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stay-up flat problems on Premiers?

Posted By: Curmudgeon

stay-up flat problems on Premiers? - 07/21/19 1:38 am

Has anyone been having trouble with the Premier Amals due to improper float level set up? I think they are running them too lean but wonder if anyone else has had trouble.
Posted By: Rohan

Re: stay-up flat problems on Premiers? - 07/21/19 3:11 am

Brand new carbs run a LOT leaner than worn out old amals.

I found this out a long time ago - the old set on a Commando barely needed to be tickled and it would start,
and the new set needed to be tickled AND choked, and then it was a one kick starter.
But ONLY if you tickled AND choked it. (from cold)
Mileage shot up too, without recording exactly how much by.

Having said that, what problems are you seeing ?
There have been stray reports of less than ideal new carbs shall we say.

Can you make it idle on each/one cylinder only.
(not forgetting to give the disconnected cylinder's spark somewhere to spark to).
Posted By: kommando

Re: stay-up flat problems on Premiers? - 07/21/19 10:08 am

The stay up float is adjustable, so check your fuel level and adjust, not sure if they set it before they send them out but sounds like they don't.
Posted By: John Healy

Re: stay-up flat problems on Premiers? - 07/21/19 1:52 pm

Rohan, did you ever ask yourself why nearly every engine that uses gasoline as fuel has to run with the choke on until the cylinder reaches operating temperature. Unlock the secret and you will have your answer.
Posted By: Tridentman

Re: stay-up flat problems on Premiers? - 07/21/19 2:37 pm

+1 with JH
If you don’t need choke plus tickling to start from cold then your carburation is set too rich.
You may be happy with it as it is but that does not alter the fact that it is set too rich.
Just my two cents worth of course.
Posted By: John Healy

Re: stay-up flat problems on Premiers? - 07/21/19 7:19 pm

I had the experience recently of my Dodge Durango with a noticeable loss in power with a drop in mileage from an average of 22 mpg to to 18 mpg. It ended up being related to why you need a rich mixture when you start the engine and a choke until the engine warms up.

Unlock the secret and you will have your answer.
Posted By: Rohan

Re: stay-up flat problems on Premiers? - 07/21/19 9:27 pm

Originally Posted by John Healy
Rohan, did you ever ask yourself why nearly every engine that uses gasoline as fuel has to run with the choke on until the cylinder reaches operating temperature. Unlock the secret and you will have your answer.


Have you become our new 'master of stating the bleedin obvious' John ?

Having said that, you often read about Commando owners removing the choke system "because it wasn't needed".
In fact a lot of bikes equipped with old well worn amals....

Meanwhile, we haven't heard back from the OP on what the actual problem is.
Posted By: John Healy

Re: stay-up flat problems on Premiers? - 07/21/19 9:42 pm

Doesn't seem bleedin obvious to me! If it was, we wouldn't have so many people running around without chokes. Just saying!
Posted By: ludwig

Re: stay-up flat problems on Premiers? - 07/21/19 10:19 pm

Originally Posted by Tridentman
+1 with JH
If you don’t need choke plus tickling to start from cold then your carburation is set too rich.
You may be happy with it as it is but that does not alter the fact that it is set too rich.


I disagree .
I have always removed the chokes from my Amals , and my bike(s) start perfectly well from cold by just flooding the carbs .
Trade off : It runs like sh.t for the first couple of 100 meters , because too LEAN .
IMO, a small price to pay for less clutter and easier maintenance .
I consume 4.1 L/ 100 km , or close to 60 mpg US on average .( Norton 850)
Not too bad , I believe..
Posted By: NickL

Re: stay-up flat problems on Premiers? - 07/21/19 10:58 pm

My T120 is not too bad with no chokes (flood it up and accept the spluttering for a few minutes) then ok to ride.
Mt A65 t'bolt is a bloody pain when cold with no choke, i wish i'd never removed it. Still, it's not that often i use
either when it's cold anyway, so i just live with it.
Posted By: Allan Gill

Re: stay-up flat problems on Premiers? - 07/22/19 7:23 am

I’ve had no issues with the float level as set by Burlen, what must be noted is that with the stay up floats you MUST NOT use the 0.080” rule to set the float height you must use the liquid level. This is best done on the bike and you MUST use gasoline to set the level if you choose to check or change it.

