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Author Topic: Cb550 rejet = no power? Can't maintain steady idle?  (Read 7072 times)

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Offline gregripko

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Cb550 rejet = no power? Can't maintain steady idle?
« on: January 04, 2013, 11:32:55 PM »
A mechanic worked on my bike and rejetted carbs with #100 Main Jet
#38 Slow Jet..... Now bike can't accelerate beyond 5k rpm and it can't hold an idle very long before engine dies.

1976 cb550k, 4-1 exhaust, air box


Please help!
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Offline Deltarider

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #1 on: January 04, 2013, 11:58:20 PM »
I suspect something went wrong in the proces. I don't think it's caused by the size of the jets.What made you change them?
« Last Edit: January 04, 2013, 11:59:54 PM by Deltarider »
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Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #2 on: January 05, 2013, 12:02:37 AM »
It had pods before and wanted stock jetting because I'm running air box
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Offline trueblue

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #3 on: January 05, 2013, 12:05:27 AM »
Get a wet rag and touch it to your header pipes, with the engine running it should sizzle, make sure all are getting hot.  It may not be firing on all 4.
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Offline dave500

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #4 on: January 05, 2013, 12:06:38 AM »
ive got 38/100 in my 550 with 4-1 and can accellerate with norton 850s!go right over your ignition again maybe,,check for full throttle action aswell,it wont be the jetting.

so this was a shop?
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Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #5 on: January 05, 2013, 12:12:21 AM »
Wish I knew more about bikes and could see what they did. It was a shop.... Has head gasket kit installed and carb kit.... Looks great but runs worse... It use to hold an idle perfect and has an insane amount of power
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Offline dave500

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #6 on: January 05, 2013, 12:13:56 AM »
take it back and ask them wtf??as soon as you tamper with their work you have no recall!!it might be something simple theyve overlooked?surely they test rode it though?

head gasket kit??cam one tooth wrong?
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Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #7 on: January 05, 2013, 12:17:35 AM »
Probably is something extremely basic... It's at shop now...
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Offline Killer Canary

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #8 on: January 05, 2013, 07:55:28 AM »
Beware the infamous mixed-up plug wires.
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Offline Bodi

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #9 on: January 05, 2013, 08:15:47 AM »
The "carb kit" scares me. Use only Keihin OEM carb jets, emulsion tubes, and needles. Aftermarket carb kits cause endless problems (someone always says that's crazy and that they saved big bucks using brand x kits and had great results, but my experience has been dismal with them).
Check that the chokes are open, open in sync, and stay open (don't vibrate closed again after opening), and there's no interference with the airbox adapter clamps.
Check the slides are in the right way around. You should see the cutaway from the air cleaner side.
Check the float height, and that they are installed the right way up.
Check that the main jet emulsion tubes are the right way up. You should see the brass needle jet protrude slightly where the needle goes in, looking in from the air cleaner side with throttle and choke open. An open hole in the carb body with the needle going into it means they are upside down.
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Offline flybox1

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #10 on: January 05, 2013, 08:25:12 AM »
^exactly.
Time for you to be an expert in your carbs.  It's really not that hard.  I visit bike shop A for tire mounting and balancing.  Tire shop B is right down thtreet.  A customer of Shop B brings his CB750 into shop A while I'm there, indicating shop B can't fix his bike running after a long storage, and he's already into it $800.  WTF!?!?!   When I came back to shop A to collect my wheels the next day, the CB750 was already fixed and out.  Shop A owner said the carbs had never been opened and we're full of varnish. :o
True story...
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Offline crazypj

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #11 on: January 05, 2013, 09:38:23 AM »
Head gasket = wrong cam timing or bent valves if they haven't worked on 550 previously
Real easy to do, search 550 oil leak/head gasket threads
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Offline goldarrow

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Cb550 rejet = no power? Can't maintain steady idle?
« Reply #12 on: January 05, 2013, 01:40:47 PM »
Shoulda hire me, for a six pack beer, but then again u only 2 hours away and may not worth the drive or hauling your bike here. 

+1 what everybody else said above.
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Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #13 on: January 05, 2013, 02:55:57 PM »
Are there any decent mechanics in southern California that are reasonably priced but knowledgeable?
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Offline mono

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #14 on: January 05, 2013, 03:05:11 PM »
Maybe he changed the position of the needles incorrectly when he rejetted? 

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Offline goldarrow

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Cb550 rejet = no power? Can't maintain steady idle?
« Reply #15 on: January 05, 2013, 03:19:53 PM »
Quote from: gregripko on January 05, 2013, 02:55:57 PM
Are there any decent mechanics in southern California that are reasonably priced but knowledgeable?

The knowledgable one I would say is you.  Your bike, know it then fix it. But if really looking for a shop, I would say google search for Valley Cycles in Chatsworth. Talked to him couple of times and he knows vintage bikes. I never had my bikes fixed there as I work on them myself. 
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Life Is Full Of Challenges - And My Backyard Is Full Of SOHC4's

CB550 K0
CB750 K0, K2, K23 JDM, K45, K5
And the little ones z50r, xr50r, st90


750k5 http://forums.sohc4.net/index.php?topic=114817.0

Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #16 on: January 05, 2013, 04:39:47 PM »
Is there a PDF or material on jetting steps for cb550?
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Offline Tews19

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #17 on: January 05, 2013, 04:49:52 PM »
Greg, listen to the advice.. Carbs wouldn't do that by swapping the jets.... You said gasket as in head gasket replaced.. definately don't take it out of that shop till it's running tops..... Do not let them charge you either.... What's the companies name?

Ask the shop to do a compression check and give you each number per cylinder... Make sure they tell you which cylinder per number
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Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #18 on: January 05, 2013, 05:18:21 PM »
Yep... Head gasket replaced... I'll keep it in shop... Couple guys in Anaheim
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Offline goldarrow

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Cb550 rejet = no power? Can't maintain steady idle?
« Reply #19 on: January 05, 2013, 09:30:59 PM »
While the bike is sitting in the shop, download the manual and study it.  Good stuff.

Wonder if one can demand money back for the work performed not to a satisfaction level?
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Life Is Full Of Challenges - And My Backyard Is Full Of SOHC4's

CB550 K0
CB750 K0, K2, K23 JDM, K45, K5
And the little ones z50r, xr50r, st90


750k5 http://forums.sohc4.net/index.php?topic=114817.0

Offline crazypj

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #20 on: January 06, 2013, 12:13:14 AM »
You won't get your money back but you should get bike running properly for free
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Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #21 on: January 06, 2013, 12:28:04 AM »
They've had the bike for almost a week.... Feel like its time to call it a day
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Offline dave500

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #22 on: January 06, 2013, 12:34:24 AM »
if the bike was deffinately running and idling better and with more obvious power before they fixed it let them know,make them ride it.
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Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #23 on: January 06, 2013, 12:36:44 AM »
I did let them know.... Hoping I hear something tomorrow
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Offline gregripko

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Re: Cb550 rejet = no power? Can't maintain steady idle?
« Reply #24 on: January 06, 2013, 02:53:56 PM »
Think what happened was an F carb kit was installed in a K model.... Could that be the cause of the problem? Or are they cross-compatible?
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