I spent some time looking into ways to permanently soften old rubber parts because I found it a pain to work with the old rock hard rubber boots on several of my CT90's and found one method that has worked well for me. I made a post at my CT90 on the method I used and here is a link to that post. The link includes a video that shows how effective the method is and I have included a link to that video here. I hope you find the info useful as its made life much easier working on my CT90's.
Softening Old Rubber CT90 Air Cleaner Boots
- Thread starter MikeCT90
- Start date
Shamrockwill
Member
Interesting. Thanks for sharing. You mentioned that it can cause swelling but that it subsides eventually. The swelling causes me concern because it could cause the boot to not make a proper seal around the carburetor. Do the boots go all the way back down to their original size?
red69
Well-Known Member
Mike, I have a feeling those parts are some kind of rubber composite or just not rubber. I soaked a carb piece in the recommended solution and it did soften up. I then tried the seat setting rubber in the solution. I'll admit that the piece was dry and had cracks in it, but the mix started to dissolve the part and it crumbles with ease. Easy fix. Just cut a new piece from 1/4" rubber sheet.
Yes, my experience has been that they get back very close to the original size and are a snug fit on the carb and air filter assembly.
Yikes! I haven't experienced any issues like what you had with the rubber part you tried, but I agree that the CT90 boots are a particular rubber compound that is tailored to be used around fuel, etc. so I wouldn't be surprised if the solution I shared attacked other materials.