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Engine basics => Four strokes only => Topic started by: Dennis Toth on April 28, 2014, 07:45:19 AM

Title: OF FS40 cylinder removal - how?
Post by: Dennis Toth on April 28, 2014, 07:45:19 AM

I have a OS FS40 that the shaft bearing was getting a little sloppy so I decided I would get new better quality bearing from Boca Bearing and replace them. I've been doing stuff to 2 strokes for 40 + years but as I got the head, push rods, cam out I discovered I have no way of prompting the cylinder up for removal.

So here I am - can anyone tell me how you get the cylinder/piston out of the OS FS40?

Best,       DennisT

Title: Re: OF FS40 cylinder removal - how?
Post by: Bob Reeves on April 28, 2014, 09:05:07 AM

Sorry, wished I could help but never disassembled an OS. Have you tried Google, maybe someone else has had the same question.

Title: Re: OF FS40 cylinder removal - how?
Post by: Jim Kraft on April 28, 2014, 11:03:38 AM

Dennis, On my old ones with the rear cam the sleeves just slide out the top after you get the head off. Since there are no ports to use for pushing it up with the piston like on a 2 stroke, you might have to use a little heat. But, I have never had any problem by just sticking my thumb in the cyl. and pulling the sleeve out. If yours has a back plate you might also remove it and push the sleeve out from the bottom. Hope this helps.

Title: Re: OF FS40 cylinder removal - how?
Post by: Robert Zambelli on May 07, 2014, 04:22:57 PM

Remove the carb and intake pipe.
Remove the rocker cover and the rocker shaft.
Remove the remaining four bolts holding the head on.
Head should come right off.

Bob Z.

Title: Re: OF FS40 cylinder removal - how?
Post by: Dane Martin on July 14, 2014, 06:30:06 PM

ok. i got some pics. cylinder and piston removal.
pull the carb and intake assembly. pull the head and push rods.
pull the back plate. push up on the cylinder from the bottom to help pop it up.
line up the wrist pin with the wrist pin hole. remove pin and pull pisyon from the top and rod from the back.

Title: Re: OF FS40 cylinder removal - how?
Post by: Dane Martin on July 14, 2014, 06:50:03 PM

as you can see, this poor engine is in bad shape. the wrist pin is locked up. i just bake the engine at 300 for ten minutes. use a #1 extractor and it should pull out by hand. if not, bake the engine until the old nitro and gunk start to sweat on the wrist pin hole of the piston. this engine was really locked up and this method worked no problem. you can't get the piston out without pulling the pin. sorry four the bad pics. the engine was a little warm to work with and hold a camera!