Author Topic: #4 Cylinder Not Firing-Figuring out why-CB550K1 (Read 8458 times)

iron_worker · « **Reply #25 on:** May 09, 2013, 01:05:18 PM »

Could be a condenser problem... only think is why wouldn't the issue occur on both #1 and #4 cylinder. You changed the plug wires and the problem did not follow. To me this suggests that is something specifically with that cylinder:

1) bad plug
2) low compression due to valves or rings
3) carb issue on only that carb

IW

saxamaphone · « **Reply #26 on:** May 09, 2013, 03:01:43 PM »

I agree with you IW. I've tried a couple new plugs in there already. I just put on a new Honda condenser on 1-4 (had a hell of a time getting it off because the bolt was very stripped). I'm still getting between 10.7v and 11.8v on the 1 & 4 through a complete revolution of the shaft. This wasn't the case when I put it away for the winter.

I'll check the coils next. Just read twotired's FAQ post on that.

Duanob · « **Reply #27 on:** May 09, 2013, 04:10:48 PM »

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

A bad wire would do that and explain the one cylinder misfire. have you tried a spark tester or just taking the plug out, put it in the cap and lay it on the cylinder to ground? You should be seeing a good consistent spark every revolution.

saxamaphone · « **Reply #28 on:** May 09, 2013, 04:14:55 PM »

I hope I checked the coils properly. Here's how I understand you do it: I checked the resistance from the black/white wire for 1-4 to the blue wire at the 1-4 points. I got 5.2 on each coil. I checked my old condenser and the new one and they both read 0.9. This is with the meter set at 200 ohms.

Duanob · « **Reply #29 on:** May 10, 2013, 08:13:30 AM »

"I hope I checked the coils properly. "

that's fine but you should start at one point and work backwards. Diagnosis is a process of elimination in a certain sequence. Start at the plug, then the plug cap, then the plug wire. Then the coils. Frankly with a one cylinder misfire I doubt its the coil. points or condensor. it could be a bad wire connection into the coil although rare, then you will need a new coil.

iron_worker · « **Reply #30 on:** May 10, 2013, 08:55:24 AM »

Quote from: saxamaphone on May 09, 2013, 03:01:43 PM

I agree with you IW. I've tried a couple new plugs in there already. I just put on a new Honda condenser on 1-4 (had a hell of a time getting it off because the bolt was very stripped). I'm still getting between 10.7v and 11.8v on the 1 & 4 through a complete revolution of the shaft. This wasn't the case when I put it away for the winter.

I'll check the coils next. Just read twotired's FAQ post on that.

Well first of all 10.7-11.8v are both in the range of LOW. If your battery is that low then it's dead. If you have that much voltage drop to your coils then you may have a problem as well.

The other thing is that your points should switch your coils from ground to open and thus the voltage should be 0v when they are grounded and battery voltage when they are open. If the points are not switching the ground then your coil IS NOT FIRING! It can't! That would be a problem on both of those cylinders though.

The way I check my points function is to unplug their bullet connectors and hook up your volt meter (set on resistance mode) to the POINTS side of the bullet connector and to ground. When the points are open you should read infinite resistance (open circuit) when the they are closed it should be close to 0 resistance (closed circuit). You don't have to have the power on to do this test.

Are you sure that #1 is firing but #4 is not? If #1 is for sure firing then it's not an issue with your 1-4 points or coil.

IW

saxamaphone · « **Reply #31 on:** May 10, 2013, 02:20:21 PM »

The battery is probably being drained as I'm turning the ignition on and off testing things and haven't charged it in a few days. Just charging it now.

I'm sure that cylinder 1 was firing because the plug was a nice brown colour and the pipe was normal hot. My gloved hand would smoke with a very quick tap. #4 you could just touch normally.

The 1-4 points are reading around 11v open and closed which I don't understand. That definitely is new since last fall. 2-3 act normally.

I found a problem but I don't know enough to know wether this could cause the #4 cylinder to not fire. The 2-3 coil wire that goes in to the dual-socket terminal by the ignition is making the shorting sound I was hearing. As I was cleaning all the connectors around the coils I saw that the socket for 2-3 is kind of broken and the bullet connector is loose in there. I'm sorry I'm not explaining this better. The socket without a wire plugged in is the broken one.

I tried bending it back so it's tighter but it just flops open when you insert the bullet connector.
Could this loose coil connection cause the problems with #4 cylinder? I went to Princess Auto (Canadian chain) and the only had single bullet connectors, no duals.

