Problems with Husqvarna 435, shearing flywheel key

[ArtofFact]

Hi all,

Long time reader first time poster.

I need advice on what might be wrong with my refurb'd Husq 435. Its had a very hard time starting and would stall out easily after cutting for a period of time even when it would be off the wood. After one intense day's use taking down a hedge apple tree the key sheared off the flywheel assembly. I bought one online and replaced it and again fought to start the saw and had to use some tactics found on these forums but still had trouble keeping the saw going and once it died it would be half an hour before I could get it going again.

I took it to the local husq shop and the guy had no trouble starting but he really slacked the chain and then started it up. Since then I've used it briefly and the again the key has been sheared off the flywheel assembly.

I'd like to buy another flywheel assembly but I'm not sure if this particular saw is a waste of money to fix or what needs to be done to correct this issue.

Whats up with this saw? Is it typical to slack the chain until it nearly falls off each time I need to start it?

 

[fearofpavement]

Sounds like you have a few different issues here, not just one.

The flywheel key should not be shearing if the flywheel nut is torqued down correctly. Even without a key, the flywheel shouldn't move. There are plenty of saws being operated daily that don't even have a key installed.

Slacking the chain should have no effect on starting a saw. If it does, there are mechanical issues that need to be remedied.

If the saw won't run well all the time, check for carb, fuel line, fuel tank vent problems or potentially ignition problems.

 

[a. palmer jr.]

Sounds like you have a few different issues here, not just one.

The flywheel key should not be shearing if the flywheel nut is torqued down correctly. Even without a key, the flywheel shouldn't move. There are plenty of saws being operated daily that don't even have a key installed.

Slacking the chain should have no effect on starting a saw. If it does, there are mechanical issues that need to be remedied.

If the saw won't run well all the time, check for carb, fuel line, fuel tank vent problems or potentially ignition problems.

Some saws with heavy flywheels need to have a key and have the nut torqued down, like my John Deere 80. That's not the case with yours. If you want it to stay on get some red Loctite and put it on the shaft but not on the nut threads. I used to have an old motorcycle that had a heavy flywheel and that was the only way I could keep the flywheel on it. On the JD I use red loctite on the shaft and blue loctite on the threads. That being said, I agree with the others that you have something wrong other than the flywheel.

 

[ArtofFact]

Thank you for the feedback.

I will pickup some red loctite and try that instead of buying another flywheel assembly, thank you palmer!

According to the shop, they checked the fuel system and the electrical system and claim there is nothing wrong with the unit. I've checked for spark and it works fine and the gap on the spark plug is good. I'm becoming more and more skeptical on this unit when I see how many refurbished 345 units are out there. I think this is just a lemon of some sort.

Another symptom is that while trying to start it is that it goes through cycles of seeming back pressure where pulling on the starter rope becomes almost impossible and there is no pressure relief valve. When this happens I have to put the unit down and wait before trying to start it again.

 

[fearofpavement]

Artofact, do you have other chainsaws or used other chainsaws in the past? I ask because if not, it is possible that your problems are related to starting technique. If there is an arboristsite member near you, maybe they can scope out your saw and see what the problems with your saw are and if needed give you some tips to keep it and you happy.

Where are you located? (not an address but what town, county, state, etc?)

 

[w8ye]

Sounds as though it is flooded sometimes?

The 435 I have run had the infamous splined needle valves that were impossible to adjust without the adjusting tool that the EPA will not let you buy. The saw I tried to run was too lean on high speed and would not run above idle until the needles were adjusted properly. It was a nice chainsaw after adjustment of the needles.

I would be willing to bet that most of the factory refurb 435's were returns to the big box stores because they wouldn't run properly due to a lean condition?

 

[a. palmer jr.]

Thank you for the feedback.

I will pickup some red loctite and try that instead of buying another flywheel assembly, thank you palmer!

According to the shop, they checked the fuel system and the electrical system and claim there is nothing wrong with the unit. I've checked for spark and it works fine and the gap on the spark plug is good. I'm becoming more and more skeptical on this unit when I see how many refurbished 345 units are out there. I think this is just a lemon of some sort.

Another symptom is that while trying to start it is that it goes through cycles of seeming back pressure where pulling on the starter rope becomes almost impossible and there is no pressure relief valve. When this happens I have to put the unit down and wait before trying to start it again.

Try to not get any red loctite on the threads, just put some where the flywheel goes. If you put it on the threads you won't be able to get the nut back off should you want to. Tighten the nut pretty tight also but don't overdo it...
I've never had a 345 but I've had several 350s and a 353 and liked them all, never had a problem with any of them.

 

[zogger]

Have you taken tthe muffler off and inspected? Any obstructions?

ya, sounds weird, maybe ..long shot..bad batch 9of mismatched pistons and cylinders, out of spec?

man who knows but it shouldn't do that.

recheck it hasn't flooded bad, turn upside down with plug out and crank it over several times.

 

[a. palmer jr.]

