1972 CB350K4 Won't Idle
Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 24
Like Tree2Likes

Thread: 1972 CB350K4 Won't Idle

  1. #1
    Senior Member barab63's Avatar
    Join Date
    Jun 2017
    Location
    NJ
    Posts
    102

    1972 CB350K4 Won't Idle

    I've been searching this forum for a while and haven't found a solution for my particular problem. So this post. Cold engine starts easily and idles at about 1200 rpm. However, after riding for a short time (maybe 5 minutes) engine won't idle when I stop unless the revs are kept at about 2000 rpm or higher. It hasn't stalled unless it goes below that, but if it does stall, one push on the starter button while goosing the throttle gets it going. Won't start unless you give it some throttle. Cruises fine above 3000 rpm and seems to have enough power and acceleration for a 350 twin. Below 3000 rpm, bike becomes a bit sluggish and hesitates. Three days ago the carbs and timing were adjusted and set properly by a professional mechanic whom I trust. During the rebuild (some of you might recall the "chirping issue I had) I completely disassembled the carbs and soaked all the parts in the gallon Gunk carb cleaner for about 24 hours, and then used wire from a wire brush, small diameter drill bits, welding tip cleaners, carb cleaner, and finished with canned compressed air.

    Opening the gas cap or turning off lights doesn't affect anything. Battery on volt meter at 3000 rpm reads a little over 13 volts. Send help. Thanks
    Current projects 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500, 2015 Triumph Trophy SE

  2. #2
    Senior Member doode's Avatar
    Join Date
    Mar 2014
    Posts
    2,169
    Hmm, does one of your float have a hole?
    What color are your plugs? You still have an air leak?
    You have the felt seals on your carb butterfly shaft?
    Paper gasket between the intake manifold and head?

  3. #3
    Senior Member Alan F.'s Avatar
    Join Date
    Aug 2009
    Location
    Boston
    Posts
    1,482
    Did you set your idle speed with the engine warm?
    Crashoverride likes this.
    CB250 Nighthawk projects 92,93,92.
    CM400C Sold 7-21-18 It's been fun, buh-bye.
    Fork Swap info: http://sites.google.com/site/alansdocuments/

  4. Remove Advertisements
    HondaTwins.net
    Advertisements
     

  5. #4
    Senior Member barab63's Avatar
    Join Date
    Jun 2017
    Location
    NJ
    Posts
    102
    Gaskets in place. I'll check other items.
    Current projects 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500, 2015 Triumph Trophy SE

  6. #5
    Senior Member ancientdad's Avatar
    Join Date
    Nov 2016
    Location
    Nature Coast FL
    Posts
    7,246
    How long has it been since you set the points and timing? Points gaps that have closed up some from wear cause retarded timing and that will drastically affect low rpm performance
    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

  7. #6
    Supporting Member jd50i's Avatar
    Join Date
    Nov 2012
    Location
    Maryville, Tn.
    Posts
    2,799
    idle circuit still dirty in carbs or not properly adjusted when warm. Lots of threads about carbs thoroughly cleaned and several posts later, carbs cleaned properly fixes the problem.
    Jim

    1973 CB 450 K6 PAMCO
    1975 CB 500T PAMCO
    1985 CB650SC Nighthawk
    1985 VF 1100S Sabre
    2012 Buddy 125 (wifes)

  8. #7
    Senior Member barab63's Avatar
    Join Date
    Jun 2017
    Location
    NJ
    Posts
    102
    Quote Originally Posted by ancientdad View Post
    How long has it been since you set the points and timing? Points gaps that have closed up some from wear cause retarded timing and that will drastically affect low rpm performance
    Points, timing and carb settings were done four days ago by a professional mechanic that I have used many times.
    Current projects 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500, 2015 Triumph Trophy SE

  9. #8
    Senior Member barab63's Avatar
    Join Date
    Jun 2017
    Location
    NJ
    Posts
    102
    Quote Originally Posted by jd50i View Post
    idle circuit still dirty in carbs or not properly adjusted when warm. Lots of threads about carbs thoroughly cleaned and several posts later, carbs cleaned properly fixes the problem.
    I had disassembled the carbs and cleaned all the components a couple of months ago, and the bike sat with empty fuel tank since then. It was my first ever carb cleaning. So far, I have two opinions suggesting the idle circuit needs a second look. Thanks
    Current projects 1972 CB350K4, 1969 CB750. Road worthy bikes: 1973 CB750K3, 1980 CX500, 2015 Triumph Trophy SE

  10. #9
    Supporting Member jd50i's Avatar
    Join Date
    Nov 2012
    Location
    Maryville, Tn.
    Posts
    2,799
    The passages are pretty small, letting them soak won't work on a fully clogged port since the cleaner needs to flow through. A lot of us have bought an ultrasonic cleaner from harbor freight, fairly cheap and the agitation helps but isn't 100%.

    Using drill bits, steel wire, etc can damage the ports, the carb bodies are a softer metal.
    Jim

    1973 CB 450 K6 PAMCO
    1975 CB 500T PAMCO
    1985 CB650SC Nighthawk
    1985 VF 1100S Sabre
    2012 Buddy 125 (wifes)

  11. #10
    Senior Member Crashoverride's Avatar
    Join Date
    Mar 2017
    Location
    St. Catharines Ontario Canada
    Posts
    860
    The part about 24 gunk soak and drill bits and wires has me wondering if the felt parts are good and if the jets might be scratched.
    Bike Build http://www.hondatwins.net/forums/1-p...rst-timer.html

    1971 CL350 - SUNRUNNER
    Rebuilt Top end with stock Pistons and Rings
    PAMCO + E Start Ignition 4000 Miles on it +
    LED Instrument lights
    Common Motor Rec/Reg
    Common Motor Black bucket + 35w headlight kit
    Custom voltmeter + Tach.
    2009 Versys 650

Page 1 of 3 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
  •