GL1200 Interstate , 84. Won't idle below 2000 rpm

[Big Ed]

I can't get the motor to idle below 2000 rpm. When the rpm's go below 2000 the engine rattles and clacks and then dies or I have to rev it up to keep it running. Checked plugs , fuel , changed oil and no debris in the filter or oil. Battery is in top shape and have cleaned connections. Vacuum lines are next.It was running fine and then this problem just happened while driving.
Any ideas to what might be my next steps or what might be going on? I have to use the choke to keep it running at the 2000 RPM area. Motor runs smooth above 2000. Any tips would be a great help.
Thanks . Ed

[WingAdmin]

You might want to put a spark plug tester on each of the plugs to check that they are all still firing when it gets down below 2000 and the problem occurs. If a coil is starting to fail, it might not be putting out enough voltage at low RPM to generate spark. Also check your battery voltage.

[starfleetengineer]

It kinda sounds like a vacume leak or maybe the timing belts jumped. I would lean to a vac leak myself. It verywell could be spark related. I have seen a plug wire and a coil start to break down when they start to get hot.

[Big Ed]

Thanks guys. I'll check out those tips in the next few days and post an update.

Ed

[thrasherg]

I am not familiar with the 84 model, but could it be blocked idle jets? above 2000RPM you will be running on the main jets but below 2000rpm you would be using the idle jets.. The fact that using the choke improves the situation would indicate a fuel problem to me and blocked idle jets seems the most logical!! Just guessing as I don't know this particular models carb setup.

Gary

[Big Ed]

FYI . It seems there is some blue smoke coming out of the left side. Not much but it's noticeable , even after running for more than 45 minutes......Maybe valves ?? Stuck ?.... seals ?? Plugs are firing , timing is dead on.

[WingAdmin]

Could be valve seals. They do wear out, and are a common cause of blue smoke.

[thrasherg]

FYI . It seems there is some blue smoke coming out of the left side. Not much but it's noticeable , even after running for more than 45 minutes......Maybe valves ?? Stuck ?.... seals ?? Plugs are firing , timing is dead on.

It's unlikely that a leaky valve seal will have any effect on idling. The smoke might be indicating a problem, but I don't think it has anything to do with your idling problem.. Need to get that idle fixed first and then worry about the smoke, until you do, just keep an eye on the oil level.

Gary

[starfleetengineer]

Thinking about this, I did have to use my choke as well. They guys told me to clean the carbs. I also replaced the jets not knowing I didn't have too. I found junk in the bowls and in the screens behind the float seat. Clean the carbs, make sure the plugs and air filter are ok or just replace them if your not sure. Then do an idle drop, then sync your carbs. I compleatly forgot about that....sorry!

[rrmiller73]

Clean or replace the idle jets in the carbs. Thats what it took to fix that problem on mine last year. 2000 rpm is about where the main jets supply enough fuel to keep it running. Thats my vote anyway.

[Big Ed]

I'll give the jets a try and take it from there.



Thanks guys. Ed

[mike2wings]

Hi Big Ed

I have a 84 GL1200, but I also have a 1976 GL1000 I semi restored . While pursuing repairs I read about an electronic fuel pump available for that model. One of the claims in a review said that with steady pressure his bike could idle down to a much lower RPM while still running steady. Could it be your fuel pump is weak and causing too low a pressure at an idle. Your symptoms reminded me of his letter . This may or may not help, but it's all I got. Mike.

[Big Ed]

Mike. That's an interesting angle to check out about the fuel pump. There is a fuel pump flow test you can perform....can't remember where I saw it ..maybe in one of my books. I'll give it a try. I've seafoamed the carbs to see if the jets clean up....no change yet. I'm not ready to open the carbs yet....but I'm getting close.
Thanks. Ed

[starfleetengineer]

Hi Big Ed

I have a 84 GL1200, but I also have a 1976 GL1000 I semi restored . While pursuing repairs I read about an electronic fuel pump available for that model. One of the claims in a review said that with steady pressure his bike could idle down to a much lower RPM while still running steady. Could it be your fuel pump is weak and causing too low a pressure at an idle. Your symptoms reminded me of his letter . This may or may not help, but it's all I got. Mike.

This is a good idea, but the engine will idle even if the fuel pump is unpluged! The fule in the bowles will allow it to idle. If it won't idle below 2000 rpm's, the problem falls in the idle circit. I can unplug my pump after it is running and it will run till the bolws run dry. Have you changed the jets or the idle screws? Have you adjusted the mixture screws? I changed the jets and mixture screws on mine and it caused all kinds of problems on mine. "NOTE" If your carbs need cleaned, Don't change the jets or screws. That was my hole problem with mine running like crap and useing too much fuel. I didn't think changing them would cause a big deal, but boy was I wrong! If your idle drop is off or your carbs are out of sync, it can give you headachs! Trust me I kow from first hand experance I will be posting my my problems and engine change later today. After everything I went through and the mistakes I made to try and fix it, I replaced the new jets and idle screw with the old ones, and now.... she runs like a top I hope what I post will help you out.

[Big Ed]

FYI....After trying all the different ideas , carbs , jets, vacuum etc. and no difference . One last kick at the can was electrical...... I swapped a CDI unit (box) and voila the engine runs like normal . It's been a few months but finally got around to it. Something inside the box must have gone POOF and the low idle circuitry (timing ?) stopped working. Now the motor runs well with no more kicking below 2000 RPM.
Thanks for all the input everyone. I just wanted to post this info to help anyone else who was at the end of their rope !
Ed

[starfleetengineer]

FYI....After trying all the different ideas , carbs , jets, vacuum etc. and no difference . One last kick at the can was electrical...... I swapped a CDI unit (box) and voila the engine runs like normal . It's been a few months but finally got around to it. Something inside the box must have gone POOF and the low idle circuitry (timing ?) stopped working. Now the motor runs well with no more kicking below 2000 RPM.
Thanks for all the input everyone. I just wanted to post this info to help anyone else who was at the end of their rope !
Ed

Thanks for the update I'll have to keep this in mind when I hear anyone else ask about this problem..

[halfjacket1234]

Good to know, thanks for the update.