Fuel Pump

[russellrewis]

I have a 5 hp chainsaw that has a walbro carb. The fuel tank is 7 ft. away and 3 ft. lower than the engine. How much suction pressure does this carb generate? The fuel has such a long way to go plus gravity, would it starve the engine? Can a fuel pump be used on a carb like this?

Any help will be welcome.
Thanks, Russell

 

[Urbicide]

10' away? Is this saw mounted on a processor? You could try a long piece of tygon straight from the carb to the tank and see if the carb can even pump it first. Would be difficult to prime by choking the carb alone. Better have a primer bulb the size of a tennis ball. May try one from an outboard motor fuel tank hose. Is the fuel tank vented or sealed?

 

[timberwolf]

Friction is not likely a big factor as fuel flow is fairly slow. upsizing to 1/4 would help though. But 3 feet of drop adds up to a little more than 1 psi. That could have a significant leaning effect on the mixture. May just need to retune a bit to make up for it.

Like Urb said, going to want a primer and maybe even a check valve to get fuel to and keep fuel up to the carb for easy starting.

 

[timberwolf]

An option is to make a day tank type set up they use for generators, just a small tank like 1 oz close to the saw then a supply line with an overfill return line to the main tank. then you can use what ever type of pump you want to set up a fuel supply loop from the main tank.

 

[russellrewis]

The fuel tank is just a red plastic 2 gal. jerry can with a hole for venting. the engine will pull the fuel up to the carb by pulling the recoil, but it takes a lot of pulls. The boat fuel pump bulb works except it causes the fuel to develop vapor bubbles in the 1/4" clear fuel line.
I like the suggestion for the day tank. So a pump pumping directly to the carb is a no-no?

 

[timberwolf]

To pump directly I think fuel pressure regulation will be an issue. If you put pressure on the fuel line into the carb it will lift up the needle valve overcoming the spring and diaphram and richen your mixture, likely flooding out the engine just like having too low a pop off pressure would.

 

[knucklepanshovel]

just an idea but they make vacuum fuel pumps not sure how good a vacuum chanisaw engines pull & would require a vacuum tap but to prime you would unhook vacuum line use a manual vacuum pump a couple squeezes & crank & then switch hose from pump to intake.

I had some friends that had tanks mounted below small engines & they used this style & it worked well. some of the go-cart racers use this style fuel pump. where fuel tank mounts under steering in some of the open classes.

Randy

 

[russellrewis]

That was my thinking but I don't have as much knowledge of these carbs as you guys. If I knew how to post a photo I'd show you what I'm talking about.

russell

 

[Scooterbum]

Couldn't you just raise the supply tank up ?How about some pictures of this setup?

 

[russellrewis]

Knucklepanshovel huh. Sounds like a Harley man to me. An old one at that, knuckle heads go way back. Any way that would be a good option to a primer bulb. A tee fitting could be put in the fuel line close to the carb and a check valve on the third outlet for the vacuum pump. I've got a auto brake bleeder vacuum pump that would do.

 

[Scooterbum]

Isn't a knuckle head someone that rides a honda cause' they don't know no better?:jawdrop:


























Just kiddin' where ya' at in Virginny?

 

[russellrewis]

Any motorcycle made in Japan used to be called rice burners by Harley riders. I'm not in Virginia. What made you think so, my accent?

 

[Scooterbum]

Any motorcycle made in Japan used to be called rice burners by Harley riders.

Oh Okay..............'

Nah I was talking to Knucklepanshovel.

 

[russellrewis]

Whoops, sorry.

 

[Scooterbum]

You could use one of those vacume type fuel pumps they use on the Briggs/Kohler type twins on lawn mowers.It's about the same as what's on your carb just larger.

 

[russellrewis]

Thanks everyone for offering your help. I picked up some good ideas and info.

Russell

1979 Pioneer P61's. Purchased new in 1980 in this cofiguration, didn't butcher antique.

 

[Scooterbum]

1 picture speaks a ................................

Awesome looking setup.I'd really like to see a video of that.

Just mount a beer keg up there in the middle of the wing.

For fuel that is...............

 

[Scooterbum]

Gotta Ask.

Maybe a dumb question.....but is this an RC or are you sittin' in a little cubby hole behing that wing?

 

[knucklepanshovel]

sweet I remember seeing the ultralights with dual engines but it has been a long time..

Randy

Thanks everyone for offering your help. I picked up some good ideas and info.

Russell

1979 Pioneer P61's. Purchased new in 1980 in this cofiguration, didn't butcher antique.

 

[knucklepanshovel]

im only 41 had a 46 knuck for a while wish I had kept it but sold it to buy a nice original pan 10 years ago still have the pan & a couple shovels & 1 flathead. I rode since I was 17 & been around Harleys most of my life..

Randy

Knucklepanshovel huh. Sounds like a Harley man to me. An old one at that, knuckle heads go way back. Any way that would be a good option to a primer bulb. A tee fitting could be put in the fuel line close to the carb and a check valve on the third outlet for the vacuum pump. I've got a auto brake bleeder vacuum pump that would do.