CB450 too rich at idle - Page 3
Page 3 of 4 FirstFirst 1 2 3 4 LastLast
Results 21 to 30 of 36
Like Tree3Likes

Thread: CB450 too rich at idle

  1. #21
    Sensei 66Sprint's Avatar
    Join Date
    Sep 2008
    Location
    Roanoke, Virginia
    Posts
    24,309
    O-ring is at top near driver slot on the long tapered 14H carb mixture needle....NO spring washer, it's built in

    https://www.cmsnl.com/honda-cb450k1-.../#.XJqboV1_OM8
    Last edited by 66Sprint; 03-26-2019 at 03:41 PM.
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."

  2. #22
    Senior Member tbpmusic's Avatar
    Join Date
    Sep 2008
    Location
    LaPorte, Indiana, USA
    Posts
    6,225
    Quote Originally Posted by 66Sprint View Post
    O-ring is at top near driver slot on the long tapered 14H carb mixture needle....NO spring washer, it's built in

    https://www.cmsnl.com/honda-cb450k1-.../#.XJqboV1_OM8
    Affirming Steve's info - no washer on the pointy 14H mixture screw.
    Should dial in at about 3/4 to 1 turn out.
    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

  3. #23
    Member Mickeyluv's Avatar
    Join Date
    Feb 2019
    Location
    England
    Posts
    38
    Quote Originally Posted by tbpmusic View Post
    Affirming Steve's info - no washer on the pointy 14H mixture screw.
    Should dial in at about 3/4 to 1 turn out.
    There's no washer on mine. I've tried the original, an OEM replacement and an aftermarket screw. I verified yesterday that all three cut off the fuel passageway when screwed in. Just to be sure I checked them without springs to see if the spring was getting coil-bound before the end of adjustment range. That's all OK. If the mixture screw is cutting off the pilot fuel supply, then either the richness is coming from the needle jet or perhaps more likely the bypass ports. At idle there should be insufficient vacuum to lift the fuel from the needle jet unless the fuel level is too high.

    Does anyone have a measurement of the fuel height taken after the fuel line is disconnected and the float bowl removed (measured from the top of the float bowl to fuel surface). I know this doesn't give the actual fuel height but it could be a useful comparison to make certain my fuel level isn't too high.

    Also, I'm setting my float height with the gasket removed and the gauge resting in the notch on both sides of the body. Is this correct? The gasket would make a difference of about 2mm.

    This reminds me that about 35 years ago thee was a UK company selling aftermarket transparent bowls for some carbs with the correct fuel level marked. That would be a nice thing to have right now.
    CB450 K4 rolling chassis fitted with CB450 K2 engine.

  4. Remove Advertisements
    HondaTwins.net
    Advertisements
     

  5. #24
    Member Mickeyluv's Avatar
    Join Date
    Feb 2019
    Location
    England
    Posts
    38
    Quote Originally Posted by tbpmusic View Post
    Affirming Steve's info - no washer on the pointy 14H mixture screw.
    Should dial in at about 3/4 to 1 turn out.
    There's no washer on mine. I've tried the original, an OEM replacement and an aftermarket screw. I verified yesterday that all three cut off the fuel passageway when screwed in. Just to be sure I checked them without springs to see if the spring was getting coil-bound before the end of adjustment range. That's all OK. If the mixture screw is cutting off the pilot fuel supply, then either the richness is coming from the needle jet or perhaps more likely the bypass ports. At idle there should be insufficient vacuum to lift the fuel from the needle jet unless the fuel level is too high.

    Does anyone have a measurement of the fuel height taken after the fuel line is disconnected and the float bowl removed (measured from the top of the float bowl to fuel surface). I know this doesn't give the actual fuel height but it could be a useful comparison to make certain my fuel level isn't too high.

    Also, I'm setting my float height with the gasket removed and the gauge resting in the notch on both sides of the body. Is this correct? The gasket would make a difference of about 2mm.

    This reminds me - about 35 years ago there was a UK company selling aftermarket transparent bowls with the correct fuel height marked. I could use one of those right now.
    CB450 K4 rolling chassis fitted with CB450 K2 engine.

  6. #25
    Senior Member WintrSol's Avatar
    Join Date
    Jul 2011
    Location
    Florissant, MO
    Posts
    2,223
    One question: do you actually have the 14H carbs?

