Softening Solution For Rubber Parts

In the Shed
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The rubber air funnels for my VF1000F (USA) were super hard and had shrunk over the years, almost to the point where they wouldn’t fit properly anymore. I’m not sure if there has been any articles here about it, but on the V4 Muscle Bike forum, there was a thread talking about a softening solution consisting of wintergreen oil and isopropyl alcohol, and I think sharing it here might help a lot of folks. In the article it was used on the carb boots, but mine were in great shape and still soft, so I used it on the air funnels.

It consists of 1 part wintergreen oil (it is cheaper to buy it as methyl salicylate rather than wintergreen by name), and 3 parts alcohol (I used 91% isopropyl alcohol), and 3 days time to soak.

Life got in the way and they spent an extra two days in the solution, but according to the article they can sit for up to 6 months without damage. They are now extremely soft and pliable. They have also swollen up a little bit. The article said they should shrink down a little bit over the next couple days, as of now they need a little bit of massaging to slip into the groove on the carb.

Here are my results (600g hammer for reference, balanced loosely on top)

Before

before front
before front1920×2560 371 KB

before side
before side1920×2560 379 KB

After

after front
after front1920×2560 383 KB

after side
after side1920×2560 293 KB

The images really don’t do it justice, they are literally like brand new, if not softer.

I will post updates on the condition of them, (shrinkage/changes in softness)

Link to V4MB article by MagnAndy: How to Soften Old Rubber (Carb Boots etc.) - Updated - V4MuscleBike.com
(Check out some of his articles while you’re on the site, he has tons of useful posts and a video series on rebuilding carbs.)

Link to Methyl Salicylate on Amazon (wintergreen oil): Amazon.com

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That has worked well for me. It softens the parts sufficiently so that they may be reinstalled easily. However, after a few months they return to their rock hard state but then, it doesn’t matter.

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Update. 2 Days in. The boots have firmed up just a tiny bit, which is probably good. They were super super soft before, very squishy. Now they’re still very soft, but they have a little bit of structure to them. They’ve also began to shrink down a little bit, immediately after soak they had swelled up bigger than the groove on the carb, with a little bit of massaging they could be squished down to fit tight, now they sit down nicely in groove without issue. Going to try to get them on the bike in the next few days.