OT Small motor carbs, gravity feed vs pump?

[sasquatch]

If that is a "Flowjet" carb, the bottom needle is the high speed adjustment.
I have used those carbs,, all with a fuel shut off tap, BUT they will not run well or at all with a gravity fed inline fuel filter. There is just enough restriction in flow to kill them.
Even a large automotive inline filter wouldn't work.
Strange, as you would think enough fuel would seep through to keep it running.
Those are a very good reliable carb.

[vpt]

I'll find and post a pic of the carb and motor I have below.

I got new tangent fuel line today, new gravity feed filter, starter relay, wire, some switches, and whatnot. Got everything together and got the motor to pop a few pops at a time and die, over and over again for an hour. I tried pressurizing the fuel tank a few times just to se if it was a fuel delivery issue and there was no change. I would adjust the lower main jet needle out some then all of a sudden the plug would be wet. I would turn the needle back in 1/4 turn and then the plug would be dry. Back and forth for hours this went on. Finally I got it to run continuously while playing with the choke and throttle plate. Still I couldn't find the sweet spot with the high speed needle. I would turn it out a tiny bit and get way to much fuel then not enough, back and forth it it never seemed to want to be consistent.

Finally I got it to run good enough to get out and drive it and kept playing with the high speed needle. By the time I ran a whole 1.5 gallons of gas threw the motor I had it pretty well dialed in. I think there may have been some junk or air or something somewhere that worked out because it did eventually be consistent with needle adjustments. Idled good, ran good at any constant throttle, but am having a bit of an issue yet with the rev up (rolling onto the throttle from idle). It will stumble some and sometimes have trouble reving up like it is not getting enough or to much fuel but when it gets up to speed it hold the rpm fine.

I have to disclaim some stuff yet, there was 1.25" of water in the bottom of the crank case for 20 years in this motor with its 2 quarts of oil on floating on the water. I have drained the oil, dumped in "clean" waste oil, ran the motor for a few minutes and drained it, and put in fresh good oil. One of the things the water did it seems is rust away the governor inside the crankcase since I can't feel or see it move ever when running. So I redid the the throttle direct to the carb. Now before you guys explain all the reasons not to do this I have to say the throttle is foot controlled exactly like a car gas peddle so I can control the engine rpm's constantly just like a car and not let it over rev. I believe I have been around enough of these motors to know what to high of rpms sounds like.

Can't find any pics apparently. I'll have to go out and take a few pics and post up in a minute.

[vpt]

Ok, some pics.

[vpt]

Oh yeah, Thanks for all the tips on the fuel shut off, I'll pick one up tomorrow and install it.

[sasquatch]

That sure looks like the "Flow-jet" carb.

Those engines that i have had do stumble as you say, going from idle up to high rpm, at least all mine did.

Think they were mainly meant for either idle or steady rpm's.
What is this engine driving?

[vpt]

The engine is driving a coot.





This one runs and performs much better than mine right now.

http://www.youtube.com/watch?v=3H0SPWfJ29w&feature=related

[vpt]

These guys push this one a little better. They are amphibious, mine has the prop shaft option on the back.

http://www.youtube.com/watch?v=Isi4NGVCIKQ&feature=related

[Black_Moons]

Best reason for fuel shutoff: Is that float WILL get stuck someday, and moreso then fill your engine up it will likey piss fuel all over. Nothing stupider then siting there as you leak a full tank of fuel everywhere wondering when it will stop.

[Willy]

Idled good, ran good at any constant throttle, but am having a bit of an issue yet with the rev up (rolling onto the throttle from idle). It will stumble some and sometimes have trouble reving up like it is not getting enough or to much fuel but when it gets up to speed it hold the rpm fine.

Have you tried fattening up the idle mixture?
If you don't have a minor vacuum leak, a slightly fat idle mixture should serve as a transition between the idle jet downstream of the throttle butterfly and main jet located in the bottom of the fuel bowl which feeds into the main venturi.

A slightly lean idle mixture usually results in sluggish throttle response in these units, although with a proper main jet setting the engine is still able to function well under load at higher engine speeds.

[vpt]

Thanks much Willy!

I didn't play with the idle jet much, I adjusted it till it idled fine without backfiring and left it. I will give the low jet some more adjustment tomorrow when I try it again.

Doing some searching and research on the coot and am thinking of rebuilding the whole thing. There isn't much there to rebuild (clean, reseal, new bushings and whatnot). After driving it a little today I think the clutches need to be gone threw as well. The drive clutch that I could see while driving wasn't closing all the way at WOT, it would start to close and work like it should and then stop about half-3/4 way to full engagement. I don't think anything has been cleaned or serviced in this thing much if at all. Seems stuff that broke was replaced or fixed and that was it, no maintenance.

[J. Randall]

It will shut off the high speed circuit. Fuel can still flow into the carb past the float needle. I think its best to be able to shut off the supply of fuel to the carb when the engine isn't in use. Should the float needle fail to shut, the fuel will overflow and those carbs do not have an overflow vent.

