'79 GL1000 losing power at high RPM's


Information and questions on GL1000 Goldwings (1975-1979)
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Kevin Clarke
Posts: 4
Joined: Thu Apr 09, 2015 9:33 am
Location: Graham NC 27253
Motorcycle: 1979 GL1000 Low mileage!

'79 GL1000 losing power at high RPM's

Postby Kevin Clarke » Thu Apr 16, 2015 10:44 am



I have a very nice 1979 GL1000 as an everyday rider with low original mileage, hard shell bags, full Vetter fairing, satellite/CD radio, etc. What I can't figure out is why at higher RPM's I lose power?
The carbs have been rebuilt, new timing belts, coils replaced and in the proper order, new plugs, new filters, electronic ignition, cables are new and the carbs have been set with new vacuum gauges to the proper settings. I've checked everything but the timing belts and hooked up a timing light.
Have I missed something and is there a correlation to the timing belts and higher RPM problems?
I have a sneaking suspicion it's the timing or ignition, but the local Honda dealer's mechanics are less than helpful. None of them have ever worked on an older bike, not that they're not good mechanics, just don't have the experiance.
I can take a drive, get it warmed up and everything is cool for a few miles then all of a sudden half power and a limp back home.
Help!



User avatar
spiralout
Posts: 1050
Joined: Sun Feb 17, 2013 6:41 pm
Location: Alabama
Motorcycle: 1975 GL1000 (gone)
1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: '79 GL1000 losing power at high RPM's

Postby spiralout » Thu Apr 16, 2015 12:06 pm

Kevin Clarke wrote:I have a very nice 1979 GL1000 as an everyday rider with low original mileage, hard shell bags, full Vetter fairing, satellite/CD radio, etc. What I can't figure out is why at higher RPM's I lose power?
The carbs have been rebuilt, new timing belts, coils replaced and in the proper order, new plugs, new filters, electronic ignition, cables are new and the carbs have been set with new vacuum gauges to the proper settings. I've checked everything but the timing belts and hooked up a timing light.
Have I missed something and is there a correlation to the timing belts and higher RPM problems?
I have a sneaking suspicion it's the timing or ignition, but the local Honda dealer's mechanics are less than helpful. None of them have ever worked on an older bike, not that they're not good mechanics, just don't have the experiance.
I can take a drive, get it warmed up and everything is cool for a few miles then all of a sudden half power and a limp back home.
Help!

These are two different symptoms. Is it you always lose power at higher RPMs or it's fine at higher RPMs for a while then you lose power?
Could be ignition timing or fuel starvation. First check would be to loosen the fuel cap and see it still does it. If so, check the timing and make sure the mechanical advance behind the ignition module plate is free and woking smoothly.

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tom84std
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Location: Arlington, Texas
Motorcycle: '84 STD 1200
2002 VTX1800
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69 BSA Bitsa
2004 Virago
VW Trike

Re: '79 GL1000 losing power at high RPM's

Postby tom84std » Sun Apr 19, 2015 10:20 pm

I was thinking about the same thing Spiralout said while I was reading the post. Another thing to check is the fuel pump. It could be original and the internal spring could be getting weak or the internal check valve is beginning to decay or become clogged. The old mechanical pumps will do this, work fine at lower speeds and begin to fail at higher speeds. Another thing is if you can tool around at 30 MPH with no problem but when you try highway speed it begins to suffer fuel starvation, that sounds like a mechanical fuel pump on it's way out. When mine failed this way I made a block-off plate to replace the pump with and put on an OEM external electric pump with the same operating pressures (2-6PSI) About $50 when the original Honda mechanical pump was nearly $200.

Kevin Clarke
Posts: 4
Joined: Thu Apr 09, 2015 9:33 am
Location: Graham NC 27253
Motorcycle: 1979 GL1000 Low mileage!

Re: '79 GL1000 losing power at high RPM's

Postby Kevin Clarke » Tue Apr 21, 2015 6:29 pm

Thanks guys, seeing the bike just sitting there is very sad. I'll get on your suggestions as soon as the local storms and I heal from a minor surgery. Can't wait to finally get to the bottom of all this and ride again!
Kevin C.

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Fred Camper
Posts: 1157
Joined: Sun Aug 16, 2009 9:15 pm
Location: Metro Detroit, MI
Motorcycle: 1977 GL1000, 1976 LTD GL1000

Re: '79 GL1000 losing power at high RPM's

Postby Fred Camper » Tue Apr 21, 2015 8:32 pm

My bet is the ignition system. Down on power is often one coil falling out. If you have an electronic ignition, then that very well may be heating up and loosing a critical connection. If you have points, seems less likely. So let us know what you find out. We need to know if you have points or electronic ignition?

Kevin Clarke
Posts: 4
Joined: Thu Apr 09, 2015 9:33 am
Location: Graham NC 27253
Motorcycle: 1979 GL1000 Low mileage!

Re: '79 GL1000 losing power at high RPM's

Postby Kevin Clarke » Wed Apr 22, 2015 9:33 am

I have an electronic ignition, the last owner did that, when I don't know. I have replaced the coils and checked the output, 3 ohms max, also replaced the voltage regulator and condensors. New plugs, traced evey wire in the harness, that was fun, found some wear and protected them, but no direct shorts.
I'm going to try the gas cap trick then rebuild the fuel pump after I check the timing belts to make sure they line up with the marks. Put a timing light on it after that, figure try the obvious first then move on to the pricey stuff. If I have to put in a new electronic ignition, so be it, but cheap first then the other.
I'm sure all of you out there are having trouble with Ethynol additives in Gas, whoever had that brain fart should be slapped. I use Stabl-fuel and it works pretty good, but here we have a normal winter and most times the bike sits for up to three months. Any longer I use the Stabl-fuel with vapors that protect the tank. Just thought I'd share that, don't want to take off the tank and have it coated if I can help it.
You folks are a Godsend! Thanks.




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