Topic: 75 CB550 K - Dead cylinder #3 & 4- fixed 2nd and final(?) time.

[scottly]

If the problem was with the points or condensers, the problem would be with either 1&4 or 2&3. Spark has been confirmed on both offending cylinders. Why would the bike not run when the coil leads were switched to 1&2? If 1/2 of each coil had somehow failed, which is unlikely, 3&4 should have run.

[Gene]

If the problem was with the points or condensers, the problem would be with either 1&4 or 2&3. Spark has been confirmed on both offending cylinders. Why would the bike not run when the coil leads were switched to 1&2? If 1/2 of each coil had somehow failed, which is unlikely, 3&4 should have run.

I agree.

Ran out of time yesterday but checking the things suggested tonight. will check back in then.

[Gene]

This is easily checked.

Do a simple test with the ignition off. First, have some plastic, business card or whatever between both sets of breakerpoints (left, 1+4 as well as right, 2+3) so both sets are isolated (both are open as it were). Then hold one probe of your ohmmeter against the spade connectors at breakerpoint 1+4 and the other against the groundplate and see if these spade connectors accidentely ground. Repeat with 2+3. Please report back.

I tested this w/a timing light having misread the advice. It's raining now so I will test w/the meter tomorrow.

Lesson today: Read in full.

[Gene]

You haven't stated anywhere but have you set the timing while running? Also what points gap and plug gap are you using?

Have you done any tests on your coils? Maybe they are bad and when getting warm they fail. Being 2 different cylinders means 2 diff coils acting up.

What plugs and caps are you running?

NGK plugs and caps. Static timing (not stroboscopic yet).  .25" plug gap, .15" point gap.

Off to dinner.  Thank you for replying.

5k ohm caps and non-resistor plugs? Should be D7ES plugs and 5k NGK caps. Also plug gap should be at a minimum of 0.028

Back to this for a sec (thanx FireBane): It caught my eye because I've seen time and time again use D7EA plugs. So that's what I bought. However, I'm a hoarder and found the plugs that came WITH the bike were D7ES. Could it be this simple? I know there are certain plugs that run hotter - and it still doesn't explain why 1 side is firing the other not - but it begged attention. Curious is all.

[Gene]

Well, sh*t.  Petcock flow is good, line is clear. Can't get at the vents really unless I take off the carbs. Just a quick eval. Started up on second kick after putting it all together (just for yucks) - same result. 1 & 2 firing, 3 & 4 not.

Pulled the plugs, wet. Dried, cleaned, tried again, same result. No change in the pics above (re: plugs), btw.

So, tomorrow, moving on I suppose. Truth is, at this point I oughta pull the damned carbs and send 'em to harisuluv for a going-through. It can't hurt and, as I've said repeatedly, I'm an accountant with a wrench. Doing my best, but sh*t. Have a real pro work on it. At least we know where we stand, right?

Anyway, great ideas so far guys, and I'll keep plugging away. I miss my 550.

Adios for now.

Gene
These are the same results you stated in reply #10 of this thread. I base(ed) my sugestion
earlier on these same symptoms you're describing. In your earlier reply you mentioned
gas pissing from the carb overflows. Does this occur now as well? Is there still spark? If a carb or two are
flooding quick enough, maybe just before start up even, the plugs for suspect cylinder(s)
can get wet fouled, and stay that way unless the carb stops flooding. You can determine
if any are flooding with the clear tube method. This is an interesting thread, it will be
interesting to find a cause. Respectfuly, I don''t mean to start a sparring contest with
anyone, and appreciate your frustration. The answer is here somewhere
and +1 on replacing 3-4 plugs.

Nobody, just wanted to respond. You're right I should do a clear tube test anyway - Still have spark, no pissing of gas since on the last few tries, but I'm also turning the petcock on for 20 seconds and turning it off during testing so I don't forget to turn it off. you have good ideas. As far as I can tell, everybody's fine on this minor thread. Thank you.

[Gene]

Quick summary: We have spark, we have fuel - at least the indicators point to both. The only think left is air. It is possible that while cleaning the jets, which I did having pulled them, and cleaning the float needle bushing which I pulled - AND THEN after re-installation, blew some compressed air through - lodged some POS from that area into the air screws. (?) just a thought.

