help me diagnose a dead spot in a '89 1500?


Information and questions on GL1500 Goldwings (1988-2000)
  • Sponsored Links
kevinfish
Posts: 1
Joined: Wed May 29, 2013 5:27 pm
Location: Chico
Motorcycle: 1989 1500

help me diagnose a dead spot in a '89 1500?

Postby kevinfish » Wed May 29, 2013 5:30 pm



Hi, my friend has an 89 1500 I'm trying to help him diagnose a dead spot.

On the side stand, if I squirt a little carb cleaner in the ports in the carb horn on the left side, the engine stumbles. If is squirt it in the right carb it speeds up. The sliders seem to be operating evenly between the sides. If I stuff a rag down either side and rev it it acts almost normal.

If I rev it up to about 1/2 throttle (which it does very slowly) it cycles between about 2800 and 3300 rpm probably 3 times every 2 seconds.

I'm thinking its a vacuum leak in something that both carbs share.

Any idea what to look for? How to fix (easily)?

Thanks in advance,
-Kevin



User avatar
virgilmobile
Posts: 7644
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: help me diagnose a dead spot in a '89 1500?

Postby virgilmobile » Wed May 29, 2013 6:00 pm

My 88 was bad about that too.Even worse.
Have a look at the end of this post at the pictures of the vacuum hoses.I found 7 bad ones on mine.
Even after the hoses,I still had to modify my Carb for a 2k stutter.
viewtopic.php?f=6&t=17130

User avatar
virgilmobile
Posts: 7644
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
Motorcycle: 1988 GL1500 I
Previously owned
78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: help me diagnose a dead spot in a '89 1500?

Postby virgilmobile » Wed May 29, 2013 6:00 pm

My 88 was bad about that too.Even worse.
Have a look at the end of this post at the pictures of the vacuum hoses.I found 7 bad ones on mine.
Even after the hoses,I still had to modify my Carb for a 2k stutter.
viewtopic.php?f=6&t=17130

User avatar
ct1500
Posts: 813
Joined: Wed Nov 10, 2010 8:09 pm
Location: Glastonbury,CT
Motorcycle: 1988 GL1500
Contact:

Re: help me diagnose a dead spot in a '89 1500?

Postby ct1500 » Wed May 29, 2013 6:56 pm

Do a little more diagnostic work and will help pinpoint which cylinders and for what reason are giving you trouble. The more you know before tearing apart the easier it is.

Will start off on the premise of an otherwise well running and properly maintained engine and has developed a driveability concern. Filters and plugs have been changed at regular intervals. This is a first check of basic systems that anyone can do.

First off is to check the ignition system. With the bike warmed up and idling remove and replace one plug wire at a time from the spark plugs. What we want to observe here is a uniform idle RPM drop when the wire is removed providing no ignition to that cylinder. At this same time we are also testing the plug wires. While slowly removing the wire from plug you will hear a distinct snapping noise of the spark jumping to the plug. It should jump from 1/2-1 inch, this tells us the wires are good with no excess resistance. In rare cases the plug will only fire with the wire partly disconnected adding RPM and is likely due to a fouled plug.

Next up is to remove the spark plugs noting their condition and location within the engine. Note the condition of the plugs below which were taken from my 1500 when acquired with no driveability concerns except a release start type of turning over. Plug gaps were on the wide side. These could have been original twenty two year old plugs as the bike had only thirty thousand on the odometer and I was still going through it with frequent starts and idling. Note the two inner plugs (cyls.3&4) look like they have been running slightly hotter or leaner than the others. This is due in part because inner cylinders on an engine will typically run hotter than the ones on the corners. Note these same cylinders are the ones the vacuum hoses are attached to in the runners which could also contribute to the slight difference. All white or all black plugs on one side usually indicate carburetor problems. If you suspect a bad plug you can swap it with another and repeat to see if the problem follows the plug. Plugs can be pulled after the following checks.

When pulling plug wires and none to little RPM drop we must then find if it is lean, rich or compression related.

And some more specific testing

A good quality carb clean spray (Cyclo) non foaming with straw is a valuable diagnostic aid and I keep a can in the bag. No full blast sprays, start with a light touch.

Bike dies on the road: While cranking spray a little in air intake, if bike wants to fire, fuel problem confirmed.

Vacuum leaks?: Spray a little around suspect area, if idle increases or smooths out found source of leak. Pinch off vacuum lines looking for downstream leaks.

Lean carbs?: Spray a little directly into its individual intake, idle increases or smooths out lean carb confirmed.

Rich carbs?: Spray a little directly into its individual intake, idle decreases
rich carb confirmed within reason.

Quick confirmation of pilot adjustments: Consistent idle (RPM) response when a little spray is introduced to each individual carb intake.

High speed miss?: Spray a little into intake stream, if smooths out and picks up lean condition confirmed.

Avoid overuse around composite parts. (1500 slides for sure) Starting fluid is too volatile and messes things up. Check that carb slides are operating in tandem.

Other bikes can use sync gauge ports for rich or lean checks. Control the uncovering of ports when screw removed idles up it is rich, spray directly in for lean check while sealing area around straw with your fingers.

A proper firing plug with 20k miles on it.
Attachments


This is what I do
Local and need repair help with your 1500, Valkyrie or ST please PM


Return to “GL1500 Information & Questions”




Who is online

Users browsing this forum: MSNbot Media [Bot] and 2 guests