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carb balancing and a heads up

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carb balancing and a heads up

Posted by richard_woolnough at April 09. 2017

numbnut question perhaps but how does one balance the carbs as there is no access to the choke when the filter is attached?

also on the BSAWDM20  forum couple of nice later commando pics one of which appears to have a back to front caliper. kind regards

Re: carb balancing and a heads up

Posted by john_holmes at April 09. 2017

Never touched the chokes when balancing the carbs, never seen mention of needing them when balancing as you tune the carbs when the engine is fully warmed so no need for chokes. Do you mean the slides ?

 

The back to front caliper could be the MK3 where they swapped the fork legs over to cure a wandering to one side with hands off.

Re: carb balancing and a heads up

Posted by richard_woolnough at April 09. 2017

yes you would of course be balancing the slides but with other machines  I have I can place balancing meters on the chokes,]   that big hole through which the air enters] perhaps it should be termed the throat, with the filter on these ar not accessible on the commando this is my query. kind regards

Re: carb balancing and a heads up

Posted by john_holmes at April 09. 2017

No need to access the slides, get the engine up to temp and then on each side isolate the opposite spark plug (connecting it to earth for EI) then tune the idle on each cylinder with only one sparking and using the mixture screw and throttle stop make sure you get the same RPM reading on the tacho for each side with the correct mixture.

Then connect both spark plugs, the idle will increase and be too high, unscrew both throttle stops equally until you get the required idle RPM.

That syncs the carbs at idle.

Next you need to get the cables synced so they stay in sync on an open throttle, you can use a balancer for twin carbs or if you have flexible hands get your hand so using 2 fingers one is touching a throttle stop screw on each carb. No need for the engine to be running and best on a cold engine, open the throttle slowly and your fingers will tell you if the slides are opening at the same time, if they aren't adjust the cable adjuster on the top of the carbs until they do. Alternatively using no hands or fingers open the throttle and then let it snap shut, 2 clicks tells you the slides are out of sync, single click and they are in sync.

Or take the filter off and look at the slides..

Re: carb balancing and a heads up

Posted by richard_mills at April 09. 2017

Balancing the carbs is done by removing the small rubber tube which connects the two inlet tracts (on top, just after the carbs).

Re: carb balancing and a heads up

Posted by richard_woolnough at April 11. 2017

thanks Richard I should have realised this, similar to the Dellorto's on the 90s they have special attachment points for such, kind regards

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