Maybe the gears?

[capnward]

ah, the mystery...

Since it runs fine in neutral, I doubt this is a fuel restriction, but a fuel pressure gauge couldn't hurt. The way I understand it, if pressure goes down as it bogs down, you have a restriction upstream of your fuel pump.
Also, check the advance weights in the distributor. They could be rusted up and not moving well. Is your choke opening properly? If it stays closed that will also cause the engine to bog down. You may be running too rich. Stuck advance weights keep it from running leaner, if I'm not mistaken.

[outoftheblue]

maybe the gears, contiued

Thank you capnward,

Interesting idea about the distributor weights. I opened it up and it was rusty as expected.
I cleaned it out, slightly greased it and managed to install two new springs.
It really looked like a sure fix for the advance in higher rpm.....
but again, it made no difference at all!
The engine ran about a minute and then gradually, very slowly the rpm was dropping and than it died like always.

Not sure what to do next? It's been over two years and nothing I have replaced, cleaned, fixed made any difference in either direction.

[Dave Neptune]

It's sounding more and more like it is fuel delivery related. This could be a lot of things but to eliminate the fuel to the carb a guage will give you an answer.

Dave Neptune

[edwardc]

...
On the other hand, originally I had a mechanical fuel pump when this problem started.

I replaced it with the electrical and it had no effect on it. Engine still slowly, gradually lost power after abut a minute in gear sarting at 1500 rpm.

This still sounds like a fuel delivery restriction problem to me. I had something similar several years ago. Enough fuel gets delivered to keep the float bowl full and the engine running at idle, but under load, the engine consumes fuel at a higher rate than it is being delivered and the float bowl slowly runs dry in a minute or two.

In my case, it was the fuel pump, but since you've eliminated the fuel pump as a cause, the restriction must be elsewhere. The two places that come to mind are any "polishing" filter between the fuel pump and the carb, and the carb's float valve mechanism itself. But, back in post #1, you said you replaced both the carb and fuel filter!

That brings me back to the fuel tank and its pickup. But in post #12, you said you ran off of a spare tank and an electric pump and it still failed, although more slowly.

When you've eliminated the impossible, whatever's left, no matter how improbable, must be the answer.

So, what's left of the fuel delivery system that you haven't changed out? Hoses, fittings, elbows? Anything that could hold a blob of crud or a piece of teflon tape that could restrict the fuel flow. Really grasping at straws here.

[Surcouf]

This still sounds like a fuel delivery restriction problem to me. I had something similar several years ago. Enough fuel gets delivered to keep the float bowl full and the engine running at idle, but under load, the engine consumes fuel at a higher rate than it is being delivered and the float bowl slowly runs dry in a minute or two.
......


So, what's left of the fuel delivery system that you haven't changed out? Hoses, fittings, elbows? Anything that could hold a blob of crud or a piece of teflon tape that could restrict the fuel flow. Really grasping at straws here.

only way to rule that out is the pressure gage right before the carb. Do you have that installed? If yes, that would rule out the whole fuel chain.

[JOHN COOKSON]

Did you ever check the stuffing box? Post #15.

ex TRUE GRIT

[edwardc]

only way to rule that out is the pressure gage right before the carb. Do you have that installed? If yes, that would rule out the whole fuel chain.

Not quite true. A pressure gauge is a valuable tool, but a good reading doesn't rule out all types of fuel problems.

<Lecture Mode>

Pressure and flow-rate are two different things. Consider a pressure-washer. It has an insanely high pressure, but would take a really long time to fill a swimming pool!

Pressure, flow-rate, and restriction are related by an equation similar to Ohm's Law, where pressure is like voltage, flow-rate is like current, and restriction is like resistance. Thus pressure is proportional to the product of flow-rate and restriction. So, if the pressure remains the same, and the restriction is increased, the flow-rate has to go down.

</Lecture Mode>

True, the restriction would have to be downstream of the pressure gauge, which is why you should put it as close to the carb as possible, but there's always a few bits of hose and fittings after.

While this is all a fun intellectual exercise, it's a really low-probability possibility (I did say I was grasping at straws!).

[Al Schober]

I've been thinking how you can ease your mind about the reversing gear. Recommend the following:
With the engine off, remove the transmission cover. As you move your shift lever, you'll see the shifter cone around the main shaft move fwd (towards the engine block) and aft.
With the shifter in fwd, you should see the cone move AFT and engage the three fingers that engage the fwd clutch pack. The fingers should go over the hump in the cone and kinda snap into place. If this doesn't happen, your shifter is likely faulty/out of adjustment.
With the shifter in reverse you'll see the cone move fwd. It should almost come into contact with the notched ring for adjusting the fwd clutch pack. 1/32 or 1/16 of clearance is fine. If your clearance is more than this, try backing off the reverse adjusting nut a few flats and try again. If you can't get the cone to move this far fwd, your shifter is likely faulty/out of adjustment.
Take some pictures if you see anything questionable. Hope this helps.

[Antibes]

Check all connections in the fuel lines. Years ago I was not leaking fuel out, but air in and she would die out after time