Vintage piston?

 I'm having a 1975 Honda XL350 engine completely redone. I mean
everything. Every seal, gasket, bearing and bushing replaced if it needs
it or not. New valves, valve seals, guides, piston and rings. You name
it, if it even looks worn, it's getting replaced. I'm doing the search
for NOS or aftermarket parts myself, to save paying the mechanic for
surfing the net for them.

I believe I've found everything but a piston. The OEM piston is 79mm
with a 8.3 to 1 compression ratio. The engine currently has a 79.5mm
piston. I want to bore it to a 81mm with 9.5 to 1 ratio. I called JE
Pistons, and they don't have the specs on file needed to make me a
piston. The best they can do is if I send them an old piston, along with
the combustion chamber volume, then they can make one. I have no idea
what the combustion chamber volume even is!

Are there any other piston companies out there that can make me a piston
like I want, by me just saying the make / model / year and size of
piston? Wiseco maybe?

TIA

 Mike Corey wrote:

Pull the head, cover the combustion chamber with a plastic plate with
a hole in it, use a burette to fill the chamber with water or oil or
whatever you like, when it's full read off how much you've used and
you've got the combustion chamber volume.


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 Bruce Richmond wrote:


Actually...  Honda already considered their piston's crown when they
came up with their compression ratio. Right? If the numbers 8.3 and 348
can be trusted, the calculated volume should be correct.

Mike Corey ought to tell JE Pistons exactly *how* he arrived at whatever
volume he sends them.

 Dave Emerson wrote:


How can you cover up the combustion chamber with a plastic plate
if engine isn't dismantled, at least the cylinder head has to be
pulled off the engine, right?

There seems to be some confusion here, some people are trying to
measure the cylinder head combustion chamber volume alone, others
are trying to point out the piston may or may not have a flat top
and it may not come up to the top of the bore, etc.

For the OP's purposes, measuring the CC volume with the plastic
plate approach, plus sending the piston to the fabricators, should
be sufficient.

--
'01 SV650SK1  '99 EX250-F13  '98 ZG1000-A13
OMF #7

 Dave Emerson wrote:

If he's already got the engine dismantled then it's even easier since
he doesn't have to pull the head.

Here's a more detailed description of the procedure.
<ttp://www.hydrostream.org/ArticleArchives/CCHeads.htm>



--
--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)