weird issues with '77 GS550

[mattd1205]

I went for a long ride (70 miles) with a friend of mine on the back of my GS550 yesterday. we encountered alot of traffic followed by miles of open road where we could go about 75mph. It was about 85 degrees. When I got off the freeway the bike stalled out and wouldnt start unless it was choked and even then it wouldnt hold an idle. I filled up with gas to see if that was the issue. I checked the MPG and it was about 38 mpg. We rode back to her place and it wouldnt rev up past 4.5k rpm. I let it cool down for 10-15 mins and rode it back to my place. It did rev a little more but not much. I checked the oil level in the sight glass and noticed that the oil level was just below the low mark which is weird considering I changed the oil to castrol10w40 as Suzuki recommends. There isnt any smoke or any leaks. I trimmed back the spark plug leads (they were slightly melted) added oil and rode for about 5 miles and the bike seemed perfectly fine. The bike has just over 21000 miles and had been sitting for 4 years prior to me purchasing it. The valves have been adjusted and the carbs were recently synchronized Does anybody have any suggestions on what my next course of action should be? Thank you in advance

Matt

[Nessism]

What condition are the points in? Replaced the condensers lately?

Is the bike stock? Original exhaust and airbox w/stock air filter?

BTW, modern auto oil is bad for motorcycles, although that's not the problem at hand. Get some diesel engine or motorcycle oil and use that next time.

[Steve]

Carbs may have been synchronized recently, but have they been cleaned and adjusted?

Any bike that has been sitting THAT long really needs to be gone over stem-to-stern before trusting it on the road.

Now, if it were your bike and you parked it for four years, you would at least know what it was like before, but since you really have NO idea what has been going on with the bike for the last 36 years, it's well past time to start catching up on the REQUIRED maintenance.

.

[mattd1205]

I doubt the condensers have been replaced in quite a while. The points look fine with no pitting or anything. The carbs were recently cleaned and adjusted as well. I used the castrol motorcycle specific 10w40 oil. The bike is 100% stock. The thing that concerns me most is the drop in oil level since yesterdays ride. The thing that baffles me is there is no visible smoke or anything. should I switch to a heavier oil in case the tolerances in the engine have gone out of whack?

[Nessism]

Are you checking the oil level with the bike on the centerstand and with a cold engine? Look in your factory service manual for the proper checking procedure. If you don't have a manual you can download one here...http://members.dslextreme.com/users/bikecliff/

[mattd1205]

I did check the oil this morning and it was low. I also made sure the bike was on level ground when I put it on the centerstand. I had my friend check and see if there was any smoke coming out of the exhaust while I was riding and he said he didnt see any.

[ndbaker]

No sure about the oil, but did you check the intake boots? I had the issue of sudden stalling, poor gas mileage, poor acceleration. Turns out I was running off only 3 cylinders because the one of the intake boots (only 2 years old mind you!) cracked.