Topic: 1978 cb550 K getting a spark

[Hare]

So this is a situation where I altered more than 1 variable at a time, not leaving me much room to isolate the problem, but such is a beginner's struggle. So this is my first bike, and I wanted to get my hands dirty, but not get in over my head. So I bought a running bike. Now it's not running, so it was for sure something I've done somewhere along the line.

the only things I have done is, clean the bike (could have corroded coils), cleaned carbs, adjusted timing.

-Right now, my suspicion is that between the timing points and coils, the engine is just not getting a spark.
-the left (1-4) points contact will not close all the way, even when I adjust all the way. Is there  a way to fix that, without replacing points?
-coils are reading between 5.4- 5.8 ohms (both the same, Y-BW, B-BW). 5 ohm for my bike? will this over resistance prevent spark?
-also, the plug boots are garbage, is there a way to replace them, repair them as well as the cables that feeds into the coils (plug to coil, thick wire)?

Thanks for the help! I'm sure I'll have more questions along the way. But priority is to get it running!

[iron_worker]

If your 1-4 points are not closing then your 1 and 4 cylinder will not be firing. The circuit must be closed to charge the coils and then as the points are opened the coils fire. What did you do to "time" the bike. If the bike was running before then the points must have been closing properly.

Your spark plug caps can be replaced if they are the stock caps... and they probably should be replaced if they are quite old.

Have you tried pulling your spark plugs out, grounding them against the frame or engine, and seeing if you get spark while turning it over.

Are you getting fuel to each carb?

Does your bike try to fire at all? Does it sputter? Does it fire up and die immediately?

IW

[Hare]

going through with a 12v bulb, I got the circuit to close using the static points adjustment in my manual. There is now a possibility that the battery is the problem (reading at 11v and as low as 8v). I'm going to replace that, and see if my local autozone has anything to replace the boots. It doesn't even try to start, no sputtering. I think there is no spark throughout, but I'm going to try with the new battery. The starter turns over, and then slowly dies as the battery loses power.

[Hare]

Is 5.4-5.6 ohms acceptable? will that prevent spark?

[superseven]

I would like to preface this comment as not trying to put anyone down or insult.  Typically when I troubleshoot I work from simple to complicated.

Since you have seemed to walk through a tune-up and now have no spark. Is it possible that the kill switch is not set to the run position.  I have done this mistake once on a snowmobile of mine and was knee deep in a engine compartment before I figured it out.

[bollingball]

going through with a 12v bulb, I got the circuit to close using the static points adjustment in my manual. There is now a possibility that the battery is the problem (reading at 11v and as low as 8v). I'm going to replace that, and see if my local autozone has anything to replace the boots. It doesn't even try to start, no sputtering. I think there is no spark throughout, but I'm going to try with the new battery. The starter turns over, and then slowly dies as the battery loses power.

I doubt Autozone will have the boots They may be able to order them. They are not like the ones you would normally put on a car.Or maybe you know the correct ones to order? Will the battery take a charge removed from the bike? What makes you think it is bad ? what test did you do? You said the bike was running if I were you I would slow down read and ask question I know it is hard to do with a new toy. The coils are probably OK. If they are long enough you can clip a 1/4in off the end of the wires. The caps screw on & off.

[Hare]

Update: I got a spark on all four cylinders last night when hooked up to a car battery. But when the terminals to the battery I have in, the same lack of power happens. That just tells me the battery is bad.
So... If I have clean carbs, the spark is getting to the cylinder, how do I make sure gas is getting to the cylinder? Is there a test I can run to check if gas is getting to the cylinder? or a way to isolate that as a problem?

[TwoTired]

A battery is a storage device, not an endless source of power.  Therefore, a low voltage reading can be a good battery that is simply drained.
The electric starter can drain a good battery in 3 -6 minutes.  It would take 10 hours of above 3000RPM operation to fully recharge it.

Place your meter leads together before making that coil measurement.  The display will show the meter error and the probe resistance.  You subtract this number from any measurement you make on the ohms scale.

I'll bet your coils are fine.  Advise to look elsewhere.

If you insist on replacing the plug wires. NGK makes a wire splicer.  Good luck on finding the correct steel strand core 7mm wire, though.  The plug caps screw into the steel core.  Copper core is not nearly so durable.  You should measure the plug cap resistance input to output.  Stock is 10K.  But, those are hard to get these days.  5KΩ is what is the easiest to install nowadays.  Not perfect, but, it'll work better than a bad plug cap.


Remove the plugs and look at the tips for deposits.  Make a note of the deposits and insure they are all dry.  Reinstall.  Make absolutely certain that the carb choke plates closing fully.  It is NOT enough to simply pull the knob out all the way.  The cable is adjustable.  If adjusted badly, poor choking is the result and can contribute to hard starting.

With the choke plates on fully, gas in the tank, and valve set to "reserve", allow the engine to crank over with the throttle open fully, say, ten revolutions.

If the bike hasn't started, pull each plug out and look at the tips again (quickly)  the choking and throttle should have made the plug tips wet with gas.  Dry indicates a fuel delivery problem between cylinder and source tank.  If only one plug is dry, look to the carb for that cylinder as a flow blocker.

If you are troubleshooting with the key switch on, removing the headlight fuse will greatly extend battery life (and improve voltage that reaches the coils).  Stock headlight draws 4-5 amps, or about 1/3 of what the entire bike consumes (starter motor excluded).

Good luck!

[Hare]

So these are the tests I ran, and the results I got:

I have a spark, from replacing the plugs, and attaching the battery to a car (jump start)
I have compression
I have good clean gas going to the carbs: the drain bowls will fill and empty when I unscrew the drain plug
I DO NOT have gas going to the cylinders as far as I can tell: I cranked over at off, low, full throttle, with and without choke, and pulled out dry plugs each time

I'm beginning to think the only problem is gas delivery (maybe an obvious observation) but I'm not sure why its not getting in there. Help me out if you know any more tests to run, or ways to get gas in there?
Thank you!

[TwoTired]

If you are absolutely certain the choke plates close fully when you pull the choke knob (there is and adjustment for this), you can take out the vacuum port plugs at the engine end of the carbs, squirt gas into each one and see if you get any life.  If so, then you have a carb problem.

You can remove one of the outer bowls (3 screws, or maybe 4, I'm too lazy to go out a look right now) to see what is inside them besides gas.  If there is a bunch of grunge, you are looking at a carb rebuild/cleaning.

[Hare]

The interesting thing is, I had cleaned the carbs. Disassembled the bowl, sprayed out each jet, and reassembled, aided by a step by step guide specific to my carb. The vacuum port, is that the entire metal housing, a screw in port, or a hose? there are two hoses, one is a vacuum hose, the other feeds gas into the carbs from the fuel tank. Is it possible that I have gas going into the wrong hole?

[TwoTired]

The interesting thing is, I had cleaned the carbs. Disassembled the bowl, sprayed out each jet, and reassembled, aided by a step by step guide specific to my carb.

What guide is that?

The vacuum port, is that the entire metal housing, a screw in port, or a hose?

When you vacuum sync the carbs, these are the plugs you remove to tap into the intake runner vacuum.

there are two hoses, one is a vacuum hose, the other feeds gas into the carbs from the fuel tank. Is it possible that I have gas going into the wrong hole?

There are two hose nipples, a large one and a small one.  The large one gets the gas, the small one is a vent line (not vacuum).