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Author Topic: 1975 CB550 won't start properly  (Read 2444 times)

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Offline I12

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1975 CB550 won't start properly
« on: July 06, 2012, 08:49:06 AM »
Hello everybody, I've recently bought a CB550 1975 that hadn't been used in years. So my first approach was to clean the carbs and then try to start it. Carbs are clean but for some reason the bike only starts on 1 cylinder (only getting one spark plug to go). I've replaced the previous spark plugs with new ones and still the same. The only thing I can think of is that the timing on the plugs is off but I'm also open to other suggestions.

Really appreciated
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Offline Greggo

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Re: 1975 CB550 won't start properly
« Reply #1 on: July 06, 2012, 08:55:54 AM »
If the bike hasn't been used in years, it will need a full 3K mile tune up, and more.  Have you done the tune up maintenance?  Do you have a shop manual?  They can be downloaded off this site if you need one.
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Offline I12

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Re: 1975 CB550 won't start properly
« Reply #2 on: July 06, 2012, 09:19:39 AM »
Thanks a lot for your quick response (^_^) , really appreciated. No I haven't done the maintenance yet, I've just check to see if the electronics (aka lights) turned on and I wanted to check if it would fire up. Once those two confirmed I was going to strip it completely and do a full rebuild, that was my thought process.
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Offline Greggo

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Re: 1975 CB550 won't start properly
« Reply #3 on: July 06, 2012, 10:01:26 AM »
Quote from: I12 on July 06, 2012, 09:19:39 AM
Thanks a lot for your quick response (^_^) , really appreciated. No I haven't done the maintenance yet, I've just check to see if the electronics (aka lights) turned on and I wanted to check if it would fire up. Once those two confirmed I was going to strip it completely and do a full rebuild, that was my thought process.

I think you're on the right track, checking that everything works before beginning a tear down, but that sounds like a mighty big bite to tear off if you're brand new to motorcycles...Many guys (not saying this WILL be YOU) start off right where you are, and end up with a pile of motorcycle parts, and lose motivation/get intimidated/lose track/never finish...

I'd suggest doing ALL the maintenance in a Full Tune Up, work on making it safe (brakes, tires, wheel/steering bearings, electrical/charging system), get some riding out of it, then decide where to go with it. 
« Last Edit: July 06, 2012, 02:58:58 PM by Greggo »
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Offline lrutt

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Re: 1975 CB550 won't start properly
« Reply #4 on: July 06, 2012, 10:49:07 AM »
What do you call cleaning the carbs?? full take off and dissassembly? If you didn't do this and make sure all the small passages were cleaned out, then that's what needs to be done.
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Offline TwoTired

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Re: 1975 CB550 won't start properly
« Reply #5 on: July 06, 2012, 11:29:35 AM »
Quote from: I12 on July 06, 2012, 08:49:06 AM
Carbs are clean but ...

No offense, but we've heard this before, many times, and then the carbs suddenly work after the reporter finishes the 5th "cleaning" cycle.

As the pilot circuits are a different circuit and much smaller, they often get cursory attention.  And many don't even know what emulsion tubes are, let alone where they are found inside the carbs.

The carbs have to have the right things cleaned before they will work properly.  Perhaps you could describe the process you performed?


If the carbs ARE actually clean and operable, then the entire tune up check list should be reviewed.  And certainly, the points cleaned of any film, visible or transparent.

You also need a good strong battery for spark to happen reliably.

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Lloyd... (SOHC4 #11 Original Mail List)
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Offline thep1pe

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Re: 1975 CB550 won't start properly
« Reply #6 on: July 06, 2012, 12:11:50 PM »
Is there a spark at the other 3 plugs?
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nibenon

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Re: 1975 CB550 won't start properly
« Reply #7 on: July 06, 2012, 02:04:52 PM »
This is my partner in crime. I know very little as well. But we have been working on our 2 new bikes together.

The carbs we're taken off  though not fully disassembled. The bowls cleaned out and all the passages there appeared to be clear. Too new to say for sure. They were cleaned out with soda blast. Guess the next step is like you said full disassembly.

The other plugs have spark, but weak. Battery is good and strong, solid 12V.

The coil read 15kohm between 1-4 and same with 2-3. With caps on 30kohm across.  5-6 ohms across the points side on each. The plugs are new.



As for doing a tune up and riding'r around, that would be a no go. No license yet, no insurance and no muffler... like he said, we are making sure it fires 1 thru 4 then tearing it down and adjusting/cleaning/rebuilding everything.


Oh and we have the clymer manual. Think its original. date inside says 77.



