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Hey All,
I've got meself a 78 Gl1000 with about 35k on it. It sat, being started up monthly, since November. i have changed oil, plugs/caps, and synched the carbs. I'm assuming the pilot jets and/or float valves are stuck up on the #1 cylynder, as it needed its idle mix screw set in almost all the way to get any even idle.


I had a mechanic check the bike, there are no vacuum leaks, but he said the O-rings are probably going on the right bank carbs, as they need rich adjustment. I flushed the float bowls, and have run some Techron in the tank. It sounds like a dead cylinder -- kind of rattling at idle and on acceleration. It's got lots of power at 4-5,000 rpm. When i pull off the plug cap at #1, the bike dies. If anything, the bike should run lean, as the baffles are gone from the OEM mufflers.

The plugs all read fairly normal (considering all the time spent idling) except #4, which gets fouled. I checked secondary coil resistance, which led me to replace all the caps and trim back the wires. The front caps now read normal, while the back read high resistance (30k ohm +). This leads me to suspect why #4 is getting fouled -- poor spark.

So, it seems I have two issues; replace coil; re/re carbs? I haven't checked the ignition timing with a strobe (its electronic), though i advanced it a little, which improved overall performance and shifting. Also haven't checked valve clearance/belt alignment.

Any thoughts? Should i swap plugs with #1 to see if the plug is actually fouled? I've also heard people suggest switching wires to check coils.
 

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The easy way would be to swap coils first as it won't take very long. If it makes no difference you can concentrate on the carbs with more confidence.
 

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When you say you've got a "dead" cylinder...,,,,, Do you mean there is no compression or no spark? If you have both compression AND spark, all you need is fuel.. Can you give some specs on what other diagnosing you've done? Has the bike been sitting for a long time? #4 spark plug indicates a rich mixture, or a lack of spark to fire the mixture. Need more info... Good luck.. Renegade:D
 

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mag wrote:
When i pull off the plug cap at #1, the bike dies.
The plugs all read fairly normal (considering all the time spent idling) except #4, which gets fouled. I checked secondary coil resistance, which led me to replace all the caps and trim back the wires. The front caps now read normal, while the back read high resistance (30k ohm +). This leads me to suspect why #4 is getting fouled -- poor spark.

So, it seems I have two issues; replace coil; re/re carbs? I haven't checked the ignition timing with a strobe (its electronic), though i advanced it a little, which improved overall performance and shifting. Also haven't checked valve clearance/belt alignment.

Any thoughts? Should i swap plugs with #1 to see if the plug is actually fouled? I've also heard people suggest switching wires to check coils
1.) Shouldnt die when pulling one wire off. Should run, but very roughly. That might indicate the other 2 cylinders aren't up to snuff.

2.) Resistance readings across both sets of coils (cap - coil - cap) must be equal, and on a GL1200, its about 27K (7 in coil, 5 each in plug cap). The cap resistors should come out with a screw. Resistance should be within 10%

3.) see that the battery voltage while running is 14 volts or so, if not, dont fool with ignition till thats fixed, these cycles are known for low charging voltage and that causes weak spark. Every GL1000 I worked on in the early 90's had horribly corroded wiring, and that wont improve with age.

4.) Good time for carburetor rebuild, due to age. 30 years old is hard on rubber parts.

Concentrate on bad wiring and leaky carbs- dont change expensive parts like ignition coils until youve been through the basics - ignition coils rarely fail.
 

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Thanks for the replies. I know the bike sat for a few years, then was bought by previous owner, who rode it for a year, then parked it in November, starting monthly.

The voltage gauge on the bike reads 13v idling, and 14v riding. Perhaps this is the problem? The mechanic who checked the bike for carb sync and vacuum leak only, spotted the fouled #4 plug. He changed it, but then I rode it another 100 miles before changing the caps/trimming wires. The resistance on the front coil is 24k, the back is 30-34k.

I tend to agree it's a spark issue, though the rubber in the carbs is probably shot. One thing i spotted is the yellow wire at the coils has a break in it -- exposed through the insulation. My shop manual says this wire goes to the points/ignition.

I will put a multimeter on the battery today to check voltage for sure. I haven't trickle charged it yet (oops) and neither do i think had the previous owner. (Also, will swap plugs with #1 cylinder.
 
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