Saw loses power during LONG cuts

[Soundchasm]

Would you guys get a set of gaskets and bits for $15 or a kit that includes more metal for $30? I guess the $30 is already assembled and less labor?

http://www.amazon.com/RB-149-Genuine-Zama-Carburetor-Husqvarna/dp/B0074L1KUC ($16)

http://www.amazon.com/Carburetor-Husqvarna-435-440-Chainsaw/dp/B00IBN9NEW ($31)

 

[jrems]

Check the impulse line first. If it's ok it's most likely the carb. Even if you change the gaskets there might be something stuck in one of the tiny orifices. If you don't feel confident you can clean out the carb completely get the assembled unit. You will need to flush the gas tank, blow out the gas line and install a new gas filter too.

 

[CountryBoy19]

I had the same issue with my string-trimmer. As it turns out the fuel pickup was caught in an "upright" position inside the tank and it wasn't getting enough fuel when running full throttle...

 

[Soundchasm]

OK, the correct fuel filter is already en route, and I previously put in a temporary replacement. The assembled carb thingy is ordered, and I found a Youtube video on the oil pump, but I bet it just needs some cleaning. It was pretty cold when I was last using it, and the bar oil was like molasses.

I'll make sure the gas line is clean. The goods ought to be here by the end of the week!

 

[Jags]

Wait - I thought it was determined that the oiler wasn't working proper. Either pull the bar and chain and test run the engine (to confirm this is/isn't the problem) or fix that oiler and retest before tearing into anything else. (you are gonna need to do it anyhow).

 

[DougA]

Wait - I thought it was determined that the oiler wasn't working proper. Either pull the bar and chain and test run the engine (to confirm this is/isn't the problem) or fix that oiler and retest before tearing into anything else. (you are gonna need to do it anyhow).

Yes! Exactly what I said.
When you troubleshoot problems, take it one at a time. Your piston looks good so make sure your oiler works and run the saw without the chain (or bar & chain) before doing anything with the carb.

I'd put on a Chinese carb as a last resort once you have make sure everything else is good.
BTW do not toss out the old carb, I would repair it and have it ready to swap out for the Chinese carb when it causes problems. I have never been happy with the cheap Chinese carbs. Your mileage may vary but they are cheap for a reason.

 

[Soundchasm]

I guess after reflection the oiler is the trump card. A working engine isn't much use w/o a bar and chain...

I was sort of hoping that if the engine ever got up to higher revs that I'd see the chain start to spit out some oil. I'll take the chain/bar off and clean everything I can see before any carb work. A video I found shows how to take some stuff off and clean the entire operation. On this model, the oiler is not adjustable.

I have to assume the carb I've ordered is from China. I'll make sure to keep the old one to rebuild it.

This forum is a great place!

 

[jatoxico]

I was sort of hoping that if the engine ever got up to higher revs that I'd see the chain start to spit out some oil. I'll take the chain/bar off and clean everything I can see before any carb work.

After getting the saw to room temp pop the clutch cover and run the saw to see if any oil is pumping. If not you'll have to diagnose if it's a clog in the line or the pump. To get to the pump you have to pull the clutch which is reverse thread. Stuff the cylider with a heavy shoe lace or some such to stop the piston from going 'round. There's a clutch tool for removal but so far I've been able to remove it by putting a wrench that will fit into the slots and turning with another adjustable wrench. Pretty easy to do. Youtube is assume for such things!

 

[hman]

Even the OEM carbs are from china.

 

[jrems]

If you are using regular bar oil and it's really cold it might not pump well. You should be using the thinner cold weather bar oil. If you don't have any, mix a little regular motor oil in to thin it out. I have done that in a pinch. Take the bar and chain off and run the saw and rev it. You should see it come out the bar oil slot. If you see it coming out Most of the time it's just the hole in the bar is clogged and the oiler is working fine. Take the chain off and get all the crap out of the groove on both sides.

 

[DougA]

Even the OEM carbs are from china.

Stihl carbs are not made in china to the best of my info. OEM is a difficult term to quantify. I am sure that the carbs my local Stihl dealer sells are from China just based on the price.
The problem with Chinese stuff is that there is some that is OK and some that is junk. The big difference is how cleanly the inside of the carb has been machined. Look at the range of options on eBay and you can see the difference.

 

[hman]

I do not buy off ebay.I always go back to the manufacture for parts.I know sometimes you have no choice to buy aftermarket.That is just the way it is.I work for a rental company and I know a lot about dealing with parts and equipment.

 

[Jon1270]

Plenty of OEM parts are available on eBay, both new and used. The original carb (a Zama, I'd guess) almost certainly was made in China, but that means nothing; all sorts of fine things are made there. I avoid the no-name stuff made by companies that have no brand to protect and thus no reason to keep quality high.

 

[DougA]

OK, did some more research and yes, Stihl carbs are made in china now.
"In 2013 STIHL has invested €17 million in the expansion of its Chinese manufacturing facility in Qingdao."

I have an older model and its not made in China. Agree that there are a very wide range of quality from China. A verse what's ago I wanted to buy the best cordless circular saw I could. Found out that every make and model that I could buy were made in China. I ended up with a Milwaukee, still made in China though. No wonder the unemployment rate is so high in North America.

 

[Soundchasm]

No parts have arrived yet, but I got the thing apart and took out the oil pump. What an amazing little device. Cleaned all of it pretty thoroughly and and determined nothing was clogged before reassembly. I don't think it was clogged before disassembly. When I cleaned the bar, it looked like BOTH oil holes were clogged so they're clear now.

