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Early GS 750 pistons

  • Thread starter Thread starter Old Colt
  • Start date Start date
O

Old Colt

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My question is, where there any different dome styles in the 2 valve 750 pistons?
I expect the answer is just the one dome height.

The reason for this question,
I am getting back to installing the GS750 pitons in a GS550. I intend to use a GS650 cylinder head mainly for its larger fin area as well as I am working with bored out 650 cylinders.

In my initial setup it looks like the compression ratio with the 650 head is going to be pretty high. I have not measured the chamber or dome volume yet so I have no true estimates yet but the closed 650 chamber is sure going to put the compression way up compared to the open 550 style.

This will have a good amount of squish area though.
 
Last edited:
The 2V 750's all used the same part number piston so they must all be the same.
 
Thank you Ed, I was expecting that was the case since it is what I remembered from the past.

I will setup and reshape the chambers for the pistons.
 
Hey Charlie,

At project like that deserves documentation. Please take some photos and don't forget to share.:)
 
I need to be a good boy and get new batteries for my camera:) They ran out earlier in the month at Watkins Glen.

I intend to start a thread once I have some content. I want to use an early straight cut crank and clutch for this and the one I just bought on ebay had been washed but not oiled so it had rusty bearings by the time I got it.:(

This should turn out to be a nice looking engine since I am building to brand new cases and head. Most everything else will be used parts.
 
I am trying to decide whether to make a shaped cutter to the curve of the piston dome or just hand form using clay to get the piston to head clearance.

What route did you go with the head gasket in yours?

I am not sure if I want to go with a copper gasket or form a MLS one.
I am also considering oringing and no gasket.
 
Old Colt said:
I am trying to decide whether to make a shaped cutter to the curve of the piston dome or just hand form using clay to get the piston to head clearance.

What route did you go with the head gasket in yours?

I am not sure if I want to go with a copper gasket or form a MLS one.
I am also considering oringing and no gasket.
Click to expand...

I actually just ran a gs650 head gasket. Worked with no problems for me.

I'd love to see you get something set up where you could cut the pistons to the right shape.
 
I have a 650 head gasket sitting on it. It overhangs the bore a small amount but the piston is down in the bore enough that it, as you have learned can work.

Cutting the pistons is doable but they might get a bit thin. But then I only need to get a millimeter or so off the outer diameter. There maybe enough meat there.
I only have the one set of pistons that are fitted to the bores now so I am not sure I want to cut into these. Maybe I can scrounge a few up to sacrifice.
 
Old Colt said:
I have a 650 head gasket sitting on it. It overhangs the bore a small amount but the piston is down in the bore enough that it, as you have learned can work.

Cutting the pistons is doable but they might get a bit thin. But then I only need to get a millimeter or so off the outer diameter. There maybe enough meat there.
I only have the one set of pistons that are fitted to the bores now so I am not sure I want to cut into these. Maybe I can scrounge a few up to sacrifice.
Click to expand...

I wish you luck man. PM me if you have any questions. I wouldn't necessarily deem my build a complete success, as I swapped it back to a 650 after a season. But the bike ran decent during that time.

I'm itching to redo it this winter though. But I'd like to pursue the route you are going of milling the pistons and/or dremeling the head.

Keep us/me posted.
 
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