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Thread: 85 250r ignition coil boot?

  1. #1
    Join Date
    Jan 2021
    Location
    NJ
    --
    24

    85 250r ignition coil boot?

    my new bike that I saw the original owner rip through the gears and sounded great and starts 1st or 2nd kick no choke every time and will idle forever but it breaks up past 1/4 throttle the couple times I've ridden it. I went to check the plug that I had put in last weekend and pulled the boot off and the boot actually came off the coil wire and there's a little crud in the boot and the wire is stiff as a board so I'm hoping that was giving me a weak spark when trying to go up in rpm's and causing it to stumble. I found a new OEM coil/wire without the boot so what's everyone using to replace the boot? I'm assuming any similar size resistor boot will work but wanted to check here.

  2. #2
    Join Date
    May 2006
    Location
    The Open Road
    --
    4,729
    Use the old one.

    They don't really wear out. It took me a year to find the correct NOS spark plug boot for my 86 250R, but by then I was riding around using my old boot. The new one set me back $70. The boot has a screw inside the wire socket end of the boot and it just twists (or screws) onto the wire of the coil

    There nothing inside them to go out or wear out and the only reason I was looking for a new one was to have as much NOS stuff in my trike as possible

  3. #3
    Join Date
    May 2006
    Location
    The Open Road
    --
    4,729
    Also it's common for them to come unscrewed from people removing them and twisting them around to plug into the spark plug a hundred or so times over the life of a 35 year old machine

    When I have a Honda machine running rough, the first thing I always check is that spark plug boot and the grounding of the coil because those are two very common causes

  4. #4
    Join Date
    Jan 2021
    Location
    NJ
    --
    24
    Thanks Ironchop. I cut the wire back about 1/4" and screwed the boot back on yesterday but haven't had a chance to fire it up and see if it's any better. I didn't know they didn't go bad so that's good to know. This one has permanent dirt stains on it so I wanted to replace it and the coil/wire since it's really stiff and probably the original coil. I really hope the boot is the issue. I checked the spark after putting it back on and it was a fat blue spark but that doesn't always mean it's strong enough to burn at high rpm. I'll also check my plug gap again.

  5. #5
    Join Date
    Oct 2003
    Location
    Las Vegas, NV.
    --
    2,446
    I can't remember the exact specifics of my oem, sparkplug boot failure, as it happened almost 30 years ago. But, as I recall, the wire & resistor pulled out of the boot when trying to remove the boot off of the spark plug. I ended up replacing it with an NGK sparkplug boot. It doesn't look as sleek as the oem unit, but it does the job.
    Red Rider's Sand Machine Updated 07/23/14

  6. #6
    Join Date
    Jan 2021
    Location
    NJ
    --
    24
    I fired it up on the first kick as usual with no choke and warmed it up but it still breaks up past 1/4 throttle. I’ve never ridden it with full power and haven’t changed anything other than adding fuel since I bought it and saw the previous owner rip it around. It sounded great and didn’t break up at all when he rode it and I loaded it up right then so I don’t know what could have changed. I used a mix rite cup to 40:1 with 2 gallons of 93 and maxima 927. The previous owner used Amsoil dominator at 40:1 and there was a little left in the tank when I poured maybe a half gallon of my mixed fuel. It’s stored in a heated shop so I don’t think the 927 separated and I run it for a few seconds after shutting the petcock off to get rid of the fuel in the bowl. I did notice when changing the top carb cap that he had the needle all set all the way lean at the top position but I didn’t look at anything else in the carb.

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