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Greetings. Just last week I purchased a stock 1980 GS550 (letter unknown at this point), 18,700 apparently original miles on the odometer. The bike ran fine (no knock) when I purchased it, and my first 20 miles were trouble free as I puttered around learning the bike.
Yesterday morning I investigated the crankcase oil sight per usual routine (round plastic window) and I noticed that the oil level seemed low, under 1/8 visible (yes, bike was on center stand) so I added 1/2 quart oil of the correct type. The sight window showed about 90% full, but the bike was cold and the new oil perhaps had not settled yet.
I hadn't yet added fuel to the fuel tank, but with the fuel cap off I could slosh, so I wasn't too worried. I took it for a spin up our local "mountain" = Cadillac Mountain in Acadia National Park in Bar Harbor, Maine. The climb was from zero to 1530 feet above sea level. The road was being paved, so I was not only climbing but riding on new & hot black road, and I had to frequently stop as the road was one-way in places to accommodate the paving crew. Ambient temp that day was 65F, cooler as I climbed. The engine was warm/hot but not sizzling.
Just as I pulled into the rest stop at the top of the mountain I heard a loud knocking from the top of the engine. At idle no knock, but taking off in 1st as I let out the clutch the engine would knock from 2,000RPM to 4,000RPM. I could feel the knock in my legs, and it was very loud, a true knock. Worried, I headed home gently and prepared for the worst. I pulled into my garage and played with the throttle in neutral and the knock was persistent.
Next morning I sadly walked out to the garage. I looked at the oil sight and it was totally full or empty, I couldn't see a line of oil. The oil was very clean, so I really couldn't tell (even with a flashlight) whether the sight showed full or empty. So as to determine, I drained some oil into a pan, about 3/4 quart, and the sight settled down so that I could see the line of oil at the very bottom of the sight. Over the next 30 minutes I added oil in dollops, watching the sight, until the oil level showed 1/2 in the sight.
Then I tried to start my bike. It fired and then stalled. I choked it, and it fired and ran with full choke, but the throttle was useless and it would stall as I rolled the throttle. I braced myself for the reality of the situation (knock, no run, nightmare) and kept trying to start it. I sprayed one blast of starting fluid into the air cleaner and it ran for about 10 seconds then died. I ran down my internal checklist and checked the fuel tank, there was hardly any slosh, and on a newbie whim I put the fuel petcock on RES.
The bike started immediately and settled down into a smooth idle, no choke, and the throttle was immediately responsive, quite nice actually, and I blinked in surprise. As I rolled the throttle I listened for the knock, and THERE WAS NO KNOCK. The bike ran like a clock, and I could tell that the bike was running far better than it had ever run for me those first few miles. I took it for a test spin to the gas station, filled up the tank, and rode home feeling better and better as the bike ran perfectly with no knock. Last night I took it for a 40 mile ride and it ran so well I came home with a big smile.
1) With too much oil in the crankcase, are these motors known to knock? I can only imagine that the engine was struggling against a "hydro" lock of too much oil, and I was hearing a slap as the pistons bounced off the oil.
2) With low and perhaps rotten fuel at the bottom of the fuel tank, is it possible that running on fumes caused the knock?
I was just about ready to pull the camshaft chain tensioner but the problem seems to be resolved.
Yesterday morning I investigated the crankcase oil sight per usual routine (round plastic window) and I noticed that the oil level seemed low, under 1/8 visible (yes, bike was on center stand) so I added 1/2 quart oil of the correct type. The sight window showed about 90% full, but the bike was cold and the new oil perhaps had not settled yet.
I hadn't yet added fuel to the fuel tank, but with the fuel cap off I could slosh, so I wasn't too worried. I took it for a spin up our local "mountain" = Cadillac Mountain in Acadia National Park in Bar Harbor, Maine. The climb was from zero to 1530 feet above sea level. The road was being paved, so I was not only climbing but riding on new & hot black road, and I had to frequently stop as the road was one-way in places to accommodate the paving crew. Ambient temp that day was 65F, cooler as I climbed. The engine was warm/hot but not sizzling.
Just as I pulled into the rest stop at the top of the mountain I heard a loud knocking from the top of the engine. At idle no knock, but taking off in 1st as I let out the clutch the engine would knock from 2,000RPM to 4,000RPM. I could feel the knock in my legs, and it was very loud, a true knock. Worried, I headed home gently and prepared for the worst. I pulled into my garage and played with the throttle in neutral and the knock was persistent.
Next morning I sadly walked out to the garage. I looked at the oil sight and it was totally full or empty, I couldn't see a line of oil. The oil was very clean, so I really couldn't tell (even with a flashlight) whether the sight showed full or empty. So as to determine, I drained some oil into a pan, about 3/4 quart, and the sight settled down so that I could see the line of oil at the very bottom of the sight. Over the next 30 minutes I added oil in dollops, watching the sight, until the oil level showed 1/2 in the sight.
Then I tried to start my bike. It fired and then stalled. I choked it, and it fired and ran with full choke, but the throttle was useless and it would stall as I rolled the throttle. I braced myself for the reality of the situation (knock, no run, nightmare) and kept trying to start it. I sprayed one blast of starting fluid into the air cleaner and it ran for about 10 seconds then died. I ran down my internal checklist and checked the fuel tank, there was hardly any slosh, and on a newbie whim I put the fuel petcock on RES.
The bike started immediately and settled down into a smooth idle, no choke, and the throttle was immediately responsive, quite nice actually, and I blinked in surprise. As I rolled the throttle I listened for the knock, and THERE WAS NO KNOCK. The bike ran like a clock, and I could tell that the bike was running far better than it had ever run for me those first few miles. I took it for a test spin to the gas station, filled up the tank, and rode home feeling better and better as the bike ran perfectly with no knock. Last night I took it for a 40 mile ride and it ran so well I came home with a big smile.
1) With too much oil in the crankcase, are these motors known to knock? I can only imagine that the engine was struggling against a "hydro" lock of too much oil, and I was hearing a slap as the pistons bounced off the oil.
2) With low and perhaps rotten fuel at the bottom of the fuel tank, is it possible that running on fumes caused the knock?
I was just about ready to pull the camshaft chain tensioner but the problem seems to be resolved.
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