Carb Balancing Technique

[LTD Project]

Just been balancing my carbs....

from left to right I found them at 28, 22, 22, 24 Hg, the book says the normal range should be 20 - 28 Hg.

Balanced using Morgan Carbtune 2. The whole thing appeared rather easy, I brought down 1 and 4 so all were reading 22 and then I began to think....

My question is: Is this ok or should I have taken them all up a bit higher, say all at 26? Does it make much difference what they are as long as they are balanced?

The idle after the balance seem less steady than prior to it, setting it to just over 1000 rpm you hear alot of the tugging on the cam chain sort of sound, which I didn't get before.

All advice gratefully received

[Pigford]

As long as the figures are similar, it doesn't matter what the value is

Try turning the idle up to 1200rpm, 1000 is a tad low... probably just clutch rattle

[LTD Project]

Pigford, thanks for the response. I will try a slightly higher idle speed and see how I go.

Was just a bit concerned as it idled ok at around 1000rpm prior to the balance.... but if you think nothing is wrong after the old "fingers of rust" had been tinkering.

Thanks again

[paulstrees]

Your carb settings are OK in tha range but I normally set the air screws first with the gunsons colortune which gives maximum revs, then balance the carbs ( as this affects the Hg reading ), then set the tickover.
Hope this helps

Paul

[Taffus]

Your carb settings are OK in tha range but I normally set the air screws first with the gunsons colortune which gives maximum revs, then balance the carbs ( as this affects the Hg reading ), then set the tickover.
Hope this helps

Paul

Hi Paul
What colour do you set the screws to?

regards mark

[Jeff Saunders]

With the older carb - esp. the Z1 VM28's, I don't spend much time vacuum sync'ing them.

Often the wear on the carbs is inconsistent across the bank of 4. You can get nice vacuum readings, but the carbs don't transition smoothly off tickover. In some cases when you pull the carbs off the bike after they are 'perfectly' sync'd, you'll see the slides are visually not even. This means the needles are clearing the needle jets at different times, and metering the fuel inconsistently through the mid-range...

I tend to mechanically sync the carbs - making sure all the slides are set at the same height - and they all clear the throat of the carb at WOT.

I do check the carbs with vacuum gauges or mercury stix, but I don't make big changes to the adjusters.

[Bruce Sexton]

Due to the imbalances that Jeff has mentioned I normally balance my carbs at around 2500-3000 revs. This is where they are normally operating at for majority of the time, yes I do use more revs before anyone comments, but like GP bikes full throttle is only used for a small percentage of most journeys/races.

Bruce

[paulstrees]

Your carb settings are OK in tha range but I normally set the air screws first with the gunsons colortune which gives maximum revs, then balance the carbs ( as this affects the Hg reading ), then set the tickover.
Hope this helps

Paul

Hi Paul
What colour do you set the screws to?

regards mark

Hi Mark
Set it to blue at tickover, as you go through the rev range it should then go yellow and then through to blue at around 3000-35000 revs
Regards
Paul