Topic: Help! Spark plug stuck!!

[MauiK3]

I'll vote for hot fuel too.

[The Lone Builder]

Even with the re-routing of the fuel hoses, the bike didn’t run.

The bike was recovered thanks to Progressive Insurance and their roadside assistance plan. A big positive review for this.

I checked fuel flow to the carbs and 1&2 were not getting a good supply. Shortening the fuel line so it didn’t run up and down so much resolved that issue. On a short test run, it lost power and bogged down at the first hint of a hill. When I got back I checked the fuel level in the carb bowls and all were about equal.

I pulled the plugs and the pic shows the story: 1&4 are shiny white while 2&3 are a bit brown; none of them were wet. So I checked for a spark and 1&4 were OK, but on 2&3 there was no spark at all, or maybe just a hint of one.

Tomorrow I’ll get the tank off and check all the coil wiring under there. What is confusing me however, is that all 4 down pipes are hot, and all exhaust outputs feel the same.

Then, if all checks out  I’ll guess the next step is to try and find a compression gauge.

[jaytee-nz]

Plugs 2 and 3 are fed by the same coil. Coils can go faulty when they get hot, which might explain why it runs good for a while and then doesn't.

[scottly]

I pulled the plugs and the pic shows the story: 1&4 are shiny white while 2&3 are a bit brown;

2&3 look normal, and 1&4 look bone white lean.

[The Lone Builder]

The problem tonight occurred when the motor was relatively cold - within 200m of starting out.

That’s what I thought, Scottly, but it’s 2&3 that have no spark!

[scottly]

You may have two different things going on, Sean. Trouble shoot the ignition problem on 2&3 first: are you running a points ignition?

[scottly]

Tomorrow I’ll get the tank off and check all the coil wiring under there.

I saw on your blog you had an oil leak behind the points cover, which may have fouled the 2-3 points? Before removing the tank, check the voltage at the points with the key on and kill switch on run: when the points are open, you should measure 12V, and when closed, zero volts. If that's ok, start the bike and look for excessive sparking at the points, the sign of a bad condenser. 

[The Lone Builder]

👍

I’m on points with Hondaman’s box.

Thanks for the reminder about the condensers. I have a couple of spares with me.

Oil leak fixed BTW.

[scottly]

The points don't carry any current with the HM ignition, so there might not be sparking, even with a bad condenser? If you can't find anything wrong, and still don't have spark on 2&3, try by-passing the HM system and running the stock points and condensers.

[The Lone Builder]

I checked voltage at the points and this was good.
No arcing when the engine was running, Although I did see a spark once at 1&4 points.
I checked for a spark again at the plugs and got a spark on 4 but not on 3. The plugs afterwards looked like the pic. All were wet, but 2&3 more so. The choke was on full while I was checking which probably accounts for the black on 1&4.

I went to the coils and checked resistance on 1º and 2º coils and this was OK.
Then I checked the resistance on the plug caps and found one, from ⅔ coil to be in the megaohms. The others were all +/- 4,7.

A trawl around all local shops didn’t produce a emplacement, but I finally found one that I will go and get tomorrow,

Is this the cause of my problem? Hopefully! 

[scottly]

The voltage test at the points was assuming a stock ignition, and may not apply to the Hondaman system. The 2&3 plugs are wet and relatively clean, which is a clear indication of no spark. You should bypass the transistor ignition and see how it runs, replacing the carbon fouled 1&4 plugs first, of course. A failure with the same system stranded a member in the middle of the Mojave Desert once...
   

[The Lone Builder]

I did both and it was OK both times. With HM box the voltage was a bit less, 10,72 vs 11,72.  ( Battery voltage 12,5). There was no sparking in either case.

It runs better with the electronic box connected.
I got no spark on No3 when I tested this am, and none on 2 & 3 last night.

Would the duff plug cap not be enough, on its own, to cause the problem?

[scottly]

No, it's not just the cap.

[scottly]

I did both and it was OK both times. With HM box the voltage was a bit less, 10,72 vs 11,72.  ( Battery voltage 12,5).

When the points are closed, do you read 0.0 volts?

[The Lone Builder]

Yes

[scottly]

With both ignitions?

[The Lone Builder]

Yes

[HondaMan]

If one plug is fouled on a given coil, the other one will usually not spark, either. Most of the current flows to the carbon-short on the dark plug. Keep that in mind?
If one sparkplug cap is essentially 'open' like you describe (megohms value instead of 5000-ish ohms) then neither plug on that coil will fire well. If, for example, the carbon-shorted plug is on the 'good' plug cap, it will suck up all the spark current, leaving none for the other plug. If, instead, the carbon-shorted plug is on the bad plug cap with high megohms, then only the plug with the good cap and good electrodes (not black) will spark. This is an unfortunate 'bug' of shared-spark systems the world over...

[HondaMan]

Scottly: who had a Hondaman Ignition failure in the desert? I have 3 of them currently running in Iraq (one on a CB350, the others on SOHC4), 2 in Afghanistan, half a dozen in Turkey, and many more in lower Africa, etc. Seems strange to me: I've run them for 28 hours in a 200 degree environment (an oven) during proving without exceeding any circuit parameter limits as leakages nor voltage loss (the coils were included, because of their proximity to the engine).

[scottly]

Mark, it's not the carbon fouled plugs that have the problem..
Mooshie's HM ignition failed in the Mojave, and Dash had to ride a tow truck to a Honda shop in Victorville, where she was able to contact you so you could tell the techs there how to by-pass it. (I bought my very first brand new vehicle, a 1982 Honda CR480R, at the same shop. ) If I recall correctly, it was on her "Cowboys and Indians" tour of the Southwest.

[The Lone Builder]

If one plug is fouled on a given coil, the other one will usually not spark, either. Most of the current flows to the carbon-short on the dark plug. Keep that in mind?
If one sparkplug cap is essentially 'open' like you describe (megohms value instead of 5000-ish ohms) then neither plug on that coil will fire well. If, for example, the carbon-shorted plug is on the 'good' plug cap, it will suck up all the spark current, leaving none for the other plug. If, instead, the carbon-shorted plug is on the bad plug cap with high megohms, then only the plug with the good cap and good electrodes (not black) will spark. This is an unfortunate 'bug' of shared-spark systems the world over...

That’s what I (sort of) understood from your book. I tried to explain it to my Uncle, with whom I am staying – he was an electrical engineer – but failed. So I have just sent him the relevant pages to read for himself. 

When I get the new cap tomorrow, I guess we’ll see. I can’t believe how hard it has been to find these – i was going to replace all 4. In Europe they are widely available.

[The Lone Builder]

Mark, it's not the carbon fouled plugs that have the problem.

That’s correct. The failed plug cap was on one of the middle plugs.

But as Mark said, that would mean neither of those were firing well.

[scottly]

At this point, I think I would remove the gas tank and check the voltage on the black/white coil wires, with the respective points set closed?

[The Lone Builder]

I did that; on the Bk/W where it comes from the kill switch going to the coils and it was 11,6.

How would the condition of the points – open/closed – affect that?

[scottly]

When the points are open, no current flows through the coils, so even if there was resistance in the supply to the coils, there will be no voltage drop. When the points are closed, there will be about 2.5 amps flowing into the coil, and out of the coil through the points to ground, and any resistance in the supply side would show as a voltage drop. Again, I'm referring to the stock ignition system; I'm not sure how the HM system fits into the picture.