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Author Topic: '74 CB550 - New wires and caps...no change.  (Read 1680 times)

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Offline Airbusboy

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'74 CB550 - New wires and caps...no change.
« on: July 17, 2015, 09:24:42 AM »
Well guys....  new plug wires and new caps didn't do squat to fix my problem. Numbers 2 and 3 STILL won't run at idle. I checked the spark and even swapped some plugs around and it didn't help.  Fuel IS in the bowls of 2 and 3.  Just to eliminate the possibility of a bad coil (though there's only 5K miles on these OEMs) I think I'll swap the leads and see if the problem stays on 2 and 3 or transfers to 1 and 4.  All I have to do is switch the yellow and the blue, correct?  I'm running HondaMan's electronic box, BTW.  Should I unplug it and re-hook the factory wires and see what happens?  I've already had the carbs off 4 times and gone through 'em, but maybe I missed something....
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Offline Airbusboy

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Re: '74 CB550 - New wires and caps...no change.
« Reply #1 on: July 17, 2015, 11:43:19 AM »
Yeah the carbs have been vacuum synced. Not sure of float levels. I just cracked open the drain valves and fuel was present.  Would a simple switching of the yellow and blue wires on the coils work to see if the problem transfers to cylinders 2/3?
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Offline Airbusboy

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Re: '74 CB550 - New wires and caps...no change.
« Reply #2 on: July 17, 2015, 11:45:24 AM »
And how do I do the 'clear tube' method of float level checking?
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Offline harisuluv

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Re: '74 CB550 - New wires and caps...no change.
« Reply #3 on: July 17, 2015, 11:53:48 AM »
Fuel in the bowls is simply proof of fuel in the bowls, that's it.  You have no evidence that the fuel is getting into the cylinder.

How about some basic trouble shooting, spray something combustible into 2/3 and see if it does anything.  If so it would point to a carb issue.
« Last Edit: July 17, 2015, 11:55:38 AM by harisuluv »
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Offline Airbusboy

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Re: '74 CB550 - New wires and caps...no change.
« Reply #4 on: July 17, 2015, 02:35:58 PM »
Yeah I'm 90% sure it's a carb issue. Those cylinders come alive off idle.  It'll be pull number FIVE if I have to pull the bank...UGH!  I'll swap blue/yellow just to be sure, but I know deep down I'll be pulling the bank tomorrow.  How's the best way to set float levels with the bank OFF the bike?
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Offline Airbusboy

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Re: '74 CB550 - New wires and caps...no change.
« Reply #5 on: July 17, 2015, 03:44:52 PM »
Got it. Thanks for the link.  I've found the measurement is 22mm for the height of the floats. I may just pull and double check the condition of all jets. The idle mixture screws say one turn out and mention the screw, a spring and a rubber washer.  Where does the rubber washer go, on the screw head end of the spring or towards the bowl end?
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Offline harisuluv

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Re: '74 CB550 - New wires and caps...no change.
« Reply #6 on: July 17, 2015, 11:37:34 PM »
There is no rubber washer on 74 cb550 air screws.  Just the screw and washer. 
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Offline Deltarider

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Re: '74 CB550 - New wires and caps...no change.
« Reply #7 on: July 17, 2015, 11:51:46 PM »
Quote
Just the screw and washer.
No washer at all, just the screw and a little spring.
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Offline Spanner 1

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Re: '74 CB550 - New wires and caps...no change.
« Reply #8 on: July 18, 2015, 12:11:44 AM »
If it's a carb issue, it's actually electrical !... Hey, if the 2-3 points are not shiny clean then they may not be passing the coil voltage to ground... Oh wait ! you have a Hondaman ign. mod ?... then clean points are even more vital as the very much reduced current applied to the points demand shiny, shiny point faces... did I say shiny enough ?
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Offline Flyin900

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Re: '74 CB550 - New wires and caps...no change.
« Reply #9 on: July 18, 2015, 03:43:24 AM »
With the cylinders that present as dead at idle coming to life off idle then I would be looking closely at the low speed jet in those two carbs. There is a very tiny passage down deep in that jet closer to the imulsion tube at the bottom of the jet that you can't see from the top.
If that is plugged then it could be the source of your non idle firing.

Were you ever a CB 900 DOHC owner on the CB 750 forum with the airbusboy moniker?
« Last Edit: July 18, 2015, 03:45:01 AM by Flyin900 »
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Common sense.....isn't so common!

