How can I Balance SU Carbs Without Removing Air Filters

nokia_aid · Post by **nokia_aid** » Tue May 13, 2014 10:17 pm

i need to balance my carbs but as it runs on lpg only i cant take the air filters off to do it, is there another way of doing it, i have a 3mm nipple on each carbs air filter for a valvesaver kit so i could i do something with that

ChrisJC · Post by **ChrisJC** » Wed May 14, 2014 5:50 pm

Why can't you take the filters off? Is it because the extra vacuum caused by the filters is needed to draw the LPG out of the mixer rings?

Chris.

nokia_aid · Post by **nokia_aid** » Wed May 14, 2014 10:45 pm

thats correct

ChrisJC · Post by **ChrisJC** » Thu May 15, 2014 9:20 pm

Have you ever tried it without? It might run well enough to balance the carbs.....

Chris.

Quagmire · Post by **Quagmire** » Wed May 28, 2014 8:16 pm

If it doesn't run without the filters then you can still whip the tops off and try the following to get you close (copy and pasted from my post on classicroverforum.net):

Here us what I do, and it seems to work for me. To set my carbs I do lots of measuring! Please check the books for how many turns in/out everything should be for the base settings, I can't remember them!

Start by removing the dash pot, spring and piston. Mine were rebuilt not too long ago (mileage wise) by me so I know that the gaps on the butterflies when fully closed is correct, which is a key starting point.

Then disconnect the linkages between carbs and wind the stops for both out fully until they are in their full resting position. Now wind each stop screw in carefully so that this is now just touching when closed.

Then add the book figure for base number of turns to each stop screw- I can't remember what it was...

Now you have two carbs that are balanced at idle, but not connected.

Now adjust the connecting rod until it looks like its the right length to not push/ pull anything. Connect it and see if the slave throttle position is moved at all. If it does open the slave throttle, then adjust and try again.

Keep doing this until at rest both are closed. Then operate the master carb and watch the butterflies on both. You will probably find that there is a delay before the slave opens, due to slack in the ball joints on the linkage. Very carefully shorten the linkage by a tiny amount and operate the throttle again. Repeat until both open identically.

Now you have carbs that are balanced through their operating range.

Next is the fuelling. I wound each mixture screw fully in to lower the jet, then raised them by the book figure, which is something like "adjust so flush with the bridge and then turn two and a half turns in ". Use a set of vernier calipers to check each jet is same distance down from the bridge

Now reassemble and start the car. When its at normal operating temp adjust mixture evenly on each carb to obtain highest rpm, and use the lift pin method to check where you are. Once done you can remove the tops of the carbs and check jets with verniers again if you like.

Then setup the choke - I haven't done this properly yet!