3rd Gen Magna and 3/4 Gen VFR diaphragm problem

Discussion in 'General VFR Discussions' started by Billy C, Oct 14, 2018.

  1. Billy C

    Billy C New Member

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    I am posting to draw attention to what I see as a potential bike killer if a solution can’t be found. Ripped diaphragms on the 94 – 03 VF750C and the 90 – 97 VFR750F. This is very odd but I currently have a rebuild rack from one of each with all 4 diaps pinholed/ripped/degraded rubber. No one offers an aftermarket diaphragm. I ordered a set from China that looked right but coded to a different bike and they are too small. New slide assys from Honda for the Magna are appx $140 each. At the moment everyone seems to think used racks are worth $300 - $400 and even buying one does not mean you end up with 4 good slides. I keep old bad slides from rebuild replacements. I tried removing bad diaps from a couple and it is a struggle. I destroyed 2 of them trying to get the diaps off. I cut one in half and I swear it looks like the retaining ring is a cast with the entire body part which eliminates popping off the retaining ring.

    So, I am looking for input from bigger brains than mine. Help!!!
     

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  2. squirrelman

    squirrelman Member

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  3. REVTMOLO

    REVTMOLO New Member

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    I've got a 96 Magna. Yes those diaphragms are stupid expensive. Even more ridiculous is that crummy little Sub air filter that a lot of people don't know about when after a while falls apart and gets sucked up into the diaphragms. Honda has some brilliant engineers, but MAN they did a few things that just makes you wonder...
     
  4. Billy C

    Billy C New Member

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    Squirrelman... Wrong diap. I need the diap for the 94 - 07 RC36 4th Gen VFR as in the pic. Truthfully, I am not sure new diaps are going to be the cure. I have played with some old slides with ripped diaps and they are a complete mofo to get the old diaps out and no idea if getting new ones in and alignded properly is even likely. I desperately need a fix. I just dropped the bad news on a customer today and I felt like I kicked his wife and raped his dog after. Anyone who has any ideas or solutions feel free to call me. Noon - 9PM-ish TX time. hp 903-567-1543 or cp 903-340-6009
     

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  5. Blackslide

    Blackslide New Member

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    Argh! Is there any way to prevent these from going bad, or slow down the process?

    Are we all looking at a 800cc efi swap sooner or later?

    Riding on the storm
     
  6. squirrelman

    squirrelman Member

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    Keeping strong solvents away from them is important. no carb cleaner or brake cleaner spray, no starting fluid spray and no deep soaking.

    i think something must be weird when 4th gen diaphragms go bad while i have 6 working sets of '86/'87 carbs with no bad diaphragms ?

    also, almost all the gen2 carbs i get for cleaning have good diaphragms !
     
    Last edited: Oct 20, 2018
  7. Blackslide

    Blackslide New Member

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    Duh! I guess that ethanol is a great way to make old carbs rot. Up here we can only get non ethanol gas in 5-10litre canisters from hardware stores. At a ridiculously high price. I bet that E1095 octane stuff is totally out of question and the "premium" E598 is borderline stuff..

    I'll have a look at the gas perservative jug, before I pour any in the tank and start the storaging process..



    Riding on the storm
     
  8. Billy C

    Billy C New Member

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    The ether in starter fluid is instant death to rubber. Carb cleaner is not instant but does leach the natural rubber out of the diaps and hastens their demise. See pic for what a good dose of ether does to diaps.
    I may have a line on new diaps, may. My 1st set did not fit but I have high confidence on this set. Even if they fit the new problem is removing the old and installing the new. These 94 and up slides are nothing like the good old 1/2 gens.
     

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  9. squirrelman

    squirrelman Member

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    red ring seems unusual, as most are yellowish, might indicate something, but i pulled these from a set of Hawk carbs with special HRC slides with red rings also.

    can't imagine why the needles could be so different or how it could run like that ?

    oct 20-2018 060.JPG

    oct 20-2018 056.JPG

    oct 20-2018 057.JPG
     

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    Last edited: Oct 20, 2018
  10. Billy C

    Billy C New Member

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    The slides with the red ring are from a 1st Gen, 84-85 VF1100S big Sabre. 1st Gens come with iirc 4 different color rings to help differentiate them as their are ever so slight differences. Red, black, white, grey with the white turning a pale yellow over 30+ yrs. Those slides in your pics are odd. Look a little like the VFR400F NC30 rack I worked on a couple years back. Short needle must indicate a short stroke on the piston.
     
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