mm over the top it is not touching the head because a head gasket is 1.3mm crushed. BUT, a piston shouldn't be more than 0.4-0.5 over the top to allow for the 'throw' when revving. it certainly shouldn't be stopping the enginbe from turning over.

it is a blessing though.

what about the valves hitting the pockets?

I don't think you're being honest? why the secrecy with the camera and the cloth?

Taffy

SandurRx · Jul 1, 2020

So the goo could be clutch. Thanx for the tip.

Piston must be to high then. Its 1mm for sure.
Cant see marks from valves tho.

Look at the new pics. You can see the piston hits the head on throw.

https://ibb.co/KFx15cc
https://ibb.co/QvYZtpP
https://ibb.co/p21F8mz

Taffy · Jul 2, 2020

hello

you need to find out 'why'?

it could be that you have the earlier long stroke crankshaft in the engine but with a longer rod?

maybe someone has machined the cases? this one is easy to answer because the cam chain will be very slack even when new.

you need to be very accurate NOW about how much the piston is ove the top. normally Husberg pistons lean over (sadly) so 0.9-1.1mm left and right would be typical.

let me know and I'll do a real compression calculation for you.

regards

Taffy

jojo09 · Jul 2, 2020

Your casing serial nr. seems odd.
They came with a printed /lasered serial nr.
Yours is stamped in.
I have never seen a 2-820 up to this point.
As they started them 04.
So
4-820 (2004)
5-820 (2005)

And so on.

Maybe a rebought new one. These came without serial nrs.

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SandurRx · Jul 5, 2020

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

Taffy · Jul 6, 2020

No, a piston is only measured across the gudgeon pin (american english; wrist pin) otherwise it would wobble back-n-front!!!!!

when stripping an engine ALWAYS check the crank float before you strip and if seekinga blueprinted rebuild; the squish. your case may serve as a warninks (sorry!) to others that there are idiots out there.

when you stip it you'll need to measure the following.
pull the GP out as much as you dare until a vernier can sit on it and the edge of the piston. this distance would normally be 13.8mm (says he without looking in his book!).

let us know.

Taffy

canolman · Jul 7, 2020

Are there no markings on the piston crown?

Taffy · Jul 8, 2020

SandurRx said:
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 · Jul 11, 2020

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 · Jul 11, 2020

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

Piston 650 to high?

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