    When I set the float levels, the gasket is not on the carb body. You said you checked to see that the floats are not rubbing; is that true for the sides of the bowls? Also, did you shake the floats to see if there is any fuel inside?
    Rick

    Mine is a mostly 1970 CB450K3

  7. #26
    Member Mickeyluv's Avatar
    Join Date
    Feb 2019
    Location
    England
    Posts
    38
    Yes, they're 14H

    The floats are clear of the bowls and move freely. There's no fuel inside the floats and I weighed them just to be sure that they weren't heavier than they should be. I also submerged them in hot water and they're sealed - no bubbles.
    CB450 K4 rolling chassis fitted with CB450 K2 engine.

  8. #27
    Senior Member WintrSol's Avatar
    Join Date
    Jul 2011
    Location
    Florissant, MO
    Posts
    2,223
    Odd that the pilot screw adjustment seems so critical; not sure why that should happen. It's been a while since I adjusted the 14H carbs, so they could be more sensitive than the 723 type, because of the shape of the tip. You should still be able to find that sweet spot, where they don't carbon up the plugs.
    Rick

    Mine is a mostly 1970 CB450K3

  9. #28
    Senior Member middletons's Avatar
    Join Date
    Sep 2015
    Location
    Kansas City
    Posts
    348
    I’ve been measuring my 14h floats from the raised rim around where the bowls sits since that’s the highest point. Correct or no?

    Edit: just looked at the manual and it seems to show the measurement from the notch as stated above. Kinda hard to see in the diagram though.
    Last edited by middletons; 03-27-2019 at 11:55 AM.
    1975 CB125
    1972 CB350
    1975 CB360

  10. #29
    Member Mickeyluv's Avatar
    Join Date
    Feb 2019
    Location
    England
    Posts
    38
    I re-checked everything again yesterday (I tried to reply a few times but there was a system problem). I also measured the fuel height - turned on fuel to make sure the bowls were full, turned off and disconnected fuel lines. Removed each float bowl in turn and measured from the rim of the bowl to the fuel surface. I read 14mm on each side. I then ran the bike for a few minutes and did the same thing - still 14mm. This doesn't seem an unrealistic reading but without a comparison from a bike that's running well I can't make a judgement.

    Can anyone also confirm that there are three bypass drillings in these carbs - two small holes and one slightly larger one? I'm still wondering if additional fuel is being pulled in here so that would come down to the pilot circuit and/or fuel level.
    CB450 K4 rolling chassis fitted with CB450 K2 engine.

  11. #30
    Sensei 66Sprint's Avatar
    Join Date
    Sep 2008
    Location
    Roanoke, Virginia
    Posts
    24,309
    IF you refer to the holes above the chamber sealed by the large aluminum (straight slot) screw and situated just to the engine side of the closed throttle butterfly plate, Then yes, there are three, two smaller and one slightly larger.....However, The one controlled by the mixture screw is larger than those and about 1/2 inch closer to the engine......Note that the "mixture" screw actually only controls the amount of engine vacuum that can act on the pilot jetting.....The amount of fuel coming in through those three holes is balanced by the amount of atmospheric pressure that can enter through the air jet (just under the slide piston) relative to the vacuum controlled by the mixture screw..... Note also, that the amount of vacuum on the engine side of the throttle butterfly is also mitigated by the amount of throttle plate opening [more air coming in under/over the plate means less vacuum (on the engine side) applied to the pilot passages through the mixture screw, so less differential with atmospheric, and less fuel is drawn/passes through the pilot jetting...]

    I fear I just got TOO technical with this explanation.......

    Are your floats adjusted to 20mm?
    Last edited by 66Sprint; 03-28-2019 at 08:18 AM.
    "I have a mind like a steel trap.....Old and rusty, of antiquated design, and hard to get stuff back out of...."

Page 3 of 4 FirstFirst 1 2 3 4 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
  •  

Similar Threads

  1. Too lean and too rich?
    By mixwell_cb350 in forum Fuel Supply and Carburation
    Replies: 16
    Last Post: 04-11-2018, 07:49 PM
  2. 3D sass... Too rich, won't idle or run?
    By doode in forum Fuel Supply and Carburation
    Replies: 10
    Last Post: 07-20-2015, 10:18 PM
  3. Backfiring- Too rich or too lean? Update 6/4/12
    By keithpip in forum Fuel Supply and Carburation
    Replies: 6
    Last Post: 05-31-2012, 01:36 PM
  4. Idle revving too high or too low.
    By Ageispolis in forum Fuel Supply and Carburation
    Replies: 3
    Last Post: 07-30-2011, 05:32 PM
  5. changing air filters and jets... Too lean or too rich?
    By Cl350k3guy in forum Fuel Supply and Carburation
    Replies: 3
    Last Post: 07-02-2010, 05:58 PM