Carb balancing by ear

[darthDassie]

Hey, just thought I would throw this in here (I ride a 1999 rd7a). Noticed in the last while that the bike was not as smooth as I remember her being, so I checked the carbs. Turns out the jets were not set the same, so fixed that (went for the standard 2 3/8 out setting). Then she ran really uneven. Would seem that the previous balancing was done on this uneven setting. Then started looking for my old bleeder screws for the balancing act, but they went missing and for the life of me I can find new ones. Which let me to try doing it by ear (heard this was possible).

The process involves taking the vacuum screw out in the one side and listening to the rhythm (feel the beat!). Then replace screw and do the same on the other end. On my bike the right hand carb determined the beat (it did not change by turning the balancing screw). The beat on the left was considerably slower - so much so that the engine would die when I took out the screw (did I mention that the engine must be running all the time and be at operational temp?). I then adjusted the screw to up the beat. Repeated a few times, till I could hear the same beat on both sides, and that was that.

All of 5 minutes. And she runs like a dream. Just thought it is useful to know that this is possible and not particularly difficult. Not sure what the true scientists would say, but I am more of a pragmatist .

[Windmill John]

Although a Guzzi, I used to balance my throttle slides by removing the K&N filters, popping a finger in the inlet just resting on the slide cutaway and lightly tweak the throttle (engine not running) and adjust the sensation on finger for both carbs.
Whilst this meant the carb slides were balanced, it did not take into account things like bore wear, valve adjsutment and wear etc. but it was mighty close and ran beautifully.
Okay the old Guzzi's were not as tight a tolerance as the AT.
On my old air head BMs, I resorted to vacuum gauges, but did also try the book method of balancing each side with the other disconnected.

Have I gone off thread!!!

[BobA]

I do use a set of guages, but to be honest if your bike is running bad, and you can set up a temporary fuel supply, balancing by "feel" is possible.

Not sure about later bikes, but on the RD04, with a temp fuel supply fitted, you can sit on the frame and adjust the balance screw through a hole in the airbox. I usually balance it at around 2000rpm ish, adjusting the screw and feeling when the engine is smoothest, and then once I'm happy with that I'll try holding it at about 5000rpm (my average cruising engine speed) and feeling it at that engine speed, possibly giving the balance screw another tweak. Obviously an engine that's not under load will differ from one that is, but it's a good place to start.



Bob

[Windmill John]

Jeepers BobA, holding your engine at 5,000rpm with no load!
3,000 should be sufficient for a short burst.
I know that balancing is different at tickover to load, but still think 3,000rpm is okay.

The next time the BBC reports an earthquake tremor felt in the South East, please post a thread to make sure it wasn't you blowing up your engine

Oh, I forgot about dyna testing, at 11,000 plus; maybe I'm wrong, but I don't like it