Dolmar 64xx/73xx/79xx series, smurfs and solo 665/675/681 thread

[huskihl]

Nice work. Extensions and bases, too

 

[whitesnake]

The squish band looks stock. I don't think it's been modified. The couple I have are fairly clean in that ring.

If the ring is still there, it hasn't been modified.

I'll post pics in a sec

I agree

 

[mettee]

Nice work. Extensions and bases, too

Guy I know did the machine work.

I'd highly recommend him.

 

[mettee]

I went back into this saw today to check out how it was wearing in. And I saw that I could take more from the exhaust and I doubke checked what I saw with a couple buddies, not sure why I left all that exhaust in there. I left a lot on the table, but I got it now.



Intake looked good and the ring was just barely starting to wear in. I cleaned it up and put it back together after I finished the additional porting on the exhaust.



So I had to take it apart because I got a piece of paper towel down in the intake by accident. It was a good mistake and I guess it was meant to happen.

BTW red armor works really really well.

 

[whitesnake]

I went back into this saw today to check out how it was wearing in. And I saw that I could take more from the exhaust and I doubke checked what I saw with a couple buddies, not sure why I left all that exhaust in there. I left a lot on the table, but I got it now.

View attachment 349284 View attachment 349285 View attachment 349286

Intake looked good and the ring was just barely starting to wear in. I cleaned it up and put it back together after I finished the additional porting on the exhaust.

View attachment 349287

So I had to take it apart because I got a piece of paper towel down in the intake by accident. It was a good mistake and I guess it was meant to happen.

BTW red armor works really really well.

Thats some nice looking work my friend. I have a beautiful 6400 here with hardly any runtime on it that could use a ported 7910 cylinder

 

[mettee]

Thats some nice looking work my friend. I have a beautiful 6400 here with hardly any runtime on it that could use a ported 7910 cylinder

I'm just a hack, I had Kevin do the machine work and I scratched in the ports. I'm lucky the recipe is pretty well known. A little birdie did share some small secrets with me...

 

[Wilhelm]

That looks like a lot of vertical streaks

Thats some nice looking work my friend. I have a beautiful 6400 here with hardly any runtime on it that could use a ported 7910 cylinder

Nothing wrong with the 6400 the way she is unless You process 24+" logs.

I have been running my stock PS-6400 with a 20" B&C setup all week.
At ~4.5hp she has power to spare lacking none and she features very good fuel economy.
My stock 7900's would have spent close to twice as much fuel without truly yielding faster cuts in sub 18" diameter logs.

I tried utilizing my PS-550 but felt the need for more power.
I considered utilizing my 73's and 79's but concluded they'd just be overkill.

This is what I am working on, many-many bucking cuts as the owner wants his firewood bucked to 10" short.



In larger diameter logs I would most likely grab my PS-7310!
In general I love the 64/73/79xx saw line, perfect in every way IMHO.
As I own all three cc models I can choose according to the work at hand.

P.S.:
You forgot to post pictures of Your 6400!
Here is mine.

 

[North by Northwest]

Morning gents . Just received my new 7900 prez2 . I have run 2 tanks through I her @ 40:1 . It was a hard decision on whether Interceptor or Dominator ? I ran with the Dominator at the advice of Kevin last yr on another thread . I ordered her with a 28" b&c Oregon versa cut & exl semi chisel . I have a few more poplar & sugar maple to get out of the way today here at moose camp , so better get back at it while the sun shines . The shooting lanes are pretty well done , the side by is loaded with saws & fuel , just finished a quick hand file on the 5105H , so into the saw box and I am out on the trail , hazelnut & Joe on the go brother !

 

[davidwyby]

@Wilhelm drop those rakers and put an 8 pin on the 7900!

don’t you have a ported 6100?

 

[Wilhelm]

@Wilhelm drop those rakers and put an 8 pin on the 7900!

don’t you have a ported 6100?

