Posted: 5/5/2009 4:50:19 PM EDT
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My FIL seized his chainsaw, I ma not sure how but he did, so I got it moving again, got it running again, hell it is just like new
the only problem is that as soon as you let off the trigger, after you have been cutting and working it, it sputters and stalls, but it will stay at idle forever if you don't touch it once started Is this something to do with a carb adjustment, or is it something worse? (For what it is worth, he said it always did this, though usually stopped once it was warmed up) |
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Quoted:
My FIL seized his chainsaw, I ma not sure how but he did, so I got it moving again, got it running again, hell it is just like new the only problem is that as soon as you let off the trigger, after you have been cutting and working it, it sputters and stalls, but it will stay at idle forever if you don't touch it once started Is this something to do with a carb adjustment, or is it something worse? (For what it is worth, he said it always did this, though usually stopped once it was warmed up) gas to oil ratio...? |
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Sounds more like a tuning issue, although if it was seized... I'd be nervous about the condition of the piston and cylinder.
Pull the muffler and take a peek. I'd say the High speed jet is lean (seized the first time) and thats what is causing the problem now. If you slowly back out of the throttle, like say give it a few blips as the RPM's die down can you ease it back into an idle? |
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OK guys, a very basic primer on two cycle engine operation. There are actually TWO compression strokes in a two cycle engine, one being the primary one the other being the secondary compression stroke.
The crankcase fills up with a fuel air mix when the piston moves to the top of the cylinder. As the piston travels back down, the primary compression stroke happens. The skirt seals off the intake port and as the piston moves farther down it stroke it compresses the fuel air mixture in the crankcase, As the transfer ports open the fuel air mixture is pushed up into the cylinder and as the piston starts it movement upward the secondary compression stroke begins. After an engine has been seized there is damage to the cylinder wall and some likelihood of a partially stuck ring. This allows the high pressure exhaust gasses to blow by the piston and contaminate it incoming charge and also causes loss of both primary and secondary compression. IF you can get the engine started, it will often (as in this case) run at high speed but will not idle. The loss of primary compression also causes issues with carburetion as the pulses from the crankcase work the fuel pump and metering lever in the carb. Unless it is an expensive saw, it probably isn't worth the cost of repairs. |
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Idle mixture, either plugged or running way to lean. A quick fix is to tighten it up all the way (remember the number of turns) and then back it out to the same spot, if there is any little crud in there this will loosen it up. You may also want to back it out another half turn.
-JTP |
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The engine was completely seized, as near as I can tell his oil gas mixture was off, my little doohickey read it as 60-1 (though it reads mine as 50-1, and I know mine is slightly less than 40-1)
I emptied the gas out of it, filled the gas chamber with TKX and kept pumping the priming button (Hoping this would get the oil into the case itself), as well as pulled the plug and filled the top of the cylinder with TKX as well I let it sit for a few hours, then carefully got the piston moving using a ratchet (the pull mechanism was off at this point), I moved it for a few revolutions to make sure it was behaving, and to get the oil out of the bore, drained what was left of the oil out of the gas tank, and refilled it with a known good mix of fuel, as well as making sure his bar oil was full (I also had to muck around with his chains stop as it was jammed as well) at this point I tried to start it, and after three pulls it fired right up, gave it gas and all was good, but as soon as I let off the Gas it stalls, if I slowly ease off the gas it will keep running, but blips for a second like it wants to stall It is a Mastercraft (Canuck version of a Craftsman) so it is not like I am overly worried about it, it is not a Husqavarna or Stihl for instance |
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the seized part of this problem is bugging me. do you have access to a compression tester? if so pull the spark plug and get a quick compression reading. if not take the muffler off and take a look at the piston, if any scarring is showing then you will have to replace the piston and possibly the cylinder. also double check what the proper mix ratio is. most saws now require 50:1 mix ratioo. get the mix off either way can cause engine damage. also buy a quality mix (husqvarna or sthil 2 stroke mix) the cheap stuff doesnt cut it. now there should be 3 screws on the side of the carb. one is labeled H for high one is labeled L for low and one is maybe labeled T for throttle. start the saw and let it warm up. now turn in the Throttle screw until it will idle fine. now give the throttle a squeeze. if it bogs down and then picks up a bit adjust the Low screw until you get a smooth transition from idle to full throttle. you may have to re adjust the Throttle screw to make it idle right. once you have those two settings where you like them now go adjust your H screw. press the trigger and hold it down. you should have a smooth rev from idle to full throttle and at full throttle it shouldnt sound like its about to blow up. it also shouldnt sound like its under powered. this is where a tachometer comes in super handy. i strongly suggest you get a tach or have a saw shop set your carb. if you set the High to "high" it can overrev the motor and cause damage. |