Latest thoughts on piston to cylinder clearance?

[Darrell]

My stock Wombat compression tests at 120 psi so it's about time for a rebuild.

Back down the road, I picked up an old 94 cylinder that came with a Victory Port and a Combat piston, both worn right out. Has anybody seen a Victory Ported Wombat cylinder before?

I sourced a new Combat piston (.030 over) and ring at the Hodaka Days swap meet. Before I take the piston and cylinder to the machine shop I'm wondering what clearance to shoot for. Is .003" still in the ballpark for piston to cylinder clearance (125cc bore) or does the latest thinking lean towards less/tighter clearance? In the back of my mind, I'm thinking I've heard somewhere that the tighter clearances increase the heat transfer potential, and the latest oils help reduce the possibility of seizure.

Should I listen to the Old School or the New Age?

[taber hodaka]

If I was recommending to someone else I would recommend for them to use the old school. Your ability to fine tune and assuredness of using the best of oils could lead you to blame the bore . I can only say I use the tighter bore. --------------Clarence

[Zyx]

Mine is set at about 0.0025 which is in between.

[racerclam]

I have done several victory ports in iron wombat cylinders , this one was for Jay Lael , done a few for Bill cook too. Clearence with an iron cylinder needs to be looser than the alumiferic later ones , the piston still expands faster than the cylinder with iron , also it runs hotter , the super combat and combat wombat can run tighter with the same piston.

Rich

[racerclam]

matbe this time the picture will up load

Rich

[racerclam]

Now?

[Darrell]

matbe this time the picture will up load

Rich

Nope, the picture didn't happen but I appreciate the feedback. I think I'll stick with old-school clearances because of your explanation of the unequal expansion/contraction rates of iron and aluminum. I suppose liquid-cooling is another factor that makes tighter clearances possible.

I can't imagine that it's very easy to grind in a new Victory Port. It seems like it would take a lot of time and focus.

Thanks to all for your input.

[taber hodaka]

You may want to check your clearance now, you could just need new rings. racerclam Rich does this porting professionally. the best I have ever seen. ===========Clarence

[racerclam]

Ok new day trying picture again

Rich

[bchappy]

Good job Rich. Looks better than factory.