stunthanger.com

Engine basics => Engine set up tips => Topic started by: Annette Elmore on October 01, 2006, 01:14:07 AM

Title: Hole in OS40fp piston?
Post by: Annette Elmore on October 01, 2006, 01:14:07 AM

When dismantling my recent (good but VERRRY dirty Ebay OS40FP) I forgot to note which way round the hole in the piston - towards the front or back?

Tony

Title: Re: Hole in OS40fp piston?
Post by: Dennis Moritz on October 01, 2006, 05:39:38 AM

What hole in the piston? Huh?

Title: Re: Hole in OS40fp piston?
Post by: RC Storick on October 01, 2006, 06:50:11 AM

There is an easer way to tell. If you didn't take the rod off the piston the chamfered side goes toward the crank.

Title: Re: Hole in OS40fp piston?
Post by: Annette Elmore on October 01, 2006, 11:29:50 AM

I could actually tell which side of the conrod had been rubbing against the backplate - so that means the hole faces forward - I hope!

Tony

Title: Re: Hole in OS40fp piston?
Post by: Greg L Bahrman on October 01, 2006, 12:29:15 PM

A stock 40FP does not have a hole in the piston. I checked my 40FSR and it does not have a hole in the piston either. so I checked my 45FSR and it does have the hole. On mine the hole is opposite the exhaust port. If your talking about the hole for the rod pin it goes fore and aft in all cases. In other words it is parallel to the crank.

Title: Re: Hole in OS40fp piston?
Post by: Mike Greb on October 02, 2006, 10:00:43 AM

I think some of the older steel piston motors had holes in the piston to let fuel into the boost port.