Author Topic: Amal MKII 2900 series needle/circlip!  (Read 108 times)

themoudie

  • Hero Member
  • *****
  • Posts: 4095
Amal MKII 2900 series needle/circlip!
« on: August 27, 2021, 10:08:04 AM »
Out on the Ducati yesterday, when the engine stalled at traffic lights and then refused to start unless choke was applied. Because temperatures were around 23°C, I thought fuel vapourisation might be the problem. But, after 10 minutes, still wouldn't start unless the choke was applied and using the throttle just caused the engine to fluff and die! Called the naughty van company for pick-up.

Whilst waiting for pick-up peered down the inlet and operated the throttle. Lo and behold the slide lifted but the needle remained seated in the main jet! :o

Slackened off the carb, took the top off and extracted the needle, then took the circlip out of the slide. Tried to put the circlip back on the needle, but the wear on the 3 points of the circlip and deformation of the needle grooves meant that the circlip wouldn't grip the needle.

Tried to apply gentle pressure to the circlip, using a pair of fly tying pliers, borrowed from a fly fisherman on the adjacent River Tay and only succeded in snapping the circlip. Spring steel doesn't like being lateraly squeezed! ???

Arrived back home and the circlip and needle came out of a spare carb. Off for a canter and the engine didn't miss a beat.

I know that some users of these carbs change the needle/needle jet and circlip annualy, due to high wear rates. This wear only took 2,500 miles of running, so just be aware if you use Amal MKII 2900 series carbs!

Good health, Bill

iansoady

  • Hero Member
  • *****
  • Posts: 1037
Re: Amal MKII 2900 series needle/circlip!
« Reply #1 on: August 27, 2021, 01:18:24 PM »
The copper clip used on the monobloc is a better item IMO. I've had the 3/4 moon shaped one on mark 1 concentrics break in a similar way to described above.
Ian.
1952 Norton ES2
2008 Yamaha 250 X-Max