[Doc Fisher]

So my 84 GL1200 suddenly started running rough like not on all cylinders. Since it is an old bike that I recently re-acquired and it showed some signs of neglect I decided to overhaul ignition and fuel systems.

I replaced both coils, all 4 plug wires and spark plugs with new OEM parts.

Then I pulled the carbs, inspected and cleaned everything I could. There were a couple of gummed up float bowl screens that could have starved their respective cylinders of fuel. I replaced fuel lines, filter and new fuel pump.

After reassembly, synchronizing and drop down setting of pilot screwsI (landed at 3 1/2 turns out), took it out and it ran so good I was grinning like an opossum eating bumble bees. On the way back as I was congratulating myself on the success of all that work about a mile from home it started running rough again. I pulled the plugs and they looked a bit lean so I backed the pilots out another 1/4 turn. Made no difference. It hesitates and sometimes backfires on acceleration.

I can smooth it out while riding by giving it a little choke. Since the choke makes the mixture richer, I wonder if I need larger main jets. It is a CA bike which leads me to also suspect the SAS. I did replace all vacuum lines while the carbs were out.

Any help here would be appreciated.

Meanwhile I am rocking Seafoam in the tank as a desperation shot.

 

[DaveO430]

Since it ran good for a while the jets didn't just shrink. The SAS has nothing to do with how it runs. Check if it's still getting a good fuel supply, thy loosening the gas cap.

 

[Bike...and Dennis]

I've seen new fuel lines cause issues on the 12s, since OEMs aren't available. Make sure a line isn't collapsing at the bend.

 

[Doc Fisher]

Since it ran good for a while the jets didn't just shrink. The SAS has nothing to do with how it runs. Check if it's still getting a good fuel supply, thy loosening the gas cap.

The jets didn't shrink?
Good point!
The gas cap is working as it should but I did try loosening it. No difference but thanks for the suggestion. I appreciate anything that I may have overlooked.

 

[Doc Fisher]

I've seen new fuel lines cause issues on the 12s, since OEMs aren't available. Make sure a line isn't collapsing at the bend.

The new fuel lines I installed are reinforced and have a thicker wall than what was on there. No kinks. Thank you for the suggestion. I can use any that you folks have.

 

[DaveO430]

Is the tank clean inside? Wouldn't take much to clog the screens in the carbs.

 

[Doc Fisher]

Is the tank clean inside? Wouldn't take much to clog the screens in the carbs.

Thanks again for your help Dave,
What I can see is clean. and the new fuel filter should prevent crud from getting to the float screens?
When I drain fuel from the tank it comes out with no visible contamination. I suppose I could try to rig a long swab to drag around whatever bottom parts of the tank I can reach to see if anything lives there.

 

[Road Ranger]

From your description it sounds like you might have a vacuum leak, have you tried spraying carb cleaner or brake clean around the carbs and seeing if the idle either increases or the engine dies.?

 

[Doc Fisher]

From your description it sounds like you might have a vacuum leak, have you tried spraying carb cleaner or brake clean around the carbs and seeing if the idle either increases or the engine dies.?

Thanks for the suggestion. I have not tried that and am not sure how to do it in a way that would identify a vacuum leak. It sounds like you are saying just spray all around and see if it changes. If it does, that means a vacuum leak? Ok how do I find the leak in that case?
And how would it run great and suddenly not?

The only thing that consistently changes how it runs is the Pilot screw adjustment so I'm thinking I did not get the circuit well cleaned when I had it apart. Looks Like I will do it again.

 

[Road Ranger]

If you still have a plugged carb passage the best way to clean them is with an ultra sonic cleaner. It sounds expensive but they can be bought for under $100 and can be used for many things, such as cleaning jewelry which will make your wife happy. As far as finding a vacuum leak the prime suspect would be the intake rubber couplers, if you spray somewhere and the idle improved then by spraying through the straw of the can or using cardboard block off section by section until you can identify the vacuum leak. Hope this helps.

 

[RambozoClown]

Another way to locate vacuum leaks without all the mess is to use an unlit propane torch to direct propane gas to the suspected areas. You will get the same change in idle speed but no liquid. And since it's a gas, it works even if you don't have a straight shot to the leak. I have one with a long thin vacuum hose on it, just for doing that on cars. By watching an exhaust analyzer you can even locate leaks that are too small to affect the idle.

