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post #1 of (permalink) Old 06-08-2018, 02:04 PM Thread Starter
GoldwingA1500's Avatar
Join Date: Jun 2018
Location: Sumter, SC
Year: 1997
Make: Honda
Model: Goldwing GL1500 Aspencade
Posts: 281
1997 Goldwing GL1500 Jerks under 2,000 RPM

Hi all!

I've been troubleshooting this problem for almost a year now. The bike runs, and I have found a few problems which I've repaired along the way. But here is the overall problem I've been having.

No matter what gear you are in, with the RPM under roughly 2,000, give or take a few RPM's, the bike begins to jerk with 1/2 to full throttle. I've test ridden other GL1500's and none of those bikes possessed this symptom. Once the RPM climbs high enough (above 2,000), the bike takes off like a bad out of hell. If you are cruising along in OD, and partial throttle, the bike accelerates very good. But as soon as you turn the throttle towards half, she begins to jerk until RPM's are high enough. And then I can sometimes smell a very rich exhaust emissions. But to me, I suspect it is a lean condition causing spark knock, especially when using low-grade 87 octane fuel. I've tried using 93 Octane fuel and it improves, but still jerks, although not as bad. It is my theory that I have a lean condition which is causing pre-ignition.

Here is what I have replaced so far:

1. Rebuilt Carbs from Ethanol blended fuel damage (likely caused by BTEX ingredients)
2. Replace a few leaking vacuum lines
3. Replaced secondary air filter which was missing
4. Recently replaced failed Intake Air Shot Air (IASA) Valve due to failure in holding a vacuum per the manuals troubleshooting procedures
5. Replaced air filter

I've also performed the following vacuum tests:

1. PAIR Valve operation - passed
2. Carburetor Control Vacuum test (suspect this might be bad at high vacuum as bike runs very rough when a manual vacuum is applied)
3. Carburetor Sync and Idle Mixture Screw adjusted to about 2.5 turns each - all set appropriately
4. AJ2 and AJ3 Vacuum test - passed
5. PAIR Valve Solenoid Vacuum test - passed
6. Spark test - passed and looks clean and new for a bike with only 39,000 miles
7. Plug Wire Test - passed

At this point, I am completely stuck and cannot seem to figure out why my bike is jerking under 1/2 to full throttle load below 2,000 RPM's.

I noticed also that the PAIR Valve vacuum line that is attached to the intake filter box has a constant vacuum. Place your finger on the vacuum line that is attached to the filter box, and the PAIR Valve intake tube stops making the burrrr noise. Is this normal? Is the PAIR Valve intake tube (attached the front ride side of the filter box) supposed to make a gurgling sound while at idle? And when I close the vacuum hose connected to the PAIR Valve, the gurgling sound stops and no more vacuum can be felt from the PAIR Intake tube (on the filter box)?

Is it possible my intake box is not sealed correctly and causing the carb-slides not to pull back far enough under low RPM?

I am all out of guesses at this point?

The bike has stock mufflers, but previous owner sawed off the baffles, and installed custom end-caps. So the bike sounds like crap and is too loud. Without the back pressure in the exhaust, will this cause jerking or possibly a lean condition? Or as with some of the V-Twin bikes, will the carbs have to be rejetted to a larger size (idle jet maybe) due to the free-flowing exhaust? Could this be causing the jerkiness?

I hope someone here with extensive Goldwing experience can help me out with this. I'm a great mechanic (aircraft and automotive), but this bike has me completely stumped. Even the Honda Dealership couldn't figure it out as they assumed it was the carbs, which have since be rebuilt but to no avail.

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