Topic: #4 Cylinder Not Firing-Figuring out why-CB550K1

[saxamaphone]

Hi guys, hope you all had a good winter.  Ours is just ending...still snow on the ground.  I got my CB550K1 running great 2 days before the snow came last October and just got a chance to ride it again this past week. 

Here's what I noticed:

The bike would stumble/lurch a bit in the low revs (I initially thought idle jet dirty).

Before I stored it for the winter the bike would start instantly every time but now can be hard occasionally.

Then I noticed that #4 header wasn't hot after a ride.  Checked the plug and it was very black and wet.  The rest of the plugs are a nice brown colour.

Put in a new plug and #4 started firing again for about 10 minutes then stopped again.  Pulled the plug and it was very black but not wet.

I cleaned the #4 idle jet, main jet and squirted some carb cleaner in the emulsifier tube but couldn't get it out with the carbs still on the bike.

Still had the not firing problem. 

I then did a compression test just after a ride and the number four cylinder came out at 120psi.  The rest were 135.  I was definitely disappointed.  I added a bit of oil into each spark plug hole and all the numbers rose significantly to 150.  I also checked the valve clearances and they were still good.

From what I've read this points to worn rings, right?

Is it possible to replace the rings on all pistons while the engine is in the frame?

One other less important problem is that the neutral light is now on all the time.  Funny how that started after sitting for the winter.

Any advice on this stuff would be greatly appreciated!

[phil71]

it could easily be that the valves are too tight .

[Duanob]

Storing anything gasoline powered over the winter is a beyotch!

As far as the comp numbers go, I wouldn't worry about it could be a just a stuck ring. The oil in the cylinder may help loosen it up. Riding will definitely help loosen it up.

You say you cleaned the idle jet but what about the pilot jet/slow jet? You need a super fine wire to be able to push through it. Also make sure the emulsion holes are clear on the pilot jet as well. I've noticed with ethonol in gasoline, when it sits and evaporates, it leaves a white powdery substance that clogs tiny jets very easily. Its almost a ritual to have to clean pilot jets after a winter storage. You may have to take the carbs back off the bike. Not a big deal, after a few times you get quick at it.

Good luck.

[saxamaphone]

Thanks guys.  The valve clearances seemed ok using the go/no go method (.002 and .003in).  I could try loosening number 4's a tiny bit.

I cleaned the slow jet as well, I was just calling it the idle jet.  Does anyone know if you can get the emulsifier tubes out with the carbs on the bike?  I'll probably have to take the carbs out anyway to be sure about them.  Any great methods for getting the emulsifier tubes out period?

[iron_worker]

Just pull the carbs. It's not that hard and will make your life a lot easier getting those emulsions out.

Not sure about the 550 but on the 750 the main emulsion tubes are threaded into the carb body and the main jet is then threaded into that.

However, looking at the parts fiche for your bike:

http://www.cmsnl.com/honda-cb550k1-four-usa_model466/needle-set-jet_16012323004/

It looks like the emulsion tube is built into the needle jet which is pressed in to the carb body from below. The 750 has the needle jet also pressed into carb body from below but the emulsion tube is not part of it.

The best way to get it out is to pull the slides out and use a wooden dowel that has been sharpened (pencil sharpener?) to drive it out with a hammer.

IW

[Duanob]

To remove the emulsion jet from a 550 I take a piece of coat hanger about 3" long and take 1/8" and bend 90 degrees. When you remove the main jet from the bottom of the carb pull the slide up and use the coat hanger ot reach in and push the tube down, it should just fall out after that. Also I would remove the slides from the carb and clean the needles with 0000 steel wool (or brass wool) as well as the emulsion tubes since they fit together.

[DustyRags]

Tried swapping spark plug wires around? I had a bad plug boot that would start arcing to the engine block, but only some of the time. Rule that out first- it's fast, cheap and easy.

[saxamaphone]

Thanks guys.  I took the carbs off tonight and I'll be making sure I get the emulsion tubes out and clean.  I didn't try switching spark plug wires yet so I'll give that a go and see how it goes.

Cheers

[saxamaphone]

So after taking the carbs off and cleaning all jets and passageways cylinder number 4 is still intermittent and the bike stutters at low rmps in each gear.  It was my first time taking out the emulsifier tubes so I recorded it thinking it might help someone else new like me.  The manual wasn't obvious to me about how to do it.

