Premier Carb help please

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Ratboiler

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Having fitted to a 1973 850 and followed your advice on 19 pilot jets the bike is now running and so far covered 300 miles.
Plug colour is light coffee colour both sides. It starts and ticks over comfortably. But on the road between the 3rd and 4th throttle position it is IMO not pulling very well, between throttle positions 4th and 1st (3/4 to full open) it pulls like a train.
I have synchronise the carbs which are new. Sorted the pilot settings and today received my float test kit and to be honest thought well I might as well try it. The drive side carb level is a good 1/4" below the bottom flange of the float bowl with the other side even further below.
The instructions state the level should be max 24 thou below the top edge of the float bowl, I will adjust the floats to suit, will it make that much difference?
Any tips on how to adjust it I have read the float tang has to be bent.
Thanks in advance.
 
One thing I don’t like about tbe new stay-up floats is that they seem to be a lot more buoyant than the old ones (even when they haven’t got fuel sloshing around inside them)

Because of this, the top of the float can be hitting the carb body, and the float needle may still not be seated properly.

I still think it’s important to adjust it the old fashioned way - by warming up the float bowl in the oven, and driving in or out the brass seat using a small parallel punch.


Having the correct height fuel level in the bowl makes a huge difference!!!
 
Hi Ratboiler, here's the instructions from Burlen..

amalcarb.co.uk

Optimising Amal Mark 1 Concentric Fuel Levels | AMAL Carburetters

The Optimising Amal Mark 1 Concentric Fuel Levels page for the AMAL Carburetters website.
amalcarb.co.uk amalcarb.co.uk

I setup this rig to do mine.


Premier Carb help please
 
I have to say, though, they are without doubt the most difficult carbs I've ever worked on to get the float heights right. They are completely arse about face. Who else would mount the floats and needle valves in the float bowl?
 
Hi Ciffa
Thanks for the picture and reference, I assume that wasn't the correct level in the picture of 6mm?
 
From the link Cliffa posted:

“The correct fuel level for all Mark 1 Concentric carburetters is 0.21" plus or minus 0.040" below the top edge of the float bowl. Thus when the needle valve is being held shut by the tangs of the float, the level of the fuel will be between 0.17" to 0.24" (4.33mm to 6.35mm) from the top of the bowl”.

Seems to me that you 6mm is ok, not optimal perhaps, but certainly not the cause of your problems...
 
Ratboiler said:
Hi Ciffa
Thanks for the picture and reference, I assume that wasn't the correct level in the picture of 6mm?
Click to expand...
No problem. I think this was the level when I finished. It's important to make sure that the pivot pin stays in the bottom of the groove, otherwise it has an effect on the level.
Premier Carb help please
 
Could be the needle and or the needle jet. What setting have you got?
If you have the chokes slides fitted why not ease the choke on while accelerating. If the carbs are rich the choke will immediately bog the motor if lean it'll go like stink until you over choke it.
Dave
 
Thanks Dave
Pilot jet 19, needle set at the top slot.
Chokes are fitted I will give it a go, after setting the float height as one is a long way out.
Thanks John
 
Needles at top slot?

Maybe weak on the needles, think I’d try raising them a notch.
 
I had a similar problem when I fitted new premier carbs on my 850 MkIII , the float levels were both low and with one lower than the other. After a lot of mucking around trying to get them right I eventually checked the original float bowls and floats which turned out to be spot on. I fitted the originals and that sorted the problem.
 
Needle yes. Stock specs top slot, but that's with the factory mutes.
Try the middle slot.
 
Ratboiler said:
Having fitted to a 1973 850 and followed your advice on 19 pilot jets the bike is now running and so far covered 300 miles.
Plug colour is light coffee colour both sides. It starts and ticks over comfortably. But on the road between the 3rd and 4th throttle position it is IMO not pulling very well, between throttle positions 4th and 1st (3/4 to full open) it pulls like a train.
I have synchronise the carbs which are new. Sorted the pilot settings and today received my float test kit and to be honest thought well I might as well try it. The drive side carb level is a good 1/4" below the bottom flange of the float bowl with the other side even further below.
The instructions state the level should be max 24 thou below the top edge of the float bowl, I will adjust the floats to suit, will it make that much difference?
Any tips on how to adjust it I have read the float tang has to be bent.
Thanks in advance.
Click to expand...

How did you syncronize the carbs? There are many ways, some of them more accurate than others.
 
Many thanks to you all, I will try all of your tips. I still have the original carbs so can use the original floats if I have a problem.
Good to know I can drop the needle a notch.
I synchronised the carbs by removing the float bowls and main jets so I could see the needles moving at exactly the same time, having followed the write up for setting the pilot and throttle stops.
 
Ratboiler said:
Many thanks to you all, I will try all of your tips. I still have the original carbs so can use the original floats if I have a problem.
Good to know I can drop the needle a notch.
I synchronised the carbs by removing the float bowls and main jets so I could see the needles moving at exactly the same time, having followed the write up for setting the pilot and throttle stops.
Click to expand...

That will get you close on the synchronization but vacuum gauges can get you closer.
 
cliffa said:
No problem. I think this was the level when I finished. It's important to make sure that the pivot pin stays in the bottom of the groove, otherwise it has an effect on the level.
View attachment 17191
Click to expand...
Like the idea of the paper clip dimension rod within the plastic tube to break up the surface tension...great thought :D
 
An update, I started the bike with the level kit attached and sure enough the float level was dropping and rising and affecting the running on that side. Stopped the bike removed the float bowl inspected cleaned and reassembled and adjusted the float level to perfect. 2 mins later it is flooding so to bits again checked it all again at least 10 times.
The carbs are new, so took out the floats of the old carb and fitted as one of you guys has done and perfect level straight away.
Took the bike for a run, and it still is lacking on pick up from around 30mph, if I give it a big handful it picks up fast.
Next is to move the needle from the top notch down one after applying the choke while riding it, I forgot that yesterday.
 
Hi ,
I really felt a difference going from the top (lean) needle positon to the middle on my new Premier carbs on my 850. The middle range pickup was lackluster . The previous carbs were set in the middle position and for all their other problems had a good sense of acceleration . I set the new Premiers to the top notch as the booklet indicated , and I am glad I did --because even as a novice I could easily tell the difference when I went to the middle ring.
Sincerely,
Kara
 
Hi Kara
Thanks for the tip, as you say the middle range felt limp. I have come back from a quick run having warmed the bike up, I did what peeeleven advised and opened the choke fully, and all of a sudden my mid range is back. My needle is in the top slot so as you did I will now move it to the middle and see how I get on.
 
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