Hanging idle

[JPaganel]

So, I got my shiny clean carbs in, and all was good for about a couple of days. Then, I started noticing idle being high when hot.

Given that this would be knocked down by applying load to the engine, I figured it was a vacuum leak. This made me embark on a quest for silicone. I wanted all the new bits I put in to be heat-resistant.

I changed out the carb holder o-rings from the hardened flattened OE ones to red silicone, and actually found some 4mm ID silicone vacuum caps that have something like 3mm wall thickness.  Also, replaced vacuum hose to the advance unit.

Each change seemed to make it better, but not go away. So, I decided to just cap off the third nipple and disconnect the advance unit.  This seems to have really calmed it down. I had to adjust idle down some after a long-ish ride.

We'll see how this works out. Seems to be OK for now.

[Pat Conlon]

Did you do a suck test on the vacuum advance?

[JPaganel]

Did you do a suck test on the vacuum advance?

I forgot.

But, on the way home from work it ran fine, and idle was normal. Seems to run better in general, although that might be just my perception.

[CutterBill]

I changed out the carb holder o-rings from the hardened flattened OE ones to red silicone...

You might want to keep an eye on those new silicone o-rings. Silicone is not compatible with gasoline, it tends to swell and dissolve. Buna-N is fairly resistant to gas, and Viton is even better.
Bill

[racerrad8]

You might want to keep an eye on those new silicone o-rings. Silicone is not compatible with gasoline, it tends to swell and dissolve.
Bill

I will gladly second that position. Back in the late 70's/early 80's when I was a kid, we used silicone to seal the go kart split wheels to ensure they didn't leak air out. My dad made a container with expanded metal on the bottom. When we dismounted tires, the wheel halves would go into this container. It was sealed to slow/prevent evaporation of the gas. The wheels would sit in there for about 30 minutes and the silicone would turn to a jelly and the majority would fall off to the bottom of the container through the expanded metal.The rest would just wipe off with a rag.

While I was a little tyke at the time, I learned early on;  petroleum and silicone don't play together.

The Intake Manifold O-Ring we supply are Buna-N

Also, in reference to the hanging idle. Make sure you have enough "slack" in the cables that when things get hot and expand, the cables aren't holding the throttle open. We have seen that a few times on bikes that have the hanging idle and the idle mixture doesn't have any affect.

Randy - RPM