Won’t start after hot

[EricBorg]

Hello all,
So my W/NG will (mostly) start first kick from cold but after I go for a little ride and the engine warms up it won’t start again unless I change the plug, (so I now carry a spare plug) what is causing this to happen???
After the plug cools down it’s good to go again.
Thanks for any advice.

[JohnnyBeckett]

i thinking it can be the mag and wen you put a cold plug in its got less resistance and it will start i know mag can play up wen it gets warm by the time you put a cold plug in its cooled down enough to start i am not saying i am i am right but this what i would look at fist

[alan.moore]

I tend to agree with Johnny, the issue you describe points towards the magneto, in particular problems with the capacitor which is buried deep inside the mag.

Has this problem just started or has it been getting worse over a period of time?

You could try a new HT lead and non resistor plug cap but my bet is on the mag capacitor / mag itself.

Cheers
Alan

[EricBorg]

Thank you for the replies,
The problem only just started with the plug.
so if a new HT lead and cap don’t fix the problem what would be my options? Send the mag off to be rebuilt??.
Any recommendations please?

[Petebarn]

Had the same problem on my NH had the mag rebuilt by mr cooper hey presto problem resolved. Pete

[paul.jameson]

I had exactly the same problem on my RH350, about 20 years after the magneto had been rebuilt. Some careful cleaning of all connections, etc., improved things slightly but the answer was to have the magneto rebuilt by Tony Cooper. It was money very well spent.

[nevhunter]

it's usually the condenser OR the coil. Both tend to break down after many years and it usually takes an hour or so 's riding but can be less and the motor may miss and not want to run at low revs.. Often the "shellac" (I'll call it that ) will come out of the windings and sometimes it will seize the armature when it cools and you can damage the shaft/chain when you try to kick it over. It's hard to tell how long an armature will last but as they fail they leak current and run hotter. I usually just send the armature away to be rewound by someone I trust and put it back together myself saving a lot of money and having more peace of mind as to how well it's assembled. It generally needs remagnetising as well, so If you don't have a good remagnetiser, (and that's unlikely) you will need to arrange that. You also need a proper puller for the races to shim the play of the bearings,. Nev

[simon.holyfield]

I'm absolutely on board with the comments about the magneto, and particularly would recommend Tony's services as he has done two for me. Folk often don't realise what a magneto can be like until they have experienced a rebuilt one.

However, I would point out that my W/NG is quite sensitive when hot and is easy to flood. The secret is to be aware of how warm it is and act accordingly.

[EricBorg]

Thanks again for all the replies, looks like the mag will need a rebuild.
Can someone please let me know Tony’s details as I live in Malta so would need to ship it to him. I assume he’s in the UK.

[PeterW]

Agree about the mag - a big spark always helps - but it does sound like its flooding. I doubt the mag is cooling much in the time it takes to swap a plug.
I find mine starts well from cold (tickle & choke & smidge of throttle) and hot (no tickle, no choke) but after a run then being left for a bit can take two or three attempts (I usually try a small tickle & a tiny throttle) but its easy to flood it.
Just out of interest is the carb getting hot?
Also, do you have a decompressor so the engine gets a decent spin?