Yeah he's a nice helpful chap , but i don't like his music .....Ill keep you posted

Yeah he's a nice helpful chap , but i don't like his music .....Ill keep you posted

nice one

...check that you have a 2-stroke needle fitted. 2-stroke needles have 1 or3 (odd numbers) of engraved rings around the top above the clip grooves and 4-stroke needles have 2 or4 (even numbers)

If I had known this a couple of weeks ago it would have a few more hairs on my head now!

Edited March 21, 201313 yr by westyfield7

Thanks for that info Westyfield7 , yeah it as the one engraved ring above the top clip groove .

It turns out i'm running too small a carb , its just under a 24mm bore , someone as removed the last number on the carb for some reason , so i'm now after a 26-27mm amal .....Thanks for all the info chaps

Ah it's amazing how sometimes it's the blindingly obvious things we all miss. Glad you're on the way to getting it sorted.

Is there any reason it wouldnt run well on a 24mm ? Carlson used to use a tiny carb on his triumph twins.

Don't want to put a damper on it Keith, but my Ossa was running really well on a 24mm Mikuni. It was fitted and jetted by Magical when he used to use the bike before he built his James and it revs until you can't hear it...

I don't think a size of 24mm will cause the problem you have, a 250 should be able to run on that.

Don't want to put a damper on it Keith, but my Ossa was running really well on a 24mm Mikuni. It was fitted and jetted by Magical when he used to use the bike before he built his James and it revs until you can't hear it...

I don't think a size of 24mm will cause the problem you have, a 250 should be able to run on that.

Interresting as Mick also helped jet my OSSA 28mm Mikuni and James 27mm Amal mk 1 1/2 and they both run fine too. If the 24mm bore size of the carb was a problem I would have thought it would only affect the performance right at the full throttle stage. Are you sure there isn't a mechanical fault with the carb itself as if the motor runs fine on somebody elses carb but just needs fine tuning then it points that way.

When I last rode the Scottish I noticed the James running a bit rough but it still ran and after a couple of sections it was only then I noticed that the carb had fell off the intake rubber on the manifold and was just leaning against it because of the hose to the airbox keeping it in place. Which just goes to prove how they can still run even if they have a bloody great air leak. I think you have got to strip the carb and make sure all the passages are clear, use an air line, and check all the jets etc. Oh yes as Andy said earlier check correct 2 stroke needle and that the emulsifier tube is correct for a 2 stroke. Amals have been known not to have the passages drilled correctly and even to still have bits of flash blocking some from the casting process.

Oh one last thing make sure there is enough fuel flowing to and through the carb to fuel the engine at high revs when it needs the fuel most. Will it rev if you run the carb without an air cleaner? just a thought that the element might be strangling i.e. not flowing enough air at full throttle? same with exhaust is it flowing properly or does too much back pressure build up as revs rise? if all these are fine then the only other answer I can think of is to contact cliff and as him to lend you another ignition system as the advance curve might have a fault or be breaking down as revs rise?

At the end of the day if the motor has a spark at the right time and the correct amount of fuel and air in the correct ratio then there is no reason why it shouldn't rev out.

Edited March 22, 201313 yr by old trials fanatic

Managed to try another carb , with help from me friend Mr G , an old 26mm Mk 1 Amal , 120 main , 25 pilot , and it revved considerably better across the range , so i'm now thinking its the carb .I've cleaned it out ,blown with airline , played with needle height , tried different jets , run without air filter and tried different type of filters .Think ill park it up , and take me fanny to poachers instead .....

Managed to try another carb , with help from me friend Mr G , an old 26mm Mk 1 Amal , 120 main , 25 pilot , and it revved considerably better across the range , so i'm now thinking its the carb .I've cleaned it out ,blown with airline , played with needle height , tried different jets , run without air filter and tried different type of filters .Think ill park it up , and take me fanny to poachers instead .....

Hmmm does look like the carb itself has something not right about it and the settings on the carb you tried are not a million miles from mine. Daft question now but bear with me. With the carb off your bike look down it and does the slide fully open i.e when you turn the twistgrip fully make sure there is no part of the slide in the venture. Reason I say this is I have had slides in the past that though they fit the carb body they are different lengths and came up against the carb top so didn't fully open. I know it's a long shot but worth checking.

No-one has mentioned the float height and fuel level.

Try switching the fuel off and see if it revs ok after say 30 seconds or so. If it does, then your fuel level is too high.

Here's what Burlen have to say - http://amalcarb.co.uk/optimising-mark-1-concentric-fuel-levels

just a point I learn't recently is about setting the throttle stop correctly. I've always unscrewed it all the way out as I ride, like most, without a tickover. In this position, If you look down the carb and slowly open the throttle you will notice that the slide moves up about a 1/16"th or more before actually opening!

I noticed an immediately better response when the stop screw was turned in so that the slide was right at the top of it's closed position.

The setting is easily found by turning the throttle stop up and then slowly out until the tickover is completely absent..sorry if I'm stating the obvious.

Hi Guys

Bit of a update on the carb problem i was having , first time out today to try out . The bike is now running on a good used Amal 26mm carb , with a 130 main jet , 25 pilot , No 3 slide and a 106 needle , bike is now running a lot better and rev's right out ...

Thanks for all the help