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<  Performance issues  ~  bigend questions

willem
Posted: Sat Oct 13, 2007 8:00 pm Reply with quote
Junior member Junior member
Joined: 06 Sep 2005 Posts: 15 Location: Netherlands
Hello,
I have a Japauto engine,
dismantled, and need new shells for the bigends.
Bigends itself are ok, but the shells have some scores.
According to this document:
http://www.honda4fun.com/man_officina/pdf_manuali/CB750_K0_K1/Cap_03_2.pdf,
there are some choices.
I know it's in French, can't read it, but I do understand the tables and pictures on the pages 42-43-44,):

It wouldn't be a problem, if the marks as shown in the picture of the crank appeared on my crankshaft, but they don't. Maybe the crank has been llightened/balanced, the crank does have a bit of a rough finish at the place where the stamps should be.
There are marks on the conrods, fortunately.
I can measure to 0.01 mm, but that's not exact enough to use that table.
Does anybody have an idea or trick to get the right data?
Maybe just buy 1 set, then I know halve of the data required, then use a micrometer to determine the remaining clearance?
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Satanic Mechanic
Posted: Sat Oct 13, 2007 8:47 pm Reply with quote
Moderator Moderator
Joined: 04 Sep 2005 Posts: 309 Location: Munich, Germany
Willem,

try Plastigauge (http://www.plastigauge.co.uk/) if the marks on the crank have become unreadable. Measure it up with one set of shells, and you should be able to determine the correct shelves afterwards. It's a bit cumbersome to use, but it's the best way to determine bearing clearances.

Cheers,
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willem
Posted: Sun Oct 14, 2007 8:16 am Reply with quote
Junior member Junior member
Joined: 06 Sep 2005 Posts: 15 Location: Netherlands
Plastigauge is better then a micrometer indeed,
but I could not get it anywhere.
On their site it seems no problem to order low quantity's,
thanks for the link.

Regards Willem.
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willem
Posted: Sun Dec 02, 2007 11:46 am Reply with quote
Junior member Junior member
Joined: 06 Sep 2005 Posts: 15 Location: Netherlands
Hello,
I measured all the bigends,
they all have a clearance of about 0.063 mm with green shells.
The crankshaft should be replaced at 0.08, so it's still okay.

The thicknes of the shells is according to the guide 15.000 to 14.something,
each color increasing 0.005 mm.
I guess these ar tenths of mm, so actually 1.5 to 1.4 something.
According to this I could use all black shells, 1.500 mm and still hav plenty of space for the oil film.

Have I understood this right?

Regards Wilem.
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