Bike Won't Go Past 4000 RPM
Page 1 of 6 1 2 3 ... LastLast
Results 1 to 10 of 52
  1. #1
    Member jgordonoglan's Avatar
    Join Date
    Aug 2019
    Location
    Fogo Island, Newfoundland, Canada
    Posts
    34

    Bike Won't Go Past 4000 RPM

    Hello all,

    I have a 1982 CB450SC. I recently changed the oil on it since the previous owner probably hadn't changed in about 5 years, but I didn't change the filter. I added Castrol 10W40. Now I'm having a few issues that I wasn't having before.

    When the bike idles, everything seems to be fine. I'm able to run the bike for a few minutes like normal, shifting gears down the road perfectly fine, but then all of a sudden the bike seems to have trouble getting above 4000RPM and also doesn't want to go faster than 60Km/h.

    When I stop the bike, there seems to be a bit of smoke coming from somewhere and when I remove the dipstick there appears to be smoke coming from there too.

    Anyone have any suggestions that may be causing this?

    Cheers!

    Jarrod

  2. #2
    Super Moderator longdistancerider's Avatar
    Join Date
    Oct 2011
    Location
    Vancouver Washington (text 408-239-9580)
    Posts
    22,383
    Remove the gas cap and see if that solves it. The tank can go into vacuum if the cap bleed hole gets plugged. If that doesn't fix it then I would check the petcock filter inside the tank and also the small screw cap filter at the bottom of the petcock.
    Doesn't sound like an engine issue.
    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?"
    Member Map https://www.hondatwins.net/forums/dcMembermap.php

  3. #3
    Member jgordonoglan's Avatar
    Join Date
    Aug 2019
    Location
    Fogo Island, Newfoundland, Canada
    Posts
    34
    Tried removing the gas cap but unfortunately that didn't fix the issue. How do I get to the petcock filter?


    New development: now the bike seems to like to stall out on me while I'm riding it.

  4. Remove Advertisements
    HondaTwins.net
    Advertisements
     

  5. #4
    Super Moderator J-T's Avatar
    Join Date
    Jun 2009
    Location
    Tea, South Dakota
    Posts
    9,401
    Close your petcock (it should always be closed when the bike is shut off anyway).

    Disconnect the fuel line at the carburetor and place the end in a suitable container.

    Open the petcock. There should be a steady stream of fuel.
    JT
    81 CM400T

  6. #5
    Member jgordonoglan's Avatar
    Join Date
    Aug 2019
    Location
    Fogo Island, Newfoundland, Canada
    Posts
    34
    Awesome I'll give that a shot tomorrow when the rain stops.

    So I should be closing the petcock every time I'm not running the bike?

  7. #6
    Senior Member pemdoc65's Avatar
    Join Date
    Feb 2016
    Location
    Shepherdsville, KY
    Posts
    488
    Yes, you should close the petcock when not riding. Otherwise you may end up with fuel in your oil.
    1965 CB450 K0
    1966 CB450 K0 (current project)
    1964 CB77
    1965 CB77
    1964 CB72 (upcoming project)
    1965 CB72 (current project)
    1964 CA77
    1972 CB350 K4
    1960 Triumph TR6 Trophy (always looking for parts to finish this one...)
    1980 CB750K
    1982 XL250R

  8. #7
    Senior Member 80cb400t's Avatar
    Join Date
    Sep 2017
    Location
    BC
    Posts
    741
    You may want to smell the dipstick for oil, it's an easy check that gives a lot of peace of mind
    To get to the petcock filter you will need to empty the tank at least halfway, then tip to the opposite side of the petcock (on a towel so the paint doesn't get scratched), keeping in mind that the gas cap does not keep gas in even when shut, then undo the nut on the petcock and the filter should come out. If it doesn't it is most likely stuck in the tank and you may be able to get it out with an easy out that matches the inner diameter or a drill bit in reverse (be gentle)
    1980 CB400T - 1 running, 1 parts bike
    1965 CB160 - 1 kind of running, 1 parts bike

  9. #8
    Member jgordonoglan's Avatar
    Join Date
    Aug 2019
    Location
    Fogo Island, Newfoundland, Canada
    Posts
    34
    Quote Originally Posted by pemdoc65 View Post
    Yes, you should close the petcock when not riding. Otherwise you may end up with fuel in your oil.
    That’s good to know. Thanks for the heads up!
    Jarrod

    1982 CB450SC - first bike

  10. #9
    Member jgordonoglan's Avatar
    Join Date
    Aug 2019
    Location
    Fogo Island, Newfoundland, Canada
    Posts
    34
    Quote Originally Posted by 80cb400t View Post
    You may want to smell the dipstick for oil, it's an easy check that gives a lot of peace of mind
    I haven’t had a chance to get the petcock out yet, I’ll be doing that after work this afternoon.

    As for smelling the dipstick, I gave it a quick sniff this morning and it didn’t really smell of gas, but it didn’t smell like the oil from the jug. I’m assuming right now that’s just from being run a bit through the engine, or is that a horrible assumption?
    Jarrod

    1982 CB450SC - first bike

  11. #10
    Senior Member 80cb400t's Avatar
    Join Date
    Sep 2017
    Location
    BC
    Posts
    741
    I think that's pretty reasonable, when it smells like gas it smells like gas. You get a whiff and pretty soon accept that you need to change the oil.
    1980 CB400T - 1 running, 1 parts bike
    1965 CB160 - 1 kind of running, 1 parts bike

Page 1 of 6 1 2 3 ... LastLast

Sponsored Links

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •