Topic: Gentleman's Express pistons in Peru !?!

[tank410]

I am on vacations visiting my in-laws in Lima, Peru and there was a motorcycle/machine shop down the block from my father-in-laws electronic repair shop. Although most of the bikes I have seen down here were one cylinder 2- storks, my curiosity got the better of me and I wondered down to look around this morning. Threw my broken Spanish/English I had a Honda Sohc4 at home. And then he showed me these.






The best I could make out somebody had asked him to make them and never came back.
So I took them off his hands for 60 Sols( about $20).
I am not sure but think they are the Gentleman's express pistons.
They measure 60.5mm at the wrist pin (so I think they are form a 750) and are 6mm in until the start angling up, but I am unsure how much has been removed from the bottom or if the depth of the shoulder is right (could not remember the measurements for that).

[seaweb11]

Very cool find
Great story: And I want one

[bwaller]

Looks as if to be safe they just removed more of the shirt than might have been necessary, but those HA pistons are flat bottomed too.

Good one!

[tank410]

I have been doing some search at it will take to run these pistons in a 500/550. And I want to check if I am right, I'll need .50 750 rings (not sure where to get them?), new head gasket (form www.cometic.com. Part number H0516SP2059F), bore the cylinder wall to 61mm and honed, and have valve pocket cut in the pistons.

I have never done anything this extensive so just want to check. When I get back to the states how much will having the machining cost? Do I just tell I want the cylinder 61mm or I want them to fit the pistons? I also hot sure how to get the right valve pocket cut.

[MRieck]

I have been doing some search at it will take to run these pistons in a 500/550. And I want to check if I am right, I'll need .50 750 rings (not sure where to get them?), new head gasket (form www.cometic.com. Part number H0516SP2059F), bore the cylinder wall to 61mm and honed, and have valve pocket cut in the pistons.

I have never done anything this extensive so just want to check. When I get back to the states how much will having the machining cost? Do I just tell I want the cylinder 61mm or I want them to fit the pistons? I also hot sure how to get the right valve pocket cut.

They will need the pistons for boring. I would bore the cylinders first. After that you will need to mock assemble the engine. Install the pistons on the rods with just the pins and some machine dye on the crowns (no c clips or rings). Slide the cylinder on. Place the head on with the locating dowels. Bring 1/4 to TDC and mark the valve locations by putting a punch down the intake and exhaust guides and LIGHTLY tapping it with a small hammer. The best punch is made by cutting the head off an old valve and sharpening the end to a center point. After you have marked 1/4 bring 2/3 to TDC and repeat. The pistons will have to be put in a piston vice (or similiar clamping device) and flycut (or cut with an end mill). Offhand I don't known what angle to hold the pistons at but that can be easily checked out by measuring the guide offset (from vertical). Be sure to leave enough clearance for the valve head in the relief.