Last fall finally had the ambition and the weather to go for a nice ride around a local lake, tebo would probably know the lake, Skaneateles.
I was on the Harley Sportster/Sidecar outfit wife on her GTV300 Vespa. As I slowed down to make the right off Route 41 on to Route 41A bike skipped and backfires a bit. Thought it might die right there but it did keep running. Told wife through intercom what happend and told her I might have to stop. It kept running just maybe a bit rougher than normal and it kept running the same the 30 miles back home.
I did some basic checks over the next couple days like inspecting spark plugs and looking for loose wires. As it was late in the season and my ambition was a bit low along with being a little discouraged I more or less put off doing much at all for a few months. A few days back decided it was time to do some more troubleshooting.
This time I did a compression test and found that front cylinder was around 90 psi while rear was right around 150 psi. Tried to do a crude leak-down test but due to the lack of easy access to see or hold crankshaft was not sure but it did not seem like any major leaking either from valves or crankcase area.
Knowing there had to be some major problem with that difference in compression decided to bit the bullet and open it up. Started with front cylinder and as soon as I had the head off it was obvious where the problem was so pulled the cylinder and piston. See attached images of front piston:
This engine has all of around 7,000 miles on it since back in 2016 when I had a shop rebuild it using Screaming Eagle Heads and Cylinders. I was able to tell from part numbers on pistons that the pistons are actually Wiseco pistons I have contacted them to see if they had any thoughts on what might have caused the failure.
To my surprise after seeing how the piston looked I expected the cylinder bore to be destroyed but the front one looks just as nice as the rear. I even had a good local motorcycle guy inspect it and he said he would at the most do a light hone and reuse it. The heads while roughed up from the bits going through we both agreed that a careful smoothing out keeping away from gasket area should make them serviceable.
I was on the Harley Sportster/Sidecar outfit wife on her GTV300 Vespa. As I slowed down to make the right off Route 41 on to Route 41A bike skipped and backfires a bit. Thought it might die right there but it did keep running. Told wife through intercom what happend and told her I might have to stop. It kept running just maybe a bit rougher than normal and it kept running the same the 30 miles back home.
I did some basic checks over the next couple days like inspecting spark plugs and looking for loose wires. As it was late in the season and my ambition was a bit low along with being a little discouraged I more or less put off doing much at all for a few months. A few days back decided it was time to do some more troubleshooting.
This time I did a compression test and found that front cylinder was around 90 psi while rear was right around 150 psi. Tried to do a crude leak-down test but due to the lack of easy access to see or hold crankshaft was not sure but it did not seem like any major leaking either from valves or crankcase area.
Knowing there had to be some major problem with that difference in compression decided to bit the bullet and open it up. Started with front cylinder and as soon as I had the head off it was obvious where the problem was so pulled the cylinder and piston. See attached images of front piston:
This engine has all of around 7,000 miles on it since back in 2016 when I had a shop rebuild it using Screaming Eagle Heads and Cylinders. I was able to tell from part numbers on pistons that the pistons are actually Wiseco pistons I have contacted them to see if they had any thoughts on what might have caused the failure.
To my surprise after seeing how the piston looked I expected the cylinder bore to be destroyed but the front one looks just as nice as the rear. I even had a good local motorcycle guy inspect it and he said he would at the most do a light hone and reuse it. The heads while roughed up from the bits going through we both agreed that a careful smoothing out keeping away from gasket area should make them serviceable.
Thank the two wheel gods you's were able to get back home safely. Lean? Hot? If so, wouldn't your exhaust pipes be all kinds of pretty colors from the heat? Funny how it happened, after you had the overhaul, using "the good stuff"... 
