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I did a thing... a CB900F thing

This is a discussion on I did a thing... a CB900F thing within the General forums, part of the Caferacer.net Forums category; the one positive thing I can say about the DOHC carbs is that they had a better idle circuit and choke than the SOHC predecessor. ...

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Thread: I did a thing... a CB900F thing

  1. #41
    Senior Member Geeto67's Avatar
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    the one positive thing I can say about the DOHC carbs is that they had a better idle circuit and choke than the SOHC predecessor. My 1975 750 you have to hold the throttle when cold just to keep it running no matter what, but my brother's 1979 750F will just sit there idling on choke. If it is below 50 it will stall once or twice, but otherwise that thing just ticks over like it's no big deal. Of course the carbs are terribly designed everywhere else so....there is no making up for that, but at least they idle nicely.
    Ews likes this.
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  2. #42
    Ews
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    Been a bit since I've been on the forum here, busy with work and camping.

    Discovered that my excessive back-pop issue is due to bad gas, or at least gas that my bike really does not like.

    Tried to adjust the timing chain tensioners. Was able to adjust the front bolt easy enough, and the rear top acorn nut kind of. I was unable to loosen the rear-bottom acorn nut without fear of rounding it off. I have not heard the piston slap noise that Geeto mentioned that I watch out for, but now I am getting what sounds like a slight loose chain slap when I decelerate in gear. With my helmet on it is difficult to tell if it is coming from the engine or my drive chain. Of course the V&H exhaust does not help the being able to hear much. I am considering taking it in to the local Honda dealer to have them adjust the timing chain, but I'd rather avoid that fee if I can.

    On the plus side, when I opened the the stater case to turn the engine over as I adjusted, I was pleasantly surprised to find it looking fairly fresh and new, no cracking in the epoxy around the copper, mags and brushes and such all seemed in good shape and hardly used or aged, must be newer lol.

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  3. #43
    Senior Member TrialsRider's Avatar
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    Is those 2 carbon contacts that will eventually wear out and then your electrical will simply quit.

    ... your bike has a chain primary drive does it not? That is what will induce drive lurch when you go from acceleration to deceleration.

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  5. #44
    Ews
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    Quote Originally Posted by TrialsRider View Post
    Is those 2 carbon contacts that will eventually wear out and then your electrical will simply quit.

    ... your bike has a chain primary drive does it not? That is what will induce drive lurch when you go from acceleration to deceleration.
    That is my first thought. I need to lube the chain again and maybe tighten it up
    Dream as if you live forever, Live as if you die today.~ James Dean

    I feel the need, the need for speed.~ Mavrick (Tom Cruise before he was a big ol' bag of crazy)

  6. #45
    Senior Member TrialsRider's Avatar
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    Quote Originally Posted by Ews View Post
    That is my first thought. I need to lube the chain again and maybe tighten it up
    Is it a sealed chain? You just clean it and put enough rust preventive coating on the outside to stop it from rusting,
    don't over-tighten the final drive chain, that is catastrophic.

    ... go down big hill, pull in clutch and drop to idle, listen to chain noise,
    maybe coast under a bridge or in tunnel, don't break the law or get killed doing it.
    oh wait Idaho :| nope, no idea.
    Last edited by TrialsRider; 06-25-2019 at 12:12 PM.

  7. #46
    Ews
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    I've only ever owned chain drive, other than my 02' Sportster. Have not over tightened a drive chain yet and don't plan to start now lol. Ive got some good lube/anti rust stuff that I will try. Supposed to be thunderstorms for the next 2 days so i will have time to give it a try
    Dream as if you live forever, Live as if you die today.~ James Dean

    I feel the need, the need for speed.~ Mavrick (Tom Cruise before he was a big ol' bag of crazy)

  8. #47
    Senior Member Geeto67's Avatar
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    could be primary chain slap. it's been a while but I think those are hy-vo chains so maybe not.

    There are two cam chains: an A and a B:

    https://www.bikebandit.com/oem-parts...51784sch404864

    make sure both are adjusted.

    these are not quiet engines normally. it's not going to sit and burble like a new R1.
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
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  9. #48
    Senior Member TrialsRider's Avatar
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    Sounds like a typical air cooled motor or bag of hammers.

    Put it gear with the motor turned off roll forward, now roll backward, now roll forward, now roll backward :| are we hearing any chain clunk?
    seeing a lot of backlash travel from the crank to the rear wheel?
    If yes we have a bagged out primary drive or something else like the rubber rear cushion drive, you are looking specifically for play inside the engine for it to be the primary drive.

  10. #49
    Ews
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    I will try that out. Thanks for the advice
    Dream as if you live forever, Live as if you die today.~ James Dean

    I feel the need, the need for speed.~ Mavrick (Tom Cruise before he was a big ol' bag of crazy)

  11. #50
    Ews
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    Tightened the drive chain this weekend and swapped the oil. No chain slap noise yet, well a tiny tiny bit, so I may need to adjust the chain a tad more and call it good. But other than that everything seems to be running as smooth as can be expected from a 36 year old motorcycle
    Dream as if you live forever, Live as if you die today.~ James Dean

    I feel the need, the need for speed.~ Mavrick (Tom Cruise before he was a big ol' bag of crazy)

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