decompression valve for starting

I think we have already given this a good airing  in another post.   Nothing commercially availiable at present .  It may be possible to  lower the primary ratio  which should help a liittle to kick over with perhaps a compression plate under the barrels.  I really fancy one of those old fashioned Coffman cartridge firing aircraft engine starters , should create a stir !! . Do you think a 12 gauge would do it?.

You would need a higher first gear such as the Daytona gear to turn it over with less effort. The engine would then turn a bit more slowly, so might then not start quite as willingly.

Try the other leg?

In my recent experiments to get the idle and pick up mixture  correct on my  high comp 99 ,I have on a couple of occasions  accidentally got an ideal starting mixture. Just turning the engine over gently prior to giving it a kick  has had it burst into life  surprising me no end.  Even a slow kick over has a better  chance of a start than NO  kickover.

A chainsaw decompressor in each cylinder using a hole drilled and tapped into the head with a small hole opening out into the combustion chamber. You pull out the knob on both for low compression, as soon as the engine fires the combustion pressure auto shuts the valves. As the valves can break up you need the hole into the combustion chamber to be only 1 to 2mm, this will still reduce the compression when the decompressor is open.

Hi David,  Not sure that a change of box gears would do what we are talking about , is the daytona kick start  a lower ratio than std box ?.

It's easier to turn the engine over when push starting in a higher gear. The Daytona first gear is higher (at 'only' 2.12) than AMC (2.55). I don't know how much difference it will make. Not a huge amount I suspect. Chain saw decompressor sounds more effective!

Its kick starting for old farts with wobbly knees we are  debating here !  ,Don't think push starting is  a likely senario . Putting a bigger engine sprocket  on the Atlas  was  easy and not expensive , don't think its as easy on the commando.

Goldies have kick-start with 1.77 first gear. The Norton box won't accept a kick-start at such a high ratio first gear. So we see riders prodding Gold Stars to little effect.  Anyway it's an expensive experiment to change first gear to look for easier starting, especially as it makes the bike less tractable on busy or hilly roads.

Like it or not we are all headed the same way .  Finding a practical solution  is something that  would enable oldies to ride a Norton  for another 10 years . I have a plan for a 250  and am working on it . Sadly it won't be a Norton .(  no pistons!!!)

The Daytona first gear pair gives a first gear of 2.1 ish with a Manx / Inter sleeve gear set.  It will be a bit lower if you have an AMC 2 or 3 gearbox.  But yes, kicking over will be easier.

The Daytona first gear was created because AMA rules insisted on a kickstart being fitted on the works Nortons racing on Daytona Beach (circa 1948), and the factory created the highest possible ratio in the Norton gearbox, using very fine teeth instead of the usual Norton tooth pairing always adding up to 42. It''s closer than the International 14:28 pair. Note that they were originally made for the upright gearbox, so if you obtain a pair, intending to fit to an AMC box, make sure the AMC-type spacing shoulder is present on the mainshaft pinion, or fit a separate spacer.

I would be interested to know what the actual tooth numbers are with a Daytona first, and where a set might be obtained.

Paul

Is your bike coil or magneto ignition?

My standard compression 88 (1956 pistons, around 7:1) with magneto needs a good kick from cold, but is very easy indeed when hot.  A couple of kicks usually does it either way. I think that's the difference of oil drag.

RGM stock them. The larger gear has is the 34 tooth lay shaft gear and is the same all the way from Doll's Head to AMC. In order to get the kick start inside it, it has smaller teeth than the other gears.  The small main shaft pinion has 20 teeth and is the same for Doll's Head and laydown, but has a longer end boss on AMC. Both types are stocked. The tooth count adds up to 54 rather than the 42 for all other gears.  I just fitted the pair in my Inter because kick start Inter first gears (27 and 14) seem not to be available. Manx has 25 and 17.

Check this post on accessnorton:

https://www.accessnorton.com/NortonCommando/compression-relief-valves-to-allow-easier-kicking.22401/page-2

https://youtu.be/5i778Ar7BWg

And from Bennie's Access Norton link it seems that the hole it fits into is a narrow (1/8" maybe) hole through the head, counterbored and tapped for the valve. Is anyone brave enough to try? You would need two of them.

do you know of a source for the chainsaw valves?

You want the genuine Stihl valves not the Chinese copies, even with the small entry hole into the combustion its better that they do not fail as then you may be trying to get home with a low compression cylinder. 

Could it be hazardous to the cylinder head in the future, or correct with a weld?

They screw into a M10 x 1.0 tapped hole (there are variation on thread pitch but 1.0 is most common), small enough to position out of the way of valves and spark plug. Would drill the 9mm hole on a vertical mill as I did for my Twin plugged B44 (also M10 x 1.0 tapped hole). If no longer needed an alloy plug threaded M10 x 1.0 on OD and loctite would fix. 

I made one for a single once by drilling a hole through the exhaust rocker cover inline with the tappet adjuster, fitting a grommet in the hole then fitting a screw through the grommet with a nut and flat washer either side and adjusting the screw just clear of the tappet adjuster and locking in place with loctite. a cable operated lever was then made which pivoted on one of the rocker cover fasteners and pushed down on the tappet adjuster to open the exhaust valve slightly when kicking the start lever initially. The grommet provided the necessary movement and also worked as an oil seal. It was only a bit of a lash up and could have done with some improving but worked for the short time I had the bike. Easy enough to try for yourself.

Regards, Al.

I fitted the Alton 8 years ago and never looked back, I even removed the kickstart lever as it was a bit in the way with rearsets. The little rubbers in the kickback clutch did get a bit chewed up when i had a missfire but it has kept on working ok. I have also replaced the starter motor brushes once as petrol from tickling can get to them. I don`t think you will regret doing it and it will add value to the bike.

Regards, Al.