Only runs with the choke pulled out

[opposedtwin]

1957 FD11. Went through mag: good spark. Replaced top crank seal. Went through carb but reused the old needle/seat. Couldn’t speak for the seat but the needle (old style without the rubber tip) looked good so i re-used it. Can’t remember if i replaced the old fuel nozzle gasket or not. Would that explain the need for the choke to be out?

Have gone through a number of these carbs this spring. The high speed needle on this one seems overly sensitive. As it is now, the hs needle is only out about 1/4 turn. Runs really nice at wot with the choke out. But from idle to fast throttle, it hesitates (like it may be flooding) then something is clicking under the cowl before it recovers and roars up to wot. Any idea what the clicking may be? I have run three of these FD models now pretty extensively. This one sounds different than the other two. It has a hissing or air pressure sound and it seems to labor a bit. 115 psi cold both top and bottom. Ideas?

Thanks for any and all advice!

[chas56x]

The motor is running lean. It may be caused by an air leak, or maybe there is a restriction in a fuel line or a dirty fuel filter.

[crosbyman]

did you pull the top plug to clean the drip chamber feeding the low speed circuit of the carb ??

make certain all passages are flushed and air pressured dry

Joining AOMCI has priviledges 🙂

[olcah]

Be sure there are sufficient needle packing washers and the packing nuts are tight. When air is leaking there, the motor does not respond well to the carb needle settings.
Maybe the clicking is associated with the throttle to rewind interlock. I would disable that for a test.

[dougs-outboards]

I don’t know about the clicking sound, but the symptoms point to a dirty carb. Anytime (in my experience) that a motor has to have the choke pulled out to run, I have noticed that a good carb clean usually fixes the problem.

Don’t forget your link n sync on the carb to spark advance. Pretty important.

BTW, My FD11 normally runs perfectly with the high speed needle about 1/4 – 1/3 out, low speed about 1-1/4 turns out. 140 lbs compression.

[ken-w]

Check the gasket between the bowl and upper carburetor body.

[fisherman6]

Scott,
With the air pressure sound you describe, I think I would look for an air leak. Possibly between the crankcase halves or at the crankshaft seals? Maybe the carb to intake manifold gasket is leaking? 1/4 turn out on the high speed needle seems a bit light, but not necessarily out of range. If the nozzle gasket is leaking some that will let a little extra fuel in and richer the mixture a bit. If it is leaking air, and that airflow increases with RPM, that may be leaning it out at higher RPMs. If you have to run the choke out, it’s too lean for some reason. If the carb is clean, that reason can be tricky to track down.

As for the clicking, is it possible you may have a plug wire or a coil leaking and grounding out at some position on the mag plate, then as you move past that spot the short stops and the plug starts firing again making the engine recover to full speed?

Others will surely have more ideas as well. Those would be things I would suspect from the symptoms you describe. Look around the engine for areas dampened from fuel mix possibly escaping from the crankcase to find the leak. You may also use an unlit bottle torch to dispens propane gas around areas that may be leaking. The engine will change RPM if it stars ingesting propane through a leak.
-Ben

OldJohnnyRude on YouTube

[fleetwin]

"clicking???" Are you sure there isn’t spark jumping somewhere? Kinda sounds like spark jumping to ground where it shouldn’t be….
Try running with the cover off tied to the dock after the sun sets, perhaps the arcing will be more evident…

[billw]

I was thinking along the lines of Fleetwin, maybe spark is arcing. That being said, it could also be a crank case or reed plate gasket leak causing that noise. Look around the block for signs of fresh fuel/oil where it shouldn’t be. Hopefully you don’t have a leak AND spark jumping!! I don’t think it would run fast at all if you forgot the main nozzle gasket. I know a 70 hp won’t. Ask me how I know this.

Long live American manufacturing!

[chris-p]

Agree with the guys above, sound like a couple different issues here.

If in fact the carb is cleaned and rebuilt, new fuel lines, tight fittings, you may need to split the crank halves to remedy the lean condition and re seal.

I too like to run them at night to verify arcing.

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