1976 carbs too lean. ??


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dingdong
Posts: 3447
Joined: Thu Apr 08, 2010 8:35 am
Location: Oklahoma City
Motorcycle: 1976 gl1000
1993 gl1500
2004 NRX1800 Rune

1976 carbs too lean. ??

Post by dingdong » Thu Jun 07, 2018 9:35 am



So after rebuild 12 years ago and the bike running great since then she has developed a problem. The first symptom was stumbling at and around 2k to 2.5k rpm after riding about a mile. Thought I might as well pull the carbs to do a cleaning. Total disassembly.

Before and after
Before and after

I found no dirt or deposits anywhere even in the float valve screens. Clean as could be and floats set exact. However the plugs (all four) are white now. Way too lean. Pulled the carbs again because I failed to check the slow jets below the rubber plug inside the tower. The rubber was disintegrating and had the jets clogged. Back together with new rubber plugs and now she runs strong with no more stumbling. However it is running very lean. To the point that the engine comes up to "fan on" temps while riding much to fast.... Fuel filter clean. Gas cap clear. Checked fuel pump and it is fine as far as volume is concerned. Don't have a gauge to check the pressure. Any ideas what could cause a lean condition on all four cylinders. And this happened from one ride to the next. I know I am overlooking something simple but.........


Tom

A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.

kndw
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Joined: Sat Jun 19, 2010 2:56 am
Location: Driebergen, Utrecht
Motorcycle: 1976 GL1000 Plempbak

Re: 1976 carbs too lean. ??

Post by kndw » Thu Jun 07, 2018 10:17 am

Did maybe ignition timing go off, or is there a hole in the air filter?

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dingdong
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Motorcycle: 1976 gl1000
1993 gl1500
2004 NRX1800 Rune

Re: 1976 carbs too lean. ?? Update

Post by dingdong » Wed Jun 13, 2018 6:59 am

Turned out to be the fuel pump. I guess it just couldn't keep up with demand therefore all 4 cylinders ran lean but with no stumbling like usually happens with a faulty fuel pump.
Tom

A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.

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Fred Camper
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Location: Metro Detroit, MI
Motorcycle: 1977 GL1000, 1976 LTD GL1000

Re: 1976 carbs too lean. ??

Post by Fred Camper » Sun Jun 24, 2018 8:21 pm

Good to know. Diaphragm pumps can tear and loose pumping so sounds like that happened. Many seem to move to an electric pump to get faster starting so perhaps it is time for an upgrade?

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dingdong
Posts: 3447
Joined: Thu Apr 08, 2010 8:35 am
Location: Oklahoma City
Motorcycle: 1976 gl1000
1993 gl1500
2004 NRX1800 Rune

Re: 1976 carbs too lean. ??

Post by dingdong » Mon Jun 25, 2018 7:51 am

Installing electric pump now. Thats how I tested to determine if old pump was decective.


Tom

A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.

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