1975 Norton 850 Mark 3 will not start :(

marshg246 · Jan 31, 2020

thackero said:
During the last 12 months my 75 Norton E/S was getting more and more difficult to start. I made the decision to finally fix my front cylinder stud that had dropped out many miles ago due to a stripped thread. Carbs (new in 2015) were also rebuilt and now its all back together however it will not start. Sprayed starting fluid in the carbs . Gas is evident as plugs are getting wet. There is a spark but it looks weak . New battery. I am running a Boyer and my thoughts are maybe under pressure the spark in the cylinders is too weak. Now I am backtracking to try to source the problem . My question for the forum is it possible to install the pushrods incorrectly ? i.e exhaust should be the shorter ones inlet the long pushrods. Could I have mixed them up ? - maybe although I pulled the rocker covers last night and all valves are showing that they close and all have the correct clearances 6 thou inlet 8 exhaust. I will check the timing tonight but I suspect Boyer could be faulty. I am running 6 Volt coils (new in 2015). Any suggestions ?
Thanks

There was a thread here a month or so ago about a bike with Pazon and a weak looking spark. At the same time I was working on a bike with Pazon and a weak looking spark. He was getting some popping. I was getting nothing.

After eliminating everything else, I tested the coils by leaving the jumper between them in place and removing the other two wires. I put 12volts across those free terminals and watched the plugs as I disconnected - nice fat spark. So, I changed the electronic ignition and it started without problem. These were Pazon, but Boyer could have the same issue.

grandpaul · Jan 31, 2020

Try swapping the wires!!!

thackero · Feb 19, 2020

I have now ordered a tri-spark ignition so maybe that will solve the problem. I fitted new 6V coils and checked the wiring was correct. Still a weak spark. Back to riding my Triumphs for the time being ......

thackero · Mar 13, 2020

Update for all. The Norton is running perfectly once more. Very difficult to isolate the exact cause/causes of my problems. The Tri-spark ignition was fitted with the new coils, I also removed the pilot jet screws and subjected the carbs to some high pressure air. Noted a small piece of aluminium swarf came out of one of the pilot holes. In addition changed out the HT leads for some 7 mm copper ones. Checked all connections.Me thinks it was a faulty intermittent Boyer coil on the points plate. I will take her for a 150 mile run this weekend and report back.

1975 Norton 850 Mark 3 will not start :(

marshg246

grandpaul

thackero

thackero

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