I tried that rakers & 8 pin thing and didn't like it - too uncomfortable when hitting gnarly knots and bucking bone dry logs (chain chatter and slip).
Also, dropping rakers just to utilize the power of an overkill saw is dangerous while bucking small diameter logs - I have had logs literally flying at me the moment such a chain touches them.
Also, as You can see in the above picture, those logs are stacked high (about 2.5m or even more) with nowhere to roll them. I have to buck them as they are, often utilizing the bars tip bore cutting to buck a log that causes pinching of another log sitting atop of it. Trust me, aggressive rakers and large sprocket is not the way to go about it.

I do have a MMWS6100 & a XS5000, same issue - they spin the chain too damn fast creating chatter and chain slip hitting any hard wood.
These beasts are great for fresh beech though!!!
Besides, I am saving them from too much work since they are special.

When bucking other people's firewood logs I need optimal performance of saw and chain to finish the job as fast as possible, with as little fatigue as possible, and with as little saw/chain maintenance as possible.
The quickest and strongest saw is not always the best choice for the job.
If that log pile had many 18+" diameter logs in it I would be utilizing my big girls.

Besides, I am just a homeowner firewood hack, I don't know poop and l simply coast along hoping for a happy finish (not getting hurt, not damaging my saws).

 

[davidwyby]

Gotcha, I agree with your logic.

 

[sledneck22]

Thanks again for all the information and pictures of the cylinders. I guess I have to believe that my cylinder hasn't been modified. But I checked squish all the way around the cylinder using what seemed like an entire spool of wire, and the lowest I found was 0.023". Maybe I'll order a new wrist pin bearing and put that in before I try and start it just for peace of mind because that's the only thing I can think of causing this if they're typically too tight for a BGD.

 

[huskihl]

Thanks again for all the information and pictures of the cylinders. I guess I have to believe that my cylinder hasn't been modified. But I checked squish all the way around the cylinder using what seemed like an entire spool of wire, and the lowest I found was 0.023". Maybe I'll order a new wrist pin bearing and put that in before I try and start it just for peace of mind because that's the only thing I can think of causing this if they're typically too tight for a BGD.

It’s possible that the piston has had .010” removed from it in a previous life also

 

[sledneck22]

It’s possible that the piston has had .010” removed from it in a previous life also

@mettee is who I bought the piston from and I don't believe that to be the case.

 

[Northern_clear]

I purchased a new 7901 a couple weeks back, pulled the gasket and got .024 squish with my 3 pieces of solder twisted together. Checked and rechecked, kept getting .024 until I used just a single strand of wire, Then it measured .014 so I tossed a thin gasket I made in there to get to .021. Anyhow I was sure I was correct and only kept checking because of huskihl's .014 advice.

 

[mettee]

@mettee is who I bought the piston from and I don't believe that to be the case.

It's a stock piston, markings intact.

 

[mettee]

Just a thought but could the calipers or mic you are using be out of calibration?

 

[cus_deluxe]

So I circled in red what I'm refering to as the "flaired" cutouts. swooping cutouts for the bottom end to feed into the lower transfers. I was unsure if those were typical for a 7910 cylinder or not. But they were very sharp with some dings so I beveled them a bit. Probably not much concern as the windowed cylinder shouldn't even travel over them. I just didn't want to remove much meat as they seem quite thin.
I also circled in green the base band. I think it was cleaned up by someone at some point because it doesn't have any build up like the rest of the cylinder head had. But it also don't have room to either in regards to combustion area.
I used a couple different solder diameters. I ended up getting the most consistent results with the .040 or .050 wire. I can't remember off the top of my head which it was. Pretty narrow stuff though.
I appreciate everyone's time and responses. I'll check once more before I button the rest of the saw up tonight but in the end, "it is what it is" and "it isn't what it isn't".
View attachment 349211

IMO, .040-.050 solder is a bit big to get it squished enough to have an accurate measurement.

 

[Canadian farm boy]

IMO, .040-.050 solder is a bit big to get it squished enough to have an accurate measurement.

Bingo. Btdt. I use .026 diameter solder. If the squish is bigger then that I’ll twist a couple pieces together.

 

[huskihl]

Mine is 1mm solder. Actually measures .037”. But it’s rosin core so it smashes easily