CB550 Slide and Needle Jet Removal

Since I had the carbs out and clean I decided to put new fuel line on as well.  I put on some clear line and I noticed that my problem might be related to my fuel line routing.  Carbs 3 and 4 might not be getting consistent fuel.  I've been messing around with different ways to route the lines but it still looks like the line to 3 and 4 has a flat spot where it's not full of fuel.  I was having trouble trying to get a constant downwards path for them.  Any thoughts?

Here's how they're routed:



Tried to get a good shot of the part of the line I'm talking about:





Cheers

[jamesbekman]

Did you put a new spark plug in?  At the very least switch the spark plug to a different cylinder and see if the symptom follows and the number 4 cyl runs now due to a different spark plug being fitted. 

[saxamaphone]

First thing I did was change the spark plug and switch plug wires.  The new plug got seriously blackened right away though.  Number 4 is better then before now and I'm betting it has to do with not getting fuel. 

[iron_worker]

Are you routing the fuel line up from underneath the inlet rubbers? If so, that's probably giving it a good place to trap an air bubble which may be causing fuel delivery problems.

Although if the spark plug is getting blackened very quickly that points to an over-rich problem. Did the missing problem clear up when you changed the plug for a while? Is it possible that you are over-rich at idle and fouling plugs and causing an intermittent miss?

Have you checked the resistance of your plug caps? Another member was experiencing a miss due to a bad plug cap.

Trimmed back the ends of the plug wires to expose fresh, uncorroded wire?

IW

[saxamaphone]

Thanks IW.  I noticed your from Saskatoon.  I bought this bike there last year.

Here's what I've done so far:

1. Cleaned carburetors and lubed/adjusted throttle cables.  Carbs are completely stock and the air filter is a Uni stock replacement.  4-1 Mac exhaust.

2. New plug - cylinder 4 would fire for a bit then get fouled and not fire.  It's sooty, sometimes wet and sometimes smells of gas.

3. Switched wires and even tried caps - #4 wire worked fine on #1 cylinder

4. Took carbs off again and reset float levels, also double checked jets - This seemed to almost fix the jerky, stumbling at low rpms but the bike then had very little power through all gears.  Also tried various air jet changes.

5. Replaced points, gapped them, and static timed.  I had experimented with retarding and advancing the timing but it had no noticeable effect so put it back where it was before I started.  Waiting to borrow a friends strobe.  The points have way more spark then my old ones but no obvious affect on the bike.

6. Re-adjusted the valve clearances and cleaned/gapped plugs.  Some of the valves had been a bit too high, but not by much. The bike ran a bit better and this seemed to help with #4 cylinder firing but the pipe didn't get as hot as the others and the plug was still fouled.  The other three looked nice and tan-brown again.  This could have been the plug clean then fouling again.

7.  Adjusted #4's valves a tiny bit tighter, .002 still fit, went for a ride and this time the bike had very little power through all the gears again, the throttle response was very weak.  The jerky stuttering was also back with a vengeance.

The small changes in valve clearances seemed to have drastic effects on the bike, although it could be the #4 plug getting fouled again.   I haven't taken the head off to check the rings on #4 and hopefully don't have to.

I'm not sure what else to do yet.  The carbs were synced last fall just before putting the bike away.  I'm planning on doing it again once I sort this jerkiness and cylinder not firing.

The low rpm jerkiness and #4 not firing consistently still continues...

[mono]

i'm running the same configuration as you (stock jets, UNI filter, MAC 4-1) and i need to leave the choke open slightly to keep it from bogging down.  I think the MAC exhaust demands larger main jets.

I know opening the choke will do nothing for your #4 issue, though.   have you checked for vaccuum leaks?  generic suggestion, but my #3 freaked out when it got a small tear in the boot between the carb and airbox.

[phil71]

did you get the emulsion tubes out? Double check that your needles are set up like this>>
can't tell you how many of these bikes I've come across missing the o-rings or the washer, or both.. and then you can't tune worth a damn.
  Also, crack the book and do a complete 3000 mile service , step by step. NO shortcuts.
You also need to stop thinking about how well it ran last season.. so many little things can make a bike run crappy ..

[mono]

Phil, what carbs are those from?   My 022A's definitely do not have any of that stuff.

[saxamaphone]

Thanks for the input guys.  I'm with you mono, the air screw washer and seal weren't with my bike when I got it.  I didn't realize they were supposed to be there.  Are they included in the gasket kits?

