Question: Raise needle or try larger main jet?

[Mith]

The picture below is of the mufflers that are on my 81 GS550L. I have no idea who the manufacturer is or what their part number is. They seem to be much more free flowing than the OEM ones that should be on the bike. The bike has had a problem where it bogs down slightly when I start to give it throttle (as it comes off idle) but I can roll through it. In trying to eliminate the problem I removed the plastic washers under the needles and replaced them with two thin washers (raising the needles). This helped quite a bit and the problem is 'almost' gone. I'm thinking the problem is the mufflers and wondering if I should remove another washer or go up a size on the main jet. Anyone have any thoughts?

[Steve]

You really need to do plug chops to see just where your problems are.
Of course, any suggestions made are assuming that you have cleaned the carbs and replaced ALL the o-rings some time in the recent past.

The bike has had a problem where it bogs down slightly when I start to give it throttle (as it comes off idle) but I can roll through it.

This much sounds like a mixture screw adjustment. How far out are they?

In trying to eliminate the problem I removed the plastic washers under the needles and replaced them with two thin washers (raising the needles).

If you had plastic washers under the needles, your carbs were assembled incorrectly. In stock configuration, the plastic spacers (washers) were to be OVER the clip on the needle, and yes, they can be replaced with a couple of thinner metal ones to raise the needle.

I'm thinking the problem is the mufflers and wondering if I should remove another washer or go up a size on the main jet. Anyone have any thoughts?

Again, this is where plug chops will tell you what you need to do.
The procedure is outlined on BassCliff's site (which you should really have bookmarked ), but it involves marking the throttle grip and the housing so you can see exactly how far you have the throttle open and can hold it there.

Two pieces of tape, one on the grip, one on the housing will do it. Place a mark on the grip's tape near the top. Place another mark on the housing's tape opposite the grip's mark. Hold the throttle wide open, make another mark on the housing's tape. Measure between the two marks, make additional marks for 1/2, 1/4 and 1/8. It will look like this when you are done:


Now follow the procedure on BassCliff's site to check your plugs.

If you are still running the stock airbox, chances are that you will have to go up a size or two on the mains.
With your raised needles and a proper idle mixture setting (probably about 2 1/2 turns out), you should be good.

.

[Nessism]

I'd sort out that washer/spacer business as Steve states, and then move up one main jet size assuming the stock airbox is still installed. Plug chops should confirm everything after this is done. And also check those pilot screws as Steve says. The 550 likes 3+ turns open in my experience.

[Mith]

Thanks guys. I didn't explain the needle business properly in my original post. The needle/slide is assembled correctly. I replaced the spacer with the washers last fall and forget how they were assembled when I posted. I did a proper cleaning and syncing last fall as well as replacing the airbox boots and intake orings and sealing the box. I also put new dyna coils and wires on. It runs great and idles beautifully it's just that momentary bogging when I start to turn the throttle. I have the idle mixture screws somewhere around 3 turns out. Not entirely sure what each one is set at since I started there and adjusted them to highest idle. I've spent a lot of time trying to make adjustments to get rid of the hesitation but I think it's a waste of time if it's the non-oem mufflers that's causing it.

[salty_monk]

At 3 turns out your next step may be to try the next size up pilot jet...

[FreshStart]

Heres your exhaust

http://www.jpcycles.com/product/4500109

[Mith]

Wow. You found the mufflers! I suspected that they were aftermarket but now it's confirmed. I went from the stock 92.5 to 95 main jets and the hesitation is gone. That hesitation has annoyed me since I bought the bike back in 1992 but no one I knew could diagnose the problem. Thanks to GSResources, and reading many hundreds of posts I was able to understand what was happening.

[chef1366]

If you roll on the throttle and can hit red line with a wide open throttle after getting past the needle circuit than your main is ok.
When you get the main dialed then work on the needle and then the pilot circuit. (idle)