First, will check with my OHMMETER the suggestion Delta made. Looking at it seems ok, not touching the plate, but my eyes suck.

I'm off for the night.

[my name is nobody]

A crap shoot, but maybe with fuel valve turned off, drain bowls of suspect cylinders,
remove plugs of nos, 3-4 cyls, dry them off. Turn kill switch off. Turn the engine over with the kickstarter to expel excess fuel if any.
 rReinstall the plugs and turn the kill switch back on. Turn the fuel on 3-4 seconds
so as to allow the bowls to refill,(but not long enough to flood) and turn the fuel valve OFF.
This way, YOU control, to some degree of normal, how much fuel is delivered to the carbs.
Then restart and note if any change. It should at least try to run cleanly, even if
only briefly, before fuel in the bowls is used up. Check the header pipes for hot.
Not to beat this topic to death, just some possibilities I'd look at knowing the
carbs have a history of running out the overflows. They can even cause low compression
if there is enough raw fuel to wash the oil off the cylinder walls.

An inductive timing light clamped on suspect cylinder wire can give an idea whether
or not the ignition is delivering spark. Consistantly flashing without interruption is good,
verifying system is producing and delivering spark. Wetness/deposits on plugs invite
misfire, as the spark tends to go to ground easier thru them if present, rather than
jumping a gap.

D7ES is the old number for the D7EA

[Gene]

Thanx Nobody

Delta - finally got around to your directive.

Points separated (open) red on blade, black on plate

1 & 4 = .007
2 & 3 = .007

Do I have the meter set correctly? I think so, but I don't know for sure. My wife the engineer isn't home.

P.s. - this is edited because the first time I checked I didn't have both open - only 2 & 3 (by chance)

[Deltarider]

1 & 4 = .007
2 & 3 = .007

That's OK.
If your meter shows '1' it indicates you need to select a higher range. At least on all of my DMMs it does.

[Gene]

1 & 4 = .007
2 & 3 = .007

That's OK.
If your meter shows '1' it indicates you need to select a higher range. At least on all if my DMMs it does.

Delta - thank you for that info, it helps a lot.

Today I'll pull the plugs again, check, pics, clean, try Nobody's suggestions and see where we are.

Late last night I put one of the old original plug caps back on 4 - purely on "feel" it seemed the new plug cap wasn't making a tight connection - and started getting activity out of 4. If it had a clean plug it may have worked better. Today I have some quality time, and a garage available, so I'll update as I go along.

[Gene]

I went through the steps Nobody suggested. No reaction, at first.

Re-set points, checked for spark (again). Everything seemed fine.

Kicked her over and had 1 & 2 firing fine. Pulled #4 plug, cleaned a little, kicked and all but 3 firing fine. I decided to "goose" it some, rev the #$%* out of it. I was getting hot compression out of 1 & 2 (hand behind the pipes). Revved some and felt warm out of #4.  Revved the sh*t out of it and got an explosion from #3, which then was firing ok until it ran out of fuel (Didn't have the petcock open - only filled to test).

Did the same agin, this time leaving the petcock open. After a little revving # 3 exploded again (black sooty discharge all over my hands, actual fire from the tailpipe.)

Do I just need to "blow this out" like you would a V-8 at this point?  Or is there something more subtle I need to tend to?

Again, we have 1, 2, & 4 ok for now. 3 seems to be the issue. Black soot exploding, flame, with a very high rev.  Low rev there is no real action at all, exhaust feels cool from the tailpipe.

It's progress, but I need to eat something tonight before I kill the cats.

Let me know if you have any thoughts.

Thank you.

[Gene]

Just for the F8ck of it I went and started it again. 3 & 4 headers tepid, 1 & 2 blazing hot.  This is like a Twin problem, but it's not a twin.

Just throwing this out there. More for myself than anyone else.

[scottly]

#3 spark plug black and sooty?

[Gene]

#3 spark plug black and sooty?

Still looks new. I just sent myself a pic. post in a sec.

While I'm at it let me check #4.

Updating. The pics aren't coming thru from my phone, but: 3 still looks new regardless of the explosions. 4 was starting to see some color, but nothin crazy. It wasn't really "wet" but smelled a little gassy.

