GS550L Resurrection Almost Complete - Thanks But...

[Anonymous]

Thanks for all the help so far. I've taken My 1981 GS550L with no start (Faulty CDI, Regulator, Gummed up Carbs, In-Line Fuel Filter, Spark Plugs) and finally got it running smoothly after 7 years of being laid to rest. So I've cleaned the carbs 3 times in order to finally get it right, I bought a new VRR, and I switched the CDI and pickup coils to points and condensers. Bike runs good and charges fine. It's even rideable.

Problem:
Backfiring and rough acceleration above 3500 - 4000 RPM. I have not had the carbs balanced yet so could that cause it? Is there a way I can balance the carbs myself. I turned each air screw exactly 1.0 turns ccw from where it shouldered. Any suggestions??

Special thanks to Earl for the detailed method for timing my bike. It worked like a clock - no pun intended.

Craig

 

[Jay B]

Depending on what carbs you have I think most folks are going from 2 to 2 and 1/2 turns out to start with. Syncing the carbs isnt that hard if you have the carb tool.

 

[Anonymous]

a cheap way to sync the carbs is with a hose about 2 ft long insterted in your ear the other end in the carb intake, listen for the hiss and adjust till they all sound the same.......sounds weird but it does work well

 

[earlfor]

Re: GS550L Resurrection Almost Complete - Thanks But...

Craig

In case there is some misunderstanding, I'll add this:
Pilot screw and air screw adjustment controls the mixture at idle primarily before the pistons in the carb are moving up. Though this adjustment does overlap into higher rpm ranges, it is virtually unrelated to backfiring and rough acceleration above 3500 to 4000 rpm. One turn out on the air screw is probably not quite enough air and causing a rich idle. However, if it idles fine and does not bog when you advance the throttle, I see no real reason to change that setting.

On balancing the carbs: YES, the vacum draw on each carb not being matched will absolutely cause your problem. It will also cause high vibration levels and if bad enough will cause your fingers to go numb when riding. J C Whitney (one example) sells a
four tube mercury manometer for balancing carbs and it comes standard with the correct adapters to fit suzuki. I got mine for about $33.00. I just love spending other people's money,
so.... seriously though, spend the 33 bucks and buy one. The difference it will make to your tune up is like night and day. When you adjust the vacums on your carbs, always adjust the worst carb. (dont go back and forth 1 2 3 4, 1 2 3 4...forget that approach. Just keep tweaking the worst one and pretty soon, there will not be a worst one. I say buy the guage because once you start getting the vacums close, you will be working with about 1/16 of a turn on the adjuster screws and there is no way you can hear that difference accurately with an ear. As a starting point, setting the carbs to what I call 25/25 will give you a middle of the road brown burn on the plugs and a safely rich mixture.
25/25 is 2500 rpm and 25 inches of vacum.

I'm happy my "oddball" timing method worked out for you.

Earl

Problem:
Backfiring and ro
ugh acceleration above 3500 - 4000 RPM. I have not had the carbs balanced yet so could that cause it? Is there a way I can balance the carbs myself. I turned each air screw exactly 1.0 turns ccw from where it shouldered. Any suggestions??

Special thanks to Earl for the detailed method for timing my bike. It worked like a clock - no pun intended.

Craig