My 361 has been running like crap for a while. It starts when it's cold, after about a minute it will die if I let it idle. It acts like it's rich/flooded out, if I hold it full throttle I can get it to restart but it still doesn't idle. It runs fine when you keep the throttle going. Last year I rebuilt the carb, that changed nothing. This year I've replaced a bunch of stuff even if I knew it wasn't going to be it since most of the stuff is cheap and the saw doesn't owe me anything. So far I've replaced the tank vent, fuel line, fuel filter, impulse hose, crank seal on the clutch side, cylinder base gasket and put a new stihl carb on it(this wasn't one of the cheap parts ) I hooked a vacuum pump up to the impulse hose with the exhaust and intake ports closed and it holds at 10in hg so I don't "think" the flywheel crank seal is leaking(would've replaced this one too but the dealer sold me the wrong seal). The only things that are left at this point are spark and the intake boot between the cylinder and the carb. The boot "looks" fine but I'm wondering if it's not sealing to the carb surface properly. Oh yeah when I bought the saw years ago I replaced the top end, the compression is still in the 160-170 range cold @WOT. Does anyone have any ideas?
Any chance the choke linkage got out of whack at some point? I can't remember how the 361's linkages are arranged, but on the 036 a tab on the plastic switch shaft pushes on a springy bent wire lever which in turn operates the choke. If that wire lever gets bent a bit out of shape then the choke won't open fully even when the switch shaft is moved to the run position.
Hmm, it runs at WOT ok so air filter, choke, fuel delivery are all good 'nuff. Ignition trouble tends to show up under load/heat..... So prolly not the issue here. If it's holding 10 in Hg then that's a pass for being air tight. Should be safe to say the boot and flywheel seal are serviceable. You replaced the carb and it had no effect? At this point I'm thinking the LA just isn't set right. But I would have thought you would see some change in behavior with the carb swap if that was the case. This might be a case where it makes sense to have a pro look at it. Even if he charges you $20-30 bucks it will save you a whole lotta headache and time.
Okay, hmm... the chain is the wrong gauge for the bar, tight in the slot, and the clutch springs are failing so that the drag from the tight chain slows the engine... Just kidding. Mostly.
Re-reading the OP and I have a question, does this saw not idle at all after it warms up or does it die after a short period of time?
Not a stupid question, yes I've spent hours chasing it on the old carb. I haven't messed too much with the new one since the problem has gotten worse since it started over a year ago. The saw used to still be usable it just wouldn't idle for long, now after it stalls it's a work out to get it to fire. The choke it operated from the on/off/choke lever,(plastic no wire for the choke) pretty much a no brainer. I check it for proper operation after your post though just to make sure I didn't miss it. I've tried it with and without the filter, pretty much the same results. This was/is my thought but at this point I'm questioning my sanity. After it dies it's hard to start, if I switch the plug it fire back up for a short time. It's either fouling the plug or the spark is weak but as you said weak spark would most likely produce a miss as rpm increased. The spark looks suspect to me but I have no reference from when it was problem free. I know it's not producing the snap/color I get from the msd digital 6 in my mustang. I check the vacuum with the intake boot off and exhaust off. Didn't figure I'd be able to plug all the possible air leak areas with the carb on it. My thought too but it's exactly the same, I'll play with it some more. I pulled the carb back off last night and there is some fuel "wetness" between the carb and intake boot so that tells me its not sealing as it should. I'm going to attempt to build a make shift gasket for it tonight to see if it helps seal it better. Now you're talking crazy! I will continue to toss parts at it until it's fixed! Most of the stuff it could use besides the carb which I figured but threw money at it out of frustration. I still think it's fuel related but I've been wrong before.
After it warms up it's darn near impossible to restart anymore so it's hard to say. When the problem started a year ago it would start ok then idle for a few seconds and die. Now it's a PITA to restart after it dies, when I do get it restarted it will attempt to idle then die, almost like you shut it off.
You should check it with the boot on, just insert a piece of rubber between the carb and the boot, similar to how you would block the exhaust. The boot could very well be your problem.
You could try a thin film of grease on the boot/carb faces during assembly to see if it changes anything. Won't be a permanent fix but could diagnose/seal a small leak before you throw more parts at it.
I'll try that, the impulse line is too short so I'll have to put a longer piece in first. That won't be a problem since when I bought the line it comes in a bulk length so I have a plenty of extra. Sounds like a good suggestion. I'll try that before wasting time cutting a gasket.
Check the pop off pressure of the needle in the carb... If it's loading up at idle, chances are the spring pressure is too light, or the metering lever is set too high.. Allowing too much fuel in at low rpm's... If it's dying due to lack of fuel, the spring is too stiff, or the metering lever is too low.. Maybe...
After thinking more and reading all the posts I went back out tonight and messed with it a little. I started with the factory settings on the carb,(thanks MM!) the H/L came preset a little less than 1 turn out, I turned out the L to 1 1/4 and started from there. After tweaking it a little the saw is now idling "decent". I can't say with confidence it's right just yet but better. It was getting late and I didn't think the neighbors would appreciate me making chainsaw noise near 10 pm. I'll try to mess with it more tomorrow and see how it does. Thanks to all who offered advise/direction up to this point!
Picked up a new plug for it on my home from work and messed with it a little after dinner. After a little more adjusting it's idling and running pretty good. The transition off idle is pretty clean and the uppers end is close to right. I made a few cuts on some oak rounds I have laying in the drive and it cut fine. The H screw may need a little adjusting but it's safe the way it is.
Some saws are picky on the low speed adjustment. Dolmar/makita 6400,(especially) cat models, are hard to dial in on the low side to me. Very little room for error. Work with it. Hopefully that's all it needs. Good luck.
Long time follow up. Saw was never right after replacing the stuff mentioned above. It pretty much became unusable. After going through all the trouble shooting steps again(vacuum, pressure test, compression test, new intake manifold boot etc) I bought a used coil off eBay. After installing the new/used coil it almost started on the first full choke pull and started on the next warm choke pull. I think the coil was failing for a long time. Issues started out with an erratic idle it progressively got worse until it would only start when cold and die as soon as you let it idle. It still had spark after dying, just not good enough. Couple of my quotes from 2+ years ago. Yep, should've went with my gut in the first place! Oh well maybe I'll be problem free for a while.
I am not a mechanic, but I had the same issue with s Stihl Weedeater. I bought a new carb, same issue within a day. I ended up dumping the batch of gas I had with ethanol, only use ethanol free and replaced the carb again. It has run perfect for over two years. I sometimes think there are as batches of gas. I am likely totally wrong with your issue, but tossed this out just in case.