I also tested the 1-4 points with the 2-3 coil wire unplugged but they still weren't stopping the current at any point through a turn of the crankshaft. No more short sound with the 2-3 wire unplugged though.

iron_worker · « **Reply #32 on:** May 10, 2013, 03:15:26 PM »

If your 2-3 coil is shorting out then it should not be firing those cylinders properly. Or do you mean it's arcing within the bullet connector itself?

http://www.vintagecb750.com/

They sell to canada and have various connectors for these old bikes.

Try testing your points like I described using resistance mode.

IW

DustyRags · « **Reply #33 on:** May 10, 2013, 04:50:16 PM »

The electricals are an issue, no doubt, but if it's not following when you move the plug, cap, wire, etc, then that isn't what's causing your cylinder to misfire.

I forgot- have you done a compression test yet?

saxamaphone · « **Reply #34 on:** May 16, 2013, 01:45:26 PM »

Thanks Dusty and IW. I'm thinking electrical as well.

Quote from: DustyRags on May 10, 2013, 04:50:16 PM

I forgot- have you done a compression test yet?

I did a compression test when this first started. 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. They're definitely not perfect but it doesn't explain the no/weak spark from the plugs.

Earlier I mentioned I was finding that the 1-4 points were showing constant power, even with brand new points from Honda. I realized that the 1-4 points weren't snapping back closed like they should. If I pulled them back manually, they'd stay open. I lubed the little part that pivots and that seems to have fixed it. Is there anything else that can cause that kind of thing? It didn't fix my main problem unfortunately.

I charged my battery again thinking maybe it wasn't putting out enough. I then had some small spark when testing the plug agains the engine. So I thought I'd go get a brand new Yuasa battery maybe things would be that easy. After charging the new battery according to the directions I was getting no visible spark from brand new plugs.

So I searched the forum on how to test electrical problems and came up with these results:

Quote from: iron_worker on May 10, 2013, 03:15:26 PM

If your 2-3 coil is shorting out then it should not be firing those cylinders properly. Or do you mean it's arcing within the bullet connector itself?

IW

The 2-3 black/white wire is probably arcing. It's loose in the connector and there's a blue spark if you jiggle it. The weird thing is that 2-3 are running fine. I was checking the spark with 1 and 4 plugs out and the bike started instantly with barely a kick on 2 and 3 only. I didn't expect that since I'd just been trying to start it with all four plugged in! I'm getting a new dual female connector.

The caps tested at 1)7.4, 2)10.2, 3)9.7, 4)9.3
I'm assuming these were 10k plug caps from these numbers. Number 1 looks finished to me but how do the rest compare? They don't really screw into the wires. Mine seem to pop off if you like. I've trimmed the plug wires about 3/4in.

I checked the coil wires end to wire end and got these results: 15.4k and 15.3k ohms. These seem to be ok from what I've read.

For the primary reading I got 5.4 for each one. These also seem to be ok from what I've read.

At both sets of points I'm getting 11.7v when open. They are firing at the F mark.

Battery says 12.7ish after charging and letting it sit. 13.4 just off the charger. I put a small needle into the 1-4 coil wire to check if current was getting to the coil. I got 11.7 with the bike not running.

I decided to clean all the connections between the battery and the coils thinking maybe there's weak to no spark due to voltage loss through the line. It didn't change anything unfortunately. I haven't done the connections in the bucket or the kill switch yet as I ran out of time. Tomorrow most likely.

Checking between the battery's positive terminal and the black/white wire going into coil 1-4 I get between 0.7 and 0.8. That's the voltage loss between the battery and the 1-4 coil according to what I read from TwoTired. As an experiment I unplugged the black/white coil wires and checked the voltage at the dual connector. It dropped to 0.3. I checked with only the 1-4 coil wire and it stayed. With the 2-3 wire back in, it rose to 0.7 again.

So I still don't really know what's going on. I'm not sure if 11.7v should fire the spark plugs or not. Any help is greatly appreciated as always.

Last thing, I have a Hondaman ignition to put on but I'm waiting to get the bike working properly before putting it on.

saxamaphone · « **Reply #35 on:** May 21, 2013, 03:35:49 PM »

I was cleaning up connections in the headlight bucket and ran across a double female connecter with two black wires in one end but nothing on the other side. I checked the wiring diagram but couldn't find anything like that. Anyone know if and what's supposed to be there? I've read about a brown wire that's there for adding extra things to but can't find anything on this.

