Makita 6401 to 7901 Plus porting the 7900 and the Solo 681

[Mastermind]

So what your thoughts on the lower transfer?
The uppers look wider on the solo

What numbers did the doom are have.

Why do the have so much intake timing and low transfer and exhaust numbers

I have notes in the shop with stock numbers.......but I didn't get them on these 7900 jugs. I've got a solid plan on those saws. No reason to measure stock numbers on them.

Small carb.....

 

[Terry Syd]

Yeah I never really looked at the 681 top end close. It must be something to It to get that 5% over a 7900.

The 7900 jug shows what happens when a big bore is put in a smaller cylinder, the transfer tunnels run close to the bore and there is a tighter turn (and perhaps less cross section) for the transfer flow. The Solo appears to have addressed the porting problem and moved the transfers out from the bore. - A 5% increase isn't going to come from a 2 millimetre increase in stroke.

I was thinking my next big saw would be a 7900/7901, but that well designed Solo jug now has me thinking about the Solo.

Can the 681 jug be used on 7900 cases and still be able to use the increased area in the lower transfers?

 

[Mastermind]

Randy,

Do the opened up lower transfers on the Solo? And would doing that to the Dolmar help??

What piston is the Solo running ? Open port or slab side? What would the effects be putting the closed slab side Dolmar piston in the Solo if it's the open piston.

Just thinking out loud....

I open both, but the Solo needs less work.

The Solo has the windowed piston. I wish I had a slab sided piston.........I bet it would help.

Will the 7900 accept the 681 jug?

Yes, but you'd have to cut about a mm off the base. That would change the timing numbers enough that you'd need to rework the exhaust and the transfers.

 

[Deets066]

Will the 7900 accept the 681 jug?

Got a little excited there and forgot they were made by different manufacturers lol

 

[Mastermind]

Got a little excited there and forgot they were made by different manufacturers lol

Solo and Dolmar designed the 7900 together. They share many parts. The jug will bolt right on.

 

[Deets066]

Solo and Dolmar designed the 7900 together. They share many parts. The jug will bolt right on.

Yeah I just looked at some pics of the solo, looks a lot like the dolmar

 

[rburg]

Will any of these saws be coning to Kentucky next weekend?

 

[Terry Syd]

I couldn't find the conversion spacer on Bailey's. Does anybody have a link?

I was wondering if the spacer makes allowance for the different base dimensions.

 

[Mastermind]

Will any of these saws be coning to Kentucky next weekend?

Sir Yes Sir !!!!!

I'll be bring the Solo, and the Makita.

 

[Jacob J.]

I couldn't find the conversion spacer on Bailey's. Does anybody have a link?

I was wondering if the spacer makes allowance for the different base dimensions.

I don't think they sell the spacer anymore- but I think I goofed. I think the spacer was for mounting their own big bore kits on the 6400/6401/665 lower, and that's what they were selling for a while. If I remember correctly, the spacer had slotted mounting holes. I actually have one in storage somewhere.

 

[fordf150]

Makes wish I could be there

 

[CapitaineHaddoc]

That's a nice thread Randy, thanks for sharing. Do you think you'll have the time to record some vids from thes saws when done?

 

[jeff taswelder]

That's a nice thread Randy, thanks for sharing. Do you think you'll have the time to record some vids from thes saws when done?

+1

 

[Sty57]

OK, now we're gonna look at how we cut the squish.

I've got a bunch of different plates made up with different bolt patterns for different saws. All you need is a 4" x 4"x 3/8" or thicker steel or aluminum plate, or some all thread.



Now, this is sorta important.........you need a pivot point under the jug.



Some washers and nuts, and it's ready to go in the four jaw.

I have a question
Wouldn't it be easier to make the base plate out of round stock instead of square? Wouldn't you be able to use a Three Jaw chuck if that all you had?

 

[Sty57]

Once all the indicating is done, cutting it takes maybe 5 minutes max. I also cut the cylinder extensions while the jug is mounted.





Then slick it up with a diamond burr.

How do you decide how much to take out of the Squish Band?

 

[MillerModSaws]

Awesome work randy! Have your ever put the solo crank in a 7900?

 

[MillerModSaws]

Is the solo rev limited just like the 7900?

 

[drf255]

So the Dolmar uppers were just as narrow in height as the Solo ones before grinding?

Or is that your point, that smaller tighter uppers make more power?

The work is beautiful.

 

[Sty57]

How do you decide how much to take out of the Squish Band?

Do you take out just enough to clean up the Squish band and then cut the base to bring down the Squish?

 

[wde_1978]

The Dolmar has had some relieving done on the right hand side. Making this comparison was an after thought.

I have a stock OEM 7900 jug sitting on a shelf, would You like me to snap some pictures for comparisons with the 681 jug?

Interesting thread.