Stihl 028 Super Update and More Help

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GezelligHomes

GezelligHomes

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So I posted a thread last month about an 028 Super I have, that I couldn’t keep running. So Now, I got it running. Problem, the thing will not idle down, its revving really hard/high I can’t get the idle screw to work, or whatever. This is the only way to describe it, than the second issue is it won’t throttle without shutting off. I’ve replaced Plug, vent line, gas-line, Carb, fuel filter, air filter is clean, spark arrestor I couldn’t remove but was clean from what I seen. Anyone have a clue? I thought impulse line but it didn’t look bad from what I could see.
 
First check to make sure throttle and linkage aren’t bound somewhere. Take the air filter off and see if the throttle butterfly is close(or close to it). You cans adjust idle screw to make sure it works and not holding throttle open.
Next start the saw and let it go it’s think...either put up and downnpressure on the handle flexing the av mounts and stretching/compressing intake boot. If you notice a change you’ve probably found the issue.
If no change, get a can of carb cleaner and while saw is running spray around the and behind the carb and impulse area. Note for decreased high idle. Double check the impulse line...I know you said it looked good but it’s somewhat hidden. If no change remove the bar and chain and spray the carb cleaner behind the clutch and flywheel and note change. If your saw idles down momentarily you’ve found the issue.
Where is your L screw set on the carb? If it’s to lean it won’t idle down either. Try turning it to the left to richening it up which should slow it down. The throttling and shutting off sounds like a lean situation, in which case the saw needs more fuel.
You replaced the carb? Why and with what?
Just throwing a lot of ideas out there....
 
Aftermarket carb previous carb didn’t look awful but it was a shot in the dark, smoking a lot. I’ve adjusted the L screw a good amount so the chain stopped moving I smell a lot of gas. I throttle but it wants to die on me. Is the impulse line difficult to get out?
 
GezelligHomes said:
So I posted a thread last month about an 028 Super I have, that I couldn’t keep running. So Now, I got it running. Problem, the thing will not idle down, its revving really hard/high I can’t get the idle screw to work, or whatever. This is the only way to describe it, than the second issue is it won’t throttle without shutting off. I’ve replaced Plug, vent line, gas-line, Carb, fuel filter, air filter is clean, spark arrestor I couldn’t remove but was clean from what I seen. Anyone have a clue? I thought impulse line but it didn’t look bad from what I could see.
Click to expand...

A two stroke is such a simple engine design and if it is revving high it is getting too much air with the mix, referred to as running lean. The air leak needs to be sourced out so the best step is to pull a vacuum and pressure test to find the leak before replacing a bunch of parts hoping to get the right one. Crank seals are the first suspect for air leaks but in my nearly 60 odd years of working on these two strokes there has been air leaks found in places one would not think would leak.
 

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