The shindaiwa I saw a diagram off had the mixture entering into the crank case via a reed valve. It then had a second reedvalve in the crank case which led to the intake valve/port. They are doing this to take advantage of the compression the occurs on the down stroke to force feed the intake port much like a two stroke.
4 strokes on trimmers, saw?
- Thread starter Tony Snyder
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NevadaWalrus
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It was like last Feb. when they went through this thing with us at the last Stihl update. We haven't seen them yet here in Nevada cause all or most of the early production has gone to Kalifornia to get their brand emission average down to meet the stricter C.A.R.B. regs. As a result I've gotten a bit fuzzy on how the Stihl works.
I seem to recall it has no reed valve. After the carb there is a channel running down to the crankcase and one to the intake. There is a narrow restriction as it enters the crankcase. Piston up vacuum draws fuel mix into the crankcase and piston down compression forces it back up a un-restricted channel to the intake. The restricted "in" channel does push some back up a ways but not all the way to the carb. The fuel sent back from the crankcase to the intake is then mixed with the larger charge direct from the carb.
Like I said, its been a while so I'm a bit fuzzy on the details but thats basically how the Stihl works.
I seem to recall it has no reed valve. After the carb there is a channel running down to the crankcase and one to the intake. There is a narrow restriction as it enters the crankcase. Piston up vacuum draws fuel mix into the crankcase and piston down compression forces it back up a un-restricted channel to the intake. The restricted "in" channel does push some back up a ways but not all the way to the carb. The fuel sent back from the crankcase to the intake is then mixed with the larger charge direct from the carb.
Like I said, its been a while so I'm a bit fuzzy on the details but thats basically how the Stihl works.
Nevada, I havent seen a diagram of the stihl, but shindaiwa has one on there site. Check it out.
Jiml, only 10,500 eh. Two strokes will stomp the thing with the same power and more rpm.
Jiml, only 10,500 eh. Two strokes will stomp the thing with the same power and more rpm.
Really. I assumed that the fs 85 reved out to 14k just like a saw. Learn something every day.
revs
The old FS80, 65, 61, etc, revvedout forever. Then I started seeing loose bearings. Problem was when you took the string head off and put on a blade it over revved. The new 80, 85 have a governed carb which limits the revs. Makes the motor last longer, and IMO, makes it stay in the powerband.
The old FS80, 65, 61, etc, revvedout forever. Then I started seeing loose bearings. Problem was when you took the string head off and put on a blade it over revved. The new 80, 85 have a governed carb which limits the revs. Makes the motor last longer, and IMO, makes it stay in the powerband.
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