(It's just a bit of dirt on the green wire.)

I'm still not getting any visible spark from 1-4 and just a tiny spark from 2-3. I cut back the wires even a bit more but no change. I'm taking apart the right switch to clean up the connections in there as well. Maybe it's the black/white wire that goes from there to the coils.

I had put on Hondaman's blade fuse holder in the winter so I plugged the old fuses back in just in case it'd make a difference. No change from that.

Hope you're all enjoying some good weather somewhere.

DustyRags · « **Reply #36 on:** May 21, 2013, 04:35:35 PM »

Man, that is weird.

But it still sound like it's not following the plug when you move the wire around, does it? Can you swap out a coupla (say, the 1 for the 4 wire, or the 2 for the 3) and get the issue to follow that coil/wire/cap/plug string? Or did you do that and I missed it?

I admit that I'm horrible with electrics, so I'm trying to get the issue back on ground I understand

saxamaphone · « **Reply #37 on:** May 22, 2013, 09:25:54 PM »

You can't be as bad as me! My first time at this. I tried swapping caps, 1-4 wires and that didn't change anything. Can you put 2-3 on 1-4, basically changing coils?

I now have spark on all plugs when I test them on the engine (looks ok to me but not a big blue one like I've heard about).

I'm still getting about 10.6v at the points when I test them with the ignition on. I was under the impression it should be the same roughly as the battery.

1, 2, and 3 are all firing consistently now but 4 is still not. A clean plug in #4 comes out wet after idling for a couple minutes.

So things are looking like it's something with the cylinder. When I did a compression test, #4 went up a fair bit after adding a bit of oil in the spark plug hole so maybe the piston's rings are stuck. I tried squirting a bit of Seafoam's Deep Creep around the piston in case it freed them up but no change after letting it sit for a day.

I put a drop of gas on the #4 spark plug and that worked to fire the cylinder. #4 ran fine once it started but when trying to start the bike normally, #4 doesn't fire. It seemed to run better with the air screw all the way out. Weird. I tried varying the float height a bit but that didn't seem to make a difference.

I'm tempted to check the piston rings to see if they're stuck. Is that possible with the engine in the frame?

DustyRags · « **Reply #38 on:** May 22, 2013, 10:26:08 PM »

Try this: Take the whole thing (coil down- so wire, cap and plug) and switch 1 for 4. 1 and 4 always fire together, and 2 and 3 always fire together, so you can swap those out and see if it follows the wires (electrical problem) or stays with the cylinder (mechanical problem). Maybe you did this already- you said you swapped caps- did you move the cap and wire assembly to another cylinder, or undo the caps from the wire and move just the caps?

It sounds like it's stuck with the cylinder, but prove it. Once we have that proved, we can rule out the electrical system (doesn't mean it doesn't have problems, but it means that it isn't causing THIS problem, or at least not entirely).

Then: If you're getting compression, then your rings should be OK. Maybe not great, but OK. Did you say that once #4 cylinder starts, it keeps banging away? That's a new one on me.

saxamaphone · « **Reply #39 on:** May 27, 2013, 03:00:59 PM »

Hey Dusty, thanks for the suggestions. I had tried switching the wires and caps for 1-4 when this started and it didn't make a difference. 4 still didn't fire and 1 did. However, I just tried it again a couple days ago and they both were firing away! Very confusing.

I've got new caps coming and I'm thinking of splicing the wires. The plug caps don't really screw in and they just pull off with little resistance. I've already cut them back at least an inch.

In unrelated news, my rear tire/tube that I got a shop to put on just before putting it away for the winter isn't holding air. Took off the wheel to bring it back which was my first time. Any suggestions for things to check/clean while the wheel is off?

I think I found where I'm losing some voltage. I get 12.6v until the ignition switch. I took it apart to clean today and when I got the plastic part out things spilled onto the floor. Felt very dumb. Found a spring and a small ball on the floor.

I haven't been able to find how to reassemble the pieces in the ignition switch so does anyone have a photo of what is supposed to go back where? Many thanks.

saxamaphone · « **Reply #40 on:** May 27, 2013, 04:26:45 PM »

I figured out the ignition switch assembly. It's not complicated but I just wasn't sure what the proper way to assemble it was. Went with intuition. I forgot to mention that I replaced the broken female connecter to the coils a few days ago as well.

Put the ignition switch back on and gave the bike a kick. Started perfectly with one kick! #4 was getting hot just like the others and it purred great at 1000 rpms.

