Topic: 1974 CB550k Boss Maroon

[brett_bike]

It’s been a while since I’ve posted here. I’ve been out of the game for a bit. Moved from Colorado to Minnesota to halo my aging father…but that’s another story.

I recently picked up a 1974 CB550k with 8700 miles. It sat for quite some time and will need a lot of work but I’m excited to get back into it.

The bike wasn’t running when I picked it up. It had about 140psi in each cylinder and the price was right so I thought I would try my luck and see if I can make this thing a daily driver.

Here’s the list of things I’ve done since I picked it up a little over a month ago…

Disassembled the carbs down to each and every jet, o-ring and emulsion tube. Ultrasonic cleaned all of it and reassembled with new fuel line and o-rings.

Cleaned the tank, petcock, and replaced the fuel cap gasket. Also cleaned the vent on the fuel cap.

 Changed oil

Performed the 3000 mile tune up (adjusted valve lash, adjusted timing chain, adjusted points, timing, etc).

Replaced coils with new 5ohm coils, wires and caps. Original coils spark plug wired were too short (all me).

I’m at a point where it runs and drives but dies after about 5-6 minutes. It doesn’t seem to be a fuel delivery issue so I’m going to start looking into electrical. Possibly condensers to start.

Any advice on what to look for or what to try next
would be greatly appreciated.











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[Mark1976]

Nice bike, great buy, condenser's sound like a good place to start, good condenser's are hard to find.

[denward17]

I was thinking fuel cap vent, until you said no issues with fuel delivery.......

But I have a couple of questions:  Do you remember what clip position the needle was in?

Do you have all original brass in the carbs?

022 carbs?

Nice looking bike ....!

[brett_bike]

Thanks!

022 carbs and I think the clip was in middle position. I plan to digging back in to confirm.


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[brett_bike]

Correction.

Stock 4th clip from top.


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[newday777]

What a great find you have Brett.
Have you looked at the points while running in a dark garage? Are they sparking profusely on one set of points or both as it warms up running? The sparking would be a sign of the condensers going.
Are the points and condensers aftermarket
Aftermarket condensers are well known for short life.
If you need condensers get them from Honda only.
The points plate assembly is the best price wise to purchase.
South Sound Honda in Washington state shows the plare assembly for $80 for on line sales. (Usually the best price you will get anywhere)

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550KA_(76)_550_FOUR%2c_JPN%2c_VIN%23_CB550K-1230001/CLUTCH_%2b_CRANKCASE_COVER/f77665b3-598c-4e35-ad4b-7a873770e3e5/e9628b6c-887c-4435-8ab4-8152ec45d23f/y

[newday777]

Correction.

Stock 4th clip from top.


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Did you get aftermarket carb kits?(shiny brass)

[denward17]

Correction.

Stock 4th clip from top.


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Thanks for confirming, I think that is the stock position.  I just put new Honda needles in my '76 550 and I raised the clip to the center position because I was a tad rich on the low end with the 4th position.  Running better now...

[brett_bike]

Correction.

Stock 4th clip from top.


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Did you get aftermarket carb kits?(shiny brass)

All original brass bits. They were pretty gummed up when I got the bike so everything went in Berrymans Chem-Dip after the ultrasonic cleaning.


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[brett_bike]

What a great find you have Brett.
Have you looked at the points while running in a dark garage? Are they sparking profusely on one set of points or both as it warms up running? The sparking would be a sign of the condensers going.
Are the points and condensers aftermarket
Aftermarket condensers are well known for short life.
If you need condensers get them from Honda only.
The points plate assembly is the best price wise to purchase.
South Sound Honda in Washington state shows the plare assembly for $80 for on line sales. (Usually the best price you will get anywhere)

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550KA_(76)_550_FOUR%2c_JPN%2c_VIN%23_CB550K-1230001/CLUTCH_%2b_CRANKCASE_COVER/f77665b3-598c-4e35-ad4b-7a873770e3e5/e9628b6c-887c-4435-8ab4-8152ec45d23f/y

Tried to post a vid, but there is noticeable sparking from the 1/4 condenser.


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[brett_bike]

What a great find you have Brett.
Have you looked at the points while running in a dark garage? Are they sparking profusely on one set of points or both as it warms up running? The sparking would be a sign of the condensers going.
Are the points and condensers aftermarket
Aftermarket condensers are well known for short life.
If you need condensers get them from Honda only.
The points plate assembly is the best price wise to purchase.
South Sound Honda in Washington state shows the plare assembly for $80 for on line sales. (Usually the best price you will get anywhere)

https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB550KA_(76)_550_FOUR%2c_JPN%2c_VIN%23_CB550K-1230001/CLUTCH_%2b_CRANKCASE_COVER/f77665b3-598c-4e35-ad4b-7a873770e3e5/e9628b6c-887c-4435-8ab4-8152ec45d23f/y

Tried to post a vid, but there is noticeable sparking from the 1/4 condenser.


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Thanks for the link for new points plate/condensers. I’m pretty sure I have a couple points plate assemblies in my tool box. I’ll try those out first before I order something.


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[calj737]

That clip position is not correct. It should go up one slot to the middle. Yours is set very rich on the fuel mixture.

If your bike is dying after a short ride, describe the condition of the bike at that time: does it run out of electrical service? Does it sputter and die even while under load? Or does it die at a stop? Is it running normally then begins just fading?

