GL1200 '84 rear cylinders dead on low rpms


Information and questions on GL1200 Goldwings (1984-1987)
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justus5
Posts: 2
Joined: Wed Jul 19, 2017 12:33 am
Location: Finland
Motorcycle: 1984 GL1200

GL1200 '84 rear cylinders dead on low rpms

Post by justus5 »



Hello everyone, first post here.

Long story short; bought myself '84 GL1200 couple of years ago, stripped it to the bare bones and trashed all the fairings.
While putting it back together replaced stator, wheel bearings, fork seals etc. I got it back to one piece this spring and amazingly
it also started right off - unfortunately with only two front cylinders running. I've been trying to narrow the problem down about
two weeks to no avail.

First I thought problem was fuel related because I'm SURE it had spark in all plugs, but not anymore. So took the carbs out and cleaned
everything. Actually did it three times. All jets ok, no stuck floats, levels ok and fuel in the bowls.

Well, as that didn't help I moved on to the ignition parts; cleaned connections, measured everything as per Clymer manual and also tried to
switch the coils. No spark, so finally I bought used ICM module, but the rear cylinders are dead and cold.

Then I read about measuring the pulse generators AC volts during cranking as the resistance might not tell everything. One PG showed
apx .5 AC volts but the secondary just barely 0.1 AC volts very randomly. So PG busted?

I did a short test ride and noticed that the rear cylinders start firing when the engine is revved about 4000rpms but not below that.
Don't know the actual rpm because my aftermarket tach doesn't play along at the moment. Would a broken PG behave this way?

Any ideas welcome before I begin to dig the PGs out from the rear (*sigh*).



Omarrivas86
Posts: 1
Joined: Tue May 05, 2020 8:58 am
Location: Palmdale
Motorcycle: Gl1200

Re: GL1200 '84 rear cylinders dead on low rpms

Post by Omarrivas86 »

I’m having the same problem just cylinder 4. Following.

User avatar
Charlie1Horse
Posts: 562
Joined: Mon Sep 16, 2013 9:35 pm
Location: Jacksonville, Florida
Motorcycle: 1986 GL1200A Aspencade
1992 GL1500I Interstate

Re: GL1200 '84 rear cylinders dead on low rpms

Post by Charlie1Horse »

Crack the fuel bowl drain on the bottom of each carburetor bowl and see if there is any gas there. I had the same problem with the right front carburetor so I removed and cleaned the right carbs and it ran well for a few days. Then it started the same problem again. I did the same process and again the same problem after a few days. I know I cleaned the fuel tube from the right rear to the right front and the rear carb had fuel so I went on ebay and bought a pair of float valves, changed them and now no more troubles. The old ones looked good but one was sticking closed and therefore, no fuel.
Russell

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justus5
Posts: 2
Joined: Wed Jul 19, 2017 12:33 am
Location: Finland
Motorcycle: 1984 GL1200

Re: GL1200 '84 rear cylinders dead on low rpms

Post by justus5 »

Got it sorted out, it was the left pulse generator or the air gap between the PG and the rotor to be specific. I measured the PG AC voltage during idling,
which showed constant 1.2V for the right side and 0.1V for the left side.

Contrary to the (Clymer) manual the engine doesn't need to be removed to access the PGs, removing the battery is enough. PG air gap is also adjustable

All four cylinders are firing now.



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