I still have the 1-4 wires/caps switched. Too nervous to put them back to their original positions

I'll time it with a strobe, and sync the carbs. I got a vacuum sync from DCC so looking forward to trying it out.

As I said, I've got new caps coming but I had a couple questions about the old ones:

The caps tested at 1)7.4, 2)10.2, 3)9.7, 4)9.3
Am I right in assuming those are 10ohm caps?
And do those readings seem way off?

Thanks guys. I'll the tire back on ride for bit and see how things go.

Vinhead1957 · « **Reply #41 on:** May 27, 2013, 05:40:44 PM »

It doesn't matter if it is on 1 or 4 let it be! Don't get nervous get a set of good caps. I think you may need the 5k look also at the plugs are you running resistor plugs?

DustyRags · « **Reply #42 on:** May 27, 2013, 08:08:44 PM »

Awesome, that's great news! Sounds like maybe it was the plug or something after all- great to hear it's sorted! Vinhead's right- get new caps! Can't hurt, and can make a huge difference.

saxamaphone · « **Reply #43 on:** May 28, 2013, 10:23:54 AM »

Cheers guys. The caps that are coming are 5k ohms. The pugs I've been using are the D7EAs.

I'll let you know how things go after I ride it for awhile. Thanks.

DustyRags · « **Reply #44 on:** May 28, 2013, 02:44:39 PM »

Vroom vroom, baby!

saxamaphone · « **Reply #45 on:** August 21, 2013, 03:53:14 PM »

Hi guys, hope you've all been having a good summer. Other than gnashing my teeth over not being able to get my 550 going properly mine's been fine.

Since I started this thread I've replaced and checked a bunch of things but nothings made a difference. My #4 spark plug gets heavily dry carbon fouled after a couple miles of riding and the cylinder stops firing.

I realized today that when checking the timing with a strobe gun attached to #4, it doesn't consistently fire. Each other cylinder has a nice steady strobe. I remember now that it's been doing this the whole time.

I installed new 5ohm Dyna Coils and wires last week and I reset the float levels for the carbs, cleaned idle and main jets again. There's good spark on #4 when I test against the engine. Air screw 1 turn out. Have tried farther out but doesn't make it any leaner.

I'm wondering what could cause intermittent firing on just #4 cylinder? My theory is that the misfires are fouling the plug quickly.

DustyRags · « **Reply #46 on:** August 21, 2013, 10:32:27 PM »

In my case, it was bad caps. They were arcing from the cap to the cylinder head. Have you replaced those yet? Cheap fix.

saxamaphone · « **Reply #47 on:** August 22, 2013, 09:55:37 AM »

Hi, I did replace the caps. I'm using the ones that came with the Dyna wires so they're brand new. Also replaced coils with Dyna coils. New points, condensers. It seems I'm having the same problem as I've had all along.

I'm finding it tough to figure out. I've cleaned the carburetor jets multiple times recently. Can incorrect timing cause one cylinder to foul it's plug?

I synced the carburetors a month ago but I've since made changes so maybe I'll sync them again but it didn't make a difference last time.

Is there anything else on the electrical side that could cause this persistent misfire on one cylinder?

DustyRags · « **Reply #48 on:** August 22, 2013, 06:21:21 PM »

Ah, got it, didn't see that further up.

I'm tapped out man, but I'm definitely still a beginner in this game. Maybe Dave or someone will rear their ancient head and bequeath wisdom upon us all?

saxamaphone · « **Reply #49 on:** August 22, 2013, 06:55:01 PM »

Thanks Dusty, I appreciate it.

I made a little headway today I think. I noticed when I would redo my static timing using a multimeter that I could have the plate in a position where it looks like the points haven't fired yet but when I tighten the plate bolts a bit, they'll spark. I tried timing it only with a gun and that seemed to help avoid that problem. I also tried to prioritize the advanced timing over the idle. I also tried adding a shim to the timing plate as per TTs FAQ post.

#4 seemed to start to fire consistently. Then I did a carb sync and got the gauges extremely close.

Unfortunately the engine is surging and hanging at a high rpm even after sync. I'm thinking my air filter side boots are leaking air. Tried wd-40 where they attach but I didn't notice much of a difference so I'll look for new clamps. Mine tighten all the way bit are still not very tight.

#4 seems to be hanging in there though!

News:

Author Topic: #4 Cylinder Not Firing-Figuring out why-CB550K1 (Read 8458 times)