Dynastart output

[David S]

I'm helping a hard-up friend to restore a 1970's Springer with a single cylinder Ducati. The boat has already had a new bottom, and we have rebuilt the gearbox but the remaining problem is working out how to get a charge out of the dynastart. It turns the engine over easily with valve lifted, and the engine starts and runs acceptably but I can detect no measurable output.

 

Previous enquiries on the forums on this topic have been helpfully answered; particularly by Sir Nibble, so I PM'd him with my problem. Thanks for your reply Jerry and I gather you'd rather deal with such queries in the forums. I'll paste your reply here if you don't mind, so we can start from the beginning.

 

<<No, I don't do that sort of work any more.

Suggest you get it running, connect a volt meter to D+ and see what you get, now do the same with a jump lead connected from DF to earth, if that brings it to life then you need a regulator. If you like I will try and help with fault finding but I would prefer it posted on the main board 'cos the pm system is more hassle to use in the five minute bites I have available.

Jerry>>

 

I have already tried all kind of combinations of connections with the engine running but so far without a meaningful reading from the meter. Can I start by asking 2 very basic question?

 

1. Any normal dynamo will run as a motor when a suitable input is connected. As the dynastart spins the engine with no problem, am I right in assuming there can't be much wrong with it?

 

2. As there don't seem to be many people who admit to any expertise on dynastarts, but several around the UK who advertise that they will rebuild dynamos, could I take it to one of these for testing or are the two machines fundamentally different?

 

Many thanks

 

David

[Denis R]

Don't know if it helps, or even if it's the same unit, but this site has some information that might be useful, especially regarding the fusible link....

DynaStart Info

[Sir Nibble]

Dynastarts have two sets of field coils wound on the same poles, a series set, heavy guage wire with low resistance carrying the start current, and a shunt set of around 8 ohms powered from the +ve brushes and given it's return via the D+ connection through the regulator. These shunt windings which take little part in the start function have a habit of collecting internal shorts resulting in higher and higher field current until the reg burns out.

Connect a 20A ammeter from D+ to -ve (with D+ cable disconnected) and operate the starter, should see no more than around 2A.