Balancing carbs

[chownsy]

Hi all

Could someone post me a guide on how to properly balance carbs as i have a day off work today and want to try and get them balanced. last time i struggled with getting to the screws inbetween the V to do the balancing.

I have vacumn gauges but dont know engine rpm etc etc

thanks

richard

[Neosophist]

http://www.carbtune.co.uk/inst.html

Carbtube instructions. (applies to all carb balancers really apart from the morgan specific bits)

General Hints
Read your workshop manual. The engine should be warm and running at just enough above idle speed so it doesn’t falter and stop during adjustments. Don’t try to balance at high engine speeds. Adjust to makers specification or average of initial readings, but the readings should be balanced to within 2 cmHg (some models up to 4 cmHg) of each other.

Adjust in small amounts, waiting a few seconds between each part adjustment. Write each adjustment down so you can go back to the original settings if necessary.

If lending gauges to a friend please ensure your friend has a copy of the instructions and is familiar with the gauges.



Ideally balance the throttle valves after you have serviced the rest of your bike.

A Guide to Carburettor Synchronizing
Carb balance will affect the response, smoothness, mileage, performance and running temperature of your engine.

Carb synchronisation consists of adjusting each throttle valve for carburettors or fuel injection throats so that they pass as much fuel-air mixture as all the others. This balances the load carried by each piston.

If one carb is opened further than the others that cylinder will run hotter than the others. The other carbs will also supply a richer mixture and mileage will suffer.

The actual mechanics of carb balancing vary a lot. Some bikes are balanced by adjusting the relative length of the throttle cables (R series BMWs) while others have a system of levers with adjustment screws but they all adjust the relative position of the throttle slides or throttle butterflies of each carb to each other or to a master preset carb.

A workshop manual for your model is very useful as the balancing procedure for different models can vary in detail. Familiarise yourself with the section on throttle valve synchronizing.

As you know, the NC30 has 3 screws, (so does the 24 et al)

Connect the carb balancer to the vaccum ports by removing the screws and washers from the cylinders... you have 4 on an NC21/24 and 3 on an NC30/35.

For the 4th cylinder on these later bikes use the fuel vaccum take-off (make sure your tank is still flowing petrol) - suck on the hose..

Anyhow.. you can't adjust one of the carbs, this is fixed.. balance the other 3 to match it.

Warm the engine up, and crank the idle just above normal.. 15-1600 is good.

Work in a circle adjusting each and leaving a few seconds to stablise... adjusting one will affect the others so might need to go a few times.

Carb number 2 is the fixed one.

[Sunnyday]

I need to do mine over the winter been saying that for three years....