Originally Posted by John Healy
Rohan, did you ever ask yourself why nearly every engine that uses gasoline as fuel has to run with the choke on until the cylinder reaches operating temperature. Unlock the secret and you will have your answer.


John knows more about these carbs than any of us could wish to know. From my experience I also agree with him, on a hot day I always try the bike without choke first, but if it soon dies or won’t start then I apply the choke. I do the same on my mates B50, always better to add the choke later than to try and clear the fuel from the cylinder.

The only thing I have found with premiers is that on some applications they require a leaner pilot jet. But I have found this to be rare.
Posted By: Rohan

Re: stay-up flat problems on Premiers? - 07/22/19 7:47 am

John appears to be saying the same thing AT me that I just said,
so I don't know how anyone can say I'm not agreeing with him. !!!!!! ?
But I said it (here) first, so he is agreeing with me....

It is rather common knowledge, after all.
Cold engines need choke, unless they are well rich, and warm engines don't (usually)
I think that appeared in the handbook of engines for about 1880, if not before....

Didn't Premiers change the pilot jet size at some point ?
Was it 17 to 19 ??
Since the OP still hasn't replied, we still don't know the actual problem....
Posted By: kommando

Re: stay-up flat problems on Premiers? - 07/22/19 9:22 am

The first Commando premiers came with 17 pilots, a 17 thou hole which is the same as the old 25 pilot bush, but it resulted in idle weakness so they now come with 19 pilots.
Posted By: Allan Gill

Re: stay-up flat problems on Premiers? - 07/22/19 9:41 am

Apologies Rohan, I didn’t mean that John was agreeing or not agreeing with you (probably aught to have gone back to previous comments first) but my agreement is that if you dont need a choke to start the bike (except in warm weather) then it is highly probable that your idle
Mixture is too rich... my bet would be also that the bike kicks back or you’ve had to retard the ignition so far to stop it kicking back.

Either that or the float level is too high and then there will be problems elsewhere in the range. Often people will raise the float height to speed up the tickling process, instead of noting that the tickler is a roll pin pushing into the tickler button, pulling the roll pin out of the button further will push the float lower and speed up the tickling process.
Posted By: Dibnah

Re: stay-up flat problems on Premiers? - 07/22/19 11:25 am

A second tickling session can be used to keep a chokeless engine running, or a hand over the bellmouth (watch out for flames!)
Posted By: bill50cal

Re: stay-up flat problems on Premiers? - 07/22/19 12:26 pm

my guess is a bad coolant temp sensor.

Originally Posted by John Healy
I had the experience recently of my Dodge Durango with a noticeable loss in power with a drop in mileage from an average of 22 mpg to to 18 mpg. It ended up being related to why you need a rich mixture when you start the engine and a choke until the engine warms up.

Unlock the secret and you will have your answer.
Posted By: John Healy

Re: stay-up flat problems on Premiers? - 07/22/19 12:45 pm

Quote
my guess is a bad coolant temp sensor.


Right answer wrong part. clap It was the thermostat stuck open.

If you know that you must know why? Why then, is it related to having to enrichen the fuel mixture to start an engine?
Posted By: Hillbilly bike

Re: stay-up flat problems on Premiers? - 07/22/19 12:57 pm

Originally Posted by John Healy
Quote
my guess is a bad coolant temp sensor.


Right answer wrong part. clap It was the thermostat stuck open.

If you know that you must know why? Why then, is it related to having to enrichen the fuel mixture to start an engine?

