mrhack
OPE Member
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- 34309
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- Sep 18, 2025
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- around the world
Don't know where to post it, so dropping it here.
Hello, first time poster.
I recently got the clone saw. Mechanically inclined and willing to work on it, so it wouldn't bother me if it had problems.
I've been chasing a bottom end air leak for a few months and it's been driving me crazy. Saw picks up idle rpm with tilted clutch-down, a throttle blip brings it back down for a second or two then it picks up again. Changed both seals carefully and to spec depth, with oil on both the crankshaft and the seal, clean of debris. Idled fine for a few minutes, called it a day. Next day I started it up again, air leak's back. Pulled the clutch side seal out, bone dry. No oil's getting to it and there was a fine dust around the inner bearing race. The bearing itself had plenty of oil, as well as the whole bottom and top ends. Carb's set ever so slightly rich on both jets. Four strokes nicely at WOT, cleans up in the cut. Saw has a lean bog at certain rpm ranges and can even die if I wiggle the throttle in them. Also, lacking high rpm range torque. Muffler's gutted, didn't like how it ran. Changed it to an Ironhorse style pipe. Made the fuel/air mix richer, adjusted accordingly and it had the same problem. Can't max rev as high with the pipe, compared to the can. Reinstalled the can and tuned accordingly. Air horn is opened, lower transfers are opened up, exhaust port is widened, secondary uppers are raised ever so slightly, intake floor is flattened without changing the duration, lower piston ring is out, to allow for the wider exhaust. Running with base gasket and 0,6mm/23 thou of squish. No changes to timing, spark plug gap's 0,45mm/18 thou. Could the cylinder have an intake port that's too high, resulting in a lot of case vacuum being pulled on it, resulting in the seals letting air through? It's the only explanation I could come up so far. On a phone call with a Stihl tech the guy said the bearing could be too fat, which would rub the seals lip off and make it fail. Could also be that, considering all the fines I found. Any and all help/suggestions/ideas would be appreciated.
Hello, first time poster.
I recently got the clone saw. Mechanically inclined and willing to work on it, so it wouldn't bother me if it had problems.
I've been chasing a bottom end air leak for a few months and it's been driving me crazy. Saw picks up idle rpm with tilted clutch-down, a throttle blip brings it back down for a second or two then it picks up again. Changed both seals carefully and to spec depth, with oil on both the crankshaft and the seal, clean of debris. Idled fine for a few minutes, called it a day. Next day I started it up again, air leak's back. Pulled the clutch side seal out, bone dry. No oil's getting to it and there was a fine dust around the inner bearing race. The bearing itself had plenty of oil, as well as the whole bottom and top ends. Carb's set ever so slightly rich on both jets. Four strokes nicely at WOT, cleans up in the cut. Saw has a lean bog at certain rpm ranges and can even die if I wiggle the throttle in them. Also, lacking high rpm range torque. Muffler's gutted, didn't like how it ran. Changed it to an Ironhorse style pipe. Made the fuel/air mix richer, adjusted accordingly and it had the same problem. Can't max rev as high with the pipe, compared to the can. Reinstalled the can and tuned accordingly. Air horn is opened, lower transfers are opened up, exhaust port is widened, secondary uppers are raised ever so slightly, intake floor is flattened without changing the duration, lower piston ring is out, to allow for the wider exhaust. Running with base gasket and 0,6mm/23 thou of squish. No changes to timing, spark plug gap's 0,45mm/18 thou. Could the cylinder have an intake port that's too high, resulting in a lot of case vacuum being pulled on it, resulting in the seals letting air through? It's the only explanation I could come up so far. On a phone call with a Stihl tech the guy said the bearing could be too fat, which would rub the seals lip off and make it fail. Could also be that, considering all the fines I found. Any and all help/suggestions/ideas would be appreciated.
