if it lives outside just do solar. cheap and easy to setup.
a switching circuit is asking for trouble. done wrong or if it fails you could have fire, explosion, acid everywhere and at worst no more machine and if your there when it happens nasty chemical burns. i have seen batteries explode it bathes everything near by in sulphuric acid. I've had acid burns from working around batteries its not fun.

the only other method is get a pulley made to take the fan belt and mount it to a alternator and have a longer fanbelt no it wont charge much as the rpm will be a bit low.
or go down the route of making a adapter out of the generator. you can make one using a piece of steel plate 2 inches of pipe, a pair of sealed bearings and a bit of shaft keyed and threaded to take the drive gear with a lovejoy coupler or belt pulley to drive the alternator.

the reason i modded the generator was it was easier for me to do and less work.

www.trucksales.com.au/editorial/details/...hes-explained-60122/

www.ebay.com/itm/303172335420

quick question what are you starting the main engiune or the pilot engine. if starting the main as in direct start you will need bigger batteries a pair of 58's or NS50's will be needed. and of course a larger box. its better to have a electric start pilot than a direct start main with these old girls as you need to build heat by turning the engine over unless it has been modified with the later model precomp chambers that had glow plugs. you also need to wind it over to build oil and fuel pressure. and this takes more battery capacity.

yes that soleniod josh described would work. and is from a electrical standpoint a very heavy relay.

and it would be the safe way to do it. not cheap either. abit more searching might get you a better price.

Thank you Josh - nice to see that there's a commercial solution available that does exactly what I want.  I will definitely be looking into that.

Trainzkid88 - direct starting of the diesel engine - not the pony.  Ok, bigger batteries then, that's not a show stopper.

I don't expect that my grader has the glow plug upgrade.  I know that the pony motor isn't working, so I think that the current owner is just bump starting it with a tractor currently.

if you want compact high output batteries the optima redtops are a good choice too not cheap but they give more performance compared to standard cranking batteries of the same physical size.

i would try and find out why the pony doesnt work. it might be a simple fix and then you have the best of both. direct electric start. and pilot start if the electrics die, you run it out of fuel or it's freezing bloody cold and wont start directly. might not get snow but we do get frosts and sudden cold snaps on occasion.

Hi Langdon How are you? I have a factory direct start d6 9u d318 engine not many factory direct starts in oz mine might be only one lots converted ones, it as glow plugs and an either pump on fire wall never used it. Just warm up glow plugs and good to go, it also has hand pump for bleeding injectors people argue its converted but clutch housing is not drilled for shaft to engage pilot motor bendex. You can fit glow plugs buy getting pre coms for like my 6 but different size thread into the head , i had a turner friend of mine turn some doown to right thread for lance jones precoms about fifty dollars. I doubt she will start with out glow plugs giggle juice in the can might be needed i dont like it they get addicted lol old 6 always needs heat and engine is good. fully charged bateries is the go to so she swings over quick kel

Hi Langdon How are you? and its 24 volt start with a 19 amp 24 volt genny which has the idler gear in the drive to spin genny faster kel

keloz your not the only person who ive heard say that about starting fluids (ether). its probably more that we the owner get lazy and dont replace the worn electrics and rebuild the fuel systems when we should. becuase it so easy to reach for the can. and the cheap stuff is harsh on them.