Don't disagree with any of that, was just pointing out that Andy had already stated the needle he was talking about was in the carb as in needle and seat. I always put a shutoff in if there is not one there already.

[J. Randall]

I'll find and post a pic of the carb and motor I have below.

I got new tangent fuel line today, new gravity feed filter, starter relay, wire, some switches, and whatnot. Got everything together and got the motor to pop a few pops at a time and die, over and over again for an hour. I tried pressurizing the fuel tank a few times just to se if it was a fuel delivery issue and there was no change. I would adjust the lower main jet needle out some then all of a sudden the plug would be wet. I would turn the needle back in 1/4 turn and then the plug would be dry. Back and forth for hours this went on. Finally I got it to run continuously while playing with the choke and throttle plate. Still I couldn't find the sweet spot with the high speed needle. I would turn it out a tiny bit and get way to much fuel then not enough, back and forth it it never seemed to want to be consistent.

Finally I got it to run good enough to get out and drive it and kept playing with the high speed needle. By the time I ran a whole 1.5 gallons of gas threw the motor I had it pretty well dialed in. I think there may have been some junk or air or something somewhere that worked out because it did eventually be consistent with needle adjustments. Idled good, ran good at any constant throttle, but am having a bit of an issue yet with the rev up (rolling onto the throttle from idle). It will stumble some and sometimes have trouble reving up like it is not getting enough or to much fuel but when it gets up to speed it hold the rpm fine.

I have to disclaim some stuff yet, there was 1.25" of water in the bottom of the crank case for 20 years in this motor with its 2 quarts of oil on floating on the water. I have drained the oil, dumped in "clean" waste oil, ran the motor for a few minutes and drained it, and put in fresh good oil. One of the things the water did it seems is rust away the governor inside the crankcase since I can't feel or see it move ever when running. So I redid the the throttle direct to the carb. Now before you guys explain all the reasons not to do this I have to say the throttle is foot controlled exactly like a car gas peddle so I can control the engine rpm's constantly just like a car and not let it over rev. I believe I have been around enough of these motors to know what to high of rpms sounds like.

Can't find any pics apparently. I'll have to go out and take a few pics and post up in a minute.

Assuming that carb has the removable main jet, did you take it out and make sure the tiny holes in it were clear? Symptoms sure sound like you might have had a slight blockage left there somewhere, tuning should not have been that touchy. Agree about fattening up the idle adjustment a little bit.
James

[vpt]

Assuming that carb has the removable main jet, did you take it out and make sure the tiny holes in it were clear? Symptoms sure sound like you might have had a slight blockage left there somewhere, tuning should not have been that touchy. Agree about fattening up the idle adjustment a little bit.
James

Yes I pulled the whole carb apart (although it doesn't look clean and fresh in the pics) and went threw every port, hole, journal, and whatnot and made sure all were clean. The only thing I can think of that could have been left behind would be some paper towel fibers or cloth fibers from rags. Today I went out and gave the low speed needle a 1/8 of a turn and started the motor, still idles good and did seem to rev up easier, but I didn't run it long to warm it up.

I started in on some more fun today and have another question lol. Are greased bearings the same as oiled bearings? I found a couple pitted bearings and races in the gearbox today and actually found the 1" trailer bearings are identical in all dimensions. Just curious if something metal wise is different between greased and oiled bearings?

Found more milkshake today.



Pulled the trans apart and cleaned it all up.


Couldn't get the secondary clutch off the shaft So I had to do all the work with the clutch shaft on the main shaft.


Everything looks good except this idler gear. These few teeth must have dipped into the water in the bottom of the case over the last 20 years. Is there any repair options for these few teeth? I can't imagine it would be easy to find this gear. File test says its hard like most gears. Can the water craters be cleaned up and filled with tig fast without heating everything up? Or heat it, weld, cool with something, or welding is not a viable option at all? I have welded gear teeth before on less stressed gears and have about a 50% fail rate but normally welding in full teeth.

[Willy]

No difference in bearing material for grease or oil lubed bearings. Grease is just a carrier for oil anyway and is used when oil is not a viable alternative for a particular application.

You should be able to verify that your Coot transmission bearings are in fact 1" trailer bearings by looking up the bearing numbers and doing a bearing number cross reference.

The gear in question does look like it should be sidelined before it does more damage to the corresponding gear that it meshes with. There are a number of options available, everything from a proper welding procedure and heat treatment to making a completely new gear.
I personally don't have much experience with gear repair so I won't comment on the process, perhaps someone else here will have that info.

Have you tried Richard's Relics for parts availability?

http://www.route6x6.com/howto/Coottrans/index.html

[vpt]

Thanks Willy!

Yes I have been looking over (all 3, lol) places that have coot parts and info. The 6x6 place has the single gears in stock apparently but not the double gear. I am getting mixed opinions on fixing the gear, I may have to give it a try yet.

I did press in the new trailer bearing races last night and they are a perfect fit. At least I didn't have to spend hundreds on weird impossible to get bearings. The gearbox says apex gear company on it, I am going to try searching that a bit and see what I find.

I have welded quite allot of things in my life but it seems I am getting the most off the wall weird jobs lately.