I want to thank Pin_Head for his videos. It helped me solve my carb problems. I had no secondary opening and my 40 was gutless on any hill. I did the paper clip test after watching the video to find that the secondary had issues. What I found was the gasket for the spacer in the middle of the carb (that should be sealing that vacuum channel) was not sealing properly. I actually found that air leak by first removing the assembly to check the diaphragm (which checked fine) and then I thought I would just shoot a light blast of air through the hole back into the carb body and feel the air come out the openings in the throttle body. Anyway, when I shot the air I felt it blow on my hand down around the spacer. I was like WTF? So I took the carb all apart and that is when I found that the gasket was actually malformed and had been barely covering the channel and finally started leaking. I made a gasket from some gasket material and that took care of the vacuum leak and once the carb was back on it passed the paper clip test and I knew it had because I had much better performance on hills near the house. But it still is no race truck!
Regarding removing the carb, I'll add some notes below in hopes it benefits others.
It is pretty simple and takes just a few minutes. Mine is a desmogged 1977. I took a torch and heated and bent a 12mm Task Force brand combination wrench so it fits nicely to get at the carb base nuts.
1. You remove the breather.
2. remove the gas lines.
3. remove vacuum line.
4. pop the throttle linkage loose.
5. remove the choke cable.
6. Unclip the throttle cut solenoid wire.
7. Then the four base nuts.
Lift off the carb. Much easier servicing it on the table.
If you are just experimenting with primary/secondary jets you can do that with the carb installed.
1. remove the breather.
2. Unclip the linkage that hooks at the choke.
3. remove choke cable.
3. remove the gas lines.
4. unclip fuel cut solenoid wire.
5. Remove all the top screws.
6. lift off the top of the carb. Watch you don't lose the pin holding the float in place.
7. Soak the gas out of the bowl with a rag.
8. Remove the two access bolts from the side of the bowl so you can get a screwdriver to the jets.
9. I ground a larger bladed screwdriver sides down that fits the jets nice so it will fit through the access holes. Makes getting the jets loose better than trying to use a smaller bladed screwdriver.
I probably missed something, but that's the general idea.
I decided this past weekend that I was going to finally take whatever time it took to get my 40 engine running its best. I adjusted the valves. Did a compression check (just to see how things were) and all cylinders checked with acceptable numbers (From 139 on the low end to 150 on some of the higher cylinders), replaced the points, plugs, cap, rotor. Check the point dwell. Fixed the secondary problem. Then experimented with jets and found a 124 made the carb backfire, but a 141 seems just right for the primary. Still experimenting a bit with the secondary, but I think I have it with around a 170 'ish jet. Might go a little larger, but it is sure running better than it ever has.
Regarding removing the carb, I'll add some notes below in hopes it benefits others.
It is pretty simple and takes just a few minutes. Mine is a desmogged 1977. I took a torch and heated and bent a 12mm Task Force brand combination wrench so it fits nicely to get at the carb base nuts.
1. You remove the breather.
2. remove the gas lines.
3. remove vacuum line.
4. pop the throttle linkage loose.
5. remove the choke cable.
6. Unclip the throttle cut solenoid wire.
7. Then the four base nuts.
Lift off the carb. Much easier servicing it on the table.
If you are just experimenting with primary/secondary jets you can do that with the carb installed.
1. remove the breather.
2. Unclip the linkage that hooks at the choke.
3. remove choke cable.
3. remove the gas lines.
4. unclip fuel cut solenoid wire.
5. Remove all the top screws.
6. lift off the top of the carb. Watch you don't lose the pin holding the float in place.
7. Soak the gas out of the bowl with a rag.
8. Remove the two access bolts from the side of the bowl so you can get a screwdriver to the jets.
9. I ground a larger bladed screwdriver sides down that fits the jets nice so it will fit through the access holes. Makes getting the jets loose better than trying to use a smaller bladed screwdriver.
I probably missed something, but that's the general idea.
I decided this past weekend that I was going to finally take whatever time it took to get my 40 engine running its best. I adjusted the valves. Did a compression check (just to see how things were) and all cylinders checked with acceptable numbers (From 139 on the low end to 150 on some of the higher cylinders), replaced the points, plugs, cap, rotor. Check the point dwell. Fixed the secondary problem. Then experimented with jets and found a 124 made the carb backfire, but a 141 seems just right for the primary. Still experimenting a bit with the secondary, but I think I have it with around a 170 'ish jet. Might go a little larger, but it is sure running better than it ever has.