So that Dodge Durango has no engine temperature gauge? LOL

Gasoline doesn't vaporize readily in a cold engine and tends to cling to the cold surfaces..So an over rich mixture is required...This is less of an issue with port injection than a "wet" intake manifold using a carb or throttle body injection..Some enginners claim part of the long life of modern engine is due in part to the lack of crude chokes washing down cylinders with fuel...
Posted By: ludwig

Re: stay-up flat problems on Premiers? - 07/22/19 3:15 pm

Starting and reliable cold running are 2 different things.
Even the leanest engine ( = the one with an empty tank..) can usually be started by pouring some fuel in the inlet.
Posted By: htown

Re: stay-up flat problems on Premiers? - 07/22/19 4:05 pm

Worn out Amals should run leaner not richer than a new carb. The wear in the slide and bore allows more air to come in and leans the mixture. But is often the case the needle jet is also worn so that richens the mixture. So replacing the needle jets could take you from too rich to too lean on a carb with a lot of miles on it.
Posted By: John Healy

Re: stay-up flat problems on Premiers? - 07/22/19 4:59 pm

htown Most of the "worn" Amal's have a needle jet that has never been replaced. Needle jet wear is more common than slide wear.
They almost go hand-in-hand. Thus with as little a .001" needle jet the mixture is quite rich. I have seem them as large as .109".

The slide wear only dramatically effects low throttle openings. As the slide is lifted it effect the mixture less and less. So at normal
highway speeds it has only a small effect.

As vacuum draws the slide to the back of the body there is some sealing. And as the slide lifts, the wear becomes less and less important.

But the worn needle jet effects running from idle, all the way through approx. 3/4 throttle.
Posted By: Andy Higham

Re: stay-up flat problems on Premiers? - 07/22/19 6:38 pm

Starting and cold running are completely different areas on Amal Mk1 concentrics
The choke slide is hidden inside the main slide until the throttle is opened, therefore it has no effect on mixture when starting. Pressing the tickler raises the fuel level in the float bowl enriching the mixture through the pilot system. Once the engine is running and the throttle opened the choke slide partially blocks the venturi restricting the air flow.

The MK2 has a system like Mikuni, Keihin, Dellorto etc where a supplementary fuel/air mixture is fed via a starter system
Posted By: Hillbilly bike

Re: stay-up flat problems on Premiers? - 07/22/19 7:11 pm

Originally Posted by Andy Higham


The MK2 has a system like Mikuni, Keihin, Dellorto etc where a supplementary fuel/air mixture is fed via a starter system


And some/most of those Mikunis, Keihins and Dellortos have accelerator pumps that can also be used to prime the engine for starting in addtion to or in lieu of using the cold start...No stinky finger...
Posted By: johnm

Re: stay-up flat problems on Premiers? - 07/24/19 12:07 am

My new experience with new Premier carbs was confused by previous experience with old Amals.

As pointed out by John and others for the first time in maybe 40 years of using Amals found I had to use the choke on my 850 commando.

- and it took a while to learn the lesson.

I changed from 17 to 19 and finally to 21 jets. I changed to a 3 slide. And still the bike was very very reluctant to transition off idle no matter how carefully I opened the throttle.

Part of the issue was my annoying experience of the useless modern cables with the "pull off" nipples. Branded cables from a normal dealer and one pulled off the throttle and then another off the choke. At which stage I threw the choke away not wishing to replace 5 times 2.

But I'm going to have to resolder all of them and fit the choke.

(And yes I did carefully inspect and clean the new "matched pair" of Amal Premiers. "Matched" so one carb came with a 200 main and the other a 260. :-) They came in a nice box carefully packaged together with 850 Commando on the box. )

Trust no one !!!!

Posted By: Allan Gill

Re: stay-up flat problems on Premiers? - 07/24/19 9:03 am

What was the nomination on side of the carb with the 200 main jet?

The standalone carb (not pre tuned to any particular bike) for a 930 is #3 slide, 106 needle jet and 200 main jet.

Also worth noting that if the bike isn’t taking throttle, then it isn’t the pilot circuit that needs changing but the slide.
Posted By: johnm

Re: stay-up flat problems on Premiers? - 07/24/19 11:53 pm

I don't have the carbs with me but the two carbs were sold and labeled as a 32 mm matched Premier set for an 850 Norton Commando 1974 Mk11 - normal airbox and peashooter exhaust. (not a MK11A or Mk 111). Normal main jet for an 850 this configaration is 260.

Both had pilot 17 jet, 106 needle, 3.5 slides. One had 200 main. The other had 260 main. They both had the 850 Commando spray tube cutaway.

New plugs, gas and aircleaner

I changed both mains to 260
I changed pilot to 17 to 19 and then 21.
I changed the slides from 3.5 to 3.

