Losing Spark on One Rotor

[David Rodgers]

I am currently in Spain 27c and the Classic has started to drop onto one rotor when hot. I have ruled out fuel starvation and suspect it is something electrical, just swapped the plugs over to see if that pinpoints it if it loses the other rotor tomorrow. After that i could try swapping the coils over. Any other suggestions?Dave

[Richard Negus]

David,You've got a Boyer ignition unit which is generally known to dislike being hot, and stop sparking on one rotor. Can you move the ignition unit, currently between the carburettor and voltage regulator, to a different location where there's a bit of fresher(er) air around it?

[David Rodgers]

Hi RichardThanks for the reply, I swapped the plugs over and had same problem ie the left rotor dropping out. So tonight I have swapped the coils over and will see which rotor goes down tomorrow. If it swaps to the right it will be the coil. If it is still on the left then I will try to get more air to the Boyer. It runs for a short period when cold so should be ok to get to the ferry next Monday, it is just frustrating not being able to do the full days ride out. I will keep you informed.David

[Dell Boy]

Have you tried new plugs? Showing classic symptoms of a duff plug.Derek F.

[johnbirchjar]

Hi David,you may find that the VR is cooking your elect/ign;box (if they are still back to back)the VR gets well hot and where it is situated on Classics hardly any cooling air gets to it,so it fries itself AND the ign:box My Classic had three each of these within 50,000 miles before I cottoned on and moved the VCR to where it got some cooling air,only time(and milage)will see if that solves the problem, I don't know of another Classic that has done the same sort of milage as mine, so we connot compare notes, good luck and ride safe,J.B.

[David Rodgers]

I have now swapped over the plugs, plug leads and coils and tried test running between each swap ie one thing at a time. It always loses the left rotor once the engine is hot which is between 6 and 10 miles. I have taken the Boyer away from the VR and left it loose behind the side cover so that it has cooling air on all sides. I noticed wheni stopped with it running on just the right rotor that the Boyer was not particularly hot, just warm. When i tried the bike again after 30 mins it ran on two rotors for about 5 miles then lost the left rotor again. I suspect it can only be the pickups/senders or the boyer box itself, but i am a novice with this bike so what do i know! I will ride back to the ferry on monday as it is only 5 miles from the Hotel and then get recovered from Portsmouth. Get it sorted when back home.David

[David Rodgers]

Have you tried new plugs? Showing classic symptoms of a duff plug.Derek F.

Just out of interest what sort of mileage do you get from a set of plugs?Dave

[gripper]

Whilst it is not a perfect test, if you wait until it is running on one rotor and then attach a plug to the failed side and earth it out, do you get a spark?

[David Rodgers]

Grounded out the plug on the fins and got virtually no spark. Just the weakest of sparks, not enough to fire the rotor.Dave

[David Rodgers]

Having been recovered home from Portsmouth i took the Classic over to Richard in a van. We swapped my Boyer for his spare one and eventually got it running ok, so we know it was the Boyer black box failing. The eventually was another problem that cropped up, namely the new Ethanol proof 'stay up floats' staying up when they should have been moving with the fuel. This caused the engine to die as the carbs emptied which added to the head scratching. Richard fixed this with one of his special precision tools ie a hammer, normal floats have now been fitted.So the old Boyer will be returned to them as it has only covered 2500 miles and i will be contacting minimagneto about their Digital Ignition System, does anyone have experience of this system? How does it perform?Dave

[gripper]

I fitted one of these to my IP2 about 2.5 years ago. I think they are a good piece of kit, combining the retard electronics and giving 25 revs of advance to restart when hot. A small led gives you a bit of an idea as to what is going on. It's probably the single most useful mod I've put on my Rotavator. As an aside, In the last two years I've had to replace the voltage regulator rectifier (twice first one only lasted about 5 months (electrex)) ignition trigger after the French NOC rally, and just today the retard switch. The trigger caused me no end of trial and tribulation and while I carry few spare parts on long runs this might be worth a think about. Trouble is to get at it is a gearbox outer cover off job. Spark plugs last me ages. I carry spares but they have never let me down. ........... I've done it now.

[johnbirchjar]

I've had a Minimag box on my Classic for ages,good bit of kit,and the guy that makes them is well helpful,rgds,J.B.ps,see else where on our forum about re-locating the VR

[David Rodgers]

Thanks Gripper and JB for the feedback, i have ordered a TT1 from Julian. John what page no and heading does the VR item come under, i have been through all seven pages but may have missed it. Thanks.Dave.

[johnbirchjar]

Hi David,It's on "5" of this very topic ,rgds,J.B.

[David Rodgers]

Just letting you know the final outcome (hopefully), the TT1 ignition is now fitted and the Classic starts easily Cold or Hot and ticks over with no 'hunting'. The sticking floats re-appeared after the bike had not been used for over a week, a couple of taps with the hammer on the flanges sorted that out. So the new Ethanol proof stay up floats were not the culprit, is this a known problem with the SU's.Dave