I have used "Brake Clean" on a couple of engines I didn't take apart, it will take all the grease, dirt and most of the paint off :thumbsup: I use a brass tooth brush and a blow gun hooked to my compressor to get into the tight spots :thumbsup: DO NOT spray it on the crank seal, its not good for the seal :doah:
DANGER!!!!! DO NOT USE PURPLE CLEANER ON ALUMINUM ENGINE PARTS!!!!! I don't mean to demean Jack's post up above but most of the purple cleaners contain sodium hydroxide which causes a chemical reaction when brought into contact with aluminum which eats the aluminum and produces copious amounts of heat and highly explosive hydrogen gas. Don't believe me? Go to Lowes; buy some purple degreaser, put it in a plastic container outdoors; drop in an old aluminum cylinder head and watch it begin to boil. I use good old fashioned kerosene and a parts brush to get the heavy gunk off of my motors; followed by a pressure wash; and then an hour or two of work with q-tips, dental picks, acid brushes, and gunk. Once that's done I glass bead blast and spray down with prepsol and you're ready for paint. It might be old school but it works every time. Ogy
I clean a lot of aluminum with purple cleaners of all concentration and have never seen boiling. If you have polished aluminum, it will haze and have to be repolished. But otherwise, aluminum brightening solutions are acid based and purple stuff is just citrus oils which are naturally acidic.
Glass beading and media blasting is great for loose parts but risky for anything assembled. Grit will get past seals and breathers and find it's way into the oiling system every time. Also, there will be embedded media so if you're going to paint it still needs a complete light sanding before primer.
Aircraft paint remover can be a good option because it's not hard on the ends of gaskets. You do have to thoroughly rinse afterward which weirds some people out, but use reasonable airflow and maybe some heat when drying and there should be no concern. Any kind of oil or grease on the surface will act as a masking agent for paint removers (or acids) so degreasing should always be the first step in paint removal.
With chemicals, anything you do to sand the paint beforehand will increase effectiveness.
At the end of the day though, it's always going to involve cramped fingers
Good luck with your projects!
Glass beading and media blasting is great for loose parts but risky for anything assembled. Grit will get past seals and breathers and find it's way into the oiling system every time. Also, there will be embedded media so if you're going to paint it still needs a complete light sanding before primer.
Aircraft paint remover can be a good option because it's not hard on the ends of gaskets. You do have to thoroughly rinse afterward which weirds some people out, but use reasonable airflow and maybe some heat when drying and there should be no concern. Any kind of oil or grease on the surface will act as a masking agent for paint removers (or acids) so degreasing should always be the first step in paint removal.
With chemicals, anything you do to sand the paint beforehand will increase effectiveness.
At the end of the day though, it's always going to involve cramped fingers
Good luck with your projects!
I used a bunch of stripper and it took off quite a bit, but not enough. Bought a $ 14.00 sandblast gun with hose and feed tube off Ebay and a $3.00 bag of play sand (sifted through a window screen first) and it got off EVERYTHING !! Then washed with soap and water and it was ready to repaint. Turned out great and way easier than stripper. Cheap & effective.
I second whay OGY says. castrol super clean and most of the purple cleaners are very strong alkaline solutions. while boil may be a little much they will foam and turn the aluminum black. Even mild solutions of simple green will turn it black. Simple green aircraft is ph balanced and is safe for aluminum. Not sure of the citrus based orange solutions
The US Navy/Marine Corps stopped using it, because of it's corrosive reaction with aluminum. No loss. When they took away the PD 680 and trifluoro trichloro methane, we were done cleaning down to the bone anyway. 
I use regular paint stripper and rubber gloves with bits of 3M pad cut to squares. I scrub while the stripper is still working. I rinse with a product I found called "Awesome Cleaner." Don't know what it is, but it beats anything purple, hands down.
I use regular paint stripper and rubber gloves with bits of 3M pad cut to squares. I scrub while the stripper is still working. I rinse with a product I found called "Awesome Cleaner." Don't know what it is, but it beats anything purple, hands down.
Although NOT cheap...hands down the best way to prep an engine for paint WITHOUT having to take it apart is to SODA BLAST it. It's water soluable...and it will get in all the fins and hard to reach areas, leaving you with a perfectly clean engine ready for paint. It won't cause any harm or leftover residue...Just be sure to take off the carb/air cleaner and cover them properly.
Yes, it's expensive, but if you do a lot of engines it's 100% worth it. I went to harbor freight and bought their 40lb tank...I rent a high end compressor for $35 for 4 hours and I do multiple engines at the same time...The soda media is expensive ($35/bag) and isn't re-usable...so I can see why a lot of mini bike buys might not prefer this method...but if you want it done right, this is the best way to do it!
Yes, it's expensive, but if you do a lot of engines it's 100% worth it. I went to harbor freight and bought their 40lb tank...I rent a high end compressor for $35 for 4 hours and I do multiple engines at the same time...The soda media is expensive ($35/bag) and isn't re-usable...so I can see why a lot of mini bike buys might not prefer this method...but if you want it done right, this is the best way to do it!
The US Navy/Marine Corps stopped using it, because of it's corrosive reaction with aluminum. No loss. When they took away the PD 680 and trifluoro trichloro methane, we were done cleaning down to the bone anyway.
I use regular paint stripper and rubber gloves with bits of 3M pad cut to squares. I scrub while the stripper is still working. I rinse with a product I found called "Awesome Cleaner." Don't know what it is, but it beats anything purple, hands down.
I use regular paint stripper and rubber gloves with bits of 3M pad cut to squares. I scrub while the stripper is still working. I rinse with a product I found called "Awesome Cleaner." Don't know what it is, but it beats anything purple, hands down.