GS 550 CARB adjustments

[Anonymous]

I have a 78 GS550 seems to need to be on choke to warm up for 5 mins or so before I can rev the throttle. What do I need to do?? Once it's warm the bike revs and runs great.

[Anonymous]

Me too

I have a gs550e '80 - same thing. Tough to start as well. Yours?

[Anonymous]

I've got a 1978 GS550, and it NEEDS the choke to start it when its cold, and tends to be finicky and rev high with the choke on. After a couple of minutes, no choke and it runs great. Im guessing this is normal for an air cooled bike jetted lean from the factory to pass emmisions.

[Anonymous]

carbs

Which screws and how much should they be turned out to fix this lean condition??

[KEITH KRAUSE]

Re: GS 550 CARB adjustments

I have a 78 GS550 seems to need to be on choke to warm up for 5 mins or so before I can rev the throttle. What do I need to do?? Once it's warm the bike revs and runs great.

If the carbs are clean inside, do the basics.
Adjust the side air screws (on the side, pointing upward) using the "highest rpm method". A search will tell you how.
If the pilot fuel screws (underneath) have been moved, they may need to be turned out a little (richer). But set the side air screws first and test. If you play with the pilot fuel screws, record all adjustments so you can put them back if needed. On a stock bike, the factory generally sets them from 1/2 to 1 full turn out. It varies from bike to bike. They're sensitive to adjustments. Try a 1/4 turn at a time? If the factory sealant is still on the screw heads and they don't look disturbed, leave them alone.
A good carb vacuum synch is important too.
Be sure you have no intake leaks. Does the bike idle at much higher rpm's after warm up?

[Anonymous]

After the bike warms it idles great and run great, but it has to get good and hot maybe run for 5 mins or a little more. Where or how do I do a search for this info?? The carbs are clean and like I said after hot runs great ....Thanks for the post ....Steve

[KEITH KRAUSE]

After the bike warms it idles great and run great, but it has to get good and hot maybe run for 5 mins or a little more. Where or how do I do a search for this info?? The carbs are clean and like I said after hot runs great ....Thanks for the post ....Steve

OK. I'll type the "highest rpm method" for the SIDE AIR screws.
But this assumes your bike is idling at 1,000/1,100 rpm's. If it's too far above this, those rpm's are beyond the side air screws range. I mention this also because many members have bikes that idle at 1,500+ rpm's and they think that's good...it isn't. The highest rpm method only works when the bike is idling at the factory recommended idle.
Turn the screws out to 1 1/2 turns first. Be sure throttle cable play is correct. Be sure the air filter is clean. Put the bike on the centerstand and warm it up completely.
Starting with any carb, SLOWLY turn the side air screw in either direction until you hear the rpm's max. The sweet spot is usually between 1 1/2 and 2 turns out. When the rpm's stop rising, stop turning. After fine tuning the screw, adjust the idle back down to 1,000/1,100 by using the idle adjuster knob.
Go to the next carb and repeat. After all 4 are set this way, you're done.
I also suggest a carb vacuum synch.
Do you have any intake/exhaust mod's?

[Anonymous]

No intake or exhaust mods . Thanks for that help I'll try that . This is a great place.

[chrissinc]

I would be leary of going too crazy if the bike runs great warmed up. Fooling around with the bike so it runs better in the first 5 mins while destroying the rest of the riding time isn't a good trade off. I have a GS750EF and it's a little weird till it warms up as well. Is it so weird you can not drive it on the choke? What I usually do is start the bike with some choke, maybe 3/4. After about 15 secs the revs usually idle at around 2100, so I back the choke off a bit untill its around 1500 rpm, 1/2 choke. I wait a little bit maybe 30-60 secs then edge the choke down again to around 1300, 1/4 choke. Then I wait untill it idles and revs smoothly then drive off with the quarter choke for maybe the first couple of minutes then dump choke and hold throttle to maintain idle as nessesary untill bike warms up and can idle on its own at 1200 rpm. Waiting a minute or two before putting load on the engine really smooths it out and keeps wear to a minumum. Wait the 2 minutes. These GS engines are a little cold blooded. Same with my GS650. A little warm up time is well worth it.


