GS550 first ride "issues"

[OzJavelin]

OK, finally got my '79 GS550 registered for road use. First ride (approx 100km) identified a few issues which peoples here might be able to help me with

1. Ride is WAY to soft. I plan on changing the rear shocks. What can I change on the front? Heavier oil? New springs? The front bottomed out a few times and I only weigh about 65kg (small frame; 5'6")

2. There is a "buzzing" sensation through almost the whole bike at about 5000rpm (approx 100km/h). It was that bad my fingers were numb after the ride. I've got a similar buzz on my Kawaka ZR550 but at 4000rpm which is not a standard speed limit equivalent RPM so it's not so bad. I'm surprised an inline-4cyl would vibrate this bad? What can I start checking to isolate this problem?

3. Speedo works but is way wrong. Worth trying another cable or just put it down to the speedo itself and live with it.

All in all a bit disppointing. The bike starts and runs OK, but highway driving is tiresome

[mike_of_bbg]

1. Up front, progressive brand springs and fresh fork oil are the standard recommendation.

2. Have you taken compression numbers? Sync'd your carbs? Try syncing at a higher RPM?

3. How far off are we talking (5%, 25%?)? Is it consistently off across the whole speed range? I think a few people have cleaned them out.

[Steve]

1. Ride is WAY to soft. I plan on changing the rear shocks. What can I change on the front? Heavier oil? New springs? The front bottomed out a few times and I only weigh about 65kg (small frame; 5'6")
Soft ride in the rear can be helped some by increasing the preload on the shocks. If the shocks are worn out, they are not usually rebuildable and must be replaced.
Soft ride in the front is quite often simply a lack of fork oil. First thing to try is assuring you have the proper quantity of oil in the forks. After adding fork oil, you may find a leak, which is why there is no oil in there now. Seal replacement will be necessary in that case. While you have the forks open for seal replacement, it's a good time to either adjust your preload spacer or change to Progressive Suspension springs. With your smaller size, you might get away with just playing with the preload on the stock springs.


2. There is a "buzzing" sensation through almost the whole bike at about 5000rpm (approx 100km/h). It was that bad my fingers were numb after the ride. I've got a similar buzz on my Kawaka ZR550 but at 4000rpm which is not a standard speed limit equivalent RPM so it's not so bad. I'm surprised an inline-4cyl would vibrate this bad? What can I start checking to isolate this problem?
Although there will just about always be some vibration, it should not be enough to numb your fingers. First, make sure your valves are properly adjusted. Next, make sure your ignition points are properly adjusted and timed. Finally, make sure your carbs are synchronized. The purpose of synchronizing the carbs is to get them to open the same amount at the same time. The time when this is most critical is just above idle speed, when a fraction of a millimeter of lift is a much larger percentage of the opening. When the throttle slides are over half-way open, that same fraction of a millimeter difference won't really nearly as much as when the slides were just barely open at idle.

3. Speedo works but is way wrong. Worth trying another cable or just put it down to the speedo itself and live with it.
Simply changing a cable won't do anything for speed correction. Are you sure you have the correct drive unit on the front wheel? Are you sure you have the correct spedometer? How far is it off? 5-10% is not uncommon, unfortunately. You can minimize that a bit by fitting a front tire that is one size larger. That will slow down the rotation of the tire, and also the speedometer.

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[OzJavelin]

Thanks all .. I'll start working thru these suggestions ..

[OzJavelin]

According to the Hayes manual I've got, supposedly the folk oil fill is a height measurement rather than by volume. Does anyone know the if you CAN do by volume and how much for a '79 GS550? (i.e. so I don't have to strip the bike if I can avoid it?)

[Pete Logan]

In theory you can do the height measurement by lifting the rear end of the bike until the front forks are vertical. Roof beam and a block and tackle. Then fix up some kind of depth gauge.

Some here claim to do it this way. I think they been smoking too much of the wrong stuff

The reason they quote fill height rather than quantity is because the quantity you have to put in depends on how much of the old oil is still left in there after you empty the forks. Some manuals quote both a 'wet' (ie: not cleaned/flushed) quantity, and a 'dry' (ie: cleaned and flushed) quantity.

[Steve]

I fully support the "level" specification, but also realize the effort that must be expended to realize it. If you do all you reasonably can to assure that virtually all of the old oil is drained, you can be reasonably comfortable by installing the same volume in both legs. Although the specs call for a level +/- 1mm, the practical application of a difference of several millimeters won't be noticed by most of us.

The worst thing you can do is to have too little oil in there and have the damping mechanism operating in air most of the time, then do a "belly flop" into the oil when you hit a bump. Probably not a large enough shock to the bike to cause any damage, but I can tell you from experience that it is very uncomfortable and causes some really funny handling.

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