Have you taken tthe muffler off and inspected? Any obstructions?

ya, sounds weird, maybe ..long shot..bad batch 9of mismatched pistons and cylinders, out of spec?

man who knows but it shouldn't do that.

recheck it hasn't flooded bad, turn upside down with plug out and crank it over several times.

I've owned a couple of the Poulan small plastic saws that did the kick back thing but I believe they may have had a defective module in them, they seemed to have the timing advanced a little. I suppose a person could set the flywheel back a few degrees..

 

[zogger]

I've owned a couple of the Poulan small plastic saws that did the kick back thing but I believe they may have had a defective module in them, they seemed to have the timing advanced a little. I suppose a person could set the flywheel back a few degrees..

Another good possibility and fix.

 

[ArtofFact]

Artofact, do you have other chainsaws or used other chainsaws in the past?

No this is my first 2 cycle chainsaw but I'm very familiar with 2 cycle engine power tools in general.

Have you taken tthe muffler off and inspected? Any obstructions?

No, but I will try that next.

recheck it hasn't flooded bad, turn upside down with plug out and crank it over several times.

I've done this and nothing comes out beside the hiss of pressure when I remove the spark plug. Then I can screw the spark plug back in and try to start it again and the back pressure has been relieved for the moment.

I have flooded the engine on one occasion but I don't follow the mfg starting instructions anymore where is says to prime the carb by pressing the fuel bulb 8 times and that seems to have remedied that issue.

I've owned a couple of the Poulan small plastic saws that did the kick back thing but I believe they may have had a defective module in them, they seemed to have the timing advanced a little. I suppose a person could set the flywheel back a few degrees..

I can definitely try that being the key is sheared.

 

[Franny K]

We are discussing a tapered fit with a key to align the timing aren't we? On other similar tapers it is in the manual to lap in the two pieces if one is replaced. Having one spin certainly would make me think without the key and some grinding paste the flywheel should be lapped by twisting. A bit surprised no one mentioned this already are chainsaw flywheels not like this for some reason?

 

[zogger]

It is so pressurized the spark plug hisses when removed?

!!

I am stumped, officially. My only thought is back to a highly restricted muffler, some stuff down in the crankcase that greatly increases charge pressure or...dunno.

 

[w8ye]

My experience with the Husqvarna 435 is that it is not exactly a chainsaw for the ladies to start. My neighbor across the street has a nice one.

There's no compression release and if cold, I have to start it on the ground with my foot through the handle.

If the chainsaw is warm, I can drop start it.

I'm a retired person so I'm not a young sprout.

I've never experienced a kick back with the 435 but my chainsaws with a compression release are a lot easier to pull over.

It is a nice chainsaw to use after it is started.

 

[galde]

We are discussing a tapered fit with a key to align the timing aren't we? On other similar tapers it is in the manual to lap in the two pieces if one is replaced. Having one spin certainly would make me think without the key and some grinding paste the flywheel should be lapped by twisting. A bit surprised no one mentioned this already are chainsaw flywheels not like this for some reason?

Dead on! The tapered fit relies on friction -- not on the key -- to keep the alignment (thus the timing) correct. The surfaces must mate precisely to jam together securely. There should be no roughness, trash, or oil present. Lapping of most modern flywheels to the tapered crankshaft is hindered by the key being cast in place in the flywheel bore.

 

[a. palmer jr.]

Dead on! The tapered fit relies on friction -- not on the key -- to keep the alignment (thus the timing) correct. The surfaces must mate precisely to jam together securely. There should be no roughness, trash, or oil present. Lapping of most modern flywheels to the tapered crankshaft is hindered by the key being cast in place in the flywheel bore.

Yeah, that's how some of the Poulan plastic saws and weedeaters are made, with the key cast in. You can't lap them in but you can do the loctite thing and tighten the nut good..

 

[jwp]

If the saw cranks better with a loose chain, then maybe the clutch is dragging.

 

[a. palmer jr.]

If the saw cranks better with a loose chain, then maybe the clutch is dragging.

I had thought about that...clutch is an easy thing to fix, probably just has some junk inside it that needs cleaned out.

 

[ArtofFact]

Hello again!

Some time has passed since I applied the wisdom from this site and I have to say my chainsaw is working better then ever!

I first scored the flywheel assembly to serve as a guide to line up with flywheel on the crank and then applied the red loctite (271) to the crankshaft (instead of the flywheel) to avoid getting any on the threads. Slipped on the flywheel assembly and bolted it down.

Next I opened up the exhaust port in the muffler to alleviate the back-pressure.

I haven't been able to do anything with the high/low carb adjustments but even so the chainsaw starts up on the 4th pull and is finally dependable for when I need it and runs well so long as I don't run it hot for too long. Throwing in idle periods here and there seems to help cool the saw off and extend my work time.

Thank you all for your assistance!

 

[CTYank]

Strange as it seems, spark plugs can act up, often making hot restarts difficult. Some are off-quality. Some even shed ground electrodes.

Best bet: replace with proper NGK. Toss all "Torch" plugs.