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1983 Honda GL650I Silver Wing Interstates (1 Red, 1 Gray)
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Discussion Starter · #1 · (Edited)
Have had the first of my two GL650 Silver Wings for a few years now. It has always had a hard start problem particularly when cold or having been sitting for a while.

Posted up this problem under another thread a long way back and the general consensus was that it was a fuel starvation problem where the fuel evaporates from the carb bowls after sitting for a while. Old thread is here: Strange Startup-Ignition Problem

Things have gotten worse recently. Two days ago I tried starting the bike. I nearly wore the battery charge down to nothing (fully charged Yuasa AGM battery that's always on a Battery Tender) before the bike would finally start. It started and ran but only one one cylinder. Normally after a minute or so the second cylinder fires up and runs.

Not this time. Bike ran for several minutes but ONLY on the left cylinder. The right cylinder never ran! I could hold the exhaust pipes right outside the head with my hand and it was barely warm to the touch. Only other symptom was that I'd get a rare backfire out of the right exhaust pipe maybe once every 30 to 40 seconds.

I dug into it today, and here's what I found:

1. Both carb bowls were still full after the start up attempt two days ago. (Verified by using clear plastic tubing connected to the bowl drains and opening the drain screws. Fuel levels were the same, about 1/4" or so below the bowl gasket.)

2. Pulled the spark plugs and inspected:
Left plug - a bit carbon fouled, but not bad.
Right plug- fuel soaked!

3. Inspected spark plug boots: Plug boot inside terminals are clean and like new.

4. Tested for spark at plugs. Inserted plugs back into caps and used a jumper to ground the spark plug body. Results:

Left plug: Bright spark between the top of the center electrode and ground electrode.

Right plug: Bright spark between the SIDE of the center electrode and the base of the ground electrode near threaded body! NO spark between top of the center electrode and ground electrode where it should be! See picture below...

Amber Audio equipment Gas Machine Auto part


Yes, I actually got a picture of that!

So, "what the hell" I thought. I've never seen that before.

QUESTIONS:

1. Why no spark between the top of the center electrode and the ground electrode where it should be? Is there a cold weld where the ground electrode is welded to the spark plug threaded body?

NOTES: Resistance between the spark plug body at the threads and the ground electrode seems to vary between 0.1 and 0.6 Ohms. The insulator around the center electrode is NOT cracked. I inspected it with a magnifying glass under bright light.

2. Is this weird "side park only" condition likely the cause of the right cylinder not firing at all? The spark is just as bright as the left plug, so there IS a spark, but it's definitely in the wrong place. Shouldn't it ignite the fuel/air mixture anyway?

What do you think?
 

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Twer me I’d want to see what happens if plugs are switched, and with new plugs. This may end up just being written off as a bad plug with little to learn from it. Interesting though.
 
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1983 Honda GL650I Silver Wing Interstates (1 Red, 1 Gray)
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Discussion Starter · #3 ·
Twer me I’d want to see what happens if plugs are switched, and with new plugs. This may end up just being written off as a bad plug with little to learn from it. Interesting though.
Yes, I will replace the plug.

But, I'm curious to know if anyone has seen this before and if the mispositioned spark could cause the cylinder not to fire and run.
 

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1983 Honda GL650I Silver Wing Interstates (1 Red, 1 Gray)
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185 Posts
Discussion Starter · #6 · (Edited)
I'd really like to see a picture of the inside of the combustion chamber of a GL650 cylinder head with the plug installed. Curious to see just exactly how much of tip of the plug actually extends into the chamber. (The FSM doesn't have one that's good enough to see.)

Would answer my question about whether or not a spark such as this bad plug produces would fail to ignite the fuel.

EDIT: Found a pic on Ebay. By the looks of this you'd think that a spark on the of the side of electrode would still ignite the mixture.

Auto part Circle Bicycle part Metal Wood


Regardless, I'll get a new plug tomorrow and see what happens.
 

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You have an excellent picture of the plug firing in the open air. Would the same plug fire when in a fuel air mixture under pressure?
 

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1983 Honda GL650I Silver Wing Interstates (1 Red, 1 Gray)
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Discussion Starter · #8 ·
You have an excellent picture of the plug firing in the open air. Would the same plug fire when in a fuel air mixture under pressure?
Right!

Obviously the current one didn't! ;)

Will get a new one today and see if it does!
 

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'84 CX650E that is evolving into a GL500
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Get two. If you think the bad plug may have been causing the starting problem for a few years they are probably overdue to be replaced.
 

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the fuel itself doesnt evaporate away - the volatile - ie readily combustable - components evaporate to atmosphere , leaving behind a full bowl of really hard to ignite liquid that looks for all the world like normal gas
 
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1983 Honda GL650I Silver Wing Interstates (1 Red, 1 Gray)
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Discussion Starter · #11 ·
Get two. If you think the bad plug may have been causing the starting problem for a few years they are probably overdue to be replaced.
Done! New spark plugs installed and the bike starts and runs great! :D

I've been chasing this problem off and on since June of 2021. During that time it has been an intermittent problem, not always present. I think it's been this one spark plug all along and that it kept deteriorating until three days ago it finally decided to become a permanent problem and not allow the right cylinder to run at all.

Permanent problems are WAY easier to troubleshoot and fix than intermittent ones!

Fingers crossed that this is the end of the mystery.
 

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2021 Benelli Leoncino Trail - 2021 CSC SG400 - 2017 SSR Buccaneer 250i - Several CX project bikes
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I had a similar problem with spark plug boots on a different bike. Wouldn't hit full speed anymore, hesitated and had a weird idle, and was sometimes hard to start. At night I had the bike running outside the garage, and as I walked away I saw something from the corner of my eye. It was a flash of spark coming from the spark plug wire right at where the boot begins, and grounding to the cylinder head.

If that hadn't been an EFI bike I'd have torn the carb down looking for the cause of the misfire. Fixed cheaply with a new set of NGK boots.

Charles.
 

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A mechanic told me an easy way to check the HT ignition system for "leaks" is wait until dark, start the engine and lightly mist water from a squirt bottle on the coils & wires. Cheap, easy and works quite well.
 

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Ever since most cars, truck and bikes have switched to coil on plugs, the knowledge of spark plug wire problems and symptoms has been diminishing. I remember my first car was bad running in wet weather and seeing sparks shooting out from the wires along their length when looking at them in the dark. Spraying them with WD40 or spark plug wire spray sealant (remember this?) kept it running a bit longer until I could change them for new ones along with a new cap and rotor.

I won't get into points, this was before my time!
 
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