It's never the carbs.

Just put a set of new Premier carbs on my 72. Was running decently before but needed the carbs that were on it for another project so decided to treat it to the new set. First start up and it runs terrible, won't idle, pops, backfires, doesn't want to pull. First line of reasoning, problem must be with the last thing worked on so I decide to raise the needle in the carb a notch to cure leaness. Still runs horribly. Then I start thinking a little bit. Needle clip position won't affect idle or up to about 1/3 throttle and thats where most of the problem is. Must be something else. Happen to notice button on kill switch is askew. Take it apart and find one of the tabs is busted off. Replace with a new button from a Lucas repair kit. Also, test battery and its a little slow taking charge. Probably it's okay but it's 3 years old and a lead acid type so I replace it with a new AGM. Checked for spark by scratching bw/by leads together on ei plate and good spark. Starts right up and runs pretty good. Little tweak on the air and idle screws and it sounds even better.
Beautiful day here, 73 and sunny so after taking the Norton out for a run decide to take out the Bonneville. Won't start, not even a pop. Take the Thunderbolt for a ride. No issues with it. Come back and start tinkering on the Bonneville and check for spark scratching the leads together. No spark. Get to poking around on the wiring and notice the ground from the second coil back to battery positive is off. Put it back on, good sparks. Go for the third ride of day.

The new Premiers need to be opened up and cleaned/checked for production debris. High liklihood of debris as reported by MANY Permier buyers.

90% of carb problems are electrical (and vice-versa)

Yep, taken apart to check for cleanliness, verify correct jets and set floats using u-tube method.

htown16 said:

Yep, taken apart to check for cleanliness, verify correct jets and set floats using u-tube method.

Click to expand...

Can you give us curious types your impressions of the Premiers compared to your old Concentrics - once you've got them dialled in

I have a pair for my 850 which took a long time to arrive, and in the meantime I got the old ones set up OK - once I changed the needles for a pair of the correct Norton-specific ones

Beginning to wonder if they offer any benefit, and as GP says, lots of reported issues with build quality - which I guess proves they're British!

I put new Prems on the 750 and it was like night and day; much better running, and no more fouled plugs.

Compression issue? Make sure head is properly torqued down.

Issues with the ignition system can give the same symptoms as carbs out of tune. Four stroke and two strokes are similar in many ways. Trying to race a two stroke with a substandard ignition system is a futile exercise. Usually you are trying to run as lean as possible, and a faulty ignition system can lead you up the garden path and cost you a bomb.

B+,
It's hard to say if you will see much of any improvement with the Premiers if your carbs are in good shape. That is slides fit well, needle jet is not worn, idle jet and circuits are clean. If you have those problems you could see a pretty dramatic improvement. Where I see the Premiers as having an advantage is in future maintanance. The slides are coated to prevent wear, they have the ethanol proof stay-up floats and the removable idle jet is a big plus. I've already cleaned the idle jet on one bike and it certainly is a lot easier to screw the jet out, shoot some carb cleaner through it and screw it back in than it is to stand on your head and try to poke a wire through an opening you can't even see.
If I were making the decision on whether to up-grade to the Premiers I'd base it on how worn the slide/body are on the old ones. Yes, you can resleeve the carb, but if you add up the cost of the resleeving, new slides, new jets, new floats, new gaskets ect the cost is starting to get pretty close to the Premiers.
I've installed 5 Premier carbs so far, two pairs on Commandos and a single on the Thunderbolt. The carb on the Thunderbolt was shot and the Premier made it into a different bike. One of the Commandos, it was a slight improvement but the old carbs were in decent shape. The other Commando is still being rebuilt. I've not found any debris or manufacturing defects in any of them. But you still want to pull them apart for a look see and to verify the vendor put the right jets in. I've also found all of them need the fuel level adjusted slightly with the float. I use the u-tube method Amal recommends to check the float level.

Acotrel,
That was basically my point. If you have a bike not running right, start troubleshooting with ignition not the carb. This is especially true with a bike with EI. A little bit of problem in the circuit feeding the box can have a pretty big affect on how the bike runs. Make sure you have a clean blue spark at the plugs before you touch anything else.
Htown