Another carb tuning question, Problem solved!! Options

[Cevan]

So I’m entering the wonderful world of carb tuning. (Please save all the FI comments. I couldn’t afford aftermarket FI and I’m using a cam not compatible with stock FI.) The engine is a recently built 2056.

I’ve sync’d the carbs using my STE meter. I adjusted the idle mixture screws per Aircooled.net’s website. It doesn’t appear to make a huge difference when I go from one turn out to all the way in, or from one turn out to two turns out. I adjusted them so that the engine ran the smoothest.

The engine seems to idles nice. So I go for the first drive. After puttering down my long driveway in 1st gear, I pull out onto the road and it goes nicely through 4th gear, maybe at half throttle. At some point (maybe ½ to 1 mile into the drive) it starts to get boggy on acceleration. Definitely a change, so I head back home.

This morning I started it back up. It’s still boggy, pretty much from 2000-4000. If I go WOT, it bogs worse. If I slowly increase the speed, it bogs less. And it smells like it’s running rich, like unburnt fuel (I did check for fuel leaks). I tried adjusting the idle screws some more. It seemed like I got it to run a little faster at idle. The engine revs fine with no load on it. I checked the carb balance again and went for another spin. Still boggy. Still smells like it’s running rich. For the next drive I need to pay more attention to any carb or exhaust popping.

I’m trying to diagnosis this problem in a logical order. I’ve already checked the dwell, timing and valves. The carbs were just rebuilt. The floats are set per the Redine website.

My plan is to pull a spark plug from either side and inspect them for signs of it running rich or lean. I’m also going to clean the idle jets as maybe something clogged the jets during the first drive. I’m also going to install a fuel pressure gauge so a passenger can see it while I drive (just in case it’s running lean), although the fuel pump is new.

If none of this helps, should I try a different size idle jet? I have 50s already. Any other suggestions?

Here’s the current setup:

Weber 40mm IDFs
Idles 55
Main 130
Air 200
Emulsion F11
Vents 32mm