Any ideas welcome - starts perfectly when cold, not once it's hot

[tlmark]

Hi Guys
Any ideas welcome on an issue I'm having. My A10 starts perfectly when cold, but will not once it's hot. Even a one mile ride to the petrol station results in  6-7 kicks to start.
on one occasion I was at a bike show it took me and 2 others 45mins to get it going we couldn't get a spark then it would suddenly spark I've changed plugs cleaned the points checked the earth bush on the mag, I'm wondering if its the condenser? she had a total engine rebuild last year so I don't think it anything mechanical, not least in the motor anyway, it's done about 700 miles since the rebuild.

Adm edit: title edited to include topic subject. & moved to correct board.

[lawnmowerman]

Hi tlmark

Certainly sounds like the condenser to me. You could try cleaning the slip ring before you part with your hard-earned - if it is covered in carbon the brushes may be too soft.

Jim

[duTch]

 That's exactly the same symptoms I had before having the Maggie overhauled (twice)- bike show and all, for six years I'd ride a mile to the show and spend the last half of the day getting started again to ride the opposite mile back to the 'ranch'...

 First time it was just old and crusty, second time was a dodgy slip-ring had a hole in it earthing to the shaft...

[mikeb]

as lawnmower man says, a dodgy old capacitor can do that (did on my b33). i *think* most fail open so adding an easycap at the points (ie, in parallel) *may* buy you some time, but also it may not help at all... luck of the draw.
there will be someone along in a minute to say this is a bad idea etc. its certainly not what you are supposed to do AND it may help for a while.

[metalflake11]

Classic symptoms of mag capacitor failure..........BUT.... I have had the same symptoms, once when the plug leads have failed, and another time when the metal inside those rubber plug caps had rusted badly. One had actually split.

Start with cheap and easy solutions every time!

The H.T. Lead failure became expensive for me. Mag rebuild and new carb before I changed the leads to fix it!

[tlmark]

Hi Guys

Thanks for your comments. It's good to hear my suspicions about the fault seem to be on point.

I'll look a stripping the Mag and checking it over and maybe some new leads to on the safe side.

[lawnmowerman]

Hi tlmark

I am not sure if you have had a K2F apart before but it is not for the faint hearted. The physical stripdown is fairly straightforward but the windings need to be tested also as they may be going open circuit when hot.
I had a professional rewind mine and fit a new condenser and never had a starting problem since.
There are many recommendations for mag rebuilders on the forum.
Apologies if you are familiar with rebuilding mags - just did not want you to end up with a pile of mag bits in a biscuit tin and possibly an even bigger problem

Jim

[Greybeard]

I had a professional rewind mine and fit a new condenser and never had a starting problem since.

Every time my bike easily starts I thank the god of motorcycles that I had my mag professionally overhauled. It was expensive but soooo worth it! 

[tlmark]

Nope never even seen a mag until I bought my A10 
So its all new to me. Sadly I'm also endowed with foolish confidence and always think I can do something.
I'm In two minds everybody keeps telling me to go electronic ignition and wave goodbye to start issues. But I like the fact that it's still all old tech but also it's no fun not being able to ride it anywhere for fear of it not starting.
mag rebuilds can cost a lot too and I have looked at the Thorspark electric system which seems reasonable. 

[Shark]

I spent more on a shop mag rebuild than electronic would have cost and I am happy with the mag rebuild? Yes indeed!! Would I do it again?? Nup I would buy the electronic system.

[ironhead]

Nope never even seen a mag until I bought my A10 
So its all new to me. Sadly I'm also endowed with foolish confidence and always think I can do something.
I'm In two minds everybody keeps telling me to go electronic ignition and wave goodbye to start issues. But I like the fact that it's still all old tech but also it's no fun not being able to ride it anywhere for fear of it not starting.
mag rebuilds can cost a lot too and I have looked at the Thorspark electric system which seems reasonable. 

G'day TL. A properly sorted maggy will be far more reliable than trusting your power source on the standard dynamo set up. Belt drive, 12v armature, LED lights etc etc may help but IMO I'd sooner ride  across the Nullabor
with a good maggy any day.

[metalflake11]

Car, bike, truck breaks down they sit at the side of the road. Boats bob about in the sea broken down.

Multi engine aircraft can fly with just one working. If a single engine aircraft breaks down, you are in big trouble!...........They have magneto ignitions!

Says it all!

[Shark]

Correct Metalflake, but those aircraft you mention have two of everything in the ignition system so if one fails you won't "fall out of the sky", they also have a mandatory "time between overhaul" which should keep them safe and they are only serviced by licensed aircraft engineers. I would not fly in a "lighty" that only had one ignition system with an unknown service history even if that system was a magneto.

[mikeb]

i don't think i'd take a plane if i knew the mag was made by Lucas.
but i do plan to keep mags on my bsas.
there are modern self-generating electronic systems that won't load the dynamo / electrics but hardly cheaper than fixing a mag and probably won't last 60+ years like these have.

[Bsareg]

I wonder how much of the magneto's poor reputation is down to bad rebuilds. I've  just had to rebuild my nephew's professionallly rebuilt mag after it failed. Nothing wrong with the rewind or the condenser used, but very sloppily reassembled, loose bearing, wrong oilseal, incorrect shimming. No mag will last long if the armature is rattling about in oil.