Motor geometry

[Wevil Kenevil]

I know this question is going to be Elementary for some of you but I'm going to ask anyways.

I have two Motors that are the same size the same CC everything matches in size and shape but when I put the two together the Piston is now striking the top of the head.

( basically what it was is one of the tabs broke off over the drive gear cover where the clutch arm fit's into the case so I took a good case with a bad head and took the head and cylinder and piston and crank out of the broken body and put it in the body that was good.)

The Pistons were the same size the Piston rods the crank the bearings the cases almost matched up perfectly except for they were just a little bit off as far as being cast or ground.

I even went as far as placing two base gaskets on it as it was before. And it still comes way up even higher than what any gaskets would be safe enough to put on it to get the clearance.

The only difference in size that I could discern was one of The Jugs has a bigger carburetor Port than the other one did and the front Notch for the motor mount was just a little bit bigger in diameter but not by much. But all of the holes match up everything matches up.

Anybody got any ideas as to why I'm running into this?

 

[Venice Motor Bikes]

The two pistons are probably different... One is probably a 'low pin' the other is a 'high pin'

 

[Wevil Kenevil]

Yep! Thanks home style...

 

[Wevil Kenevil]

Since the piston and rings are wore into the jug I am using should I use the old rings or put new ones in to reduce seating wear?

 

[Sidewinder Jerry]

Since the piston and rings are wore into the jug I am using should I use the old rings or put new ones in to reduce seating wear?

My philosophy is if you're on a tight budget use as many original parts as you can. If you have the finances, replace older parts with new ones.

 

[Greg58]

I have replaced rings before in a old engine and it ran find, I broke a ring while putting the cylinder back on after porting. You’ll hear that you need to replace all parts but I had good results.

 

[Wevil Kenevil]

Thanks fellas!

 

[Mossy]

Cabor rings 47 x1.5 mm check your old rings for thickness some of the 50mm 100 rings are 1.2mm for example... But basically there for saws and one less thing to worry about...