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Mastermind meets the Dolmar 7900

cgraham1

cgraham1

I feel old
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Feb 25, 2014
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Damn strait! Stock out of the box these are potent saws. Ported they are even better, obviously!
My 7900 has sure impressed me, I was just wondering how well they take to being ported. :)

BTW, your Makita is on the way. Hopefully you get some use out of it. ;)
 
bryanr2

bryanr2

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Dec 31, 2010
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Clint- they are the King of the 70cc range. At 79cc, Id have to group them in the 80cc range though- and I think they hold their own pretty well in that class too. Many have considered the 064 to have had the best power to weight ratio in the past, that was until the 7900 came out. It is the reigning "power to weight" king.
 
RiverRat2

RiverRat2

Serio Tree Freak
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Oct 16, 2006
Messages
7,336
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N. Orange County, TX
I happen to have some 372 parts
And a 7900...
[]
And an appointment with Mastermind... So, what am I missing?
Time money and patience,,, oh and 7900 are great saws,,, Zama carbs are not the best

Clint- they are the King of the 70cc range. At 79cc, Id have to group them in the 80cc range though- and I think they hold their own pretty well in that class too. Many have considered the 064 to have had the best power to weight ratio in the past, that was until the 7900 came out. It is the reigning "power to weight" king.
Yes on all counts!!!
 
Mastermind

Mastermind

Work Saw Specialist
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56
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Tennessee
Good question.

Lean issues are what I see mostly from the Zamas that I have issues with. Heck.....not all of them are any trouble either.
 
Terry Syd

Terry Syd

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Dec 24, 2008
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All the Zama carbs I've looked at all have the same jetting - two .25mm jets. The jets can be drilled and the flow increased considerably. When a Zama is used on a bigger engine, they need a lot more flow. I've also tried blocking the auxiliary jet on a Zama and just used a drilled idle jet and with a stronger metering spring it may turn out to be an even better approach.

I'm just starting on modding the HDs. They are a bit more difficult to mod as you have to pull the welsh plug and redrill the air bleed/transition holes (and drilling the body of the carb is permanent, you can't replace the jet like on the Zama if you go too far). Since the HD-12 seems to be a popular carb, it would be great to find out what size holes are used on the carb body, that way someone could drill their existing carb to the HD-12 specs. Although, the HD-12 was used on a 71cc engine, so even the HD-12 might benefit from a bit of tweaking to use on a 79cc engine.
 
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