You stated you don’t believe it’s a fuel issue, but gave no diagnostic assessment of proving that to be correct. Try riding the bike with the fuel cap open (not clipped shut) and see if that resolves the issue. Also, examine your fuel lines closely. And deep bends from too long a fuel line can trap air in them and cause havoc.

[brett_bike]

That clip position is not correct. It should go up one slot to the middle. Yours is set very rich on the fuel mixture.

If your bike is dying after a short ride, describe the condition of the bike at that time: does it run out of electrical service? Does it sputter and die even while under load? Or does it die at a stop? Is it running normally then begins just fading?

You stated you don’t believe it’s a fuel issue, but gave no diagnostic assessment of proving that to be correct. Try riding the bike with the fuel cap open (not clipped shut) and see if that resolves the issue. Also, examine your fuel lines closely. And deep bends from too long a fuel line can trap air in them and cause havoc.

From the documents I’ve seen the 4th from top is stock for the 74 CB550k.  Do you have documentation to confirm clip position?

I am seeing a rich condition on plug #1 but none of the others. 

When I leave my house it accelerates smoothly through 1st and 2nd up to about 30 mph. This is after a few minute warm up at idle. When in 3rd, sometimes 4th gear it’ll start to sputter while at cruising speed. Not accelerating hard, just cruising.

It will die when I come to a stop about a mile from my house. It will not start again for about 2-3 minutes.

I also thought it may be a fuel issue when this originally happened. I popped the cap and tried to limp home but the issues was the same as mentioned in OP. I’ve also confirmed no air trapped in fuel line and lines are short enough to continue a downhill route to the carbs.

Last night night I checked my condensers by starting it up in a dark garage and saw excessive sparking coming from the 1/4 condenser so I’m thinking that might be the thing to focus on next. This may explain the rich condition I’m seeing on plug #1. However plug #4 looks a little on the lean side.  I have done a carb sync and all carbs were adjusted and air screw 1.5 turns out from full in.

I have a few points plate assemblies from previous builds I may try to install. I also have a HM transistorized ignition module I’ll be able to install soon.

I took a video of the sparking condenser but don’t think i can post a video here.


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[newday777]

Do you have an in line fuel filter?
How are the fuel hoses run?(pictures!) Are the fuel hoses hanging lower than the carb inlets?

[calj737]

I would encourage you to pull plugs from 2/3 also to check their mixture.

As to which position for the needle clip, I’ve always been told 4th position from tip is correct for this year. Many have moved the clip to middle to enrich their carbs, or when they run pods. Second position is very rich by standard means.

It’s possible that the arcing you are seeing at the points plate is causing your issue since it seems associated with RPMs and timing advance, but there’s many questions to confirm that. What RPMs are you running in 1st, 2nd or 3rd? If it’s a timing related issue, then it would surface in any gear if you are hitting an advance issue. Normally, when the ignition plate fails due to heat-related problems, it takes much longer than a few minutes to rectify itself.

You could take a test ride with the points plate off and see if the issue abates. If so, then there’s a decent indicator.

To me, it sounds like the engine is flooding due to being to rich. You don’t need to let the bike idle to warm up; fire it up, little to no choke, jump on, ride off, choke off. Run the engine above 4,000 and nearer 8,000. These motors need/want to run in the upper rev range. Too many folks “lug” the engine trying to baby them because they’re nervous about their age when in fact you’re causing it undue burden shifting below 3,000 (if this is your case).

[Stev-o]

Nice find, don't see original Boss Maroon that often.  +1...change condensers with known OEM

[brett_bike]

I found my stack of old Honda parts and installed another condenser. No longer sparking so I took it for a ride.

Unfortunately no change in the issue I was having.

Here is some updated info on what happens.

The bike will pull hard in the upper RPM range until I roll off the gas and just cruise. Then I can hear sputtering and it stumbles the whole time. It’ll stall out like before so it doesn’t appear it was the condenser.

Not sure where to go next.

I’ll be perusing the forum for information while I start over on the tune procedure.


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[denward17]

Did you pop open the fuel lid while this was happening?

[calj737]

Pull all plugs to confirm their condition.

[brett_bike]

Did you pop open the fuel lid while this was happening?

Yes. No change


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[brett_bike]

Pull all plugs to confirm their condition.

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[brett_bike]

Given the state of my plugs, maybe I should be chasing a fuel/air mixture issue.


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[calj737]

Given the state of my plugs, maybe I should be chasing a fuel/air mixture issue.

Yes, you should be.
1-3 look pretty fouled. 4 looks unusually lean compared to the others.

If it were me, I’d be moving the needle back to the middle, confirm fuel levels in the bowls with the Clear Tube method, reset the air screws to 1.5 and pop in a fresh set of plugs. It’s about an hour’s worth of work and it gives you a better point to baseline from now that you’re experiencing issues and fouling.

My $0.02.

[brett_bike]

This might not be the entire issue, but it ain’t right. Carb #1 was really black in previous post  fuel level isn’t set correctly. The rest look good. Correct me if I’m wrong.
Carb 1 & 2.

2 looks to be set correctly
Carbs 3 & 4. Both look fine to me.


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[denward17]

yes, #1 is set with too much fuel in the bowl.  The others look great to me.