There are a couple of ways. by (Login BlacksmithCycles) Horsemen

I would also get one of those replacement covers for the solenoid that is a manual push button. When you push it in it makes the contact for the starter as well as pushing the gear into engagement. You CAN take the cover off the solenoid and push in on the plunger. I don't recommend it though unless it is a last resort. When you let go of it, the spring will push it back out and if it comes out a little too far or gets crooked it will make a nice light show inside the solenoid!! You can drill a small hole in the solenoid cover and use something to push in the plunger. Lots of people make their own push buttons this way. I believe Ripper (I think it was him) posted up here years ago how he did it.