3ed Gen Intake Rubbers

Discussion in 'Mechanics Garage' started by Hingley, Jan 18, 2021.

  1. Hingley

    Hingley New Member

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    I have a 1990 VFR750 with only 15,000KM ( 10,000 MILES ) on the speedo and have a simple but perhaps strange question

    How do you determine that the carb intake rubbers are bad and are in need of replacement?

    Is it the number of miles they have on them ( hot/cold cycles ) over the years?

    The age of the Rubbers?

    How can you tell by looking at them that they should be replaced

    Thanks
     

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  2. Diving Pete

    Diving Pete Member

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    Couple of questions?
    Do you have air leaks?
    Are you planning on removing the carbs?
    If yes to either then buy new ones.
    They make a painful job (using old rubbers) into an easier one..

    Yours are 30 years old. they will be hard and brittle - compared to new ones..
     
  3. Diving Pete

    Diving Pete Member

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    let me add - if you are still on the original tyres they will not handle as well as new rubber.. - even though you haven't done many miles. Treat it as a service item.
     
  4. Hingley

    Hingley New Member

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    Thanks for the reply
    I had the carbs redone last summer and since than I have found the bike idles well but does not like to run down the road unless you are above 5000 grand, ( carbs were balanced )
    and also after you have it really warmed up I have noticed if you blurp the throttle she will hang at 2500 or so for a few seconds before she will come back down to an idle
    I have also noticed she is on the rich side but I figured with the full Yosh exhaust and K&N it would be good, maybe not
    Last but not least I have noticed a couple of times that if she has been sitting a while and I go to start her she will fired up but for a moment or two she will run rough and the two back cylinders can be cold
    Maybe I have more than one problem
     
    Last edited: Jan 18, 2021
  5. ridervfr

    ridervfr Member

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    Carburetors need to be sorted better. While you/or someone else is in there, its prudent to replace insulator boots (intake boots) among other things. Like your thermostat and the two rubber hoses from that along with associated o-rings on it. Its pretty much endless what you can replace, your dealing with a 30 year old motorcycle, lots of rubber/plastic parts have literally changed at a molecular level - ie plastic is brittle, rubber is hard etc. I am in the process of changing my fuel tubes on one these bikes currently (I have two, other one was done already) If you stay on top of the maintenance its just the ancillary stuff that can bite you in the arse. Once there are brought up to favourable condition, I would not hesitate to ride either one of mine across the US (wishful thinking) Have fun wrenching PEaCe
     
  6. Diving Pete

    Diving Pete Member

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    ok, now the carbs hanging suggest they need some work... that's about the transition point from slow jets to mains so would suggest some are plugged - doesn't matter they need pulling apart.

    Whats the turns on the mixture screws....

    When was the bike last serviced?

    A new set of plugs can cure a thousand ills.... lol

    Check the leads & the earths..
     
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