Stupid question of the day - PD carb balancing

[SPR]

Ok - so thanks to Ken I’ve a carbtune carb balancer and I’ve pipes / fittings on the way ....

All the videos I’ve seen show I presume the older carbs with the screw on the manifold and adjustment done via visible lock screws.

I don’t have either so am I right that the gauge connection is the screw in the picture and adjustment is under each carb top cap ?

Yep basic I know

Thanks

Simon

[K2-K6]

Yes to both questions.

Should have carb number two as no adjustment/fixed as you balance all the others to this one as master.

[SPR]

Yes to both questions.

Should have carb number two as no adjustment/fixed as you balance all the others to this one as master.

Many thanks

[keithtraffic]

Will be interesting to see how you get on with this.

I have just complete re-built my PD46 carbs - new just about everything! They are now back on the bike after a big struggle and  and it seems to run reasonably just after a static balance (setting all the throttle sliders to the same height), but I do want to balance them properly.

The info I have seen suggest that you should double check the timing and the valve clearances before trying to balance the carbs or else you may get misleading answers - would be interesting to see if those who actually have done it before really did go to this trouble first.

What vacuum gauges are you using - these are something I will have to get.

[Nurse Julie]

There is no point in trying to balance the carbs unless the bike has had a full service, tappets checked and timing checked and cam chain adjusted . But, once the carbs are balanced they shouldn't need doing again, except if you have PD's of course.

[K2-K6]

Will be interesting to see how you get on with this.

I have just complete re-built my PD46 carbs - new just about everything! They are now back on the bike after a big struggle and  and it seems to run reasonably just after a static balance (setting all the throttle sliders to the same height), but I do want to balance them properly.

Strangely enough bench synchronisation and with gauges are the same thing. Gauges just allow you to complete it without dismantling the carbs from the bike.
Parity of carb slides is ultimately for running at equal combustion under full loading as any significant variation will cause unwanted vibrations in that range.
Admittedly it has the byproduct of smoothness,  or improved smoothness, at idle,  but it doesn't have the resolution in mechanical design to fully resolve tickover refinements.  This is completed by adjusting the idle circuits for each cylinder to produce parity of combustion at this speed range,  which do have the resolution to control it. They are in effect individual throttles with micro adjustment.

[keithtraffic]

So, does that mean that if they have been statically balanced its no necessary to use the vacuum gauges for anything?

[SPR]

So, does that mean that if they have been statically balanced its no necessary to use the vacuum gauges for anything?

I suspect the skill used when static balancing plays a big part - mine looked OK when I had them off but the gauge showed that they were way out

[Nurse Julie]

So, does that mean that if they have been statically balanced its no necessary to use the vacuum gauges for anything?

I suspect the skill used when static balancing plays a big part - mine looked OK when I had them off but the gauge showed that they were way out

I think if you have access to a decent set of vac gauges, it's worth checking your bench sync if you want to double check the result. We never vac gauge after bench syncing, our bench syncing is so close but, it's takes experience to get it spot on.

[K2-K6]

http://www.sohc.co.uk/index.php/topic,17769.0.html

Above link is a very elegant way of working through a set while on the bench.

Obviously it will give greater accuracy than just doing it by eye.

[Bryanj]

I remember writing that after several posters on both here and US sites had the experience of a 3000 rpm tickover after a difficult start, yes it does take skill but so does using feeler gauges properly.