OS 91FS question
 

Hello,


I am reassembling an OS 91 FS Surpass engine. I'm a little confused as to which way the connecting rod should be installed.


As you can see on the pictures, both sides of the bushing seems to have a bevel, (chamfer?). The way the rod was installed was with the "R" stamped side facing backward ( got the engine used, I don't know if it was correctly assembled ). Can you tell me if the R should be facing forward or rearward?



Also, is it possible to install a helicoil in the exhaust port, I don't want to spend 100CAN$ for a new head (just spent that amount for a new crankcase).


Thank you,

RE: OS 91FS question
 

The other side

RE: OS 91FS question
 

The head. What size helicoil if possible to install one??

RE: OS 91FS question
 

The lower connecting rod end has a brass bushing. On one side, it's milled flush with the side of the rod. The other side has a small bevel on the edge. The bevel goes towards the crankshaft counterweight.

We'd have no idea if there's a heli-coil available to fix the threads in the exhaust port of your engine. It's a very fine-pitch metric thread. The thread size is M11 x 0.75

RE: OS 91FS question
 

Thank you for the reply.



My connecting rod seem to have both sides beveled. That's why I'm unsure which one must go towards the crankshaft counterweight. The bevel seems to be more pronouced on the first picture, but this side was facing the rear of the engine, not the counterweight... So I tend to believe that the rod was mounted the wrong way. It's hard to take a picture of such a small part, but if you look closely at both pictures you can see there's one end with a more pronounced bevel.

RE: OS 91FS question
 

The picture in the first post looks like that's the side of the rod that goes towards the counterweight. The other picture shows the side that goes towards the rear cover.