Got it back together with the new correct fuel filter, and was so confident about the oiler I put the bar and chain back on. To my utter amazement (and relief), it ran just as badly as before, so I didn't leave the rope in the cylinder!! This saw has always seemed to be pretty frugal with the oil, and I usually only see it on clean concrete on a hot day, but I couldn't make any out on the snow.

Didn't have the guts to pull any fuel lines, but I guess I'll get that opportunity when the carbs get here.

Don't know if this matters... I had the starter fluid out and the air filter off while I was pulling it to get started. After it fired and began chugging along, I shot some starter fluid in there, and the engine nearly died. Is that meaningful or meaningless?

 

[jatoxico]

his saw has always seemed to be pretty frugal with the oil,

I agree with you on that. I have Husqvarna chain oil which flows adequately in hot weather but switched out to cheapo HD brand (PowerCare?) which is thinner. Oil use is more like tank for tank with gas now.

 

[Soundchasm]

Checked out some carb vids, and everybody swaps out the fuel line. Dagnabit, should have thought about ordering that first, but it is on order.

JT, it's not often we get use a word like "parsimonious", but Husqvarna must be helping to conserve natural resources. But I've never had left over oil when I'm out of fuel, until now. I think the oil pump designer left to design some of those low-flow shower fixtures.

 

[jatoxico]

it's not often we get use a word like "parsimonious",

And fewer still while talking about chainsaws!

 

[Soundchasm]

Well, der Husky saga continues. I'll try to lay it out so it makes sense. I got the carb piece this week. Just one fuel hose showed up.

After much weeping and gnashing of teeth I got the thing that holds the air filter and then the carb unit off. Did not disassemble the old carb yet. If you try this on this saw you are going to want a loooooong allen wrench.

I kept cleaning everything as I went. The new carb went in. I did not try to replace the fuel lines. They look like the grommet is built into the hose and I didn't see any easy way to tug on anything to get it out, let alone back in. Lines weren't cracked and I made sure they were clear. I had to get the thing back together before I forgot how it goes. The primer bulb has successfully moved gasoline throughout this endeavor.

Got the linkages, choke trigger and throttle thing all hooked up. Set the carb adjustments to 2.25 turns each. Made a total-guess of 5 turns for the idle screw.

My gut feeling is a fuel line was clogged, but there was no way I'm going to test one piece at a time. This is a lot like fixing a computer when you get frustrated and try 20 things, reboot, and it works. Who knows which one?

If this thing starts Monday it'll be a miracle.
My one question is how snug should that boot be, and should it cover more than it does. Sorry I don't know the names of things.
Here are some photos for your amusement.

It's possible I could have REVERSED the two wires for the kill switch. I took a photo, but the lighting made both wires look identical. I didn't catch that until I was going to reference it to reconnect them. I'll let you know if it fires!!

 

[DougA]

Kill switch wire should not matter. It's either connected or not. I don't own a Husky so I can only help a bit.

 

[Jon1270]

That arrangement is a bit more complicated than most of the saws I've worked on. Does that long hose from the right rear corner connect to the primer bulb?

Were did you get the 2.25-turns-out starting point for the mixture screws? The saws I'm familiar with all start at somewhere between 3/4 and 1 1/4 turns out. You mentioned awhile back that you had "open and shut" both of them. Are you normally comfortable tuning a saw? Subtle changes can matter a lot here, so you might be throwing extra variables into the mix.

My gut feeling is a fuel line was clogged, but there was no way I'm going to test one piece at a time.

This is a situation where it's nice to have a pressure/vac tester, because it lets you test one piece at a time quickly, without having to reassemble the saw and try it for each one.

Hope it runs for you today!

 

[Soundchasm]

That arrangement is a bit more complicated than most of the saws I've worked on. Does that long hose from the right rear corner connect to the primer bulb?

Were did you get the 2.25-turns-out starting point for the mixture screws? The saws I'm familiar with all start at somewhere between 3/4 and 1 1/4 turns out. You mentioned awhile back that you had "open and shut" both of them. Are you normally comfortable tuning a saw? Subtle changes can matter a lot here, so you might be throwing extra variables into the mix.



This is a situation where it's nice to have a pressure/vac tester, because it lets you test one piece at a time quickly, without having to reassemble the saw and try it for each one.

Hope it runs for you today!

It did fire up. Whoopee! It's very similar to the original condition. Now it idles but dies when the throttle is opened. I've got a video I'll try to post where you can hear it.

I'm not an engine guy, but my small engine guy and I did tune the carbs a few years ago. From the factory, the thing wouldn't start and only ran full throttle. I've got a nice detailed write-up on what to listen for, etc, and I'll dig that paper back out, but I'm pretty sure we ended up at 2+ turns. I know I wrote it down, but this is a different carb. There was one Youtube video where a guy started at 1.75 turns and the next day concluded 2.25 was his final answer. It was a very similar Husky.

Stay tuned, film at 11.

 

[KenLockett]

You still have not confirmed if you have oil flow through the slot with the chain and bar off. This is important. I had the same issue with my 450 running too viscous of bar oil. The oiler pump is a displacement type plastic unit and is easily destroyed if oil too thick. This happened to me and had to replace pump. If working properly the oil will flow easily and clearly through slot.

 

[Fishnuts2]

Original post said you'd poured the last of the fuel from a container. If you got some dirt along with the gas, you may have gotten the water from the bottom of the can too. (Unless you use non alcohol gas). It's happened to me until I could get gas without that crap in it.

Drain the tank, flush the lines and filter and fill it with Tru-Fuel till you get it running.

Just my thoughts.
Good luck!

 

[colin.p]

According to my 455 Rancher repair manual, it's 1 1/2 turns out for the "L" screw and 2 1/2 turns for the "H" screw to start. Then of course you will need to dial it in from there.