'29 to '31 starter motor type?

[Howard Wright]

Quite right Howard except the one on the RN I bought 40 years ago, it looked correct but the engine would't start because it was running the wrong way.

Hi Dave

It may well be that CAV starters of this type were fitted to other makes that required anti clockwise starting?

Rupert if you find a CAV starter check it is correct by making sure the quickthread is LH.

Cheers

Howard

[Dave Mann]

No Howard somebody had been at it, it now works correctly.

[Steve kay]

On the subject of starter motors, many of the books indicate that they are robust enough to be used as 12 volt, as well as the 6 volt originally installed. Does anyone have serious reservations about this?

[Charles P]

On the subject of starter motors, many of the books indicate that they are robust enough to be used as 12 volt, as well as the 6 volt originally installed. Does anyone have serious reservations about this?

I used mine on 12volts for years. It did get through brushes fairly regularly but since the engine is pressure fed I insist on turning the engine over on the starter until I get at least 10 pounds on the gauge. I figure that way No 4 big end stands a better chance of being adequately lubricated. 

C

[RupertW]

Many thanks all for all the input.

Quick question on starter button amperage ratings - even the heavy duty generic ones I've seen seem to be rated for only about 50 or so amps which I'd think is well below what the starter would draw, especially on a 6v system. Is the amperage rating for continuous current, and so okay to use for a starter motor as it would hopefully only be used for a matter of seconds at a time?

[Dave Mann]

Most Seven starter switches I've opened show the signs of 90 years of abuse and I dress up the contact faces before use. I've run three Sevens on 12 volts for about 30 years and have never experienced a switch failure despite handling a lot more current than originally intended. The starter motors just work but I think it is important to check them over before use.

[Robert Leigh]

When a six volt starter is used on 12 volts the current drawn initially is higher than when using six volts, but it very quickly drops as the motor gets up to a higher speed than in the original application. My Ulsteroid is using the same motor as I fitted 20 years ago and seems very satisfactory operating from a 12 volt motorcycle battery.

[Steve kay]

Thanks for starter motor info. I have a much rebuilt magneto engine that is proving just a bit difficult to fully complete. It fired up well, but showed no oil pressure. So turning over an engine with plugs removed has been a nessecary part of the diagnosis procedure to find out what isn’t working. A starter failing to work more than briefly suggests that there is a starter problem. If Charles can spin enough to get 40 lbs on a hc engine, I should be able to get some lbs with no compression at all!

[Charles P]

Thanks for starter motor info. I have a much rebuilt magneto engine that is proving just a bit difficult to fully complete. It fired up well, but showed no oil pressure. So turning over an engine with plugs removed has been a nessecary  part of the diagnosis procedure to find out what isn’t working. A starter failing to work more than briefly suggests that there is a starter problem. If Charles can spin enough to get 40 lbs on a hc engine, I should be able to get some lbs with no compression at all!

Only 10lbs Steve, and it’s a blown engine so the static compression at starting isn’t horrible. 
After any major work or an oil/filter change I always take the plugs out an spin it up to pressure, to give the starter an easier time.

C

[Steve kay]

Charles, us Ruby trundlers wander round paddocks and lawns always amazed by the mighty machines whose evolution began at Longbridge, but are now almost much faster and always sound better than lesser marques! My experience has indicated that the rear facing starter was almost indestructible. The great similarity of the forward facing starter suggests it should also be, it has been recommended as such on the forum. Forumists now tell me that a bacon slicer should be able to a spin a plugless engine enough for me to find out whether the little challenges I have are to do with indicating oil pressure, or generating it.