Phil, I did get the emulsion tubes out.  All jets were spotless.  I've taken the slow/idle jets out a few times over the past couple days making sure they were ok.

I've done everything from the 3000 mile service except a carb sync, which I had done just before putting the bike away for the winter.  I now have a vacuum sync but was planning on doing it once I sort everything else out.  Since I only got the bike ready for inspection last fall I've probably barely put 60 miles on it.  I changed the oil when I got it last summer, again before putting away in the winter, and again just before getting it going this spring.  The oil that sat in it over winter came out pitch black.

Edit:  I also haven't replaced any condensers if that's included in a 3000 mile tune up.

[phil71]

those needles are from a 78 cb 550

[LesterPiglet]

those needles are from a 78 cb 550

So they aren't the same as the OP's then. Didn't the 78 have PD carbs?

[dave500]

how old are the plug caps?try measuring the resistance through them.

[saxamaphone]

Hey guys, the plug caps are in very good condition but came with the bike so I have no idea how old they might be.  I'll try measuring the resistance on them.  I have a new set if need be.  That said, I've trimmed the wires a bit and 1-3 are working fine and 4 on 1 works fine as well.  Just the #4 cylinder seems to be having some trouble firing.  Took the #4 carb bowl off, cleaned jets, checked float height again and cleaned the plug but no dice, still not firing really.  Pipe is barely warm and plug gets fouled quickly. 

For the air screws, I guess the earlier CB550s didn't come with the small washer and gasket ring?

[iron_worker]

Small changes in valve clearance should have pretty much imperceptible effects on how the bike runs. You have something else going on ...

Have you checked for compression on that cylinder? Get back to the basics.

IW

[Duanob]

"I've taken the slow/idle jets out a few times over the past couple days making sure they were ok."

How? Do you have a K&L carb tool? If so then you should be able to get the second to the smallest wire through the slow #38 jets, anything less and they are partially clogged. I found out after a few cleanings. I bought a new set of pilot jets for another bike and for kicks and grins I tried the carb tool. I always thought the smallest wire was the one but after trying the new jets I could go one size bigger wire. After thoroughly re-cleaning my current jets with the bigger wire, and it took some doing, my bike ran better than ever off idle. Still does.

Also is your tank full? Here is a forehead slapper, I had the same problem as you when I first got my bike. Number 3 was firing but not great, number 4 was barely firing. I went through everything, except the amount of gas in my tank. Thinking a half gallon would be plenty even on reserve it wasn't. Another gallon of fuel later and the bike fired right up and ran excellent. For some reason the 3/4 split was'nt getting enough fuel. Of course a 76 has a different fuel tap. Just a thought.

[goldarrow]

have you checked the spark plug wire of number 4?  the copper inside may be broken and cannot be seen, try to bend along the wire to get the feel of it. 

on my bike, no.1 was only warm/cold, cut the tip of the wire didn't help, then i bend the wire, felt something strange along the middle of the wire that i had the feeling that the copper wire inside broke, so i ordered NGK plug splicer, for about $5, installed it.  engine has been hot ever since.  now my bike is running rich, air screw at 2 turns out.  but that's separate issue lol

[saxamaphone]

Thanks guys.

Duanob- I've been using carb cleaner and a high E guitar string.  The B string is too thick.  Even medium gauge E strings can be slightly too big.

The tank still has lot's of gas and I've had the bowl off with the fuel tap on checking the flow and making sure the float closes the valve and stops the fuel.  At first I thought is was a fuel line thing.

I've tried the #4 wire on the #1 cylinder and it fired well on that cylinder and the plug was still brown.  The #1 wire did nothing to help the #4 cylinder.  Even traded just the caps.

I was just out installing allen head carb screws and decided I'd do the valves, points and timing again.  Yesterday I had just put on brand new Honda (TEC) points I got from the Honda dealer here.  I had gapped them yesterday and checked the timing.  Today however, I realized the 1-4 points don't have enough spring in them to close, even off the bike.

I also noticed that there is continuously current going through them.  I put on my old 1-4 points with plenty of spring in them and there was still always current running through them, even when open.

When 2-3 fired I heard a distinct electrical spark type sound coming from one of the coils.  I don't remember hearing that before.

Does this sound like a condenser and/or coil problem?