I'm going to see if I can get at the vent that serves 3 & 4 carbs. check for blockage. To me it seems the most logical thing.

if fuel is getting there, and spark exists, it has to be air. So I will see if the fuel is being delivered properly (i.e. vent not blocked on 3/4) and then check my air screws.

If that's not the case then the carbs have to come off, having realized all else seems in order (at least spark, if not proper fuel allocation, BUT fuel delivered-otherwise no "explosion") and I'll take out from there.

I do apologize if this seems overly troublesome. Seriously. I'm doing my best to try everything suggested and if I have overlooked something I rely on you all to point it out. Otherwise, it's just step-by-step.

[Gene]

Today I was able to start the bike with the leads swapped. 3 on 2 and 4 on 1 etc. I am faced with the same situation. 1 & 2 firing, 3 & 4 not.

I attached a piece of line to the vent for 3 & 4 and blew some compressed air through which resulted in fuel spitting out of somewhere from the carbs themselves and spilling onto the engine. I was unable to determine where the fuel was coming from as it seemed random. I checked the air box and it didn't seem like any fuel was being forced into it.

I adjusted the air screws on 3 & 4 to make sure they are 1.5 turns "out" - they are on the air side of the carb.

Sad thing is, bike starts now on 2nd or 3rd kick, unfortunately just 2 cylinders.

At this point I think it's the carbs - perhaps the emulsifier? - not getting the proper mix?

Any info is welcome. I can't logically figure it out.

I will do a test around the boots to see if there is a leak - spray some carb cleaner while running and see if we get a rev.  If that's it, easy fix.

[Gene]

No leaks around the boots. I only wish I had a clear engine so I could see what the hell is going on in there.

Walking away for today.

[Keith]

I would go back to basics...Have you adjusted your valves? Check your compression. with a dwell meter, both sets of points should read the same. Remove air cleaner box, with bike running spray carb cleaner into no. 3 carb. Does it fire then?

[Brian G]

I thought I'd seen something similar a while ago:

http://forums.sohc4.net/index.php/topic,144305.0.html

The eighth posting, from Hondaman, mentions why a plug might not fire even though its partner does and one of the reasons is a bad coil. Although, as stated, both coils failing is unlikely, you've pretty much eliminated the wires and caps with

I was able to start the bike with the leads swapped. 3 on 2 and 4 on 1 etc. I am faced with the same situation. 1 & 2 firing, 3 & 4 not.

I wonder if, although you can see spark when testing against the head, it's failing inside the cylinders under compression with a fuel mixture?

Regards,

[my name is nobody]

I'm goin out on a limb, at risk of looking stupid..Each coil has the same power source thru the blk/wht wire coming off the kill switch.
Diagram shows a two separate connections between kill switch and coils. Could a bad connection in the circuit make both coils flake out? Or possibly 1 coil bad, making the other malfunction?

[calj737]

Easy enough to confirm the coils by measuring their primary and secondary resistance.

[Gene]

Back at it this weekend. I'll check the coils first, respond. Update as I go along.

Valves/tappets seem to be gapped properly, will check again.

Thank you all.

[Stev-o]

If not solved by Monday, I plan to start a  Go Fund Me acct to fly Cal out to Cali to address!

[calj737]

If not solved by Monday, I plan to start a  Go Fund Me acct to fly Cal out to Cali to address!

Gracious of you, Stev-o. And please, dear members who live in, and like California, take no personal offense; but there ain't enough money in this hemisphere to get me aboard an airplane to land in California. Personal issue. Anywhere else, love to help.

BTW - I only added the reference to checking coils, but with the issue on 2 separate cylinders served by 2 coils, the odds are mathematically lower that I would fly to California than this being your problem. Just saying.

[Stev-o]

Must be warrants keeping Cal out of Cali! I know the feeling, I couldn't go to Hawaii for seven years til the statue of limitations ran out on the 7 traffic tickets I got while riding a Honda!

[calj737]

Must be warrants keeping Cal out of Cali! I know the feeling, I couldn't go to Hawaii for seven years til the statue of limitations ran out on the 7 traffic tickets I got while riding a Honda!

No legal issues at all. Not in any state, nor country. Just personal reasons. Lovely place. Glad its 3,000 miles away