skive

I bought an OS 40FX engine, with unknown history, on ebay. It's a great place to buy well used engines, for more than they're worth!

Just out of interest, I measured the bore and was surprised to find it has a 46 sized piston and liner. A previous owner appears to have made a swap.

Does anyone know if this is an okay thing to do? I was hoping this engine would have a long and dependable life. Should I keep it as is, or get a 40FX liner for it? Any advice would be great.

Thanks!

Bax

My Feedback: (11)

That's something we've not tried.  Usually, the liners don't interchange because the bore in the case is not the same for the different-sized engines.  If it works, go ahead.

skive

Thanks for your advice. That's what I'd have thought. The 40FX and 46FX do have different crankcase part numbers, so that'd make sense.

So it's still a mystery engine. It may be an aftermarket piston/liner, but they look like OS parts to me so I don't think so.

If anyone out there takes their 40FX head off one day, measure the bore and let me know what you find, maybe they're all .46 cu in! Mine has a bore of 22.0mm (and a stroke of 19.6mm), so definitely a 7.45cc / .455 cu in capacity. A 40FX should have a bore of 20.5mm.