 

[icechopper]

There's a good chance something clogged up one or two of the pilot jets. I've had success removing the adjusting screw and giving a blast of carb cleaner into the passageway. If after doing this the engine runs better, you 'll know that you're on the right track. The "choke cure" does indicate a pilot circuit problem. Good luck.

 

[Smoothrider]

Does the 84 have the small screen in the fuel line just before the fuel pump? If so did you clean it?

 

[Doc Fisher]

There's a good chance something clogged up one or two of the pilot jets. I've had success removing the adjusting screw and giving a blast of carb cleaner into the passageway. If after doing this the engine runs better, you 'll know that you're on the right track. The "choke cure" does indicate a pilot circuit problem. Good luck.

YES! After I removed the pilot screws and blew carb cleaner in and followed with a blast from my air compressor it ran great for a short while then crappy again. So I figured there is still something in the circuit and did it again. This time I noticed one of the small o-rings was toast so I replaced all four and their washers with new ones from Randakk. afterwards it ran a bit better but still not right.

 

[Doc Fisher]

Does the 84 have the small screen in the fuel line just before the fuel pump? If so did you clean it?

Just the fuel filter between tank and pump. Replaced it with a new one along with the lines.

 

[Smoothrider]

Just the fuel filter between tank and pump. Replaced it with a new one along with the lines.

my 85 LTD has a very small screen inside the fuel line at the connection for the pump which caused me similar problems. The 84 non Fi model may not have the same screen but I figured it might be something to look into.

 

[icechopper]

YES! After I removed the pilot screws and blew carb cleaner in and followed with a blast from my air compressor it ran great for a short while then crappy again. So I figured there is still something in the circuit and did it again. This time I noticed one of the small o-rings was toast so I replaced all four and their washers with new ones from Randakk. afterwards it ran a bit better but still not right.

You're picking up crap from the pilot circuit passageways, carb boogers like the junk you've cleaned out of the float bowls. You're going to need to pull the carbs out again or you'll be chasing this problem forever. Road Riders' got the right idea about an ultrasonic cleaning, of find a local shop that's got a hot tank for doing such work.

 

[Doc Fisher]

You're picking up crap from the pilot circuit passageways, carb boogers like the junk you've cleaned out of the float bowls. You're going to need to pull the carbs out again or you'll be chasing this problem forever. Road Riders' got the right idea about an ultrasonic cleaning, of find a local shop that's got a hot tank for doing such work.

NOT YET!

Ok, I was all set to bite the bullet and pull the carbs today. I was feeling a lot of resistance because it is a lot of work with these 75 year old arthritic fingers. And I was so sure that I did the job right the first time. Sure it had been at least a decade since the last time I rebuilt carbs but I worked slowly and with care, down my best to get it right the first time. At my age patience is not a problem.

Meanwhile, I had noticed a periodic clacking noise from the new fuel pump and I had emailed the company that makes it here in CA. asking if it was normal. They did not say it was or was not but they did send another pump. Well I figured I would swap it out before pulling the carbs again. Just in case. First thing I noticed was the same clacking at about 1 second intervals. Not the ticking or clicking you sometimes get with electric fuel pomps but a fairly loud clack.....clack.....clack. But when I tweeted the throttle the response was good. A nice smooth acceleration. So I took it on the road thinking it would crap out under load but it ran perfectly. So I took it on a nice long ride, let it sit while I ate a sandwich, fired it up and it ran perfectly all the way home.
I am keeping my fingers crossed as it has run well briefly twice before since I started all this service. That and I don't trust that clacking noise is normal.

But for now I'm riding again.

Thanks for all the helpful suggestions. You guys are great!

 

[AZgl1800]

the electric pumps without a motor in them, do a lot of clacking, and that is normal.
put your ear buds in and forget it.

 

[Doc Fisher]

the electric pumps without a motor in them, do a lot of clacking, and that is normal.
put your ear buds in and forget it.

Actually I only hear it when my head is near it setting idle or jets or syncing carbs. Can't hear it riding. Even without my ear plugs.