1982 CB450SC jet sizes - Page 2
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Thread: 1982 CB450SC jet sizes

  1. #11
    Super Moderator longdistancerider's Avatar
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    They've been cut. Both ends should be closed. I'll look and see if I have a pair.

    All I have left are a pair of VB21 springs, stiffer than the VB22's so that's no good.
    Last edited by longdistancerider; 08-31-2019 at 06:29 PM.
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


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  2. #12
    Member mikemo's Avatar
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    That's really nice of you Jim. Thank you!!!

    Dealing with this old bike makes me feel a little bit like a detective. Seeing the evidence left over by the "perpetrators", and trying to figure out what happened.

    Was someone looking to improve performance? I assume that's why the top of the airbox was cut open. Then there's the jets that were installed that were all too small. Why did that happen? Maybe the bike wouldn't start after sitting, and the shop used a carb kit from a 750 because that's what they had on the shelf? Maybe after the carbs were "rebuilt" using the wrong parts, someone was trying to fix a lean-condition? There is also sealant on the seal on the end of the throttle shaft. So the bike was super-lean, then they tried to fix air leaks, then chopped the piston spring trying to get more fuel?

    It looks like there are some "jet kits" that include instructions to modify the piston spring. Maybe someone got a hold of a kit for the wrong type of bike and just installed it?

    Who knows. The bike has only done 240 miles a year since it was built. Obviously, it sat for long periods of time. I'm really looking forward to getting her on the road soon and breaking the cycle of neglect.

    Thanks for the help in untwisting the mystery
    1982 CB450SC Nighthawk
    2 x 1988 Toyota MR2 Supercharged (one finished, one under reconstruction)
    2018 Honda Civic SI

  3. #13
    Member mikemo's Avatar
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    It's running great! I could only take it for a short spin because the tires are ancient, the tag is expired and I'm a little worried about the front brake.

    I did noticed just a tiny bit of fuel at the drain on the left carb. Not dripping, but could see it when I touched my finger there. Not sure if that's an issue or not. But, it started easy, idled great and moved down the road with gusto! Thanks again to all who helped, LDR, J-T, Ancientdad and all the others who chimed in.

    By the way, how do you turn the idle mixture screws when the carbs are on the bike? The right carb screw is directly above the neutral switch. Even a stubby-screwdriver wouldn't fit. Any tricks to this?

    Here she is, running like a Japanese sewing machine! BTW, I do have the side covers. I just had them off while fooling with the carbs.

    1982 CB450SC Nighthawk
    2 x 1988 Toyota MR2 Supercharged (one finished, one under reconstruction)
    2018 Honda Civic SI

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  5. #14
    Super Moderator ancientdad's Avatar
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    Quote Originally Posted by mikemo View Post
    Dealing with this old bike makes me feel a little bit like a detective. Seeing the evidence left over by the "perpetrators", and trying to figure out what happened.
    What we do on our vintage bikes absolutely is like being a detective... and some of the stuff done by POs before us borders on criminal behavior to these bikes so yes, in some cases they could be called perps

    Quote Originally Posted by mikemo View Post
    Thanks again to all who helped, LDR, J-T, Ancientdad and all the others who chimed in.
    Thanks, but all I really did was comment on the current hurricane situation... I doubt that contributed to your success

    Glad it's running good
    Tom

    CL450 project reboot, street legal this time
    Budget drag bike project
    CB350K1 full patina project
    Ride along at the drag strip


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

  6. #15
    Super Moderator longdistancerider's Avatar
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    The original mixture screws had caps on them with a limiter tab so they could only adjust almost 1 turn. I've been leaving the caps on, they're glued to the screw, and cutting the limit tab off the float bowl. Makes it easy to adjust with fingers plus the tab gives a reference point of positioning.
    If you don't have the caps maybe try some small vacuum hose forced over the end of the screw
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


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  7. #16
    Member mikemo's Avatar
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    I went down to the DMV today to get my title and registration for the bike, so I had a chance to run it a little more at higher speeds. Out-of-state titles require a VIN check so I had to bring the bike "in person".

    I noticed that when going from part throttle to WOT that there seemed to be a little bog or delay, then it would pick up. It's not horrible, but noticeable. Once it was opened up it seemed to run as it should all the way to redline. Could that be because of the cut springs? I would think that the piston would raise up faster than stock, so maybe it is a little rich until the motor catches up?

    I've been looking for replacement springs, and apart from buying a complete parts bike I haven't found any yet. I'm keeping my eyes open.

    Thanks guys
    Mike M.
    1982 CB450SC Nighthawk
    2 x 1988 Toyota MR2 Supercharged (one finished, one under reconstruction)
    2018 Honda Civic SI

  8. #17
    Super Moderator longdistancerider's Avatar
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    Springs could easily be the cause.
    Also the accel pump. With the air box boots off you can watch the nozzle by the choke plate squirt with fast throttle twist. Real booger to clean those since they face backwards
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


    https://www.hondatwins.net/forums/22...d-attempt.html and https://www.hondatwins.net/forums/1-...r-attempt.html
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  9. #18
    Member mikemo's Avatar
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    Thanks Jim.

    I think my accelerator pump is good. I bench-tested that when the carbs were reassembled. Twisting the throttle plates gives a skinny stream of fuel straight back to the throttle plates.

    Once I get my new tires on I'll be able to test more thoroughly. I was driving on rock hard tires with an expired tag yesterday, so that limited my shenanigans

    I did notice that the on-off and off-on throttle transitions were buttery smooth. No flat spots or jerkyness, and better than many fuel injected bikes I've owned. The only issue I noticed was when going from 1/2 throttle to WOT. That's when I noticed the flat spot. Maybe my accelerator pump adjustment is off? I had trouble following the adjustment procedure from the manual. I couldn't get a feeler gauge in the spot between the pump rod and the actuator with all the other hardware in the way. Even then, the clearance is TINY. 0.01mm? That's 10 microns! Is that a typo in the manual?

    Thanks again
    Mike M.
    1982 CB450SC Nighthawk
    2 x 1988 Toyota MR2 Supercharged (one finished, one under reconstruction)
    2018 Honda Civic SI

  10. #19
    Super Moderator longdistancerider's Avatar
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    Spec is .01mm to .04mm or .0004" to .0016". Just use a 1/1000th feeler gauge
    Jim O'Brien
    1979 CM400T "road bike" modified for travelling
    1978 CB400T1 restored
    1972 CL350 nuts and bolts restore in progress


    https://www.hondatwins.net/forums/22...d-attempt.html and https://www.hondatwins.net/forums/1-...r-attempt.html
    Road Trip https://www.hondatwins.net/forums/11...here-i-go.html or "where's Jim now?"
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  11. #20
    Member mikemo's Avatar
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    Thanks Jim.
    The smallest one I have is 2 thousandths, and it is super flimsy. A 1 thousandth feeler gauge must be hard to handle.

    I'm going to keep looking for replacement slide springs. I was also thinking that maybe that giant hole that someone cut in the top of the airbox lid might be having an impact too. That part is easy to find. The springs haven't been. I really don't want to buy a set of carbs just to get the springs.

    I'll update when I know more. My tires arrive today, so I've got work to do in the meantime.

    Thanks
    Mike M.
    1982 CB450SC Nighthawk
    2 x 1988 Toyota MR2 Supercharged (one finished, one under reconstruction)
    2018 Honda Civic SI

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