starting up on one cylinder

[paulwolf]

Can anyone help me with the problem on my 1993 Commander,When i start it from cold with full choke it fires on both cylinders then go to one and the rev counters stops working,after about 2 mins the other cylinder comes in and it is then ok untill i stop,even for 5 mins because when i come to start it again the same thing happens,it fires on one for about a 30 sec with no rev counter then the other cylinder comes in the rev counter works and it goes like it should.I have changed the plugs and cleaned the connetions in the plugs going to the ign module but it is still the same,.Thanks Paul

[Richard Negus]

Hi Paul,The tacho takes its signal from from the negative terminal of one coil. I can never remember for sure whether it's the black/white wire or the black/yellow; the latter I think. No signal from the ignition unit to that coil = no spark+no tacho. Since it mends itself after a short while suggests that there's an intermittent connection. There are blade-type connectors at the coils, a squirt of WD40 and a good 'wiggle' may cure the problem. The coils have a short sub-harness to the main loom with a three-pin connector - corrosion in there may also be the cause of the problem .If those connections are all good, then suspect the ignition unit itself. Improved replacement units are available. www.minimagneto.co.ukR.

[paulwolf]

Hi Richard,Thanks for the reply,i will check what you said and see how i get on.Thanks Paul

[paulwolf]

Hi Richard,I bought a new ign unit from minimagneto and it fixed the problem,Thanks for your help.Paul

[Ian]

My Commander has done this since I bought it in 1995!If I use it daily it's fine. If I leave it for 2-3 days or more it starts on the right rotor only, after about half a mile and much spluttering and banging, the second rotor chimes in and then it's fine all day.I've put this down to the frame drain doing it's best to drown the LH plug. Have I had a Boyer (it's still the original) that has been failing all this time?If I need a new ignition to cure this should I go for Graham's Minimag, which seems fine or is it better to go large and use ANIL's digital unit with new coils, etc. Assuming they're still available.Ian

[Richard Negus]

Ian,The usual fault with Boyer ignitions is that they're ok when cold, but fail as they warm up. I would, therefore, suspect something else such as a corroded connection somewhere between the ignition unit and the coils.I know access 'up there' is somewhat restrictive for normal sized hands, but changing the tacho connection (the yellow wire) from one coil to the other will tell you if it's an electrical fault, or carburation/mechanical.You could eliminate the scavenge pipe as the source of the problem by temporarily blanking it off.Do you usually leave the bike on the centre or the side stand?And the perennial question - when were the carbs last overhauled and re-set?R.