1st outing on the 69 Commando over the bank holiday. 2 miles down the road started popping and backfiring. Got worse and ended up cutting out every half mile. Limped back home. Pushed last 500 yards
My suspects were poor fuel, tappets too tight, dodgy plugs, Lean idle mixture. Ignition is Wassel.
Found a clogged fuel line on the reserve hose just past the reserve tap before the in line filter so good to sort that.
New plugs fitted, checked tappets, swapped fuel, richened idle mixture. Still no better.
Credit to a previous post by John Holmes.....Smoking gun seemed to be the idle mixture jet. Removed idle screw and cleaned out with #79 drill and a guitar string then a big squirt down the hole with carb cleaner. Could not see any crud on the drill or string but I'll tell you what...quick blast up the road and it seems to have cured it completely. Now runs and idles fine. I'll pack them with my tool kit.
Regards
Eddie Cross
Its always a mystery why…
Its always a mystery why this works when no obvious blockage can be seen, but it works too often to not be some blockage. That's why its always my first fix to try after a layup and the bike misfires. Good to keep the tools with you, you may have just pushed the offending blockage back into the carb and its just waiting to come forward again. Wait until winter and get the carbs ultrasonic cleaned for 100% piece of mind but every winter layup brings the risk of a pilot circuit blockage.
On Boyers I fit a block of sponge under the points cover so the wires are held firmly to the stator, this stops the wires breaking internally which happens on Commando's more than any other engine.
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And so it begins!
Great thread! I'm trying to find the same issue, as only just bought it thought it was OK till I touched the n/s silencer which was warm whereas the o/s was well hot!
Balanced carbs, new plugs, swopped coils, all to no avail, so now two plans of action, idle jet and Boyer wiring to check!
Love the resource available on these here forums!
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Hi Richard
Hi there Richard,
Glad this could help you. Cracking bike you have- Saw it on E-Bay. Did look great. I have just lined my fibreglass tank on my 69 using POR15 and seems to be holding up fine. If you haven't seen it, the Greg Marsh site is great for ID information, rebuild tips and has some excellent wiring diagrams split out by circuit.
GME - 1972 Norton Wiring (gregmarsh.com)
Cheers
Eddie
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Thanks for comments - now resolved!
Eventually gave up on tweaking carbs, called NORVIL who suggested changing carbs. After noting in the box of "bits" that came with the bike contained various floats, jets, needles and air slides, decided to bite the bullet! New 9/32 Wassell replacement's and cables fitted, it has so transformed the bike! Starts, idles and runs well, yet to do a long run but well happy! :) All I have to do now is get the brakes working well enough as stopping distance is a tad frightening at the mo!
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... very similar with a Boyer equipped Commando. The cause was the cables coming from the pickup coils fracturing and making intermittent contact. The problem is that although the Commando feels very smooth the engine is still bouncing around and this flexes the cables.
But you may have fixed it.....