Carb tuning

As you have new carbs, I would suggest that if you can't get a good idle by screw twiddling as per the manual, your problem lies elsewhere, probably ignition. I have used a wide band O2 sensor to tune a programmable ECU, but with a relatively crude device like an Amal it is pointless. You should be able to to achieve good running without one before entering the narrow band of precise control required for optimum efficiency or environmental performance as required for modern engines.

Tick over has nothing to do with slides rising together. The slides need to be 'just' off the cables and the slides resting on the slide screws. Then you get the mixtures sorted, then you get the two tick-overs sorted-THEN you worry about the slides 'lifting' together on the throttle cables.                I wonder is it possible that there is small air leak or even a slightly sticky valve on one side??      Or is it ignition? If it is electronic then that cannot be the issue. But then there is coils and certainly a double ended coil is suspect! Can we identify which side is 'misbehaving' ? 

Disappointingly, tiny bits of swarf are not uncommon in these new carburettors. Make sure your pilot circuits are clear.

Best regards, Al.

I purchased a new Aluminium 930 Concentric 18 months ago. When new it was brilliant but from a cold start needed a minute with some choke before my 650 Norton would pull away. Now I just need some choke when starting from cold and I can ride off almost immediately.

The problem I have is the drain plug in the carb bowl keep filling up with black silt every 1000 miles. This then blocks the main jet and also gets into the pilot jet. Three times now this has led to the engine cutting out and not running again until some cleaning has taken place.

I have three filters in the fuel line. The fuel tank tap, the carb feed and a third one inline between the other two. Where is this jet blocking rubbish coming from?

Thats curious Phil,  Have you got some black rubber fuel tubing thats disintegrating?. or an old cap seal to the tank?. Can't say i have ever seen the like on a bike. Do you tend to buy your fuel from the same place?  perhaps they have an issue where someone has used some black silicone to seal something , I once tried to seal a car tank gauge sender with silcone,  What a mess !!. Still learning.

Hi Alan, I might be mistaken but aren’t premiers supplied with #17 pilot jets? I’ve recently changed over to 19’s on my MK3. It is also running on Premier Carbs but had 17’s fitted and it’s made a world of difference to setting up the tick over since l changed to 19’s. It now runs and ticks over very nicely at 1k revs. It’s also stopped the occasional popping I had when rolling off the throttle. If memory serves me correctly the #17 pilot jets have two rings and the 19’s three rings. Unfortunately you have to take at least one carb off to remove the pilots but from my experience well worth it.

But we don't know what the original problem is? Lot's more information on the original problem is needed.

Roberts suggestion on rubber fuel lines seems likely. Another possibility is the inline filter. I have read reports on filters unable to catch very fine particles. A more efficient filter might be the answer.

 My new Premier carb has a 3 ring Pilot jet. Setting the idle speed is difficult unless the engine is hot. The fuel line set-up has Ethanol proof tubing which is about 4 years old. The centre filter never gets anything like the drain plug fills up with.  See photos.

This version of the Premier 930 has a Pilot jet that can be removed from the outside. If the Pilot Screw is also taken out then a squirt of WD or similar will do a quick clean job.