Throttle butterflies
Posted: Fri Nov 24, 2017 1:29 am
Re:
" I'm ordering new spindles and butterflies as I suspect the throttle adjusting arms have been drilled in the wrong place and the slot in the spindle is too far over one way stopping the butterfly being fitted. To overcome this it looks like he's filed the sides of the butterflies."
Norman, as you correctly surmise the difficulty I getting a slow enough tickover is almost bound to be an air leak of some kind. As others have pointed out there is a right way and a wrong way round to install the butterflies as there is a chamfer top and bottom to ensure a snug fit to the choke. This is easy enough to check for along with manifold leaks. However, you state that there are gaps on the side of the butterflies rather than the top and bottom which is where leaks would occur if they were incorrectly fitted. Surely no one would file the sides of the butterflies to fit a an item which was fouling the sides of the choke? And if so they would only have to file one side, not both as you state. So this leaves only one other explanation, the choke is out of round, but I find it hard to believe that this would occur on both carbs. Come to think of it the chance of getting both butterflies wrong would be unfortunate. As an aside, if the spindle is incorrectly drilled, a difficult job to get right at the best of times, I believe Burlen have operating arms which clamp on this saving paying for relatively expensive new parts. Unless originality is important that is.
Regards Ian Thomson