Mastermind Ported Dolmar 6100

[Mastermind]

I'll pull the 6100 carb back of tomorrow Terry.

 

[Terry Syd]

Great! OK, the low speed needle only controls the idle mixture. It is the brass jet that controls the total flow through the low speed circuit.

So here's what you can try. The jet is probably a .25mm jet. If you drill it out to .3mm you will increase the flow through the low speed circuit. That may give you some more low end torque and resistance to bogging - then you can try .35mm. You will have to lean the high speed needle out each time you open up the brass jet.

We'll worry about throttle response after we get the fuel flow right in the carb.

I hope you saved the brass jet you pulled out of the old carb. If you go too far in drilling the brass jet on the 6100 carb, you can replace that jet with the old carb jet and go back to the size that worked the best.

 

[exSW]

You guys are talking way over my head.


But it's cool. I'll just read it four five times .

 

[Terry Syd]

Here's the 6100 carb.....

Opps, where did that extra hole in the wet side come from. Is that feeding fuel to the low speed needle?

 

[Mastermind]

Opps, where did that extra hole in the wet side come from. Is that feeding fuel to the low speed needle?

I can't find any place that the EL42 is getting idle circuit supply. That brass jet is far too small to be the supply........I can see it being a limiter. Where in the heck is it getting fuel from?????

That other hole in the 6100 carb might be the idle fuel supply, but I'm not making any assumptions. lol

 

[Mastermind]

You guys are talking way over my head.


But it's cool. I'll just read it four five times .

Hang tough Ross........we be learning stuff.

 

[Mastermind]

I was sure there would be a passage from the main nozzle over to the idle circuit, but nothing.

 

[Terry Syd]

Yeah, we have two similar carb bodies that have been drilled different.

We have to find out what that extra hole in the 6100 carb is feeding. Here's what I suspect, the hole is feeding fuel directly to the idle needle, so the idle needle is still just controlling fuel flow through the idle circuit.

I then suspect that the two welch plug chambers are no longer joined together. In other words, the brass jet mod will still work to increase the fuel flow in the low speed circuit through the air bleed/transition holes.

The ugly part is you may have to pull the welch plugs to confirm the circuits. Hopefully, you have a source of welch plugs handy.

 

[Mastermind]

I probably have welch plugs.

I've used smoke to trace circuits before.......might work here.

 

[Terry Syd]

That EL 42 is getting ALL the low speed circuit and idle circuit fuel through that brass jet.

If your modding a 562 again, you might want to try a slightly bigger brass jet. It may drive the computer nuts for a bit, but it might give the saw a bit more low end.

 

[Mastermind]

But where is the EL42 getting it's dang idle supply from.......it's driving me crazy.

 

[Mastermind]

That EL 42 is getting ALL the low speed circuit and idle circuit fuel through that brass jet.

If your modding a 562 again, you might want to try a slightly bigger brass jet. It may drive the computer nuts for a bit, but it might give the saw a bit more low end.

The EL42 is from a 359.

 

[Mastermind]

If that little brass jet is feeding the whole idle and transition circuit, I'll probably drill into the needle area like I do on the 3120 carbs......

 

[Mastermind]

If that little brass jet is feeding the whole idle and transition circuit, I'll probably drill into the needle area like I do on the 3120 carbs......

Nope.......that would be unmetered straight thru the idle hole......

 

[David Young]

I think the el42 uses a common supply

And semi fixed low?

The dm27 seems to have one for high and one for low.

 

[weedkilla]

If that little brass jet is feeding the whole idle and transition circuit, I'll probably drill into the needle area like I do on the 3120 carbs......

Nope.......that would be unmetered straight thru the idle hole......

 

[Terry Syd]

But where is the EL42 getting it's dang idle supply from.......it's driving me crazy.

As you mentioned, the low speed needle is seating BETWEEN the two welch plug areas. The idle circuit is taking fuel out of the transition circuit, which is getting fuel from the little bitty brass jet.

 

[Terry Syd]

The EL42 is from a 359.

I wonder how the 562 carb is configured - I seem to remember an off idle hesitation....

 

[Mastermind]

View attachment 32625

Is that a problem? LOL

 

[Mastermind]

I wonder how the 562 carb is configured - I seem to remember an off idle hesitation....

I'm gonna be dreaming about this crap tonight.