Reinstalling carbs with old, hardened carb boots in the airbox is a drag so this post is about reconditioning old, hardened ones when someone doesn't want to buy new boots.
I have some carb work ahead of me this winter but my carb boots are old and hard. They won't fold/flip/turn back onto themselves to secure with zip ties for carburetor installation. Since I can't afford to spend the money for nice, new, pillow-soft boots I spent the last hour searching online for how to soften rubber. I read through a lot of vehicle restoration forums and read numerous suggestions, such as using heat, olive oil, motor oil, brake fluid, atf, armor-all, glycerine, silicone grease, dialectric grease, wd-40, gasoline, or even orange hand cleaner.
Finally, I found, what I believe might be the answer -- Wintergreen oil, using Xylene as a carrier (or wintergreen mixed with water). No, I'm not kidding. Wintergreen oil, also known as Oil of Wintergreen. It's chemical name is methyl salicylate.
The people on the Single Over-Head Cam 4 Forums seem to have figured this out, while rebuilding Hondas. Here are the links to their postings on this topic: http://forums.sohc4.net/index.php?topic=29707.0http://forums.sohc4.net/index.php?topic=49393.0http://forums.sohc4.net/index.php?topic=62328.0
Some of their members experimented with different solutions and some believe that water makes just as good of a vehicle to carry the wintergreen oil into the rubber than xylene (which is supposedly commonly available at hardware stores and Home Depot). Xylene's primary industrial purpose is as a thinner or carrier, and it's meant to evaporate completely from whatever it's thinning (ink, rubber, resin, paint, or adhesives).
"I have been using a mixture of 30% wintergreen oil (methyl salicylate) and 70% xylene to restore old rubber parts and it works beautifully. This is the same ingredients and proportions for the commercial product Rubber Renue according to the MSDS sheets."
I read through most of these posts and saw very little contradicting the Xylene-Wintergreen or Water-Wintergreen methods....Except for one guy who used Xylene-only and got good results and another guy who also tried the water method and his boots wound up gooey--but they may have been chemically-damaged before he tried his restore with hot water and wintergreen.
Ratios, Volumes and Soak/Simmer Times:
- Two ounces Wintergreen and 1/2 gallon of Xylene
- Put 4 oz of Wintergreen in a can and place boots into it. Pour enough Xylene to cover the boots. Leave until soft.
- 8 oz of Wintergreen and one gallon of water (which you must heat and keep stirring)
- Put ~2oz of wintergreen oil into a pan with enough water to cover a set or two of carb boots (maybe 1/2-3/4 gallon depending on pot size). Put a screen in the bottom so they don't touch the pan, and heat them to near boiling (when those little bubbles start forming on the boots) for 30 minutes
- 30% wintergreen oil, 70% xylene. (4 oz wintergreen to 13.5 oz xylene), soak for 12 hours
- 8 oz wintergreen to 1G water and simmer them at 200F
- Simmer in the wintergreen oil/water for about 2 hours
- Simmer the carb boots in a solution of 4-8 oz Wintergreen to about a gallon of water at 200F for between 15 to 30 minutes
- 4 oz wintergreen in 1/2 gallon of water, heat to just below a boil for 15-20 minutes
- Wintergreen oil and boiling water with a pan and a vegetable steamer to keep them off the bottom of the pan. Soft and supple after 20 minutes.
- 4oz wintergreen and 1 gallon water, simmer for 1 hour
- 4oz wintergreen, enough water to cover the boots and 30 minutes boiling
Some of their guys claim their boots are still as soft and pliable two years after wintergreen oil treatment so I'm going to try it. The xylene's job is to introduce the oil inside the rubber. When the xylene evaporates away, it leaves the oil inside. I'm pretty sure the hot water method just makes the rubber soft enough for the wintergreen to penetrate without a solvent.
They say that Wintergreen oil can be located at pharmacies, online, and ebay so I'm not going to reinvent the wheel here and experiment with other oils. I'm going to try this in the near future and I'm leaning towards a xylene mixture. Not letting the boots sit in the mixture too long seems to be a caveat. If anyone else wants to give it a shot, please post your findings.