Dolmar 7900 Carb upgrade?

[Poleman]

Awsome Terry,

That will be a very good carb to mod!!!!

I WILL be following!!!

 

[Poleman]

Well...heres some pic's of the Farmer Tec carb. For the most part it looks good. It apears a little less finished on the inside but still good.

I guess the test will be performance and not looks.

 

[ncfarmboy]

Thanks guy's this is the stuff I look for and really appreciate the time & effort to do the work and post it.
Shep

 

[mdavlee]

Well...heres some pic's of the Farmer Tec carb. For the most part it looks good. It apears a little less finished on the inside but still good.

I guess the test will be performance and not looks.

Is this going on the 7900?

 

[Poleman]

It could. I have all my saws equipped with modded carbs and trying to get a stock 7900 to test as I have A Mastermind ported 6401 and a 84cc b
Big bore I,'ve been using. I'd like to see if there is any difference.

I have sent a couple carbs off but no feedback because of more important family health issues and I have one going to Randy to put on a 7900 he will be porting. I think that will give a ton of information and feedback....I expect Randy to put it through its paces and tell me how it is!!

Actually, I was going to start setting this carb up for a 365-372 BB. Mine has a Walbro and I want to see if I can get the same gains out of it as I did the Domars!! The second carb may go on a Husky BB 350 to see what happens there.

The only difference this carb has from the Dolmar carbs is the size of the choke lever attachment....its a little larger for a
Husky.( see last photo) but that's no big issue.

So until I get a 7900 I will be using these on whatever I can to get results, but yes I would sure use one on a 7900!!!!!

Sorry, long drawn out answer..,..just letting all know what my thoughts are and where I'm going.

 

[mdavlee]

It could. I have all my saws equipped with modded carbs and trying to get a stock 7900 to test as I have A Mastermind ported 6401 and a 84cc b
Big bore I,'ve been using. I'd like to see if there is any difference.

I have sent a couple carbs off but no feedback because of more important family health issues and I have one going to Randy to put on a 7900 he will be porting. I think that will give a ton of information and feedback....I expect Randy to put it through its paces and tell me how it is!!

Actually, I was going to start setting this carb up for a 365-372 BB. Mine has a Walbro and I want to see if I can get the same gains out of it as I did the Domars!! The second carb may go on a Husky BB 350 to see what happens there.

The only difference this carb has from the Dolmar carbs is the size of the choke lever attachment....its a little larger for a
Husky.( see last photo) but that's no big issue.

So until I get a 7900 I will be using these on whatever I can to get results, but yes I would sure use one on a 7900!!!!!

Sorry, long drawn out answer..,..just letting all know what my thoughts are and where I'm going.

If you want one tested on a 7900 I'm game. I've got one that's going to be worked over this next week or two.

 

[cgraham1]

I have one going to Randy to put on a 7900 he will be porting. I think that will give a ton of information and feedback....I expect Randy to put it through its paces and tell me how it is!!!

My saw will be shipped out next week...

 

[fordf150]

My saw will be shipped out next week...

ring show up yet?

 

[cgraham1]

ring show up yet?

Maybe today? I haven't been to the PO. I'm sure it will be there Monday. Thanks!

 

[fordf150]

Maybe today? I haven't been to the PO. I'm sure it will be there Monday. Thanks!

just checked. ready for pickup at the PO. I guess paying the extra for 3 day priority was worth it.

 

[cgraham1]

... my 7900 is headed your way!

I have a carb for it already here waiting.

I wanna see if we get the gains from the carb I'm thinking we will......

I got the ring! It's shipped to Tn. With the saw... This should be interesting!

 

[psuiewalsh]

need a new master monkey videoopcorn:

 

[mdavlee]

Is this a modded stock carb?

 

[cgraham1]

Is this a modded stock carb?

Yep.

Well....worked on the Zama that will go to Randy today...little bit different than the others. This had a double D Hi screw, than I noticed these carb had a hole drilled in the throttle plate. I measured it at .80mm.

Drilled the jets to 30/40, double checked needle height and tested this way. Started easily but was running rich and needed more air. It did have idle adjustment the way it was. I then opened up the throttle plate hole to .90mm and retested.....better. One more try this time to 1.00mm. This seemed to do the trick for adjustability and engine performance. The throttle was a little slow now so I tryed a shim and a spring change....nope not it. Left the shim and put original spring back in....that's more like it!!!!

The saw was still a little rich, but I figure after Randy gets finished doing his port work on the 7900 it should be real close...or that's my intentions. This carb has a lot of top end to work with!!

Looking to make these as painless as possible to put on a saw and go!! Hopefully I will be getting some feedback soon as to how accurate settings are and power results.

 

[Poleman]

Drum roll please.........
.............in your Tallented hands Randy!!!!!!


Rich

 

[Poleman]

I think this will have a lot of interest.......hope it's not a disappointment.......

 

[cgraham1]

I think this will have a lot of interest.......hope it's not a disappointment.......

My saw was delivered to Mastermind today!
Now... We wait. opcorn:

 

[Fly By Night]

I'd like to try these mods on my 7900 do you guys have a feeling for what affects altitude has? I live at 6,500 feet and usually am higher when I'm running my saw.

 

[fastLeo151]

You can just put a 395 carb on it.... I have a ported 6401 and the 395 feeds it fine.

 

[Poleman]

I think I would start at .30/.35 and see how the saw runs at your altitude. You will be giving the saw a lot more fuel and after modding the carb the air flow is an issue. The throttle plate will need a notch/hole to give it air at idle.....just don't go to big. Also this changes the H setting as the saw is getting more fuel through the idle circuit. I m not sure if at 6000 ft you can get enough air through so saw doesn't run way to rich. I'm at 4000 ft and can use 35/40 drill size.

I think this will work for you, just go slow to see how the first mod works after that its a 10 minute change to increase to larger size.

I have still to pull the idle jet and drill larger air bleed hole in carb as Terry has suggested to alleviate the need for a slow taper idle screw and/or throttle plate alteration.

You will definatly see/feel a lower power increase at this stage!! This mod is all about torque.....saw wont run faster just have a LOT more usable power in the same power curve and hold RPM in the cut!! I also feel this would help feed a ported saw in its added fuel requirement's giving it what it needs from its alterations also. Only limit is the limited coil on the 6400-7900 Dolmars. It may not run past 13,500 but may be able to run close to that in the cut......who needs it to run more RPM's if it can do that!!!!!