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Thread: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

  1. #16
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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power


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    Quote Originally Posted by Julian_Boolean View Post
    Is it possible to bypass the fuel pump and use a gravity feed?

    What exactly are the symptoms?

    Does it tickover?
    How long will it tickover for?
    Does it run at all above 3k?
    Is there any fuel in the carb flost bowls when it cuts out?
    If yes, how much?
    How much is in the float bowls 10 minutes later?
    There are drain screws in the bottom of the carbs.

    Sent from my SM-T560 using Tapatalk
    Does it tickover? Yes
    How long will it tickover for? all day
    Does it run at all above 3k? nope (only after a carb rebuild and then for only a few miles - carb is spotless inside, floats are set correctly (checked with clear tube from drain)
    Is there any fuel in the carb flost bowls when it cuts out?yes
    If yes, how much? 4/5 full
    How much is in the float bowls 10 minutes later? same amount
    There are drain screws in the bottom of the carbs.

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    Quote Originally Posted by FJBristol View Post
    a trip to Fowlups or another specialist garage will end up with a bill of pretty much what it cost me...
    Perhaps this is the reason it was cheap in the first place!
    Set the mixture back to stock as it only affects pilot circuit. Maybe another set of carbs. Have you checked the emulsion tubes for ovality?
    As a check, get the motor spinning and when the bike splutters, keep going til hopefully it will stall or run really badly. Kill the ignition and have a look at the plugs.
    Wet and dark too rich
    Dry and grey, too lean.
    You have put a fresh clean air filter in haven't you?
    Nothing blocking the intake, rag/toolkit

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    I'm terrible at diagnostics so sorry if this irrelevant, but are the plugs wet or dry when it cuts out?

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    So these jets were new, only had a few miles on them (see pic)

    I have a theory which is useful to share....

    The previous owner had the tank sealed after pinholes had appeared. And had no issues. Neither did I until I added some redex carb cleaner to the tank. It was very soon after this that i started having problems.

    Now the gunk that was all over the jets has a glueish type quality. My guess is that the addititive I put in has affected the sealant causinng it to disolve...

    Anyway. Whilst I had the tank reversed on the seat i managed to knock it off causing a good sized dent. Since its full of random gunk anyway, I think it is time for a good clean second hand tank - if anyone has one please pm me!

    I have taken the carb apart completely now, everything off needle valves, mixture screws the lot and will run compressed air through it...

    ill post an update when I get a new tank on it!jet.jpg

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    that's an emulsion tube, the jet is screwed into the top. does look pretty horrible though

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    Should Get Out More 1888's Avatar
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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    Quote Originally Posted by sadlonelygit View Post
    that's an emulsion tube, the jet is screwed into the top. does look pretty horrible though
    Mikuni when i bought new ones list them as Needle jet with the Main what screws into the top.

    http://www.motocarb.com/mikuni-needle-jets.html

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    Quote Originally Posted by 1888 View Post
    Mikuni when i bought new ones list them as Needle jet with the Main what screws into the top.

    http://www.motocarb.com/mikuni-needle-jets.html
    mikuni can call them nigels for all i care, they're still emulsion tubes

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    Quote Originally Posted by sadlonelygit View Post
    mikuni can call them nigels for all i care, they're still emulsion tubes
    Mikuni can fuck off

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    The sealant is coming off the inside of the tank, I've got two Z1100R tanks that are doing this, I'm probably going to have to get one of them cut open, shot blasted and new base made.

    Usually bikes won't tickover when the carbs get blocked, because the small openings are used for low speed running.

    You could also have ignition problems.

    Sent from my SM-T560 using Tapatalk

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    I had a Honda Bros 400, only had 500km on the clock when I bought it, but had been stood for ten year and the inside of the tank was very very rusty. It would run fine at part throttle, and full throttle for short periods, but if you were blatting it down the M-Way, you'd get 10 miles and it would just cut out.

    I put an inline filter in and you you see it clogging up with crap. Left long enough the float bowls would refill and you'd get going again.

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    there's no way the emulsion tubes should be like that, get a paper fuel filter, not a mesh one (if that's what it has) and try it with another tank. You might have got lucky if it was OK at idle. The holes in the emulsion tube are there to help with fuel delivery by the main jet, and they make a big difference.

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    Quote Originally Posted by FJBristol View Post
    Neither did I until I added some redex carb cleaner to the tank. It was very soon after this that i started having problems.

    Now the gunk that was all over the jets has a glueish type quality. My guess is that the addititive I put in has affected the sealant causinng it to disolve...
    I had this with redex but i had no sealant - my guess is the redex doesn't like ethanol. I could repeat the same effect by mixing redex with IPA, it gave a stick residue at the bottom of the bottle.
    It left a sticky residue on all the jets, inside of the tank but probably most significantly on the little nylon strainer that fits on the end of the fuel tap pipe. It caused fuel starvation.
    It was an absolute bastard to remove too. I put everything in an ultrasonic cleaner and filled it with redex to dissove the glue, then some detergent supplied with the ultrasonic cleaner then petrol then IPA.

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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    I used to add IPA to a diversion as a remedy against carb icing. Do the FJs ice, could he have added alcohol to the fuel?

  16. #29
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    Default Re: FJ 1200 rebuilt carbs.. works for a few miles 100% then no idles but no power

    Carb float heights. Sorry, been a while since I've had a FJ1200 (1988 3CV model). I rebuilt the carbs and changed all the jets for new ones with the pilots and mains changed. Also reset the float heights because I had fitted straight through ART Race cans. Sounded glorious and revved straight through to redline with no issues at all after that work. I did have to clear the tank breather and also make sure there was no kink in the fuel line. Was also very careful getting the choke setting right as well. I did however pay for the shims/valves to be sorted and that made a big difference as well. Dependent on where you are located, www.fjclub.co.uk is what you need to get hooked into for tips and tricks. I had Doc service my bike and it ran so well afterwards.

    Just remembered. Also clear down the vent holes for the tank. Lawnmower strimmer plastic down the hole and WD40 sprayed in there till it dribbles out the bottom tube. They do get blocked. You might have to remove the tank cap to do this properly as the gunk builds up between tank and cap as well.
    Last edited by Makman; 05-12-18 at 08:03.

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