Fooling around with the jetting is the LAST thing you should do. Trust me you don't want jetting headaches when the real problem is having patience to wait 5 mins untill the bike runs smoothly. I would try adjusting the choke to keep idle around 13-1400 and driving off with it and use throttle to maintain proper idle as nessesary untill its warmed up than trying mixture settings. It can get very expensive and time consuming if you screw it up. Try the cheap(free) stuff first.


If you want to make the waiting time seem shorter do this:

1 On the kick stand, start the bike and wait 15 secs or so so you can maintain idle at 1600-1800 rpm steadily without it climbing or over revving.

2 Once the idle is stable, start putting on your gear: jacket, helmet, gloves

3 Give the bike a quick once over with your eyes after you've got your gear on, check RPM's arent surging and lower choke to maintain 16-1800 RPM or so. Check the tires quickly to make sure no nails or glass is imbedded in there, kick them both if you like

4. Sit on the bike and put the bike upright. RPM's may surge a bit so adjust choke if need be. Make sure your seated comfortably and adjust mirrors as nessesary.

5. Using the choke lower RPM's to just over warm idle, say 1300-1400 or so, by the time you've done this A. You've done a quick pre-ride inspection, and B have half warmed up the bike already. It sounds like alot but it's faster than you think. Remember these are carbuerated bikes not fuel injected, so they need a bit of warm up time.

[AOD]

I didn't see anything about you guys with the carb problems say you cleaned them first, or not. As Keith said, clean them first, then try to diagnose.

You'd be surprised what taking them apart and cleaning the orifaces out with carb cleaner spray will do.

~Adam

[KEITH KRAUSE]

I would be leary of going too crazy if the bike runs great warmed up. Fooling around with the bike so it runs better in the first 5 mins while destroying the rest of the riding time isn't a good trade off.

Fooling around with the jetting is the LAST thing you should do.

The guy wants advice because he wants the bike to warm up faster, as it should. He's not looking for advice on how to live with it.
There are basic adjustments for the VM carbs. His could be adjusted wrong by a PO. The side air screws on his VM carbs are supposed to be adjusted for the highest idle. Cold or hot, all three jetting circuits, the mixture won't be right if this method of adjustment isn't made.
If the bike still has the problem, the pilot fuel screws may be set too lean. Adjust them in small increments. Keep records of their settings. Test. If the problem goes away, great. If not, put them back where they were. If the side air screws and the pilots are adjusted correctly, and the carbs are clean and in good shape, the bike will run right all the time. You won't be sacrificing anything to make it warm up better.
Also check the choke operation. His problem is either the choke circuit, or pilot circuit, or both.
If the above is checked/adjusted right, then a carb cleaning, o-ring check, float level check, and vacuum synch should be done as basic maintenance.

[chrissinc]

Sorry didn't mean it to come out that way but I've seen too much pain and suffering with jetting "tweaking". I didn't want him to run out there and have a bunch of problems if the bike was running ok when warmed up. A 1/4 turn on the mixture screws should be ok as long as they are marked so you can go back. Hope it helps. By the way I love those old GS550's they're great bikes.

['79 550]

Reddragon774

Just to clarify, if you are choking to idle and turn the throttle, does the engine start to die/die out completely? This is the problem I am having. Have not had the patience to wait 5 minutes, but will try it out. Have cleaned the carbs and changed the o rings, no luck. Have you solved your problem?

Thanks.

[KEITH KRAUSE]

Reddragon774

Just to clarify, if you are choking to idle and turn the throttle, does the engine start to die/die out completely? This is the problem I am having. Have not had the patience to wait 5 minutes, but will try it out. Have cleaned the carbs and changed the o rings, no luck. Have you solved your problem?

Thanks.

Opening the throttle by-passes the choke circuit. When choking, the throttle should be closed. Opening the throttle just takes things longer to warm up. The choke circuit supplies the richest mixture available.