All without the chokes.

The bike takes throttle when warm but not when cold.

I will now put the chokes back in and start again with 19 pilot and 3.5.

I don't have any issue with using the chokes rather the frustration of replacing all the tiny nipples on both the throttle cable and the choke cable. Honestly they are pure **** and I don't trust any manufacturer these days including Venhill because I have personaly witnessed so many pull off.
Posted By: John Healy

Re: stay-up flat problems on Premiers? - 07/25/19 3:18 pm

Quote
The choke slide is hidden inside the main slide until the throttle is opened,


With the proper cable installed, the air valve (choke) drops in front of the slide cutaway blocking air flow.

It has the same effect as if you installed a richer slide.
Posted By: Dibnah

Re: stay-up flat problems on Premiers? - 07/26/19 5:33 am

Originally Posted by johnm


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-
The bike takes throttle when warm but not when cold.

-
-


How long does it take to warm up before it's rideable?

My 650 Tiger has no choke, starts first or second kick from cold (with tickling) but needs about 30 seconds idling before riding away, otherwise it stalls.
Posted By: Andy Higham

Re: stay-up flat problems on Premiers? - 07/26/19 2:09 pm

Originally Posted by John Healy
Quote
The choke slide is hidden inside the main slide until the throttle is opened,


With the proper cable installed, the air valve (choke) drops in front of the slide cutaway blocking air flow.

It has the same effect as if you installed a richer slide.


Yes, it comes into effect when the throttle is opened. When the throttle is closed as for starting it is ineffective, hence the need for a tickler
Posted By: bill50cal

Re: stay-up flat problems on Premiers? - 07/26/19 4:31 pm

it IS effective at idle BUT as it does not completely close off the air flow is the reason you still have to tickle the carb. as I have not tried it but my guess is you could kick it through several time with the ign. off than turn it on and have it start with out the tickler.

[quote=Andy Higham

Yes, it comes into effect when the throttle is opened. When the throttle is closed as for starting it is ineffective, hence the need for a tickler[/quote]
Posted By: gavin eisler

Re: stay-up flat problems on Premiers? - 07/26/19 7:11 pm

i didnt ride my bike for over a week. normally i use gravity to start it ( bump) only the choke no tickling. For science sake i tried to start it on the kicker , 3 kicks choke on ignition off to clear the clutch, ignition on, fired next kick, didnt catch, caught two kicks later. The choke does work, not very well, but it does work. it was a balmy 15 degrees C.
i hate tickling the carbs.
Posted By: Allan Gill

Re: stay-up flat problems on Premiers? - 07/26/19 9:07 pm

The pilot circuit is metered by the pilot jet and the air screw (which gets its air from the outer hole on the back of the carb) however.... the slide is not completely closed when the throttle is shut, there’s a small gap underneath. You’ve probably got around 3/32 of open gap from the slide cutaway when the chose is down it closes this off.... the purpose doing so causes more vacuum to be drawn through the welsh plug and from the pilot circuit.

If your chokes aren’t touching the bottom of the bore then there’s a cabling issue.
Posted By: Irish Swede

Re: stay-up flat problems on Premiers? - 07/28/19 7:04 pm

What "Stay Up Flat" motorcycle tires are available?

OH! SORRY! It's a "stay-up- f l O a t" thread.
Posted By: johnm

Re: stay-up flat problems on Premiers? - 07/28/19 9:54 pm

Originally Posted by Dibnah
Originally Posted by johnm


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-
The bike takes throttle when warm but not when cold.

-
-


How long does it take to warm up before it's rideable?

My 650 Tiger has no choke, starts first or second kick from cold (with tickling) but needs about 30 seconds idling before riding away, otherwise it stalls.


Perhaps three minutes. But i don't like to leave the bike idling that long because it is bad for camshafts in my opinion. I like to run the bike at about 2000 rpm as soon as it is started.
Posted By: Allan Gill

Re: stay-up flat problems on Premiers? - 07/28/19 10:02 pm

Originally Posted by Irish Swede
What "Stay Up Flat" motorcycle tires are available?

OH! SORRY! It's a "stay-up- f l O a t" thread.


facepalm
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