1974 CB450 loosing power/bogging down
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Thread: 1974 CB450 loosing power/bogging down

  1. #1
    Senior Member Rscottp's Avatar
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    1974 CB450 loosing power/bogging down

    I was out for a ride the other day and toward the end of the ride the bike seemed to loose power and bog down. It didn't want to rev past 4-5k almost felt like it was running on one cylinder but I don't think it was. There was also some minimal backfiring going on too and it wanted to stall at idle. Took it out again yesterday and after about 2 miles it started doing the same thing again. I don't think it's a carburetor problem but perhaps it's a clogged fuel tank vent. I tend to think its some type of electrical issue but am looking for some ideas from the wealth of knowledge here. BTW I'm running stock points. Thanks in advance.
    1981 Honda CX500D
    1974 Honda CB450
    1986 Yamaha Radian 600

    Martha's Vineyard Ma

  2. #2
    Supporting Member 12ozPBR's Avatar
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    Simple thing is to check your timing. Mine jumped time suddenly this spring while out riding and wanted to die at idle. Turns out it was slightly retarded.
    Runners
    1971 Triumph Tiger
    1972 CL350
    1974 XL350
    1974 CB450

    Current Project
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  3. #3
    Senior Member Rscottp's Avatar
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    If mine had jumped the timing wouldn't it run bad consistently? Yesterday when I took it out it ran fine the first couple miles then went all wonky, makes me think it's something else but I'm far from an expert.
    1981 Honda CX500D
    1974 Honda CB450
    1986 Yamaha Radian 600

    Martha's Vineyard Ma

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  5. #4
    Senior Member tbpmusic's Avatar
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    Change out your spark plugs - they're most likely fouled out, any trouble shooting would be futile....
    Figure out why they fouled out in the first place.
    It could be as simple as a compromised battery.
    Rscottp likes this.
    Bill Lane
    Honda Twins Founding Member

    No advice, just info

    '75 CB200T, '71 CB450 K4 Half-Breed, '72 CL350 (Sold), '81 CM200T, '72 C70M
    and a little red Chineeze scooter

    http://www.bikeexif.com/honda-cb450-restoration

  6. #5
    Senior Member WintrSol's Avatar
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    I'd take off the exhaust valve cover, to make sure the oil pump didn't quit on you. The only other engine I've had do this broke the pump.
    Rick

    Mine is a mostly 1970 CB450K3

  7. #6
    Senior Member Rscottp's Avatar
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    Quote Originally Posted by WintrSol View Post
    I'd take off the exhaust valve cover, to make sure the oil pump didn't quit on you. The only other engine I've had do this broke the pump.
    That's a scary thought, hope I didn't cook the motor.
    1981 Honda CX500D
    1974 Honda CB450
    1986 Yamaha Radian 600

    Martha's Vineyard Ma

  8. #7
    Senior Member ancientdad's Avatar
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    Can't hurt to look... hopefully that isn't the issue
    Tom

    Ride along at the drag strip - https://www.youtube.com/watch?v=20jFPazXlvU



    running points... because I'm too old for mysteries that begin with pushing

  9. #8
    Supporting Member 12ozPBR's Avatar
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    Quote Originally Posted by Rscottp View Post
    If mine had jumped the timing wouldn't it run bad consistently? Yesterday when I took it out it ran fine the first couple miles then went all wonky, makes me think it's something else but I'm far from an expert.
    Perhaps I misspoke this morning when I said “jumped time”. What I meant was my timing became slightly retarded during a longer ride and the bike would not hold an idle without dying. It did run good at higher revs. A simple adjustment of the timing when I got home corrected the problem.
    Runners
    1971 Triumph Tiger
    1972 CL350
    1974 XL350
    1974 CB450

    Current Project
    1966 CB450 Black Bomber

  10. #9
    Senior Member WintrSol's Avatar
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    Quote Originally Posted by Rscottp View Post
    That's a scary thought, hope I didn't cook the motor.
    That would be bad. It's the first (and worst) thing that came to mind when I read your description. It could just be the carbs over- or under-filling, though.
    Rick

    Mine is a mostly 1970 CB450K3

  11. #10
    Senior Member Rscottp's Avatar
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    Woke up feeling like crap today so I don't feel like wrenching. I will update once I start digging into things.
    1981 Honda CX500D
    1974 Honda CB450
    1986 Yamaha Radian 600

    Martha's Vineyard Ma

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