Choke removal

Greetings,
I have read previously of Norton owners who remove the choke valve/door/slide from their Amal carbs. Due to a recent loss of a cable end I am considering doing the same. I was wondering what if anything could or should be done to blank off the choke cable hole in the top of the carb. I trip to the local hardware store found no bolt or screw to match the very fine thread of the cable adjuster. Any suggestions appreciated.

GB

Replace the choke cables. If the bike is jetted correctly, you won't be able to start it wthout a choke.

I used silicon. I ran my norton for years without a choke through the snowy winters and 90' summers, no problems.

I ran without a choke for a while and had harder starting, I'm not as hardy as those Canucks so now I use chokes or enrichening valves on all my bikes.

I removed the chokes several years ago with no adverse effects. I cut down the body of a nail whose head fit well to the cable hole and then covered it with silicon.

GB,

As I recall you live in Florida? If so you should be able to get by without them. Here in Colorado I don't need the chokes in the summer but the rest of the year I do (two seasons in Colorado you know: winter and July!)

You do need to plug the holes with something. I have a couple of blanking screws that came with my 750 that I've used but I suppose silicone would work. I believe the screws are 2BA and you certainly won't find those at the local hardware store!

Debby

Tapped mine & put in short set screws. Good tickle when cold, starts 1st kick.

If a motor starts without choke and continues to run when cold, the mixture will be, by definition "rich" when the motor warms up.

For a gasoline engine stoichiometry (the chemically “correct” point at which the most complete combustion takes place under no load) is 14.7 parts air to 1 part fuel (14.7:1).

Steady state throttle under steady state load the optimum mixture would be about 13.2:1 and with this you get peak Brake Mean Effective Pressure (BMEP).

Under acceleration the correct mixture with a cold engine is 12.1:1 and when warmed up 12.7:1. (You can see why "pumper" carburetors are performance enhancers, alternatively, you adjust the mixture somewhere between the steady state optimum and the acceleration optimum on conventional carburetors)

To start maintain running a cold engine the mixture needs to be between 11.01:1 and 10.3:1 depending on the ambient temp.

The above mixture ratios are pretty much accepted by tuners, although to meet emissions requirements engines run much leaner than optimum these days.

So, while a rich mixture is certainly preferable (and the bike will run satisfactorily) to a overly lean mixture, running rich reduces performance somewhat, uses more fuel, causes more carbon build up and over time introduces fuel into the lubricating oil in 4 strokes.

geo46er said:

Greetings,
I have read previously of Norton owners who remove the choke valve/door/slide from their Amal carbs. Due to a recent loss of a cable end I am considering doing the same. I was wondering what if anything could or should be done to blank off the choke cable hole in the top of the carb. I trip to the local hardware store found no bolt or screw to match the very fine thread of the cable adjuster. Any suggestions appreciated.

GB

Click to expand...

I left the old cable adjusters in then dabbed silicon into the hole to block it, avoid the mistake of a nut and bolt , nut is inside gets loose falls off goes into engine makes rattling noise and ........................ :!: :idea:

montelatici said:

Replace the choke cables. If the bike is jetted correctly, you won't be able to start it wthout a choke.

Click to expand...

Not even if you flood the carb slightly?

I removed mine when I realised that I didn't use them from year to year and that the choke slide was causing additional throttle stiffness. I filled the adjuster with epoxy.

It will start with tickling in freezing conditions. Presumably the richness to achieve this is a result of the standard pilot bushing and needle jet ?

A pair of flooded downdraught Amals seems to be more than adequate for starting and running whilst the cylinder head temperature increases.

The Commando defies the laws of physics in so many ways, why should those relating to carburation be any more relevant ?

79x100 said:

A pair of flooded downdraught Amals

Click to expand...

I think you mean side draught, down draught carbs are usually found on cars while down draught animals are found in pubs.

plj850 said:

montelatici said:

Replace the choke cables. If the bike is jetted correctly, you won't be able to start it wthout a choke.

Click to expand...

Not even if you flood the carb slightly?

Click to expand...

That probably greatly varies depending on ambient temperature and specific tuning of said bike. I'd be wary of any blanket statement like "it won't work".

Last time I ran with no choke was in Maine and it was only an irritation when very cold. When you come out of work at midnight and the weather has gone to a cold snap with snow flurries, the oil feels like honey, and the bike kicks with a slurp, a choke is nice. If your bike is a bit rich anyway and the weather isn't that bad it will be fine. I used to ride all summer with no problems at all.

"That probably greatly varies depending on ambient temperature and specific tuning of said bike."

Not really, except if by tuning you mean that a motor is jetted rich. While Nortons may defy physics, I suspect many people run very rich jetting on road going Nortons combined with sometimes dirty air cleaner elements, hence haven't the need for a choke.

The ticklers themselves are an enrichment mechanism, so depending on your location you may not need additional chokes and it doesn't necessarily mean the bike is too rich under normal operating conditions. RGM motors in the UK do some nice dedicated blanking plugs for this application.

Filling the float bowl with the tickler will get the maximum fuel that the jetting allows to the combustion chamber. If the motor starts it will be at the air/fuel mixture that will result in combustion with a cold engine. That air/fuel mixture, optimum for starting, will be rich when the motor warms up. It is just physics. But, if you disagree, ok.

By the way. I bought my first Norton (brand new) at Elite Motors in Tooting in 1970. Brand new they would deliver it with larger jets and the needle up a slot and they supplied you with smaller main jets and instructed you to install the smaller jets and drop the needle one slot after break in. They delivered the bike rich to assist in break-in and once broken in they wanted you to lean it out for optimum performance. I doubt many dealers went to the trouble, hence most Nortons are probably set up a little rich from new.

My understanding is that tickling the carbs overfills the float bowls thus allowing atmospheric pressure to act on a larger volume of fuel and providing additional enrichment for starting (in the same way that a high fuel level will result in rich running), once the bike is started I agree it will then rapidly revert to its standard mixture delivery from the carb and in very cold conditions some of the fuel will adhere to the cold manifold, intake ports etc. and produce a weak mixture until normal operating temperature is reached. Under these conditions a choke is helpful in maintaining a reasonably accurate stoichiometric mixture until the motor is up to temperature, however in practical terms many people (especially in mild climates) indeed find that once the bike is started on ticklers only it is not difficult to keep it running and soon enough it can reach operating temperature with no undue richness thereafter. On a technical note it was said that a group of eminent scientists did an assessment of the aerodynamics of a bumble bee and came to the conclusion that it was impossible for such a design to fly, but someone forgot to tell the bumble bee!

Yup,

It will work but the first few moments can be ugly and you have to be willing to warm it in place. I don't do that myself, oh shades of engine damage! I tend to start them up on the choke and as soon as I have oil pressure I drive gently with choke on, releasing as it gets power. My Hondas don't get fully warm until I'm halfway to work. I think the Norton is pretty good in a block.