jc510 Posted August 3, 2014 Report Share Posted August 3, 2014 Hi I am having trouble with my 72 510 Electric Dizzy (black box) SU carbs. The symptoms seam random: 1 - Engine pings at low engine speeds and not all the time (i started running non ethanol fuel which helped for a little while) 2 - idle goes up and down 3 - Tach starts to bounce and or show higher revs than engine speed 4 - The engine cuts out and has died only to start up a short time later 5 - Possible not related is fuel runs out of the over flow tubes (wasting fuel & possible fire) I have replaced the cap and rotor, ignition coil, inspected the Dizzy, the Plug wires are newer Taylors, and had the carbs tuned. Oh it's my daily driver too... Another note, is there another location this thread should be in? Can it be moved? Thanks Quote Link to comment
datzenmike Posted August 3, 2014 Report Share Posted August 3, 2014 The tach bouncing (to me) sounds like a loose connection. Engine cuts out and dies is another reason for thinking this. First make absolutely sure that the distributor is fully grounded. Usually there is a lug on it for a ground wire. On this one it's the upper right mounting screw for the black box... Other things... This could be the power wire to the positive coil terminal or to the matchbox. It could also be on the other side... the coil negative wire or where that wire connects to the matchbox. SU flooding can be too much fuel pressure. Stock mechanical pumps are ok. Replacement after market or electrical pumps may be too high a pressure for the SUs floats. Quote Link to comment
jc510 Posted August 3, 2014 Author Report Share Posted August 3, 2014 Thank you, this is great, I will test these out. Hopefully a ground wire... Quote Link to comment
datzenmike Posted August 3, 2014 Report Share Posted August 3, 2014 Thank you, this is great, I will test these out. Hopefully a ground wire... Yes but can also be the power wire from the ignition. Quote Link to comment
jc510 Posted August 3, 2014 Author Report Share Posted August 3, 2014 I don't have a ground wire or tab like the top right one in the photo you uploaded on my Dizzy, I was thinking about using a eye bolt and alligator clip a wire to the body just to test it. How would I be able to diagnose the power to the matchbox? (will a test light work or do I need a multi meter?) Quote Link to comment
dr.feltersnatch Posted August 3, 2014 Report Share Posted August 3, 2014 Su floats are known to sink, causing it to flood. Pull them out and shake them. If you hear gas in them they need to be replaced. If no gas is inside them then check the float level. Quote Link to comment
datzenmike Posted August 3, 2014 Report Share Posted August 3, 2014 Make a permanent ground wire. Crimp a lug on the ends and bolt it on. If there are breaks in power they are likely short duration and a meter may not be fast enough to show them. Just inspect for tight connections. Carefully unscrew the matchbox and look under the rubber here... Thee two wires should be firmly seated. Quote Link to comment
jc510 Posted August 3, 2014 Author Report Share Posted August 3, 2014 Ok, I will dig a little into the Dizzy and connect the ground. Thank you for the visual help too, takes all the guess work out of it. Quote Link to comment
jc510 Posted August 3, 2014 Author Report Share Posted August 3, 2014 I replaced the Floats a few months ago with the New Foam ones. I do have an older after market pump on there, I think I have the stock on in a box. Time to dig Quote Link to comment
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