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Thread: 1986 Yamaha Radian Question

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  1. #1
    A Bit Bored
    Join Date
    May 2019
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    Default 1986 Yamaha Radian Question

    Hello everyone,

    This was really helpful with another issue I had, so I thought I'd try my luck again. Just bought a 1986 Yamaha Radian, fixing it up and before I dive into tearing out the carbs, I have a few questions about symptoms.

    The bike starts well, I've detected spark on all plugs, fuel tank, petcock and hoses checked and all good, delivering fuel well. Bike idles perfectly, but throttling up quickly kills it immediately, and throttling up slowly climbs a few thousand rpms then dies, unless I quickly return the throttle to zero. The idle responds well to the idle adjust screw.

    To me, it seems like a carb issue, and that possibly only the idle jets are clean enough, but on this bike there is a carb system I'm not familiar with. It's called a Carburator Air Vent System and it has an electrically activated control valve. I will test it (it's really simple), but in the mean time can someone explain what it does? What are the symptoms of a malfunctioning one?

    Also, if the problem is in the carbs itself, should I try syncing them first before cleaning them (I don't have experience with syncing carbs or the symptoms of out-of-sync carbs). I will eventually clean them regardless, but I'd like to know if it could be a sync issue. The old plugs looked good, by the way. Thanks for any advice!

  2. #2
    Should Get Out More KungFooBob's Avatar
    Join Date
    Aug 2012
    The Forest Moon of Endor
    Liked 7,971 in 4,534 posts

    Default Re: 1986 Yamaha Radian Question

    Fuel starvation.

    When you say the pipes and petcock are delivering well, what did you check/how?

    Probably worth checking the float valves in the carbs too.

  3. #3
    Should Get Out More Makman's Avatar
    Join Date
    Feb 2008
    Barking at the moon.
    Liked 1,936 in 1,178 posts

    Default Re: 1986 Yamaha Radian Question

    I have a horrible feeling you bought a bike I know.... Green tanks, small ding on the rear of it? It is the carbs. You need to clear out the jets as they are prone to blocking and causing that very issue. The bike was sitting for ages. The exhaust is a one off fitment and works well. Check the valve stem seals as well, as they were perishing.

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