Installed a Bing 48 carb on my 036

[Terry Syd]

I'm thinking if one were to manually press the metering diaphragm for a moment it would provide a prime of fuel through the main nozzle from the pressure that builds in the fuel tank.

If the tank didn't have any pressure, it might still work. Pushing on the diaphragm will lift the metering valve, but the reed valves on the PUMP diaphragm should keep the fuel from being forced back into the tank. The fuel under the diaphragm would then be forced out of the carb and into the engine.

 

[paragonbuilder]

If the tank didn't have any pressure, it might still work. Pushing on the diaphragm will lift the metering valve, but the reed valves on the PUMP diaphragm should keep the fuel from being forced back into the tank. The fuel under the diaphragm would then be forced out of the carb and into the engine.

So Terry, this could do what we are looking for? If we wanted to prime the engine and could find a way to press it?


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[Terry Syd]

I've never tried it, but theoretically it should work. If the diaphragm cover had a hole in the center so you could push down on the steel button in the center of the diaphragm, you could push down a couple of times to prime an empty carb and also push some fuel into the engine.

EDIT: It might be a good idea to test the idea while holding the carb in your hand with the fuel hose hooked up. If you could pump fuel into the carb and out into the venturi, then you just have to figure out how to do it with the carb on the saw.

 

[dall]

i have a old shindiawa weedeater in my building that has a lever mounted on the pump side cover to prime the motor

 

[Terry Syd]

How far does the lever move the diaphragm? There is probably a working stroke, which if it is exceeded may damage the carb.

EDIT: The working stroke could vary a fair bit between carbs. I expect that the 'coil bind' on the metering spring would occur at different spots between different carbs. If you pushed down on the diaphragm after coil bind is is likely you could bend the metering lever. You would just have to check each carb and know what the limits were.

 

[Chainsaw Jim]

Jim that's a great thought! How could we achieve that with the saw all put together?


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Use a cable similar to the Husqvarna throttle trigger cable linkage to locate it somewhere convenient. There are quite a few different little spring loaded buttons that I'm sure could be modified to connect to a cable. Connecting it to the cover plate on the carb shouldn't be a super pain with a little fab work and soldering.

 

[rocketnorton]

just a quick comparo. have a s here w/zama, m w/bing, both 038 carbs w/no choke. ran both on the m, seat of pants diff in bing's favor.

 

[Al Smith]

The Bing was said to be the better choice on the 038 Mags than others .I don't have an 036 but I do have an 034 super which is about the same .If I find the time I'll experiment and see if some how a filter with a choke can be adapted to fit under the cover and with the choke/kill button shaft .If memory serves I think I have a filter that has a choke that is slightly smaller than the 038 .What it's off or where it's at now is the big puzzle.--Good thread by the way ---

 

[psuiewalsh]

i have a old shindiawa weedeater in my building that has a lever mounted on the pump side cover to prime the motor

Didn't some of these work by unseating the valve and overflowing the fuel?

 

[Mastermind]

@Mastermind put one on John's 026 if I remember right

Yeppers

Great thread here! @Canadian farm boy nice description on the set up. I like the before and after to show gains.


I tried the primer bulb set up before and it did not work out well. The carb would draw fuel by the bulb at wot. The bulb I tried was off a poulan weed eater. Maybe a different style would not do that.

All you have to do is melt a small hole in the top of the bulb that you can cover with you thumb when you pump it. Then at wot it will keep the bulb from pulling fuel from the tank.

 

[Mastermind]

 

[paragonbuilder]

Yeppers



All you have to do is melt a small hole in the top of the bulb that you can cover with you thumb when you pump it. Then at wot it will keep the bulb from pulling fuel from the tank.

That is brilliant! If it sucks a little air it don't matter. I like it!


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[Stihlbro]

Yeppers



All you have to do is melt a small hole in the top of the bulb that you can cover with you thumb when you pump it. Then at wot it will keep the bulb from pulling fuel from the tank.

And that's why you sir, are the "knocker of smarts"

 

[Al Smith]

Clever idea!Bravo

 

[Al Smith]

Now on those Bings if you can't get the choke closed all the way they will start but you'll nearly pull your arm out of the socket before they do .Choke closed they fire right up .Been there done that,bound control shaft .Live and learn

 

[drf256]

View attachment 37218 View attachment 37219 View attachment 37220

Spectacular.

Can you go over the line routing of that setup for us?

 

[Mastermind]

It's just a line from the tank to the primer, then from the primer to a fitting installed in the carb. The fitting is an old inlet from another carb epoxyed in the choke shaft hole.

 

[Canadian farm boy]

I got out today and tested out a bunch of different carb and air filter combos on my 036.

I ran the same 20" bar, 3/8 full comp round filed chisel chain and a 8 pin sprocket in each video. All testing was done in the same white ash log.

I've got 5 videos to post.

 

[Canadian farm boy]

Video #1
038 intake boot, Bing 48 carb, v stack with foam filter.
Wot 15800
Holding 12800 in the cut.
Fastest 3 cuts averaged 5.5 seconds

 

[Canadian farm boy]

Video #2
038 intake boot, Bing 48 carb, 036 metal mesh air filter
15800 wot
12600 in the cut
Fastest 3 cuts averaged 6.3 seconds