Club 80-90 Forums

Carbs need balancing?

To be honest, when I rebuilt the Carbs, I stripped them down and cleaned them out and replaced the gaskets, upon rebuild I didn't change any of the settings on them as I don't have the necessary equipment to test or balance them, judging by the condition of the plugs it might be running a bit rich, as for balancing them, I haven't done that, is this within reach of an amateur mechanic, or more of a specialist job? I would imagine that unbalanced carbs would cause a lack of power, could unbalanced carbs also produce a miss?

Melvin

Hello,
This:

https://www.youtube.com/watch?v=najLc9GlLJ0" onclick="window.open(this.href);return false;
and this
https://www.youtube.com/watch?v=KkyBAMMHpa4" onclick="window.open(this.href);return false;

may help.

Cordialement,

I'm thinking a couple of things:

Fuel enrichment for acceleration
Spark plug / HT lead failing under load.

You can buy equipment to balance the carbs up, (airflow measurement) but it can also be done with an experienced ear listening to the noise into the throttles. My 412LS runs twin Solex's too. If there's a leak on the balance pipe it's a bugger to get it idling and just won't run right. I don't think that's your problem, but worth a simple check. I set mine up by ear and used an old Gunson CO tester to make sure the mixture was about right. I have initial hesitation, but once on throttle she runs sweet, but that's another story.

Unbalanced carbs mean one side of the engine will run richer than the other. Do the plugs show that ? scrub that, brain fade an imbalance in fuel/air mixture volume to each side

It might be worth just banging another set of plugs in - cheap fix, and something you'll need one day even if that's not the problem.

Did mine last weekend, used a set of gauges similar to these - https://www.ebay.co.uk/itm/Motorcycle-C ... Sw6GJaOiRh" onclick="window.open(this.href);return false;
You need to ensure your ignition/plugs etc. are in a good state first.

The right hand carb linkage has a threaded linkage that an be adjusted to synchronize the opening.

I've also backed off the both auto-choke unit on each carb as far as possible so the chokes come off quicker. In this cold weather a couple of pumps of the accelerator pedal give enough fuel for starting.

Thanks chaps for your pointers, Think I might go for new leads and plugs first, both appear to be in good nick and have only had about 10,000 miles on them but it will be the simplest thing to try, and its best not to overlook the basics, then Ballance and then resetting the carbs, I've been resisting that as I don't want to "cock" it right up but I might digest sarrans video give it a shot..... Wish me luck!

Melvin

Now, not sure this is possible and it might be just my mind but is it feasible/possible that a misfire can happen at the same frequency even when the engine speed changes?
On the way to work this morning I was thinking about my misfire (as I do most times I am driving) and I was giving it beans in 3rd to get up a hill, engine soft misfiring as per normal and when I dropped it into 4th the misfire still seemed to happen at the same intermittent frequency? Not even sure that it is possible for this to happen so it might be in my mind, just thought I'd post it up here as someone might go "oh yea, it's your blahdeblahblah that needs changing.

Sorry for my rambling.....

Melvin

Any update on this Melvin? I had running issues with Solex PDSIT carbs a few years back and found the instructions on the Itinerant Air-Cooled forum to be really helpful; another source for you to consider. http://itinerant-air-cooled.com

937carrera wrote:
Unbalanced carbs mean one side of the engine will run richer than the other. Do the plugs show that ? scrub that, brain fade an imbalance in fuel/air mixture volume to each side

Using gauges so that each carb opens at the same time makes the initial pick up much smoother when pulling away

Just bought a Gunson carb balancer thingy, in the middle of replacing the tank due to the fact that I let it run out of fuel the other day and it ran really bad afterwards, tank was hellish rusty so I'm glad it happened, I'll report back after the weekend to see if balancing them has improved my running!

Melvin