makita 6421 carb replacement

[remduck1]

Just picked up a used 6421 and would like to put the big bore kit on it. I have noticed the carb can not be adjusted on the high side. Will this carb support the big bore kit? If not, which carb do I need to replace it with?

 

[watsonr]

Only difference in those saws is the jug and slug, everything else is the same.

 

[nstueve]

Yes it will support the big nor kit b/c it works on the 7900 too. Did you remove the limiter caps or is there just no h-needle?

 

[remduck1]

There is no H needle. Can this be modified to be high end adjustable?

 

[bikesandcars]

Can you post a pic?

I just modded a 6401 and it does have the H needle... but I needed to close the needle (make it leaner) to get the RPM's right with the BB kit.

different carbs are different carbs... but if the 6401 needs leaner then maybe the 6421 non adjustable is rich enough to run the BB kit.

Dont' forget, the mixture needle doesn't control fuel outright (like fuel injection), it controls fuel in relation to air (flowing through the venturi).. the BB kit pulls more air and thus more fuel (maybe too much now) so it isn't a rule that you need more mixture adjustment with bigger displacement. You will however run into a wall with the carburetor on a highly tuned item, but like said above this carb is the same for the 7900 so it has proven to be adequate.

You can probably replace it with a carb from the previous generation DCS6401 or Dolmar 6410

 

[watsonr]

And give the model number of the carb? It should be a Zama C3 ???

 

[TreePointer]

+1 on pictures.

Getting your screwdriver to the carb adjustment screws through the saw body on this saw can be a little more difficult than expected. That is, you must have the screwdriver at the proper angle. If you're not sure, take off the cover and air filter so you can see what you're doing. While you're at it, unbolt the carb, take a razor blade and shave the tabs off the limiter caps.

 

[nstueve]

I've been working on Dolmars and makita's for a long time now and have never run into a non-adjustable carb. They al have limiters but have never found one without the h-needle...???

x3 on pics...

 

[nstueve]

I need to recant some of the above... The 6421's have been known for non-adjustable carbs and if you have one of those I would look for a good used 6400/6401/7300/7900 carb...

 

[w8ye]

I bought a 6421 (2010) and there was a steel pin in the high speed adjusting screw hole in the case. It came out with pliers and and the carb was fully adjustable. It came too rich from the factory.

 

[dozerdan]

Just picked up a used 6421 and would like to put the big bore kit on it. I have noticed the carb can not be adjusted on the high side. Will this carb support the big bore kit? If not, which carb do I need to replace it with?

I am not a big fan of a Zama. If I did have to change a carb on a 6421 it would not be with another Zama. I would use a Walbro off of a Husky 372. Its a direct bolt on except for the choke lever hole in the carb linkage. The dolmar uses a smaller diameter choke lever then the Husky. Just weld or braze the hole and re-drill it.

Later
Dan

 

[makguy]

To answer a few questions on this thread; depending on the generation of DCS6421 the carb may either be fully adjustable with limiter caps, it may have all adjustments blocked off with an epoxy over the screws, or it may have tamper proof adjustment screws that require a special Dolmar screwdriver to adjust. However, the DCS6401 carb is a direct fit (but you may have to trim the black rubber piece on the side of the saw that blocks the adjustment screws if it interferes with the carb sitting properly in the saw.)

 

[remduck1]

I pulled the carb and it is definetly not adjustable on the H side. I will try to get pics posted.

 

[remduck1]

It looks like a steel pin on the H side but the L side is the regular adjustment screw with no limiter cap

 

[makguy]

I suspect you have the current generation of carb that is adjustable, but requires a special tool

 

[remduck1]

carb numbers DM18 239A

Cannot get my pics to upload through the attachments section

 

[w8ye]

Mine had a steel pin stuck in the rubber adjusting guide on the high side. I just pushed the pin out from the inside and then the high needle was completely adjustable.

 

[remduck1]

The rubber adjusting guide is not blocked. The H side looks like the base of an adjustment screw with no head. I cannot upload the pics for some reason.

 

[fin460]

The rubber adjusting guide is not blocked. The H side looks like the base of an adjustment screw with no head. I cannot upload the pics for some reason.

I'm looking into trading for a 6421, I'm interested in the info here, email me the pictures and I will try to post them for you, [email protected] is my email.

 

[166]

I suspect you have the current generation of carb that is adjustable, but requires a special tool

The rubber adjusting guide is not blocked. The H side looks like the base of an adjustment screw with no head. I cannot upload the pics for some reason.

Yes it sounds like he has the DD adjustment screw.

Easiest option would be to grind a slot in the HS screw to take a regular screwdriver.