Dolmar 64xx/73xx/79xx series, smurfs and solo 665/675/681 thread

[huskyboy]

Prolly not so many vibes with .040" spun off the top of the piston

I’m not sure what recipe Mike used (and I probably wouldn’t tell if I knew out of respect for him, unless he was ok with it). But there is a shiny spacer and two base gaskets between the cylinder and cases . So I’m guessing it does not have material removed from the top of the piston from what I saw. Would be interesting to try one that way though.

 

[Deets066]

I couldn’t tell the difference in vibes from the 46 piston to a regular one. If there is any, it’s not much

 

[huskyboy]

 

[mdavlee]

I’m not sure what recipe Mike used (and I probably wouldn’t tell if I knew out of respect for him, unless he was ok with it). But there is a shiny spacer and two base gaskets between the cylinder and cases . So I’m guessing it does not have material removed from the top of the piston from what I saw. Would be interesting to try one that way though.

I didn’t remove anything from the pistons normally. There might be a little out of the chamber.

 

[huskyboy]

Stock 6400 ports.

 

[huskyboy]

Woods ported and port matched to muffler. I took a lot of material off the piston but didn’t take pics of that. It already free ports with the base gasket deleted, the ring pin almost goes in the intake at BDC and the combustion chamber is small compared to some. They didn’t leave much on the table that’s for sure.

 

[RI Chevy]

Nice. But you need a smooth bit to smooth out the grinds. Lol

 

[huskyboy]

Nice. But you need a smooth bit to smooth out the grinds. Lol

Polished gains nothing other than helping carbon build up in the exhaust port.

 

[RI Chevy]

Well... we'll agree to disagree on that one...

 

[huskyboy]

Well... we'll agree to disagree on that one...

You’d be surprised what you see inside some of your saws. Take them apart and have a look. Port shape and timing numbers matter more than a mirror finished exhaust port.

 

[RI Chevy]

I hear you...

 

[huskyboy]

I don’t have a video but she turned out pretty good. Holds 9500-10,500 in the cut with a 20” buried in oak with me running it like a gorilla. I think I’ll call this saw hammer, because it has quite good torque for a 64cc saw.

 

[RI Chevy]

So...you name all your saws too? [emoji2357]

 

[huskyboy]

So...you name all your saws too? [emoji2357]

 

[huskihl]

Well... we'll agree to disagree on that one...

He must not've had "Because it'll make Jeff all warm and fuzzy inside" on his mind when he ground his exhaust out.

Some guys say rougher surfaces grab more heat and cool faster, also. No idea, myself. I just slow down with the hammer and chisel when I get it close to where I want it

 

[mettee]

60-80 grit paper is all you need for the intake. I do think a smooth exhaust is a good idea just to stop gunk from building up.

A bur finish is also fine as long as you didn't create big divots

 

[tickbitintn]

Two general schools of thought on polishing of exhaust ports.

One is:
Polished does not allow carbon buildup.

The other is:
A thin layer of carbon helps channel heat into the exhaust (muffler) and not allow it to transfer into the cylinder.

A "rough" surface allows for a better "boundary layer" of "stationary air" to improve flow in another theory.

So does that help????
Clear as mud now???

Sent from my XT1635-01 using Tapatalk

 

[huskyboy]

Just so you guys can see what I’m talking about with the free port. This other 6400 cylinder just barely gets by. The one on my saw does freeport with the gasket deleted . But it was worth it for the compression increase . I’m thinking theres no way a guy could get a substantial increase without welding a popup unless they were ok with huge freeport. Or find another piston option. Or just buy a 7900 cylinder if you want a huge gain lol.

 

[Deets066]

Free port won’t hurt ya

 

[huskyboy]

Free port won’t hurt ya

Saw seemed to run just fine to me with it