The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: barry2 on 23.08. 2019 03:27

Title: Idles great when cylinders isolated Both working lumpy/missing and at low speed
Post by: barry2 on 23.08. 2019 03:27

Hi All
been trying to sort this out for ages ,,,,my Super Rocket has lumpy /misses  tick-over  also  misses when starting and   misses at fairly low speed ( not all the time though ) goes great at all other speeds done everything recomended here,   had 3 set of new plugs NKG/ Champ ...points , cleaned out the slip-ring area , checked in dark w/ mag cover off , no sparking anywhere , the other day I isolated  the cylinders ( to see if one was worse than the other  but both seem to miss the the same amount ), When I had the cylinders running isolated  each one idled perfect by it self no missing at all,   tickover was like a single,, Conected both up lumpy / missing ,, any ideas?
Barry

Title: Re: Idles great when cylinders isolated Both working lumpy/missing and at low speed
Post by: Billybream on 23.08. 2019 08:28

I would treat the carb to a good clean, pilot circuit could be the culprit, not an easy task on an Amal, once throughly clean would be best to add an inline fuel filter. Theres plenty of useful video's showing best methods to clean a carb.

Title: Re: Idles great when cylinders isolated Both working lumpy/missing and at low speed
Post by: bikerbob on 23.08. 2019 10:44

Just had a similar problem on my A65 missing on tickover turned out to be a blocked pilot jet removed the jet cleaned and replaced now tickover perfect.

Title: Re: Idles great when cylinders isolated Both working lumpy/missing and at low speed
Post by: muskrat on 23.08. 2019 21:52

G'day Barry.
Have you cleaned the slip ring thoroughly? Sparks may be tracking.
Most mag problems are carb related  *pull hair out*. I agree with Bob and Billy, give it a good clean out. Ultrasonic cleaners are good for doing the pilot circuit.
Cheers

Title: Re: Idles great when cylinders isolated Both working lumpy/missing and at low speed
Post by: chaterlea25 on 23.08. 2019 22:34

Hi All
Agree with Muskie, Shagged slipring
Been there  *sad2*

John

Title: Re: Idles great when cylinders isolated Both working lumpy/missing and at low speed
Post by: duTch on 23.08. 2019 22:46

 double ditto re skpiring- even though you say you did it, maybe do again... same symptoms I had not so long ago

Title: Re: Idles great when cylinders isolated Both working lumpy/missing and at low speed
Post by: morris on 24.08. 2019 20:01

I’d go for the slipring too. Usually the problem is too soft brushes leaving a carbon path which makes the arc jump around the slipring. Cleaning the slipring will only solve the problem (very) temporarily as the brushes will soon leave carbon deposits on the slip ring again and the misfire will be back.

Title: Re: Idles great when cylinders isolated Both working lumpy/missing and at low speed
Post by: barry2 on 25.08. 2019 07:35

Hi Mates
I was the slip ring, Fist time I cleaned it w/ meths , this time I got some 240 W/dry paper in there and kicked it over w/- the plugs out , back to normal now, will get some harder brushes, thanks for all the help
all the best Barry