You're very welcome on the chemical tips.
Most parts washers use mineral spirits. Something I didn't mention is that kerosene and diesel are very similar and actually have a higher flash point. Whatever you do, don't use gasoline. Even though it doesn't have lead in it any more, it is flammable. I had a carb on a 64 1/2 Mustang backfire and belch gasoline on me. I looked up and my hands were on fire. Then I noticed my head was on fire! Did a great Richard Pryor imitation as I ran down the driveway with my hair on fire. Lit up the night sky in a spectacular fashion! I used my jacket to smother the fire on my head. That coat still has flash in it after many washings. Grimmmmm....
Back to the solvents. With regard to skin contact, these aren't corrosives (like oven cleaner, etc.) but it will "de-fat" the tissues. Think of it this way- if it will take the oil off your part, it will take the oil out of your skin. Either use gloves or put some oil back in your skin with lotion. Black rubber gloves aren't too good. Solvents will soften them. The best glove is actually cheap and light weight. Look for some light green nitrile gloves. They provide good chemical resistance and lightweight enough to give you some good dexterity.
I have a buddy who owns his own ATV repair shop and has permanently gray stained hands he says is from working in solvent so many years. Could be.
As for the trike, its probably 111 trichlorethylene or trichlorethane. One was banned and one is still available. As I avoid chlorinated solvents like the plague, I forget which one right now. In any case, we haven't been able to use these ingredients in the industrial market for years yet you get a whiff of it every time you use a magic marker or the older version of "Liquid Paper." These chlorinated chemicals are not friendly to your kidneys, eyes, liver and brain. Pretty rough on the environment, too.
Again, I don't hug trees but I do love to ride between them at a high rate of speed. ;)
One little tip that may help- there is a chemical called M Pyrol or Methyl Perillidone (sp?). It is common in paint strippers. If you can get a hold of a little of that, its a great carbon remover. Dissolves carbon great! Cuts paint pretty good, too. Its expensive but doesn't evaporate too quickly. It also has a very high flashpoint for better safety.
My father loved the stuff. He cleaned out a few engines with it. Tried on his 310 hp turbocharged airplane engine. Then he found out they paint the insides of the valve covers with epoxy paint. Did I tell you how good it eats paint? Cost him $2000 in repairs and almost a $20,000 engine. Ouch.
One more thing, you may want to remove any rubber o-rings or other rubber parts. Solvents can deteriorate rubber. Some of mine will make an o-ring swell up big time. Mineral spirits shouldn't be much of a problem but why risk it?
Even though these are really mild, please put on a pair of safety glasses. Back in the 70's I was cleaning a carb with aerosol carb cleaner. It back splashed into my eyes and I ended up in the emergency room. Ever had blisters on your eyes? Good news, the eyes heal faster than any organ you've got. Best plan- protect your eyes first so there won't be any healing needed.