Installed a Bing 48 carb on my 036

[Terry Syd]

OK, back on page #9 of this thread we discussed making the high speed and low speed circuits separate. It looks like that is what needs to be done with this carb.

Once the high and low are separate, then a fuel access hole has to be drilled for the low speed needle.

The auxiliary jet may or may not be needed once the low speed circuit flow has been increased.

 

[Stihlbro]

You are correct and it backs up what I said, just different wording.

The first hole from the throttle side supplies fuel when the blade is closed. Known as the idle hole. The second hole(called transistion) supplies fuel when part throttle. Part throttle uses the first two holes closest to throttle blade. Both are under the Welch plug. The third hole, different manufacturer name it differently actually take in air and pressurized under the Welch plug to deliver 1.) idle 2.) transistion hole.
Now at wide open throttle the air thru the carb is drawimg fuel out the main nozzle. Fuel is still being drawn out the idle and transistion holes.

We really need to do a thread on explaining how carburetors work. I'm guilty of calling out terms and not explaining well.

 

[Stihlbro]

OK, back on page #9 of this thread we discussed making the high speed and low speed circuits separate. It looks like that is what needs to be done with this carb.

Once the high and low are separate, then a fuel access hole has to be drilled for the low speed needle.

The auxiliary jet may or may not be needed once the low speed circuit flow has been increased.

To do that , gonna have to block off the hole in carb body from the main nozzle. If not, separating the two circuits could feed the main nozzle from an additional feed and likely the high side will not tune properly.

 

[Backtroller]

We really need to do a thread on explaining how carburetors work. I'm guilty of calling out terms and not explaining well.

Yes, this would be very helpful.

 

[Terry Syd]

I'll string together my posts from page #9, it will save going back to it. The second post explains how to block the circuit.

Holy Sh!t, I think it may get its fuel from the main discharge nozzle tunnel (like on some Walbros). This configuration keeps the low speed circuit LEAN as the carb comes on the high speed circuit - it is another way to meet EPA guidelines. It tends to decrease the torque down low (and therefore less emissions) and makes the operator have to run the saw at a higher RPM where there will be less mixture blown out the exhaust port.

You will have to push out the main discharge nozzle to see if that circuit goes all the way to the main discharge nozzle tunnel.

If it does, we can mod this carb to work a lot better.

Stihlbro, if you can confirm that the brass jet does not have a discharge port underneath it then your carb will be an easier mod. All you have to do is drill out the limiter jet on the low speed circuit.

If it does have a discharge port into the main body, then it is an auxiliary jet to help with throttle response and the carb should have the same low speed circuit as Backtroller's.

I think that is the hole from the High Speed needle. Remove the high speed needle and shine a light through there and you'll probably be able to confirm it. However, if the hole has been drilled at an angle, then you are probably right.

If the low speed circuit drew its fuel from the nozzle circuit, I would expect there to be TWO holes in the discharge nozzle tunnel. One from the high speed needle and one from the circuit that has been blocked.

If there aren't any more indications of blocked off circuits (look for more plugs on the carb), then it appears that both high speed needle hole and angled circuit have come together in one hole. In which case, the mod is going to be more difficult to do. If there were two holes, you would block the hole to the low speed circuit with a bit of JB Weld (I do that on the Walbros)

What we want to do is isolate both circuits from each other. If they both come together in the nozzle tunnel, then you will have to drill further back from that hole and into the feed to the low speed circuit, perhaps 5 mm will be enough. However, you don't want to drill too far back along the circuit or you may hit where the low speed needle comes into the carb.

After you have drilled down and found the circuit, you can probably open up the hole you drilled with a bit bigger drill to make the next move more easily. You need to fill up the hole with JB Weld so that the circuit is blocked and no longer connected to the nozzle tunnel.

Once the circuit is blocked, we will drill another hole over the low speed needle to provide fuel to the low speed circuit. - Then you can start tuning a whole different carb!

After you get the high and low speed circuits independent of each other, you can then tune them to get the fuel curves you want.

When you increase the fuel flow in the low speed circuit the high speed circuit will have to be leaned out. You may run into a common problem with these kinds of mods, that is, the high speed circuit can't be leaned out enough. What you then have to do is block the jet on the back of the main discharge nozzle. Just put a dab of JB Weld on the back of the nozzle.

Another potential problem will be the brass jet that Stihlbro has on his carb. I THINK (it hasn't been confirmed) that that jet is to help with throttle response. You can find out by seeing if it has a port that goes into the carb body for the fuel to discharge from. If it does, then it is an auxiliary jet for throttle response (a common configuration on these EPA carbs). - What happens is that after making the high and low circuits independent, the low speed circuit will likely go rich. In which case, that brass jet may provide too much fuel for right off of idle. If it tends to bog off of idle then you will have to block the brass jet with some JB Weld.

 

[Canadian farm boy]

I haven't forgot about this thread.

It's just a busy time of year for me and it gets dark so early now I haven't had much time to play around with the Zama carb.
I've ordered a set of micro drill bits from eBay. Once things slow down here again and I get the drill bits I plan on going back at this again.

 

[Tpagel]

This thread is awesome.
Thanks for all the info although it is far above my level it is great to see what can be done.
I have seen the 026 to 044 carb in a thread would that 044 carb fit in the 036 as well?



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[huskihl]

I have seen the 026 to 044 carb in a thread would that 044 carb fit in the 036 as well?



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No. That's the problem with the 036. It's a design all its own.

 

[drf256]

This thread is awesome.
Thanks for all the info although it is far above my level it is great to see what can be done.
I have seen the 026 to 044 carb in a thread would that 044 carb fit in the 036 as well?



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I'm still wondering this as well. Perhaps with some custom linkage parts it would work.

Not sure if all the work would be worth it though. I don't really love the 026 with the 044 carb. Yes, it will piss rev higher, but I'm not so sure it's any faster in the cut with the bigger carb.

 

[rocketnorton]

hd guys spent big bucks to find out same. s&s carb/filter kits on stock motors. any given motor will only eat so much air/fuel.