Amal 10TT9

When I bought my 1954 Norton International Model 30, it came fitted with its original Amal 10TT9 carburettor. I asked a few people about it on the relevant forums; some loved them, but many did not.

I did try the bike with the 10TT9 on it; cold starting was relatively straight forward, but I simply couldn’t get it to start easily when it was hot. The 10TT9 carburettor is one I’m not familiar with, and soon found out it had no idle facility so wouldn’t sit patiently at tickover.

Once again I consulted the experts, who told me some people just used the cable adjuster to keep the throttle slightly open…the downside being that the idle speed changed as you turned the handlebars. Others told me they drilled a small hole in the throttle slide, gradually increasing the size until the bike idled steadily.

The 10TT9 won’t idle by design…they are intended for use on the track, and if the rider comes off, he wants the engine to stop rather smartish!

My intention is to use the bike on the road…that’s exactly what I’ve been doing too…very nice it is. However, I replaced the 10TT9 with an Amal Concentric, built to order by Amal to suit my bike. I don’t want a difficult starting procedure if I accidentally stall the engine at traffic lights. Note: Surrey Cycles will also build you a suitable carburettor, or supply you with a new 10TT9.

Anyway, I am reliably informed that this is the best method to start a motorcycle fitted with an Amal 10TT9 carburettor:

  • turn on the fuel
  • set the mixture lever to the normal running position; you may have to experiment with this when cold or hot
  • set the ignition to its midpoint
  • press the tickler briefly, just a quick jab, and wait for fuel to just start to drip from the carburettor; it may take up to ten seconds
  • give the bike light throttle, ease it over compression with the valve lifter, then give it a good swing on the kickstart and it should fire up
  • once the engine is running, turn the fuel back on and off you go

Here are some comments from ‘experts’ on the t’internet:

Scott Technicalities Forum:

The correct float height is found when petrol starts to weep (difficult to see…be patient) out of the ‘hole’ underneath the pilot screw when the tickler is pushed down for an instant, i.e. a jab, not a push and hold down. The petrol should then continue to weep out of the hole, slowly forming a drip. This will only stop on switching the petrol off. If you have raised the float too high you must drain some petrol off before starting again. Under static level conditions there should be no petrol coming out of this hole.

I use a torch to help my aged eyes (you may be more fortunate), then you can
see the film of petrol leaving the hole before a drip forms. All tests should be done with the bike level. Take your time, and you should be rewarded with easy starting and good low and high speed performance. I think TTs are magic!

Britbike Forum:

OK, all of the ‘racing’ Amal carbs have no idle stop screw, even the new ones! Back in the day, this was done for safety…the engine would stall if the rider’s right hand was not holding the throttle open.

But, unlike what many say… there IS an idle mixture/low speed screw.

So, some guys have adjusted the throttle cable to hold the carb slightly open. I do not suggest this.

I (and others) drill a small hole in the front side of the slide to give the bike an idle. Some guys file a notch, but that is less precise. If drilling you can start small and enlarge as needed. If you go too far you can solder the hole and start over. I would start at about a 0.080″ hole and go from there. You need to make sure the engine is fully warmed up and the mixture screw is adjusted for slightly rich from fastest idle. Ron.

Ron- Is the front of the slide the side nearest the engine?

Yes, the side nearest the intake valve…pretty simple, start small then go larger until you are happy. It works every time!



So…there you have it…how to start your motorcycle if it has an Amal 10TT9 carburettor!

My 10TT9 is safely stored in a box, complete with its two cables. Once day, I may decide to try it again…but it needs to be kept in case I ever sell the bike.