Help diagnose what a Saw needs from audio:

[sliceoflife]

Copied from my Mac stalling thread. It's a Mac 250 and was stalling because there was no intake section of the fuel line (duh). Got the saw running, but Both Carb adjustments are almost fully in and the idle throttle is engaged a significant amount too. Middle video is me trying to back out the carb adjustments and how it fails when I do.

Hoping some people can advise my (not knowing much about 2 stroke engines) self on what is the problem and how to fix it.

Assuming needs a carb rebuild, but if that can be confirmed or if there's potentially other problems I'd like too find them out sooner rather than later (if/when it still struggles after the rebuild)

Videos (nothing worth seeing but hopefully the audio will help diagnose)

 

[link]

Last video, it starves.

 

[sliceoflife]

Yeah in that video I back off the idle throttle until it died. Until I did that, did it sound alright? Not running too rich or anything else obvious?

I'm mostly concerned because the carb adjustments are basically fully turned in when I'm able to get it to sit and idle... as well as having a decent bit of idle throttle... and it just feels like that shouldn't be the case. Is that just how these old saws run? I assume cleaning/rebuilding the carb will help... mostly concerned there's something more serious underlying that will be discovered when I do that and hoping more trained ears can ease or confirm my worries.

 

[link]

Yeah in that video I back off the idle throttle until it died. Until I did that, did it sound alright? Not running too rich or anything else obvious?

I'm mostly concerned because the carb adjustments are basically fully turned in when I'm able to get it to sit and idle... as well as having a decent bit of idle throttle... and it just feels like that shouldn't be the case. Is that how these old saws run?

You starved the engine at idle by adjusting the idle fuel blend adjustment with the clock too much.
It first rises the rpm then it slows down and dies, the same thing will happen if you enrich it too much. You should be in the middle between those two...
Then when you hit the throttle it should accelerate without hesitation, if it starves - enrich the idle blend a 1/8 turn.

 

[sliceoflife]

So I started with too much idle gas and ended with too little... need that somewhere in the middle?

 

[link]

So I started with too much idle gas and ended with too little... need that somewhere in the middle?

You should adjust it with the clock carefully till it starves and slows down ready to quit (like you did), then you should adjust it the other way (against the clock) until it starts to slow down and sputter - you should be in the middle between those. Engine running easy, not too much fuel - and not too little fuel.

 

[sliceoflife]

Thanks, I'll give it a go.

 

[link]

If you adjust the hi/max rpm be careful so that it doesn't lean out (starve), because you could score/damage the cylinder. If it starves at max rpm it will get too hot and get too little lubrication.
After you have adjusted the max rpm fuel blend (if you do) you might need to re-adjust the idle blend.

 

[sliceoflife]

So I think I adjusted them in, but unless I'm mistaken it seems like it's just pouring gas out of the throat of the carburetor I would say there's an ounce or so accumulated around the carburetor after maybe 3 minutes of running....

Any idea what might cause this?

 

[link]

So I think I adjusted them in, but unless I'm mistaken it seems like it's just pouring gas out of the throat of the carburetor I would say there's an ounce or so accumulated around the carburetor after maybe 3 minutes of running....

Any idea what might cause this?

So it does run now, how does it run? You got a video with you starting it, running at idle and then accelerate to max rpm?

 

[sliceoflife]

It idles just fine and seems like it holds up well with the throttle in too, but there's a steady drip from the throttle right under the flapper for the choke with the saw sitting down that I think is gas. I'll try and get another video

 

[link]

Im not an expert on those veteran saws but there are some people in here that is, so you just have a little patience till they chime in. @Pioneer

 

[sliceoflife]

Video:


No startup because I fought with it before noticing I had the shutoff switch on, then forgot to restart video until after it kicked up.

I just dance around max throttle because it's loud, and if there IS something wrong, I'm worried about destroying the thing by sitting on full throttle. But a lot of "idle" (clock is still having to be way in to keep it alive) and Im trying to show in the video the accumulation and dripping from the carb. There is a slight drizzle, but not enough to explain all that liquid, and it smells and feels like gas... plus I see dripping out of the back of the carb.


Also... After shutting the saw down, dumping out what's in there, and leaving it sit... I came back to more accumulation in there (In my basement, not outside, so not rain)... so I'm assuming that's from the fuel line "siphoning" gas even with the saw off and dumping it into the carb?

 

[sliceoflife]

Here's what it looks like a few minutes after I turned it off, dumped out everything from the body of the saw, and then set it down inside.

Looks like a tablespoon or two worth of gas got siphoned up and dumped through the carb.

 

[link]

Yea you should not keep it running at max rpm without a bar and chain anyway.
Thats a lot of excess fuel in there no doubt, but where is the air filter?

 

[sliceoflife]

It's off to show the carb dripping the gas. It's pretty rough anyway and probably another thing that's due for a replacement. I assume I'll have to retune the carb once it's back in place as it'll effectively choke a little bit, correct?


Google basically says bad carb seals cause carb gas leaks and the solution is to rebuild the carb... so I'm hoping that is all I need to get this thing running a lot better (and not spitting gas everywhere).

 

[link]

Google basically says bad carb seals cause carb gas leaks

Bad carb seals cause the saw to draw false air, it wont run at idle and need excessive rich idle blend to run at all.
Every old saw sputters gas at idle out the carb, but the airfilter catches it...

 

[sliceoflife]

Ah, very good to know. I'll slap the saw together and put the bar on and see how she runs. No chain till my safety gear gets here though. I don't trust myself to go slapping this thing around and stay in one piece.

 

[link]

Ah, very good to know. I'll slap the saw together and put the bar on and see how she runs. No chain till my safety gear gets here though. I don't trust myself to go slapping this thing around and stay in one piece.

You need the chain on it to run it at max rpm, it gives it some resistance.

 

[sliceoflife]

With filter and cover on it started up first pull and ran great for 5-10 seconds then got a little bit sputtery (but never stalled). Think I should give the clock another quarter turn in to try and get rid of that sputter or as long as it doesn't stall, leave it be? Or maybe try using the Carb's L adjustment to get rid of it (not sure if this is an option, I think it's already as rich as it'll go)?


edit: There was another 1/4 turn left in the L adjustment, and turning it all the way in DID clean up the idle quite a bit. Not quite perfect, but I'd buy that without rebuilding the carb, this may be as good as it'll idle. Doesn't sound on edge of dying constantly at least.

And yeah, I'm not gonna give her full throttle again till I get the chain on. She sounded quite angry when I tried.