Edit:  battery now dead.no means to recharge. Jumping with car battery.
« Last Edit: July 06, 2012, 06:22:28 PM by nibenon »
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nibenon

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Re: 1975 CB550 won't start properly
« Reply #8 on: July 06, 2012, 02:26:02 PM »
Gonna bust out the timing light I guess ?
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Offline crazypj

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Re: 1975 CB550 won't start properly
« Reply #9 on: July 06, 2012, 02:30:59 PM »
Are plug leads on correct plugs? 1/4 & 2/3
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Offline Greggo

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Re: 1975 CB550 won't start properly
« Reply #10 on: July 06, 2012, 02:59:55 PM »
Quote from: nibenon on July 06, 2012, 02:26:02 PM
Gonna bust out the timing light I guess ?

How do the points look?
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Offline TwoTired

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Re: 1975 CB550 won't start properly
« Reply #11 on: July 06, 2012, 03:13:53 PM »
Quote from: nibenon on July 06, 2012, 02:04:52 PM
The carbs we're taken off  though not fully disassembled. The bowls cleaned out and all the passages there appeared to be clear. Too new to say for sure. They were cleaned out with soda blast. Guess the next step is like you said full disassembly.
It's not full disassembly that's required, it is "strategic" disassembly that is essential.  Follow the fuel path.


Quote from: nibenon on July 06, 2012, 02:04:52 PM
Battery is good and strong, solid 12V.
Sorry, that's not reassuring.

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Lloyd... (SOHC4 #11 Original Mail List)
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nibenon

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Re: 1975 CB550 won't start properly
« Reply #12 on: July 06, 2012, 03:24:20 PM »
Well actually... we've been jumping it with the car because we killed the battery.

Any good sources for disassembly, dont want to damage anything in the carb.
« Last Edit: July 07, 2012, 07:03:34 AM by nibenon »
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Offline TwoTired

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Re: 1975 CB550 won't start properly
« Reply #13 on: July 06, 2012, 05:41:46 PM »
Quote from: nibenon on July 06, 2012, 03:24:20 PM
Fine, I lied... we've been jumping it with the car because we killed the battery.

So, the strategy is to lie to people you are asking for help?

I think I'll be busy going for a ride.

Good luck!
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Lloyd... (SOHC4 #11 Original Mail List)
72 500, 74 550, 75 550K, 75 550F, 76 550F, 77 550F X2, 78 550K, 77 750F X2, 78 750F, 79CX500, 85 700SC, GL1100

Those that learn from history are doomed to repeat it by those that don't learn from history.

nibenon

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Re: 1975 CB550 won't start properly
« Reply #14 on: July 06, 2012, 06:08:17 PM »
Sorry the point was the  charge isnt the issue.  And the reading bdfore we killed the battery was 12.69V. Sitting at 10ish now
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Offline Greggo

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Re: 1975 CB550 won't start properly
« Reply #15 on: July 06, 2012, 06:11:23 PM »
Here's a guide for disassembling CB750 carbs, which are very similar.  Be gentle with the screws, as the holes strip easily.

http://www.salocal.com/sohc/tech/carb/carb.htm
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nibenon

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Re: 1975 CB550 won't start properly
« Reply #16 on: July 06, 2012, 06:19:45 PM »
Thanks. Ive found that before. Was hoping there might be a better resolution picture. I guess theyll make more sense with the carbs beside it
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Offline harisuluv

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Re: 1975 CB550 won't start properly
« Reply #17 on: July 06, 2012, 06:29:04 PM »
You took the bowls off the carbs and then cleaned them with soda blasting?  I'm not following.  If you are shooting into an undisassembled rack of carbs..  where is all the soda going and the gunk you are blasting off? 

So far this thread is very hard to follow.  Maybe you should regroup and give us all the details.  The REAL details.
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nibenon

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Re: 1975 CB550 won't start properly
« Reply #18 on: July 06, 2012, 06:44:49 PM »
Bowls off.  Soda blast the varnish  went mostly in my hair. Cleared all passages after with air.

Carbs now coming off and being cleaned as per link. Tracing all paasages and checking they are clear. Following by reassembly when cleanjng and bench setting has been exhausted.

Double che king all.wiring connections.  Pulling tappet covers to make sure the timing is in sinc with piston position valve positiln and points position.

 Recap ia that ita only firing on 1 cylinder.  I think ive recapped everythibg and layed out everything that we have planned to get some fire in 1 thru 3. Might have missed something.
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nibenon

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Re: 1975 CB550 won't start properly
« Reply #19 on: July 06, 2012, 07:36:08 PM »
Really appreciate the ideas and council from you guys. Been roaming this forum for about 2 months and reading everything I could. This is new to me, so if I could apologize for not knowing certain terms or thinking I've completed something but obviously hadnt followed the extent of the advise.

Progress will be slow on these next steps as they are monumental to us (read no experience) and I have some time commited to school for the next little bit.

Would appreciate any other ideas, will gladly try to clarify anything and hope we can sort this out on our end.

Will post results as they come.
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