1966 CL77 - 305cc - Gentleman's Scrambler
1967 CL175K0 - Scrambler #802 engine
1972 CB350F - Candy Bacchus Olive - Super Sport
1973 CB350F - Flake Matador Red - Super Sport
1975 CB400F - Parakeet Yellow - Super Sport
1976 CB400F - Varnish Blue - Super Sport
1976 GL1000 - Goldwing Standard
1978 CB550K - Super Sport
1981 GL1100 - Goldwing Standard
1982 CM450A - Hondamatic
1982 CB900C - Custom
1983 CX650E - Eurosport
1983 CB1000C - Custom X 2 Bikes now - both restored
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Offline Restoration Fan

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Re: '74 CB550 - New wires and caps...no change.
« Reply #10 on: July 18, 2015, 04:11:11 AM »
It does sound like a carb issue.  But I'm also not a big believer in coincidences and the mere fact that 2/3 are on the same coil would force me to look at my coils as well.  Try swapping the wires that go into the wires so that your 2/3 cylinders will be running on the coil that is currently pushing 1/4.  If 2/3 still don't fire at idle then you've eliminated the coil as the issue.  If however your 1/4 now start to be the problem cylinders, you have some issue either with the coils or potentially with the 2/3 wires that go to the coil.

Just like the guys are suggesting, try eliminating one potential problem at a time.
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Ron

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Offline Airbusboy

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Re: '74 CB550 - New wires and caps...no change.
« Reply #11 on: July 18, 2015, 02:50:59 PM »
Update...  I pulled the bank AGAIN.  The low speed jets in 2 and 3 were plugged.  #4 wasn't much better.  I've cleaned these and reinstalled at least three times already.  I've got the carb jet wire tool and used it to clean 'em out but they still clog after a while.  The tank is SUPER clean and there is a screen in the petcock and an inline filter on each fuel line. The bike sat for 38 years and two separate pros have cleaned the carbs, plus me twice. I gave up on these jets and ordered 4 new ones from Honda. In about a week I'll get 'em, install 'em and hold my breath. I did set all floats to EXACTLY 22mm while I was at it though.  Coils seem fine. New wires, caps and NGK Iridiums. Oh, and new runners on BOTH sides of the carbs.  These jets MUST be the problem. We'll see.....
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Offline Airbusboy

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Re: '74 CB550 - New wires and caps...no change.
« Reply #12 on: July 18, 2015, 02:58:49 PM »
Oh and Flyin900.... could've been me. I've had a few 900s and currently have a CB1000C and am on the DOHC site a little as well.  This 550 is actually a little smoother (when it's running) than the 1000!  I'm thinking maybe there was so much old deposits and gum inside the low speed jets that as I use it the new fuel 'loosens' more garbage inside the jets and/or carb body that didn't get totally clean and finds it's way into the low speed jets. This is the FIFTH pull of that bank and it's getting REAL OLD! 
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Offline Flyin900

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Re: '74 CB550 - New wires and caps...no change.
« Reply #13 on: July 18, 2015, 03:58:22 PM »
It was you over there airbusboy I am sure and it has been a few years since I was real active over there too.

The slow speed jets just stuck out for me as a fairly obvious choice if the bike runs well off idle on those two cylinders. Coils would act up at all speeds not just at idle and then be fine at a higher RPM in my experience.

Those jets can be very hard to clean and I normally use a very fine single wire strand off a wire brush, as my jet cleaning wires are for welding tips and are still to large to fit the small opening up inside the lower section of that low speed jet.

If you get those completely clean I am sure you will find a noticeable difference in the bikes idle and off idle response.

Cheers.
« Last Edit: July 18, 2015, 04:05:04 PM by Flyin900 »
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Common sense.....isn't so common!

1966 CL77 - 305cc - Gentleman's Scrambler
1967 CL175K0 - Scrambler #802 engine
1972 CB350F - Candy Bacchus Olive - Super Sport
1973 CB350F - Flake Matador Red - Super Sport
1975 CB400F - Parakeet Yellow - Super Sport
1976 CB400F - Varnish Blue - Super Sport
1976 GL1000 - Goldwing Standard
1978 CB550K - Super Sport
1981 GL1100 - Goldwing Standard
1982 CM450A - Hondamatic
1982 CB900C - Custom
1983 CX650E - Eurosport
1983 CB1000C - Custom X 2 Bikes now - both restored
1983 CB1100F - Super Sport - Pristine example
1984 GL1200 - Goldwing Standard

Offline Airbusboy

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Re: '74 CB550 - New wires and caps...no change.
« Reply #14 on: July 28, 2015, 11:18:18 AM »
Update... Well, new low speed jets did the trick!  While I was in there I blew out all the passages and set each float assembly to EXACTLY 22mm, too!  Now she is purring like a kitten or, 'Smooth as Buttah'!  I found/cleaned out some small amounts of trash in the bottom of the petcock bowl, confirmed the screen was clean and scrubbed each float assembly as well.  I don't know where else trash my come from so from here out I'm hoping she STAYS running properly! Tomorrow, the fork seals and springs get changed......
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Offline harisuluv

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Re: '74 CB550 - New wires and caps...no change.
« Reply #15 on: July 28, 2015, 11:20:33 AM »
Good job Airbus.
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Offline RevDoc

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Re: '74 CB550 - New wires and caps...no change.
« Reply #16 on: July 28, 2015, 03:18:10 PM »
PM sent
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Dana

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As soon as you straddle a bike expect every other driver on the road to suddenly start competeing for the title "Dumbestsonofa#$%*inallNorthAmerica!!"
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