My piston sets and fixtures.

Please post your bike pics here

Moderators: Volker_P, tidd650

Cb673
Posts: 12
Joined: Sat Sep 29, 2018 12:52 pm

My piston sets and fixtures.

Postby Cb673 » Tue Oct 16, 2018 12:42 am

I've had a few 650's and someone Once said I can't get overbore pistons.....
Image
So I have 66, 64.75, 62, 61 and 60mm piston sets I have modified for the 650.
Most for stock cam, 1 set for turbo, 2 550 sets, and 1 set for a lumpy cam. 9 useable sets in total.
Cb750, kz650 and kz750 pistons are the easiest to mod I have found in abundance.
The piston pots and mill fixture are made by me.


L8r

kerryb
Posts: 77
Joined: Fri Oct 19, 2018 3:18 pm
Location: Buffalo, N.Y.

Re: My piston sets and fixtures.

Postby kerryb » Mon Oct 22, 2018 9:10 am

That's a skill I would like to know about. I'm sure some other non-machinists would love to see a write-up with pictures on how you modify pistons for another engine! Are you a machinist by trade?

Cb673
Posts: 12
Joined: Sat Sep 29, 2018 12:52 pm

Re: My piston sets and fixtures.

Postby Cb673 » Mon Oct 29, 2018 10:47 pm

Yes I am a machinist. Trained in '98/'99 been in the trade ever since. Lots of repair shops, manual machines, and vtl lathes. I'm CNC functional.... more a fat finger at the console programmer than a mastercam user.
(mastercam writes the program for you once you draw the part in 3-d in mastercam)


I first got the idea of modifying pistons when I saw what NOS piston sets cost, and I found 1 overbore set that sold on ebay for over $600.
I was told there is no way to getting a 650 overbore for a fair price on a few honda cb forums.
At the time my 650s motor was starting to smoke(slightly stuck ring or two)

So I ended with the first useable set I could get rings cheap for.
A 76?77?... the first year of the cb750 hondamatic.
It has a higher dome than any other cb750.
Thats the first piston pot I made. 61mm. Shortly after, piston pot for stock 59.8mm pistons.

Turned only a little off of them in the manual lathe, I think it was the skirt mainly.
I basically copied a cb650 skirt length, deck height.

That first set, I set a manual mill up, and angled the head and positioned the valve pockets by mimicking where they were on a stock set.
And now I had 2 piston lots, 59.8mm and 61mm.

The piston pot is basically a thick walled aluminum sleeve with a custom bolt that goes through the wrist pin bore to hold the piston while machining it in a lathe.
In a mill it was a challenge to be able to get both valve pockets in the exact position in 3 axis, without 2 setups.
But I came up with a fixture I could set a hardened steel pin to center a cnc z,y,x on, and run 2 programs, one for the intake, one for the exhaust valve pockets.

had to use a manual mill to make the aluminum fixture, but I now have a fixture that fits a common good quality vice in most machine shops.


Been a while since i looked at them, but with the overbore to 62mm going on, thought I'd show them off since they were out.


L8r

JKenzi
Posts: 1
Joined: Sun Oct 28, 2018 3:15 am

Re: My piston sets and fixtures.

Postby JKenzi » Tue Oct 30, 2018 11:22 am

Cb673 wrote:Yes I am a machinist. Trained in '98/'99 been in the trade ever since. Lots of repair shops, manual machines, and vtl lathes. I'm CNC functional.... more a fat finger at the console programmer than a mastercam user.
(mastercam writes the program for you once you draw the part in 3-d in mastercam)


I first got the idea of modifying pistons when I saw what NOS piston sets cost, and I found 1 overbore set that sold on ebay for over $600.
I was told there is no way to getting a 650 overbore for a fair price on a few honda cb forums.
At the time my 650s motor was starting to smoke(slightly stuck ring or two)

So I ended with the first useable set I could get rings cheap for.
A 76?77?... the first year of the cb750 hondamatic.
It has a higher dome than any other cb750.
Thats the first piston pot I made. 61mm. Shortly after, piston pot for stock 59.8mm pistons.

Turned only a little off of them in the manual lathe, I think it was the skirt mainly.
I basically copied a cb650 skirt length, deck height.

That first set, I set a manual mill up, and angled the head and positioned the valve pockets by mimicking where they were on a stock set.
And now I had 2 piston lots, 59.8mm and 61mm.

The piston pot is basically a thick walled aluminum sleeve with a custom bolt that goes through the wrist pin bore to hold the piston while machining it in a lathe.
In a mill it was a challenge to be able to get both valve pockets in the exact position in 3 axis, without 2 setups.
But I came up with a fixture I could set a hardened steel pin to center a cnc z,y,x on, and run 2 programs, one for the intake, one for the exhaust valve pockets.

had to use a manual mill to make the aluminum fixture, but I now have a fixture that fits a common good quality vice in most machine shops.


Been a while since i looked at them, but with the overbore to 62mm going on, thought I'd show them off since they were out.


L8r


Very well explained ..


Return to “Show it off”

Who is online

Users browsing this forum: No registered users and 2 guests