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cl100 loses power

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I have a cl100 that I built over the winter. Because it was a budget build I scuffed the cylinder with 220 grit wet paper and replaced the rings. I also replaced all the gaskets and seals, new clutch and some other stuff.

It ran ok during break in and just smoked a little - light haze like a rich running bike almost. During a top speed run yesterday it lost power dramatically at about 60 mph, when I stopped it was smoking. The next day on start up it smoked heavily for about 5 minutes then ran well with just light smoke.

Yesterday on a longer ride it lost power gradually like it was climbing a hill that was not there. When I stopped it idled down and died. After sitting for a minute or two it started and ran like it always did. It did this twice on the way home too - after about ten miles it would begin to act up.

After the top speed issue I rechecked everything, gapped and timed the new points, checked the valves, raised the clip one notch as it was a bit lean, charged the new battery again.

My guess is that I broke a ring during speed trials. I think I need to take the top end apart to get a real answer but the power loss has me baffled. Any ideas? Are the smoking issue and power loss the same? It seems to run fine otherwise and revs up to redline in every gear.

Sorry for the long winded post and here are some pics for those of you that hung in there all the way through.

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Your cylinder/piston were probably worn too much if it smoked right away, either that or you have worn valve guides/seal. Also when it died was it hard to kick over? I have an sl125 that did a similar thing and it turned out to be a plugged oil passage to the upper end which seized the cam. My bike was really hard to kick over until it cooled a bit. loosen the right rear cylinder head nut and kick it over about 20 time. A good amount of oil should come out.

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Your cylinder/piston were probably worn too much if it smoked right away, either that or you have worn valve guides/seal. Also when it died was it hard to kick over? I have an sl125 that did a similar thing and it turned out to be a plugged oil passage to the upper end which seized the cam. My bike was really hard to kick over until it cooled a bit. loosen the right rear cylinder head nut and kick it over about 20 time. A good amount of oil should come out.

You can also just loosen up the nut while its running and oil should run out.

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Why did you use sand paper on the bore? Were there gouges or wear marks? You need to take the head and cylinder and piston to a machine shop and have them evaluated. The valve guides are pretty tough so the clearances are probably okay, but there is a valve stem seal on the outlet valve which goes bad. You need to have the bore checked for round and taper and have the piston to cylinder clearance checked. The tolerances are in thousands of an inch so its likely your bore is worn, ergo the smoking and possible ring damage.

Nice looking bike BTW.

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