- Joined
- Apr 22, 2020
- Messages
- 3,217

This is a story based on what I do with my P11, not a plea for advice, or an example of how to do anything with a sound mind. It is just stuff I do. LOL
I believe the intake manifolds I have for my Mikuni 34mm carburetors came from MAP, but to be honest, I'm not sure. At the time all that was available were twin Mikuni carburetor setups for the Commando. Having a P11 with an upright motor required a little modification to the intake manifolds. If I knew how to weld, I could have made a better set, but I never have taught myself how to weld.
The intake manifolds were originally designed for the crappy flange to spigot style rubber mounts for the carburetors. I wanted to make a spigot mount and have the option to change the length of the intake by using automotive fuel filler hose for the section between the intake manifold and the carburetor. So what I did was hacksaw chunks of the flange off to get a rough roundish looking spigot end, and then hand file what you see below for the spigot mount. It looks out of round but that is the outside diameter not being perfect. I also smoothed out the inside of casting with a Dremel, a little cutter, and some hand sanding, but did not polish the interior. The intake manifolds go from 34mm to 31mm and the intake runners start at 31mm on my FBS ported head. Nuff about that.
Today 27 years later... I used some drip irrigation fittings, that's right, drip irrigation fittings to install hose barbs for the balance tube. I'll not bore you with the details, but they are installed with a press fit. I did that because the only small brass hose barb fittings I had that I could thread into the manifolds did not match. I tested a drip fitting in a small bowl of fuel to see if they would dissolve. They don't.
Result was that the balance tube actually did do what people say it does. It smoothed out the idle from what was like a lumpy big cam, to a relatively smooth mild performance cam idle. I did not have to do a thing to the tune. It just worked. YMMV
I only posted this because this P11 forum is slow.... and I have nothing better to do before I put the burgers on. If this mod has been done a hundred times already opps.
I believe the intake manifolds I have for my Mikuni 34mm carburetors came from MAP, but to be honest, I'm not sure. At the time all that was available were twin Mikuni carburetor setups for the Commando. Having a P11 with an upright motor required a little modification to the intake manifolds. If I knew how to weld, I could have made a better set, but I never have taught myself how to weld.
The intake manifolds were originally designed for the crappy flange to spigot style rubber mounts for the carburetors. I wanted to make a spigot mount and have the option to change the length of the intake by using automotive fuel filler hose for the section between the intake manifold and the carburetor. So what I did was hacksaw chunks of the flange off to get a rough roundish looking spigot end, and then hand file what you see below for the spigot mount. It looks out of round but that is the outside diameter not being perfect. I also smoothed out the inside of casting with a Dremel, a little cutter, and some hand sanding, but did not polish the interior. The intake manifolds go from 34mm to 31mm and the intake runners start at 31mm on my FBS ported head. Nuff about that.
Today 27 years later... I used some drip irrigation fittings, that's right, drip irrigation fittings to install hose barbs for the balance tube. I'll not bore you with the details, but they are installed with a press fit. I did that because the only small brass hose barb fittings I had that I could thread into the manifolds did not match. I tested a drip fitting in a small bowl of fuel to see if they would dissolve. They don't.
Result was that the balance tube actually did do what people say it does. It smoothed out the idle from what was like a lumpy big cam, to a relatively smooth mild performance cam idle. I did not have to do a thing to the tune. It just worked. YMMV
I only posted this because this P11 forum is slow.... and I have nothing better to do before I put the burgers on. If this mod has been done a hundred times already opps.
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