Rejuvenate Rubber Carburetor Isolators
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Thread: Rejuvenate Rubber Carburetor Isolators

  1. #1
    Senior Member JamesPal's Avatar
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    Rejuvenate Rubber Carburetor Isolators

    I have a 1985 GL1200 Interstate that I put back on the road last year. It was plagued with poor running. It was fine up to about 3800 RPM and then it would break into a stumble and then clear it throat at around 6000 RPM. Removing the carburetors on one of these bikes is a pretty major job, so I put it off until the riding season was over here in Western Washington. One of the things I did was rejuvenate the rubber on the intake runners. I had heard about this but was a skeptic. One of the guys at work who is pretty smart told me about it. Based on him I went ahead and did it. It cost about $25 and the results were astonishing. I made this video for the guys over at GoldwingFacts.com. If somebody told me this would work so well, I would need a video to believe it. From here on I am not buying new carb boots without trying this first and rejuvenating the boots is part of my standard carb overhaul:

    bilbikek411 likes this.
    Jim Palmer
    '85 GL1200I (Garage Find)
    '81 GL1100 STD (Project)
    CB450 K5 Done
    https://www.hondatwins.net/forums/1-...s-cb450k5.html
    What I learned from Restoring a CB450 K5
    Watch Mike and Jim Take on Mt Erie Washington State
    "If everything seems under control you are not going fast enough" Mario Andretti...

  2. #2
    Senior Member Rob Axel's Avatar
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    Wow.. I have seen different ways to "soften" hard rubber.. I recently had a intake boot on a s90 that was rock hard...
    Tried using "brake fluid".. and it softened up a lot..
    I've got some others for my cb450 DOHC that could use some softening.. I just may give it a shot..

  3. #3
    Senior Member tbpmusic's Avatar
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    The wintergreen oil is expensive and unnecessary, the xylene works fine by itself.
    The treatment will cause the rubber bits to swell, but after a couple days they recover their normal dimensions, and will remain semi-flexible for a time.
    They will get hard again, but at least you'll be able to install the carbs and the rubber parts will conform before they get hard again.
    So it won't make them like new, but at least will de-fossilize them for a while.

    FWIW, plain ol' deisel fuel will do the same thing. Car guys will pour deisel on the crusty old rubber gaskets on windshields to soften them up for removal. I learned this from a local glass shop.
    Bill Lane
    Honda Twins Founding Member

    No advice, just info

    '75 CB200T, '71 CB450 K4 Half-Breed, '72 CL350 (Sold), '81 CM200T, '72 C70M
    and a little red Chineeze scooter

    http://www.bikeexif.com/honda-cb450-restoration

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  5. #4
    Senior Member Lefty's Avatar
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    Good vid Jim, I was going to try this once but was too cheap. It looks like you did all right though. Interesting about deleting the wintergreen Bill, I wonder what it's purpose is for. Wonder what the shelf life of that mix is.

  6. #5
    Senior Member JamesPal's Avatar
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    Quote Originally Posted by Lefty View Post
    Good vid Jim, I was going to try this once but was too cheap. It looks like you did all right though. Interesting about deleting the wintergreen Bill, I wonder what it's purpose is for. Wonder what the shelf life of that mix is.
    I read a lot on the internet about this. There were many testimonials that said the rubber (synthetic) was still soft aft a year. I will see if I can find some other pertified rubber and try it with just the Xylene. The Wintergreen Oil gives the bike such a nice smell
    Lefty and bilbikek411 like this.
    Jim Palmer
    '85 GL1200I (Garage Find)
    '81 GL1100 STD (Project)
    CB450 K5 Done
    https://www.hondatwins.net/forums/1-...s-cb450k5.html
    What I learned from Restoring a CB450 K5
    Watch Mike and Jim Take on Mt Erie Washington State
    "If everything seems under control you are not going fast enough" Mario Andretti...

  7. #6
    Senior Member JamesPal's Avatar
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    Follow up

    I got the 1200 back together this afternoon. The intake runners clamped nicely. There was a break in the rain so it was begging me to ride it. First time out on wet roads in 20 years. BIKE RAN PERFECT! I got it out on the flat and cranked it. The rear end broke loose at about 4000 RPM and then it spun up pretty quick. By the time I got it shut down did about 6 or 7 tank slappers. Nice to get it to run right, it has been one year last October since I bought it.
    bilbikek411 likes this.
    Jim Palmer
    '85 GL1200I (Garage Find)
    '81 GL1100 STD (Project)
    CB450 K5 Done
    https://www.hondatwins.net/forums/1-...s-cb450k5.html
    What I learned from Restoring a CB450 K5
    Watch Mike and Jim Take on Mt Erie Washington State
    "If everything seems under control you are not going fast enough" Mario Andretti...

  8. #7
    Senior Member Rob Axel's Avatar
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    Congrats... well done

  9. #8
    Senior Member bilbikek411's Avatar
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    Jim,
    Do you have contact info for the company that makes the carb. slide diaphrams ?

  10. #9
    Senior Member JamesPal's Avatar
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    Quote Originally Posted by bilbikek411 View Post
    Jim,
    Do you have contact info for the company that makes the carb. slide diaphrams ?
    This is the ebay store for the guy I bought mine from:
    Micha`s double shop | eBay Stores

    After I bought the diaphragms, I found this company:
    JBM Industries Rubber Carburetor Boot Socket Holders & Diaphragms

    I have no experiance with JBM Industries. However they are quite a bit less expensive that the German ones. They have the diaphragms for the 350 and 360 engines. I also read they can fit other engines if the customer provides measurements.
    bilbikek411 likes this.
    Jim Palmer
    '85 GL1200I (Garage Find)
    '81 GL1100 STD (Project)
    CB450 K5 Done
    https://www.hondatwins.net/forums/1-...s-cb450k5.html
    What I learned from Restoring a CB450 K5
    Watch Mike and Jim Take on Mt Erie Washington State
    "If everything seems under control you are not going fast enough" Mario Andretti...

  11. #10
    Member SeanFD's Avatar
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    Hi,

    What happens is the xylol soaks into the rubber taking the oil with it. Then when you pull it out of the solution, the xylol evaporates and leaves the oil behind.

    I have done this using acetone based paint thinners and ordinary soyabean (cooking oil). I put them in the mixture sitting on some aluminum foil and heated till the fluid boiled. Then covered container and left them overnight plus a bit.

    Worked very well and is much cheaper than using Wintergreen.

    I also saw on another forum that somethig called Thor's #12 Tire Treatment works a treat - it's apparently used to soften go-kart tires.

    Sean
    Sean D

    After a lifetime of asking, I still have more questions than answers.

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