Low CFM carb

[Geo46]

Hi All, can anyone suggest a low CFM carburetor for a small engine, this is no a conventional engine. Looking for something in the range of 66CFM , no purge bulb.
Thanks

 

[sparkwizard]

Look at chainsaw carbs.
Weed whacker carbs ae pretty small, too.

 

[creia]

Provide us with more details and photos of the engine it will go on...
Michael

 

[Geo46]

Good morning, PZ 19 leaks gas out of the throat, this mounted on an unconventional engine, I’ll post pics, what are the 2 ports in front of the choke plate? Which adjustment screw should I start with, what position should the throttle be in for starting, I did crank it over and it popped but would not stay running, spark is present, I may have posted this under a different topic, not sure.

 

[cl350rr]

Considering that the previous carb and now this one leak, you may have a head pressure issue created by the height of the fuel tank.

 

[Geo46]

Hi, should I try lowering the tank on maybe closing the petcock a bit?

 

[cl350rr]

You could rig up a temporary tank, mount it just above the carb and see if it still leaks. Do you know the displacement of the engine? Throttling the petcock will not change the pressure on the needle valve, it is a function of height.

 

[sparkwizard]

If I am not mistaken, this is a hit and miss engine, and the exhaust valve stays closed to "coast" and only opens to pop a couple of times in order to keep the big flywheels spinning. I think they were not "throttled" but had a fuel mixer. If that s the case, there is no vacuum signal to the carb except when the exhaust valve opens.
If that is the case, it might explain the difficulties you have been having with traditional carburetors leaking.

 

[cl350rr]

The op has two threads running on this carb issue, recommend combining or closing one and focus on the other.

 

[Geo46]

If I am not mistaken, this is a hit and miss engine, and the intake valve stays closed to "coast" and only opens to pop a couple of times in order to keep the big flywheels spinning. I think they were not "throttled" but had a fuel mixer. If that s the case, there is no vacuum signal to the carb except when the intake valve opens.
If that is the case, it might explain the difficulties you have been having with traditional carburetors leaking.

If I am not mistaken, this is a hit and miss engine, and the intake valve stays closed to "coast" and only opens to pop a couple of times in order to keep the big flywheels spinning. I think they were not "throttled" but had a fuel mixer. If that s the case, there is no vacuum signal to the carb except when the intake valve opens.
If that is the case, it might explain the difficulties you have been having with traditional carburetors leaking.

 

[Geo46]

It’s not a H\S it’s throttle governed.

The op has two threads running on this carb issue, recommend combining or closing one and focus on the other.

 

[Geo46]

I realize I have 2 not sure how to combine them or close one.

 

[Geo46]

You could rig up a temporary tank, mount it just above the carb and see if it still leaks. Do you know the displacement of the engine? Throttling the petcock will not change the pressure on the needle valve, it is a function of height.

 

[bruces]

That carb is widely used on motorcycles with an elevated tank ,cannot see how that is the problem .On some scooters ,the tank might be 2ft above the carb .

 

[Geo46]

Displacement is about 60cc, that’s why we switched to this carb, good thought on the tank height, I realized after that the petcock wouldn’t reduce pressure, I’ll try that at some point, not a lot of opinions , it does have to be above the slightly I believe, no fuel pump involved.

 

[Geo46]

That carb is widely used on motorcycles with an elevated tank ,cannot see how that is the problem .On some scooters ,the tank might be 2ft above the carb .

 

[Geo46]

Thanks, at this point I am open to suggestions.

 

[cl350rr]

A bit more info needed about the leakage of these carbs. Do they leak with the engine not running or do you get fuel out when you are trying to start it?

 

[Geo46]

Fuel leaks out when trying to start .

 

[cl350rr]

You might want to take a bore and stroke measurement, the engine in the pic below is 18cc, I believe you might be much larger than 60cc.

The leakage you are seeing may be due to the long cold intake track, fuel condensing on the walls then running back down the carb throat to the intake opening.

I suspect it would clear up after the engine reaches operating temperature.