dolmar 6400/7900 big bore kits. how are they holding up?

[Mastermind]

Then top of the piston being up in the port is no problem. 80% of the exhaust flow happens when the port first cracks open anyway. I'll use the thin gasket, or none at all if there wasn't a squish clearance issue.

 

[Trzebs13]

OK, that makes sence but dosent seem totaly right. I measured the spacer and its actually about .061" thick and got a piece of thicker solder and the squish measured .093" so with no gasket it would be .032". Still seems big to me. But I'm guessing that the added compression would far out way the piston no clearing the entier port.

 

[Mac 6-10]

These kits also fit a solo saw that has a 1 mm longer stroke. That is why your kit came with that thick spacer. Run it no base gasket (double check you'd squish) and go cut wood. That's what I did and haven't looked back!

 

[nmurph]

You also need to check the top of the bore. Some of these BB kits aren't plated all the way to the corner---> black ring of death. As long as you are running a base gasket you are ok. But if the gasket is removed the ring will end up on the unplated area.

 

[blsnelling]

As mentioned above, that spacer is not for your saw. Pitch it.

 

[watsonr]

You also need to check the top of the bore. Some of these BB kits aren't plated all the way to the corner---> black ring of death. As long as you are running a base gasket you are ok. But if the gasket is removed the ring will end up on the unplated area.

Not that the aluminum can't take the heat generated by combustion, the aluminum can't take the ring rubbing it.

 

[Trzebs13]

Yes I did notice that, I did start it so I should be able to see a line where the rings were coming up to and get a measurement on it to make sure.

 

[Trzebs13]

As far as the Muffler goes, should a guy just remove the inner baffle with the Cat in it and open up the existing outlet and call'r a day?

 

[Mac 6-10]

I did the same thing you did with the muffler. But I left only the shell.

 

[madhatte]

My BB has been running since early '10 with no troubles. I wish I could say the same about the chintzy plastic flange that couples the carb to the boot, though. Be careful not to over-tighten the thing or it will spin the nuts in their keeper. So far that's my only real complaint about these saws, and that only because of the risk of an air leak. Oh, and of course, there's still no real dealer network.

 

[nmurph]

My BB has been running since early '10 with no troubles. I wish I could say the same about the chintzy plastic flange that couples the carb to the boot, though. Be careful not to over-tighten the thing or it will spin the nuts in their keeper. So far that's my only real complaint about these saws, and that only because of the risk of an air leak. Oh, and of course, there's still no real dealer network.

Not only can you spin the nut, but you can also deflect the manifold and cause it not to seal. I had one recently that gave me fits finding the source of the air leak until I pulled the carb and checked it over carefully.

 

[Trzebs13]

What kind of RPM's are you guy's running yours at?

 

[watsonr]

I'd need to take a tach to the pile... maybe tomorrow. I have one here with a 32" bar and two tanks thru it. Was going to be put to mill duty but the buyer decided that a 2100CD would be a better option.

 

[ClassicSWC]

I've been following these threads because I have an interest in bumping up my 6400. It seems that the 84cc bbk isn't as strong as the 79cc oem. If that's correct, what's the reason for that? Is one easier to tune that the other? Just curious about learning a little. Thanks

 

[nmurph]

The BB kits have very narrow transfer tunnels. You increase the displacement but it can't breathe to take advantage of it.

 

[Mac 6-10]

here is my build thread for the kit from Watsonr.

http://www.arboristsite.com/communi...ar-p-c-kit-from-watsonr-arrived-today.246983/

 

[nmurph]

They are pretty close to OEM in terms of power.

 

[Trzebs13]

The BB kits have very narrow transfer tunnels. You increase the displacement but it can't breathe to take advantage of it.

So if you were to get in there and open up the transfers you think that it would preform that much better? Now granted not easy to do but not impossible.