Makita DCS6401 carburetor replacement

[donatello]

I've had this Makita dcs 6401 since 2008 and it has worked great until i was cutting thru some nice oak when it lost power and stalled. I waited 15 minutes to cool off, pulled cord and no compression (easy pull). I installed a replacement big bore kit after finding some damage (i think I can salvage other kit) and decided to go thru the carburetor. I used compressed air (line pressure 100psi) that I found was not a good idea after the fact. I decided to get a new Zama carb and located one the was "almost" the exact part number, but the ad stated it was also for a DCS6401/7900. I received it and a couple things bother me... the extra fitting on the bottom (plug it or swap original plate on it?) and no high speed adjustable screw (no big deal? or will original screw right in?). See photo's. Also, how many turns out for the high and low speed adjustment screw for a baseline to start with?

 

[Poleman]

That sounds like a 7910 carb and exactly what you need with a BB kit.
The extra fitting is just an upgrade to keep the diaphragm clean. Don't plug it or it will restrict the diaphragm movement and the saw won't deliver fuel like it should. You can swap the one off you other carb if you so desire. There should be a H adjusting screws but it is a double D tool fitting I believe. You can take the needle out to where you can notch it with a Dremel to fit a screw driver.
One turn out on each to get you started, then tune from there.

 

[donatello]

Thanks Poleman, I really appreciate the info. All the answers I needed ! Have a great Labor Day!

 

[Poleman]

Thanks, glad I could help!!
I will!!!! Back attcha!!!!!

 

[Wood Doctor]

The Makita 6401 is worth fixing, no doubt about it. I'm crazy about mine:
With the BBK on board, it will pull a 32" bar and as you see above, I've needed that on occasion. Big elm will do it every time.

 

[Poleman]

Me too Doc!!!!

 

[fordf150]

what are the numbers on the carb? vastly different initial settings depending on the exact revision.

I install C3M-DM11's on everything since they are a bolt in replacement for every version, are cheap($48), still have straight screwdriver for H an L but the latest 7910/EA7900 come with C3M-DM18's.

 

[Poleman]

Nate, didn't the 11'S come on the 6400'S and the 12'S on the 7300-7900'S ??? Then the 18 on the 7300-7910"s? Not sure what the smaller saws (6401/6421) had for carbs.

 

[fordf150]

all saws take the same carb(look on some of the old IPL's and it shows the same carb fitting all saws and even the new IPL's that separate out each model still call for the same carb)....dm11 is just an early non limiter capped, non DD carb.

different designations on the end...dm13, dm14, dm17 just designate updated carbs...either updated internals or epa approved adjustment screws. thats the reason for different base adjustments based on revision numbers. their may also be different venturi sizes but i havent looked into it very deep because most of the newer carbs dont have that data published.

this is my understanding of it, I could be wrong though as research time is kinda limited on my end.

 

[Poleman]

That makes a lot of sence. It must be a coincidence that I see 11's on 6400 or smaller cc saws and 12's on the larger saws. As you noted I have seem different style adjusting screws on different model carbs.
As far as venturi size they have all been the same between what I've seen.
I'll be keeping a sharper eye out for more sutle differences between the models in the earlier series. The 18 is easy to spot the differenced on the outside.

 

[fordf150]

yeah you can date the saw to a certain time period based on which carb is installed. DM11/12 would be an early saw.....before 2012 IIRC

 

[Poleman]

That sure explaines the carbs I see as most of the saws are the earlie era other than the 7910's.
Good information!! Thanks