Friday, May 1, 2015

Finally, Balanced

Balanced carbs are a wonderful thing. I had relied on BobK, a fellow airhead, for balancing the carbs on the Beemer with his Hg sticks. The Ural seemed fine when I picked it up. Over the winter, I had raised the idle speed a little so that would have messed up the balance and I could feel the vibration. I was waiting for the Harmonizer, another electronic tool, to be built again but decided that I was tired of waiting. The TwinMax electronic balancing tool made in France and I believe that it's been around for a while, and though not quite as slick as the Harmonizer it is $25 cheaper. I picked it up from A&S BMW and the first one I received didn't work (doesn't sound promising) but the replacement arrived today and it worked like a charm. The needle essentially displays the difference in vacuum between the two hose connections.

The two vacuum hoses from the TwinMax are plugged into the vacuum ports on the two carbs. On the Ural, the left carb vacuum port is used to control the fuel petcock so after disconnecting the vacuum hose, the petcock needs to be turned to the "Pri" (prime) position. The TwinMax is powered up, sensitivity knob to max and the zero knob is adjusted to center the needle. The warmed up engine is started and after setting the idle speed to about where you want it, in the case of the Ural, right around 1000 rpm, the idle speed screw on the right carb is adjusted to center the needle. Before doing this, you want to make sure that the throttle cables are not tight. Then, using the throttle, you speed up the engine to around 2500 rpm and by adjusting the throttle cable on the right carb, you center the needle. If there is too much slack in the throttle cables, the slack can be taken up using the adjustment on the throttle. You can use either carb to make your adjustments but the adjustment points are easier to reach on the right carb.

Both idle and high speed adjustments were needed on the Ural. Afterwards, I took the rig on a short test ride and the difference is engine smoothness was pronounced. Now there is very little engine vibration at any speed. I was hoping that this tool would arrive this week so I could balance the carbs before my road trip to Anchorage on the 7th.

Tomorrow afternoon, I head back to Barrow to finish the installation of the new Ubiquity radios.

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