Done practically EVERYTHING!

[Rein]

So I've supposedly finished most of the maintenance on my 650GL, but it still won't run right.

What I've done (engine wise):
Clean carbs, new orings, valve adjustments done (two intake valves at around .009-.01mm ), bought new intake boots and orings.

The symptoms: Bike fires up easy, and warms up fine, but once it's ridden for a bit/warmed up, it acts like it's lean (slight hanging, faint popping). I set the mix screws at 2.5 turns out initially, and then set to 3 turns out, and it helped smooth it out. It still hangs a bit at the top before dropping back to regular idle. The idle drops a little slower than it rises. Also, when it goes back to idle, it hangs at 1500 rpms before dropping to 1200. IE, blip the throttle and it goes to, say 3000, hangs at 3000 for a second, drops to 1400 for a

Also, it randomly pops/backfires (not too loud) at idle.

Plugs are reading rich, except #2, which is a little brown/tan, but still on the rich side.

Hasn't been synced yet, would that help?

 

[Rein]

Okay, seemed to have solved the hanging problem, spark plug #3 wasn't tight in the spark plug hole. However, the rpm's don't drop as fast as they rev still. There's still some popping going on.

 

[seuadr]

sounds like you have a vac leak, except that your plugs are reading rich.

next thing you should look at is syncing your carbs up, that can cause alot of headache with it's running.

when you cleaned your carbs, did you clean the pilot circuit? sometimes that gets forgotten.

 

[duaneage]

I suspect the carbs may not have been reassembled properly. Not trying to be harsh, just making a guess. Float height? How about the jets in the bowl, were they inserted tight enough? How about the choke actuating lever, did you replace the rubber gasket on it and make sure that it is tight enough?

Check the boots on the airbox to carb connections, they should be tight. The intake boot on the carb side should have clamps tight all the way, there is a lot of vacuum on these.

Last, did you synchronize with a mercury stick or Morgan carb tune? Out of sync carbs (really far out) can cause all sorts of problems.

Removing the carbs is a bitch but necessary. Even if this is all old news revisiting it might reveal you forgot something. Happens to us all, they call it experience.

 

[Rein]

sounds like you have a vac leak, except that your plugs are reading rich.

next thing you should look at is syncing your carbs up, that can cause alot of headache with it's running.

when you cleaned your carbs, did you clean the pilot circuit? sometimes that gets forgotten.

Carbs were done in an ultrasonic cleaning tank for a few hours, came out spotless, and like they were brand new from the factory.

Have not done a sync other than a bench sync.

Jets in the bowl are nice and secure, although, float heights may be the culprit. Removing carbs isn't as bad anymore, it's just redoing the throttle cable that irks me.

Duaneage, when you say rubber gasket, do you mean the oring on the plunger? If so, then yes, replaced.

 

[seuadr]

Carbs were done in an ultrasonic cleaning tank for a few hours, came out spotless, and like they were brand new from the factory.

Have not done a sync other than a bench sync.

Jets in the bowl are nice and secure, although, float heights may be the culprit. Removing carbs isn't as bad anymore, it's just redoing the throttle cable that irks me.

Duaneage, when you say rubber gasket, do you mean the oring on the plunger? If so, then yes, replaced.

hmm. if they are bench synced, i don't think they would be causing such a problem..

it's odd, everything points to an air leak, but you say your plugs are reading rich...

did you try shooting a little starter fluid around the boots? i stil lwonder if they are pulling in excess air somewhere.

 

[Rein]

Hmmm, just discovered a few things:

Upon inspection of the carbs, the choke plungers (14mm hex) were only finger tight. That's what I get for asking my brother to assemble that part while I did the valve clearances.

All pilot jets were clean, however, #3 mainjet and washer were rolling around in the bowl. Went through all the jets and made sure they were secure and tight, which they were. Odd isn't it? all but one were nice and tight.

Also, prior to removing the carbs, I found that #1 and #4 cylinders were not firing, ala water trick. Put the carbs back on today, and #2 #3 #4 are firing great, however, #1 is not. Swapped spark plugs with #2 to see if it was the coils or the plugs, and voila! #2 is not firing, fouled or bad spark plug. HAve not tried revving it to check for hanging idle yet, but I want to get the plug out of the way.

Anyways, I'll be off later to pick up a set of plugs, but could that be the reason for my ails? I think the faint popping/fart noises at idle was the cylinder not firing. Upon observation, the popping is indeed sequential and repeating.

 

[duaneage]

Choke plungers can let a LOT of air past the nut if they are loose, but the other issues were certified problems. This is a classic case of many little problems looking like one big one. On a 4 cylinder engine with 4 carbs and 2 coils everything must be ticked off and sometimes rechecked

Make sure the floats are 23 mm to the top of the float from the carb flange, or 57/64th if using a scale. It's important that they all be equal, you have 1mm of tolerance on the float height.

Set the air screws about 1 1/2 turns out from bottoming. This is a decent starting point.

Check the choke plunger needles to make sure they are clean and sharp, then look in the holes to see if any debris is in the hole. The plungers should return easily to their original position. If they hang open you get the fast throttle and rich plugs you were talking about. It does not take much for this to happen, just a little corrosion or debris and the carb richens the mixture too much.

 

[Rein]

update!

Reassembled the carbs, new spark plugs (D8EA), charged the battery, and fired it up.

It's odd really, after turning it on, it acts like it should be, revs up and drops correctly, no hanging at all! Sounds fantastic! Fires up without choke.

however, after warming up/riding for a good 5 minutes, it begins to hang at 1500 before dropping to 1100-1200. After that, it will idle perfectly, no popping, no misfire/backfires.

carb boots and orings are new, could it be I'm running a little lean? My screws were set to 2 turns out each, should I just turn them out a bit? didn't ride it long enough to get a plug reading.