'82 GS650E Barn Project

[jamieofansa]

(edit: problem resolved see my later post in March 2022)

8k miles on odometer. Bike is a bit of a rust bucket, stored in a barn and knocked over by a tractor, and some time in a garage. When purchased started on choke, ran crappy, no power in 2nd and couldn't get revs up past 3-4k. Confirmed that all four cylinders were firing with IR temperature gun on each exhaust by engine. Started working on it and now I'm having the opposite problem. Very frustrated.

Currently the bike fires up without choke almost instantly and runs at an estimated 5-7k RPM on idle (tach cable snapped, waiting on new one). Have petcock on prime the whole time (in my mind to eliminate any potential fuel issues). White smoke comes out of exhaust which has limited my testing out of fear of damage. I did use a single, half second spritz of starter fluid but even after waiting a half hour it still has crazy rpms. When the tank was set on top ajar it wouldn't start with full choke (this puzzles me). I haven't recreated the tank ajar no start condition.

Work I've done:
Utrasonic cleaning of all jets in vinegar, spray cleaning of carb bodies/passages
Cleaned and oiled stock air filter and air filter box
Replaced champion brand spark plugs with Clymer manual recommended NGK 2120 plugs
Cleaned tank with muriatic acid then swished marvel mystery oil around to prevent rusting. Emptied excess marvel oil out before filling with 1.5gal 87 octane gas (at sea level).
New Amazon boots and orings (from carb to engine) since cycleorings is done
New Amazon petcock, confirmed it functions in prime and on positions

Tried adjusting four mixture screws on from 2 turns to 1 turn.
Tried adjusting air knob from all the way in (clockwise until seated) to 2 turns out.
Tried blipping throttle, it goes back to the crazy high rpms
Confirmed choke bar that choke cable actuates has mobility and is in off position. When I pull the bar to add choke I can hear it rev even higher (which is terrifying as a cruiser only guy to hear it scream)
Checked throttle cable slack and tension, can see slack at carbs and feel slack when rolling throttle. Can blip throttle and hear it go up and back down.


Things I haven't done yet:
-compared jets to stock size. Has original airbox, original exhaust, original looking carb internals and looked unmolested so I didn't write down the sizes.
-valve clearances (8k miles didn't think it could be a problem)
-sprayed rubber boots with carb cleaner (the rpm are so high I'm too scared to let it run for more than 10-30 seconds).

I'm posting and sleeping on it. Am super frustrated so I'm thinking I'll leave her sitting until my choke assembly and tach cable comes in. Also have an aux fuel tank coming in so I can better tune without juggling the tank.

Please help me sages my rust bucket project has me going gray and scratching bald spots onto my head.

[jamieofansa]

Also, what is the factory setting for the four mixture screws and the factory setting for the air knob under the carbs? I've had trouble finding it on the forum.

[phydeauxmutt]

"Air knob (under the carbs)"??? Do you mean the "idle speed control"?

One of the first things you need to do is to check valve clearances. Although 8k miles don't "seem like it would be a problem", you have already past the time of greatest wear. The valves will change the most the first time you fire up a new engine. That is why the factory recommends the first check at only 600 miles, then at 3000 and every 3000 miles after that. On that schedule, your bike should have already been checked three times.

"Factory settings for mixture screws"? Forget them. Nobody knows what the original settings were. They were set by a machine to meet emission requirements then sealed. Those of us who have opened up multiple sealed carbs have found them in the 1.5 to 2 turn range (from lightly-seated). Over the years, the internal passages of the carbs have changed ever so slightly. Over the years, the fluid that flows through them has changed a bit more than "slightly". They were set rather lean to start with, so some richening is called for. Many here suggest starting at 3 full turns out to provide a richer mixture, then, after the bike is warmed up, you can lean them down until you hear the engine slow down a bit, then turn the screw back out a bit. Most find that 2.25 to 2.5 turns is a good range.

Your "air screw" is the idle speed screw. There is no set position for it other than setting it where the engine idle speed is correct.

[tom203]

At a quick glance here , I’d be suspicious of those Amazon carb boot o-rings, cuz it sounds like you got a serious airleak. They got to be fat enough to squash down to seal.
Note Robert Barr’s post on theses things

https://www.thegsresources.com/_forum/showthread.php?262414-O-ring-sizes-as-promised&p=2671014#post2671014

[jamieofansa]

Morning everyone, it's been near freezing overnight and I woke up at sunlight to try again with a clearer head, sunlight, and sleep.

I rechecked the tank lines, choke slack, and throttle slack. When I went to start it at .5 turns, ice cold, with no choke it gave one big belch like it was going to start and then went to the standard no start noises.

Started working up to 2 turns out a half turn at a time, having no hint of the starter catching. Sprayed a tiny bit of starter at 2 turns and it still wasn't turning over. Currently have battery on a charger and am going to wait until later in the day when the temps are in the 50's instead of high 30's now.

[Datsa Noydb]

Started working up to 2 turns out a half turn at a time, having no hint of the starter catching.

Evidently you did not read post #3.

..., having no hint of the starter catching. Sprayed a tiny bit of starter at 2 turns and it still wasn't turning over. ...

Earlier, it sounded like it would turn over, but not fire. Now you say the starter is not catching or turning over.

Please stick to one story at a time.
Does the starter engage and turn the engine over? You can tell by the noise it makes.

[Rich82GS750TZ]

2 good links in my signature for you. First is the top 10 list. Second is BikeCliff’s Website, where you’ll find a link to the proper way to clean and set up your carbs. It is the Mikuni BS (CV) carb rebuild tutorial by Mr. Nessism.

[jamieofansa]

I determined the issue after a forced break from holidays, a hospital stay due to COVID pneumonia (hurray being a 5%er), and bitter cold winter. I did manage to check valve tolerances before hibernation and they were all beautifully within tolerance.

Anyway this 45F morning I got her running on a bottle to rule out tank issues. I had replaced the snapped tachometer cable and the idle was 4K not the 6-7k I thought it was. I took my time and set the idle speed knob under the carbs and brought it down to 1.8k by turning counter clockwise. I had been working with tightening it all the way and going three turns out but this gave wayyyy too much air.

This is why I kept asking before what "factory default" settings were. My inexperience with anything but a vtwin had me *@%^$*@%^$*@%^$*@%^$ing my pants thinking the engine was going to explode due to the inline 4 sound. Getting the tach working, calmly adjusting things, and being logical solved the issue.

The project continues with the bike legal and rideable

[rphillips]

Can you get the idle down to appx. 1K, 1.8 is wayyy too fast.

[Nessism]

If the sync is way off the idle will be inconsistant.

[sacruickshank]

For the original poster, here is my recent data points from rescuing an '83 GS650L that is now 100% roadworthy, reliable starting, strong pulling, smooth power, etc..
Mixture screws set at 2.5 turns out, except carb #1 whose idle port (the hole in the carb throat where the idle mixture comes out) was a little too large due to PO drilling it out. set that carb to 1.5 turns.
OEM intake manifolds.
Carbs def needed on bike syncing to get a nice stable idle. Bench syncing was ~OK, but #1 and 4 were off. Morgan carbtune is the best.
Idle now set to ~1200 rpm when fully warmed up. It can be stable a little lower when warm, but that makes the cold idle very low.
Factory airbox and new OEM filter. Surprised filter was still available.