Poulan 260 pro issues when hot

[vizette]

So I've got this Poulan 260 Pro as part of a group of saws I picked up... It's actually a nice little saw, and this one doesn't appear to have been used all that much. Piston looks clean from the exhaust port. Plug looks good.

I replaced the fuel lines and put some fresh gas and bar oil in it, and it fired right up! Tinkered a bit, got a good idle, throttle response, and WOT actually had me looking forward to testing it out once I got the chain sharpened, and then I got distracted with something else for a few days.

Today I sharpen the chain, take it out to tune it in a cut, and as soon as it gets warmed up it flakes out - dies like it ran out of gas, so I add some, as it was getting a little low. I take it back out, seems OK at first, and then back to acting up. Won't idle, won't start without the choke, when I can keep it running it hunts hard and is just plain erratic no matter what I do with high/low needles. If I let it cool down, same deal once it warms up again.

At this point I'm assuming it's the carb "adapter" between the carb and the cylinder, and when it gets warm there's an air leak. Or could this be a vent issue? Hmmm haven't tried pulling the fuel cap off when it starts and seeing if that helps... How do these vent?

I did pull the carb apart and everything seems OK there, and I would think if that were the issue it'd run like crap regardless, but the first few minutes it runs, it starts and runs smooth as can be.

-Rich

 

[s sidewall]

I believe the vent is in the gas cap, green duck bill valve held by a small retaining ring.

Steve

 

[Jasonrkba]

260's where decent saws for the money. Could just be the plug if it only acts up when hot. Or coil. I had to replace the carb adaptor on one. It was one of my first and a learner saw. I over tightened it and cracked it. Take the cap apart using a pick. Try not to bend that crazy washer that holds everything together to much and check the duckbill.

 

[vizette]

I think it is the vent. I got it warmed up today to the point that it quit, cracked the cap, started it up again, set it on it's side with the cap loose and it idled just fine for a good five minutes. Didn't have time to take apart the cap, but I know what you mean - I've found them separated before, it's like a big star washer. Will tackle that next to check the duckbill. Thanks!!

 

[scottr]

Hey Rich , does your PP260 have the aluminized cat muffler or does it have the pre cat black muffler ?

 

[vizette]

Black steel can, nothin' fancy

 

[vizette]

Took the tether out of the gas cap, then got the duckbill out. Duckbill looks like new, but underneath that seems to be something metal - I can't tell what it is. A small screen maybe? Would make sense I suppose, so you don't pull in gunk from the outside of the cap. However, I can't verify that the cap is venting even with the duckbill out.

I screwed the cap back on without the duckbill, laid it on it's side with gas against the cap for a few minutes, and no leak. I expected it would leak out without the duckbill there. I'll try to blow some air through from the outside, but not really sure what to expect from a vented cap like this?

-Rich

 

[Jasonrkba]

I would think without the valve it should have leaked.

 

[s sidewall]

That the filter that you see, fine brass sintered filter. Try back flushing it with carb cleaner.

Steve

 

[vizette]

Turns out there was a crack in the carb adapter - after a freezing cold -> hot cycle, the adapter snapped completely off on one side. Got a new one on there and runs solid as can be now. Nice little saw. Not really a fan of that design though - why not just bolt through all the way from the carb to the cylinder? Then you're not pulling a plastic adapter from both sides, which is destined to fail like this one did.

Not sure if there was ever an issue with the gas cap, or everything was just a symptom of the cracked adapter. Could be I cleared out something in there when I opened it up, but no way to know now.

Thanks all for your time/suggestions!

-Rich

 

[LegDeLimber]

Just a thought that pops in my mind, so take it as only being worth the cost of the time to read it.

Could be that through bolts would carry too much heat from the cylinder and grow a bit much when the motor's hot?
IF the part is named as an insulator then I'd think the separate fasteners would probably be to break the heat path to the carb.

Then, sometimes, we're just left shaking out heads at some ideas that made it into production.
Those reasons for revisions, eh.

 

[vizette]

That would definitely be something to consider. That said, the mac110 I have (that was my grandfathers and that I still use) bolts through for the carb and the coil, on top of the same insulator. Still runs like a little Tasmanian devil, and it's had a hard life. It does have some sort of thick fiber washer on the bolt heads though - I'm thinking that compensates for expansion and contraction.

I'm wondering how many homeowner Poulans and Huskys get tossed or left behind because of a cracked insulator though? I got a pile of Poulans from someone that was clearing out, and they're great little saws when setup right, but this seems to be a common component across them. Only found this one bad so far though.

Thanks for the reply/thoughts!

-Rich

 

[LegDeLimber]

Of course the mention of the common, carb and coil bolts (plus fiber washer ), made me curious and looked for a Mac-110 diagram.
The mention of the fiber washer gave me a hunch or reminder.

Yep. Insulator washers under the screw heads #32 and notice that insulator tube #33 and of course insulator #36 between the carb and engine.

http://www.mymowerparts.com/pdf/McC...0016C-MAC-110-01-77-to-02-83-IPL-95807-R2.pdf

The insulator tube is to keep the screw from working like having a heating element, right beside the carb.
I've seen this setup over the years.
Lots of people don't get the insulator tubes back onto the screws.

The fiber washer is to block~slow conducted heat.
The tube, around the screw, is to block~slow radiated heat.

The heat can have an effect on the carb tune.
Heating the carburetor sorta changes the -effective- vapor pressure of the fuel.