Dosolo Question

[Poleman]

Ok guys.....been playing with putting a Solo 665 P/C on a Dolmar 6400. Got my setup, cut the base and got the stock numbers and a plan where I wanted to go. Did all the work and assembled.....saw started on 3rd pull. I'm running one of my big carbs and an unlimited coil......saw runs amazing!!!
I cut almost 2mm off the base and didn't take into a count the amount of drop this would be on the transfers. After running the saw I pulled the plug for a look inside.....to my amazement the transfers weren't completely open at BDC. They probably would have been almost closed if I hadn't raised them. I'm thinking there's still more to be had here but the only way to open the transfers would be to notch the piston......does that sound like a good solution??
Here's what I'm seeing at BDC.

Thoughts????

 

[mdavlee]

Lots of saws don't have the transfers all the way open pat BDC. If it runs awesome as is I'd just leave it be. Pistons aren't that easy to come by if you go backwards on notching it

 

[Miller Mod Saws]

Well hello rich! Ya beat me too this experiment. Lol. How's it run?

 

[Poleman]

Mike, thanks for that info....never thought of it that way.

Carl, it runs amazing. Have only done initial start, run and tune and one short cut......first impressions it's as strong as a good stock 7900/7910. It does have the larger carb & coil trick going on though....

 

[Redfin]

How much area do you have now compared to a stock transfer?

 

[Poleman]

I'm guessing I have slightly more area than stock, with the bottom 3rd being blocked by the piston crown and in my mind causing a blockage of the full flow into the cylinder.

 

[Redfin]

I agree with Mike. The transfer flow is following the top of the tunnel anyway.

 

[Miller Mod Saws]

Rich you have the timing numbers on it now?

 

[jacob j.]

I wouldn't modify the piston crown. There were a lot of builders doing that in the 80's and 90's and it doesn't make a great running saw. Sometimes it's necessary on saws like the Mac Sp-81 where the cylinder and crankcase are all one piece, but on a modern saws it's better to get duration out of the ports.

 

[Poleman]

I think I do Carl. I got 105-135-78 after I cut the base. Still had 2.82mm to free port, leaving 5.12mm thickness on the base.

 

[Miller Mod Saws]

I think I do Carl. I got 105-135-78 after I cut the base. Still had 2.82mm to free port, leaving 5.12mm thickness on the base.

Ok rich. Ya know I'm gonna do this thread as an xmas build and your helping me a lot so thank you! The numbers you have are very good numbers. The not clearing at the piston is no big deal. So let's start with comp. What's your comp now? I was gonna try and find a taller piston. Here's my first canidate!

 

[Miller Mod Saws]

We know this is a 47mm bore engine. So there is good piston options out there. 359 husky etc. But that said his numbers are a good start. Rich are you running a base gasket or not?

 

[Miller Mod Saws]

Need to tap into baileys and look at the piston pin to crown heights. I havnt started yet so let's get rich threw this build and it will make my job much easier. Lol.

 

[Redfin]

Just as a reference Rich. I ported my 261 using cut off wheels before I bought my ra head. I could not get deep enough into the transfers to clear the step the wheels had created. I had the same area at the face of the tunnel but the flow was slamming into the side of the piston.

All that to say, I bought an ra because of that cylinder. I evened out the roof of all the tunnels and it is a completely differnet saw. The piston does not clear the floor of the transfers.

 

[Miller Mod Saws]

For you gear heads wondering why rich did this. The 6400 is an open port motor with 6 transfers. Generally speaking you can get better performance out of a closed port motor. Or that's what I'm going to try. A stock 665 runs very well but that said it's to many cc's to compete in the 4 cube class. Has to be under 65 cc.

 

[Miller Mod Saws]

The 665 has a 1mm shorter crank than the 6400 putting you under 65cc. Direct compition for the 365 husqvarna. Or that's my goal. Lol. Let's see what rich hammers out here!

 

[Poleman]

I made a .005 base gasket to use.Squish was .011 with a taper so I added the gasket to get it to .016 on the outside edge. There was no interference after that. I also cut the cylinder extention that extends into the case as it wouldn't seat with such a big cut.

 

[Poleman]

Wouldn't the taller piston close the port more than the stock one is??
I still have to look inside to see what the lower transfer area looks like when assembled....thinking the cylinder extention could be cut more for more flow...

 

[Poleman]

The taller piston could help in not having to cut so much off the base, dropping the transfer below the piston crown, that way keeping it open.
I hadn't thought of looking for a taller piston.....I just kinda wadded in with what I had..... Atlas I had this much thought out....lol.

 

[Miller Mod Saws]

I'm hoping I can find a taller piston that will do just that. We will see.