RCU Forums - View Single Post - Internal differences between .60FSR and .61FSR?

11-19-2008 | 04:05 AM

#28

DarZeelon

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From: Rosh-HaAyin, ISRAEL

RE: Internal differences between .60FSR and .61FSR?

Quote:

ORIGINAL: Roguedog

I was able to get a FSR piston and liner into a SF case. In order to get it on the crank-pin I had to heat up the the con-rod with a heat gun through the rear of the the case without the liner. It finally went on. I had to do the same to get it off. Someone made this suggestion here in one of the forums about how to get the SF con-rod off the SF crank-pin. So I figure this must be SOP for getting the con-rod off of single piece cases (no separate front housing).

Brian,

Since the FSR used the current 24x22 mm bore and stroke; and the newer SF is the 'Long Stroke' design, with 23x24 mm, the engine you now have is a 'square' 24x24 mm...

It is now a .66 cid; not a .61... And you will need to see that your engine still have the correct squish clearance and reasonable sleeve port timing numbers.

You may need to rework the head accordingly...

The FSR piston; being larger in diameter than that of the SF, may be slightly heavier, which will result in elevated vibration levels (compared to the SF).

You may also need to mill the piston's skirt, to clear the crankshaft counter-weight and the back-plate.

Also, make sure your milling, or the original design, do not allow 'sub-piston induction'...from the piston exposing the exhaust port to the bottom crankcase, as it goes further up than before... It is the worst power detriment, if you are using any type of muffler.

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