Dolmar 7900

[artwood]

I finally got to see a 7900 up close and make a few test cuts. Real smooth power. But what's up with the tiny stock air filter? The guy that let me try his saw, modified a Husky 365 air filter to fit the Dolmar cover. He said rpm's went from 12,800 to 13,500 with this mod.

Any ideas for modding the catalytic muffler on this saw? - Eric

 

[cuttinscott]

ERIC thanks for the email the 7900's as of yet do not have catalytic converters. the stock rpm is goverened by the coil at 13500 rpm. We have sold many many 7900s and the air filters have not been a problem none of my customers are complaining about maint. look for my email back at you

scott

 

[keith c raymond]

Ive just had delivered 8-10 cord of log length hardwood {red ,white oak and a few maplesticks} average diameter 10 -18 inches,Im running stihl chain with a 20''Windsor bar to hog it up.The 7900 went thru the wood like a laser. And the cleanup that i do every time cut showed a air filter and carb area that looked like I was running my 346.Very clean,I was suprised since i was throwing chips 4-6 feet away.I have no issue with the filtration system at all.

 

[Stumper]

I love my 7900. The air filter has plenty of suface area-until the fins on the bottom pack with chips. The filter is easily removed and cleaned but it is an "issue" when compared to the K&N filters I run on my Huskies.

 

[Dolmar_Tech_Mgr]

THere has been some talk about an accessory kit for the PS-7900 to add a K&N filter to the saw. Right now just talk but seems to be more and more interest.

 

[artwood]

I was pretty impressed with the saw overall. It just concerned me to see an air filter that should be on a 45cc saw choking this motor. It seems like the filter was an afterthought when the engineers finished designing the saw for less wind resistance on the back of my truck. LOL

Much of my cutting with a saw this size is of a ripping nature. Just worried that the little filter will clog with fine dust quickly.

It makes the 385xp feel like a real pig.
Eric

 

[TonyM]

Rip with the grain if you can, not across the grain. Then you will make shavings, not dust. I've never had any issue with the filter on mine. It doesn't plug near as fast as the older Dolmars and Stihls I've owned.

 

[Dolmar_Tech_Mgr]

This is going to be very weak but anyway, I guess if you rip with the grain it would make you grainripper.

 

[timistall]

I find with the large Dolmars, they need more air thru the cover. The filter seems OK, just bring with you a small paint brush and compressed air to remove dust and chips.

 

[artwood]

Timistall, that almost looks factory! It looked llike the cover was designed to draw the air sideways across the carb so it could be sucked up from the pleats underneath. Wouldn't your mod load up the top of the filter more?

EHP are you addressing this in your modding of the saw?
Does porting require more air? ( you never got back to me with a price on modification)

Eric

 

[rbtree]

ERIC thanks for the email the 7900's as of yet do not have catalytic converters. the stock rpm is goverened by the coil at 13500 rpm. We have sold many many 7900s and the air filters have not been a problem none of my customers are complaining about maint. look for my email back at you

scott

Well, I do not care for the flocked filter on the 7900, or the 357. They clog way too quickly and are hard to clean...Compressed air won't do th job, you have to use a thin tool like a piece of wire or a file handle to get the chips out. So I got mesh filters for all the saws....presto, problemo solved...And I can tell that they are filtering plenty well as there are no deposits on the carb throat.

 

[timistall]

ARTWOOD.......the cover on the left was Big Daves idea and the one on the right was mine. They need air to fart I have not noticed more filter cleaning.

 

[Molecule]

I did the same thing on one of my 540s, which after I drilled out of the basket inside the muffler and opened up the outlet, felt like it was starving on the intake side. So, I cut a 1/4" x 3" slot on the back of the cover, with a heated razor knife, and champhered the edges with a file. The slot goes from flywheel side to just across the handle. I kept the clutch side closed.

Comparing two saws (one factory-quiet one with modded muffler and cover-hungry), I haven't noticed any more filter clogging. If I flatten the chain on something, dust will get into the carb box just the same. With a sharp chain, it's almost easier to clean the filter on the modded cover, a few chunky Chips in there keep down the dust. hahahaha

IMHO, the modded muffler definitely likes the easier breathing at the carb end. On acceleration, the sound on the carb suction is almost as loud as the muffler, but different.

 

[tonka]

How they're getting all that power with that small filter I don't know but I'm not compaining. As far as the filter needing cleaning, I keep checking but almost no build-up. Then again the way it throws chips nothing has time to get sucked in.

 

[artwood]

7900 muffler mod

Anybody have some pics of their 7900 modded muffler? There must be a big basket inside that muffler (really thought it must be catalytic from the size).

Also, I noticed that the blue version has different specs. 5.8 bhp vs. 6.4 on the Dolmar. What would be the discrepancy? - Eric

 

[bwalker]

The muffler on the 7900 does have a basket, but it has a slot in it thats uit large so its not that plugged up.

 

[Molecule]

closed transfer ports v. open

Anybody know if the cylinder construction on the 7900s has open or closed transfer ports?

Somewhere, I read a thread that said the 6400 and 7900 saws (I think it was a Makita thread) were open port transfers-with one ring pistons, and the 7300 was a closed port transfer-also with a one ring piston. The more expensive closed port on the 7300 probably chosen to compete with the 044.

If Dolmar is using closed port cylinders and Makita open, as per the Dolmar 115 v the Makita 520, that might account for the difference between the blue to orange bhps.

If the 7300 is closed and the 7900 open, I'd almost go for the 6cc fewer cubes with higher torque and better gas consumption of a closed port cylinder.

Also, the Makita website now shows only the Home Depot 6400--are they dropping the 7300 and 7900?

 

[bwalker]

I think they are all closed port cylinders and the Makitas are identical to the Dolmars with the exception of color and badging.
I honestly dont understand why anyone would buy a 6400, or a 7300 when a 7900 can be had. No weight penalty and more power.

 

[pallis]

The 6400 is open port. The 7300 and 7900 are closed port. I would think that a lot of people go with the 6400 because of the $200+ difference. I got a new 6400 for $350, and once I decided I liked the saw, I put a 7900 cylinder/piston on for an additional $200.

 

[TonyM]

Makita has had several errors in their literature. The horsepower ratings of the Makita and Dolmar versions are identical. Use the Dolmar numbers, those are accurate.