OS 61rf rear bearing

I have two OS 61rf non pumped engines but they have two different size rear bearings can someone tell me why this is from the outside they look the same !

I would guess the larger bearing engine is a later model

Edited By Owdlad on 31/07/2016 04:50:13

Thanks Owdlad could it be one is a long stroke and therefor has bigger bearing !

All sorted now new bearings on there way from Modelfixings,Owdlad I think you are right !

OS have specified some "odd" sizes in the past - it may be that they were getting difficult/expensive to source and they modified the casings to take off the shelf bearings.

You are always best measuring the old ones very carefully - it's not unknown to find bearings in model engines with a mix of imperial and metric dimensions!

Edited By Martin Harris on 02/08/2016 17:28:26

thanks Martin I got an OS 61rf in a model along with a spare rear bearing I then purchased another OS 61rf which needed a rear bearing so I thought I had a bearing that would suit but hey ho the new engine had a larger bearing but all sorted now sent them off to Modelfixings and the new ones aRE IN THE POST !

Yep, correct; the earlier RF/SF (long-stroke) OS .61's had a smaller rear bearing, whereas the later ones had a bigger dia (I think, for a bigger dia crank as well as OD). Look closely at the engine crankcase, and the earlier ones have a more noticeable reduction in case dia at the brg position, the later ones show only a very slight reduction in diameter.

Bill

Received bearings today from Modelfixings and they fit like a glove cant wait to run it and tune it to my pipe! My other RF obviously has the smaller bearing.Great service from Modelfixings by the way !

H9

You'll find it's the other way round I think. You tune the pipe to it..........

Yes Percy the wording came out wrong !