Mastermind Meets The Dolmar 7910

[Mastermind]

Here she is.....a brand spanking new 7910. Ain't she a beaut??????

I'm finally getting caught up a little and can get out of the shop early enough to do a thread.

I've had this saw for a few weeks now. I've done a lot of thinking about it....wondering just how much different it was than the 7900.

Notice the muffler deflector is different.

I like the brace.....I feel that it was needed on the 7900.

The decompression valve is in a different place....

The coil is a new and different color.......I've not checked the limit yet.

The new slab sided light weight piston is on board.

 

[bryanr2]

hmm. what happened to the Johnsered 2188 thread we were promised in Brad's 390 thread.:msp_sneaky:

And it's about time you did a thread- good reads have been scarce. Been making do on usual AS Drama.

 

[Mastermind]

Everything looks the same here except the decomp....

7900 on the left.......7910 on the right.

Yeah we are porting it so the squish band has been cut.

A few shots of the stock ports.

Here's where it gets different......

 

[Trx250r180]

looks like decomps on the angle up on top are getting more common now

 

[Majorpayne]

hmm. what happened to the Johnsered 2188 thread we were promised in Brad's 390 thread.:msp_sneaky:

And it's about time you did a thread- good reads have been scarce. Been making do on usual AS Drama.

What happened with the Echo twin you were going to do?

 

[Mastermind]

hmm. what happened to the Johnsered 2188 thread we were promised in Brad's 390 thread.:msp_sneaky:

And it's about time you did a thread- good reads have been scarce. Been making do on usual AS Drama.

Sorry.........

Here's a peek at the 390XP.....same saw ya know.

http://www.arboristsite.com/chainsaw/210537.htm

 

[Mastermind]

What happened with the Echo twin you were going to do?

I've not got there yet. I was pretty far behind after the KY GTG.

 

[barneyrb]

Here's where it gets different......

Is that molded in or is it an insert? Can't tell from the picture

Edit; I see it molded in from another picture

 

[Mastermind]

The inside of the muffler.......

 

[Trx250r180]

Is that molded in or is it an insert? Can't tell from the picture

Edit; I see it molded in from another picture

looks like the sleeves smaller than the casting on the jug

 

[Mastermind]

It's fairly straightforward to dissect the muffler. Just heat and uncrimp the bottom and up the sides a bit.

Then it just slides apart.......with a little bumping and stuff.

There's nothing to support the flange after removing the crackpipe thingy......so we made a steel support and brazed it to the back half of the shell.

Then we bolted it to the reshaped exhaust flange and matched it to it.

Now we fix this.....

 

[166]

The 7910 is rev limited to 12,800. I have both 7900 & 7910 cylinders here and they look identical except for the deco valve and the exhaust. I have tried using a 7900 muffler on a 7910 and it does run more like a 7900 with that exhaust.

The major changes from the 7900 to 7910 are the cylinder, muffler, crank, & coil.

 

[Adirondackstihl]

I recognize the dealer sticker on that there saw

opcorn:

 

[Plan-b]

Here's where it gets different......

[/QUOTE]

That looks to be a reverberation ridge.

 

[Mastermind]

In these pics those screws look huge. They don't block the outlet the way they appear. The deflector is 15mm deep and 40mm x 40mm the whole area under it is open and screened.

Ported jug........y'all have seen plenty of those.

 

[Mastermind]

 

[166]

I recognize the dealer sticker on that there saw

opcorn:

I recognize the saw with that dealer sticker on that there saw

 

[bryanr2]

Sorry.........

Here's a peek at the 390XP.....same saw ya know.

http://www.arboristsite.com/chainsaw/210537.htm

Umm, no it aint.. Nuttin can be compared to a johnny.

 

[Mastermind]

I recognize the saw with that dealer sticker on that there saw

I hope you didn't mind me gutting that muffler. :msp_biggrin:

 

[Adirondackstihl]

I hope you didn't mind me gutting that muffler. :msp_biggrin:

I dont mind a bit.... :msp_thumbup: