- Joined
- Jan 9, 2011
- Messages
- 111
As this question seemed to get lost in the other thread I will repost it here.
Honing for piston clearance is about where I am at on a project engine I am building and having been doing some research.
One of my references is Modern Motorcycle Mechanics by J.B. Nicholson.
The clearance stated there for Combat Commando 750's with solid skirt is .0065" (top of skirt) and .0045" (bottom of skirt).
750's with thermal slotted pistons are listed as solid skirt is .005" (top of skirt) and .0035" (bottom of skirt)
Similar for an 850 with solid cast pistons. .0065" (top of skirt) and .0045" (bottom of skirt).
What is the reference (bottom of skirt) about and how does it work with the clearance called top of skirt?
Would this not cause a taper in the bore?
This is what I think is being described. This is a 850 that was bored for 40 over pistons that later seized up.
These are new 40 over JCC pistons and how they fit. Right now a very snug .004 at bottom of cylinder and a looser .005 at the top.
or
http://s225.photobucket.com/albums/dd50 ... ter=images
These feeler gauges are just under a 1/2" wide and conform nicely to the bore. As this method also involved using a spring gauge to pull the feeler, hence the hole, the non conformity of the gauge in relationship to the clearance would be calculated in when the specification was developed I would think. My guess is most folks who use this method go by feel and experience and not the spring gauge. This is after all all 1930 to 1950 tech.
Is my understanding correct?
Thanks
Honing for piston clearance is about where I am at on a project engine I am building and having been doing some research.
One of my references is Modern Motorcycle Mechanics by J.B. Nicholson.
The clearance stated there for Combat Commando 750's with solid skirt is .0065" (top of skirt) and .0045" (bottom of skirt).
750's with thermal slotted pistons are listed as solid skirt is .005" (top of skirt) and .0035" (bottom of skirt)
Similar for an 850 with solid cast pistons. .0065" (top of skirt) and .0045" (bottom of skirt).
What is the reference (bottom of skirt) about and how does it work with the clearance called top of skirt?
Would this not cause a taper in the bore?
This is what I think is being described. This is a 850 that was bored for 40 over pistons that later seized up.
These are new 40 over JCC pistons and how they fit. Right now a very snug .004 at bottom of cylinder and a looser .005 at the top.
or
http://s225.photobucket.com/albums/dd50 ... ter=images
These feeler gauges are just under a 1/2" wide and conform nicely to the bore. As this method also involved using a spring gauge to pull the feeler, hence the hole, the non conformity of the gauge in relationship to the clearance would be calculated in when the specification was developed I would think. My guess is most folks who use this method go by feel and experience and not the spring gauge. This is after all all 1930 to 1950 tech.
Is my understanding correct?
Thanks