By
erthnet
I'm going a little nuts trying to nail down what's causing this. Any help help or feedback would be so much appreciated.
Once warmed-up, I'll get blue exhaust smoke, and the plug will gets a sooty black coating. I'm assuming it's an oil problem. My gut says rebuilt the top-end, my wallet and watch both scream no.
Bike was a non-runner when purchased. Story goes: was a barn-find from an old man that only rode it occasionally, seller "didn't want to" put time into rebuilding the carb. Odometer is just over 1,200.
First thing I did, was drain the crankcase: thin oil with strong gas smell. After the 1st oil fill, I ran the bike ~5 minutes to warm and circulate that new oil, and then I flushed and filled with new oil a 2nd time. Didn't overfill either time (added 3qts, 2 minutes running, 15 minute rest, and then topped to middle of oil window). New oil filters too. Also replaced the petcock, and a new in-line gas filter. Diaphragm had a hole, so I rebuilt the carb. Float level is 12.5mm (within spec), pilot screw @2.5 turns (spec is 2 7/8), needle clip in 3rd groove (I'm at 1,000ft).
Bike starts easy: slightest press of the starter, and its idling nicely. Once warmed, I got blue smoke. Engine also bogs; will not climb a 10% hill once warmed, but it'll do it when cold (if I'm gentle on the throttle).
I've changed the plug a couple times during this process. Every time, it starts and idles fine...until its warmed-up. Then it's a little more difficult to start, and it smokes once running (and warmed). Bike also tends to die if shaken side-to-side. Only times it didn't die when shaken side-to-side, is when I had the air filter off. Still not sure if the dying is due to an electrical issue or not...haven't traced that one out yet.
Leak-down shows no issues, either warm or cold (even did it with the oil filler cap off...just in-case of a plugged crankcase vent):
I can't tell if the bike is burning oil or not, as the seller left me a little surprise (yea, it drips from the cover ~10x/minute while the engine is running):
I'd expect blue smoke on starting it this was a valve issue...but there's no hint of smoke when the engine is started/ran cold. I'd expect a leak-down to show pressure losses if this was bad rings...but cylinder holds pressure whether hot or cold.
Does this still sound like a top-end rebuild project? Or am I overlooking something?
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