Robin 3PG engine rebuild kit retrofit to 2PG

[kondiik@yahoo.com]

Good morning,
Since you can't buy full 2PG engine rebuild kit (cylinder, pistons, crankshaft and gaskets and seals) I'm wonder if I can buy 3 PG and fit it on 2pg engine. What is the difference?

Second, I was thinking if I can't fit 3pg I might but just cylinder for 2pg and buy crankshaft and crankshaft gasket from 3pg.

The third option would be hone it and buy crankshaft seal. Where can I buy set of rings and pistons for honed cylinder?


Thank you this forum is awsome.

[kondiik@yahoo.com]

I found post by Dave Box telling what has changed:
"The piston is about the only part that works in either engine. The crankshaft & clutches, the exhaust system, the carburetor, air intake & control cables all changed"

The questions regarding his post: can you still fit cylinder despite a sparkplug turned upward. Does the piston rings are the same? How about gaskets and seals? How's the crankshaft changed?

[Gws67]

I have the same issue on a 1986 2pg engine. I tracked a rattle in the engine to the piston end of the connecting rod. Excessive wear where the bearing sits in the rod.

However, I am wondering if the connecting rod from a 3pg crankshaft could be installed on the 2pg crank. 3pg crankshafts are available from several sources. I have not been able to find any technical information on the connecting rod specs for both model engines. If the rod can be swapped then you could install a new 2pg top end kit that is available.

From what i can determine by looking at photos of the 3pg crank, the crankshafts use the same bearings and I believe (but can't confirm yet) that the flywheel side of the crank are the same. Possibly only the clutch side is different (shorter). I do know that the cylinder base gasket on the 3pg is different than the 2pg.

[Nascarfastcar]

Originally Posted by Gws67

I have the same issue on a 1986 2pg engine. I tracked a rattle in the engine to the piston end of the connecting rod. Excessive wear where the bearing sits in the rod.

However, I am wondering if the connecting rod from a 3pg crankshaft could be installed on the 2pg crank. 3pg crankshafts are available from several sources. I have not been able to find any technical information on the connecting rod specs for both model engines. If the rod can be swapped then you could install a new 2pg top end kit that is available.

From what i can determine by looking at photos of the 3pg crank, the crankshafts use the same bearings and I believe (but can't confirm yet) that the flywheel side of the crank are the same. Possibly only the clutch side is different (shorter). I do know that the cylinder base gasket on the 3pg is different than the 2pg.

I believe the connecting rods are the same. But not the crankshaft. A 2pg piston uses wrist pin bearing spacers while a 3pg piston is tapered and dosent require bearing spacers.
I have a 2pg piston in a 1990 3pg engine..

[Gws67]

So I guess that brings up a couple of other possibilities.

1). Installing a 3pg rod and piston on the 2pg crankshaft and installing a 3pg cylinder with the 2pg head or 3pg head if it would work with the cooling cowling.

2). Installing the 3pg crankshaft and clutch and relocating the engine further back to align the belts due to the shorter crankshaft. (Would have to look and see if there is a difference in the clutch side housing between the two engines and if they can be interchanged).

Sad if these older engines cant be saved because the crankshafts are no longer available. One dealer i spoke with said he is hoping a new distributor can be located to make the cranks.

[kondiik@yahoo.com]

Originally Posted by Gws67

So I guess that brings up a couple of other possibilities.

1). Installing a 3pg rod and piston on the 2pg crankshaft and installing a 3pg cylinder with the 2pg head or 3pg head if it would work with the cooling cowling.

2). Installing the 3pg crankshaft and clutch and relocating the engine further back to align the belts due to the shorter crankshaft. (Would have to look and see if there is a difference in the clutch side housing between the two engines and if they can be interchanged).

Sad if these older engines cant be saved because the crankshafts are no longer available. One dealer i spoke with said he is hoping a new distributor can be located to make the cranks.

What dealer? Does anyone knows who make these crankshafts?

[stephensimmons]

If a crankshaft could be made would they sell is the question? I know someone who has crankshafts made for older vintage mopeds and could ask the question.