77 GS550 lacking umph!

[Guest]

Hello all,

Been looking at these forums for a while for answers to some questions and its been very helpful. After some searching I've got my own question that I am hoping to have answered....

Ive got a 77 GS550 I picked up about two months ago. She was idling really rough so I had the carbs cleaned and synched. Idles beautifully now. The big issue now is a noticeable lack of power. The mechanic said it might be running lean and need to be re-jetted. There is an aftermarket 4-1 Kerker exhaust on it and a stock airbox. I am unaware if it was re-jetted since its install. I checked the plugs yesterday. They all look good when compared to the "how to read a spark plug" guides. I am really not sure if it is infact lean, or if its running rich, and bogging down with fuel when rolling on the throttle.

Looking for a solution that doesn't involve me taking it back to the mechanic, as I wont see it for another month (they get really busy around here).

Of note, before I had the carbs cleaned and when I could get it to run, It would pull really well in 1st and 2nd gear. Now, not so much. My 0-60 time is probably something like 8-10 seconds. My experience with motorcycle maintenance is very limited; learning as I go.

[CrazyCloud]

Welcome to the site! You should probably do some plug chops at different throttle positions to start with, it is much more useful than a generic 'ride around and check at home later' approach. Start here: http://members.dslextreme.com/users/...plug_chop.html. Check your air cleaner to see if one is there and if it's clean. Bookmark the BikeCliff website while you are there and download a manual. Between that site and this one, you should be well set for info.
Good luck, keep us posted, and put up some pics of your bike for goodness sake!

[collinsra]

Welcome to the site! You should probably do some plug chops at different throttle positions to start with, it is much more useful than a generic 'ride around and check at home later' approach. Start here: http://members.dslextreme.com/users/...plug_chop.html. Check your air cleaner to see if one is there and if it's clean. Bookmark the BikeCliff website while you are there and download a manual. Between that site and this one, you should be well set for info.
Good luck, keep us posted, and put up some pics of your bike for goodness sake!

Quick update: When I got home I did a bit of a poor man's test to see whether I am running too rich or lean. I took the top of the air box off and inserted a small hand towel inside to restrict the air a bit more....and presto! Night and day difference. Great pick up and thrust. Guess I just need to rejet and that should theoretically fix it....right?

[Nessism]

What maintenance have you done? Adjusted the points and valves? If not, please check the Newbie Mistakes thread linked in my signature for some tips on what to do.

[collinsra]

And here is a picture. Having issues uploading others...I'll work on that.

[collinsra]

The only thing I have done to it is had a professional sonic clean the carbs, rebuild and sync them. It was quite the difference when that was completed. The mechanic did mention that he believed a jetting was needed but wasn't sure. Would have taken another month to get it back after that...and probably another 250 out of my pocket.

Also, I had the shop do a full inspection on her. Compression, leaks, rust in the tank, petcock functionality, etc. All was good except the carbs were nasty.

Judging by some videos I've seen, it seems pretty simple to rejet yourself.

[CrazyCloud]

Yes, you should be able to do the jetting yourself no problem. Just have to pull the carbs off. Doing plug chops will tell you where to go with your jetting. You will do separate tests for the pilot jet, needle setting, and main jets. This is done by looking at the plugs after running certain throttle opening; like in the link I posted. Read thoroughly a few times before you do it. You will need to do as Nessim says and address the newbie mistakes, it will save you a lot of time in the long run. These guys have been there and done that, and distilled everything down to what to check and fix. Following their advice is very wise.

If you have the stock foam air filter (or K&N for that matter), make sure it is oiled properly. If not, oiling it will help richen up the system a bit.

Nice ride by the way, looks pretty clean. You're starting with a better 'base' than a lot of us!