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Husqvarna 435 teardown/rebuild (Husky Clamshell Rebuild)

TK

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Bear with me, I'm not the greatest of teachers. This thread is going to be a somewhat start to finish teardown and rebuild of a Husqvarna 435 clamshell saw.



This should be very similar and apply to the following models:

136,137,141,142,340,345,350,36,41,435,440,445,450

The first thing you want to do before going into something like this is determine the cause of failure. Fuel condition? Carburetor settings? Air filter condition? Loose spark plug? Loose muffler? Vac/pressure test? Fuel line condition?

This one was obvious. Box store saw, set up a little on the lean side for our lovely EPA, and also an improperly clamped air filter allowing blowby. There was also a little water in the fuel. All in 3 months use.... Built in September of 2011.

So now that the problem is discovered, we proceed to tear it down. I like to have two containers on hand. A small one for holding screws and miscellaneous small parts, and a large one for holding larger parts such as bar/chain, covers, handle, fuel tank, etc.


Remove the bar/chain/side cover. Remove the top cover. Drain fluids.



Disconnect fuel lines from primer and carburetor to allow seperation of crankcase and fuel tank. The next steps involved can go differently depending on the order you like to work. I chose to leave the carburetor attached to the cylinder to be removed later. On saw models involving primer bulbs, this may make it a little more difficult if you're not used to it as there is some manipulation needed. If you get frustrated, remove the carburetor before proceeding. Once you disconnect the fuel lines, you can remove the three AV mount screws. One is under the left rear cover snap, another is through the handle mounting to the cylinder, and the third is with the chain catcher under the bar mount. Moving back from the bar mount area you have a motion limiter screw that much get removed. Once completed, a slight twist motion while pulling and voila, you have seperated the crankcase from the fuel tank. You may have to feed the fuel lines through the holes they come through.



Ignition coil and wires, and flywheel get removed next. Coil is easy. Flywheel is a little more difficult. It helps to have the right tools. For those without factory tools, follow these instructions. Loosen flywheel nut a couple turns. Rotate flywheel so you can pry on the backside of a weighted section (i.e. magnet side or counterbalance, I prefer the counterbalance side). While applying moderate pressure to the backside of the flywheel, strike the flywheel nut with either a hammer, or hammer and punch, so as to break the flywheel free from the crankshaft taper. The dealer tool is called a flywheel knocker, it is essentially a 2 inch long piece that threads to the crankshaft that you strike with the hammer. It saves messing up the flywheel nut and/or balancing a punch, screwdriver, hammer, etc. Pop the flywheel free, and remove it.





Clutch removal. Again, it helps to have the right tools. There are different ways to do this. I have the clutch tool and a cordless impact. Bam, done. I still recommend you get a clutch tool from a dealer, order one online, or even go to the dealer to have them remove it. They should do this no charge if they are nice at all, seeing how it takes a mere 10 seconds. Some will say take a punch and a hammer and knock it off, I don't like that. Now, for those not having an impact, I'll tell you the proper way to remove the clutch. Remove the spark plug, stuff starter rope into the cylinder. Rotate clutch forward until it is stopped by the rope. Insert clutch tool into clutch, and turn with a wrench until the clutch pops free. You can also buy a piston stop tool, but I don't like them, see too many break. Rope works great.



 
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TK

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Once the clutch is off, remove the clutch drum, bearing, oil pump driver, oil pump cover, and oil pump.



I wait until now to remove the carburetor, however like I said before it can be done before this point. The screws are easiest to access once the crankcase is seperate from the fuel tank.



Remove the four screws from the underside that hold the cylinder to the base, and remove the engine. Piston should be at BDC for easiest removal - it positions the crankshaft counterweight at their highest position and out of the base.





Everything gets cleaned before going back together, no worries.

I remove the crank seals for inspection and cleaning while everything is apart. They are cheap enough and should be replaced while doing this, but I forgot to order them so they're going back in. The saw again is only 3 months old, shouldn't be a problem.



Muffler gets removed from the old cylinder. Two 5mm allen bolts hold it on.

 
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TK

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And remove the intake and AV spring - as seen in the previous picture laying next to the muffler.

I jumped ahead here, didn't get a shot of installing the new piston. Lube everything. I lube the crank bearings, piston pin bearing, seals, cylinder, piston, rings, you name it - with 2 cycle oil for assembly. The new piston came with better wrist pin clips, the factory ones were c-clips, the new ones (OEM) are clips including a tang to grab with little pliers. Once installed, place the crankshaft assembly back into the base. Make sure the seals are inside the base, you may have to apply pressure to make sure they fit properly. And FYI - the arrow on the piston points to the exhaust side. The piston ring locator pins are on the intake side. Make sure you put the piston on in the right direction!





I then reinstall the intake and carburetor setup. You may want to wait until you get the cylinder back on as it does require some finesse to get everything in there properly with the primer bulb assembly. Either way is doable.



And reinstall the cylinder setup onto the base. These cylinders are nice, you don't need piston ring compressors as it's tapered and does it for you. Just make sure they are turned properly so they don't hang up on the locator pins when you slide the assembly together. Everything should be oiled - so it will slide together easily, no need to force anything. Torque them bolts, and it's starting to look like a saw again....



Pop the muffler and flywheel back on there. Remember to use the rope trick to stop the engine from turning over when you're torquing the flywheel nut and the clutch.



Install the ignition coil, make sure it's gapped properly from the magnets for proper ignition.



Install the wires with the coil, one of them goes under a coil screw. Then install the flywheel shroud and route the wires properly. Hook them up to the kill switch assembly before you forget.

 
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TK

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Alrighty now, reinstall the oil pump as it was removed, cover it up with the bar plate/cover, and install the pump gear onto the crankshaft.



Nows a good time to hit that clutch drum bearing with some grease, and when you pop that drum back on - make sure it's lined up with the oil pump driver.



Install the clutch in the reverse of how you removed it.

Here's a shot of the motion limiter hole in the fuel tank assembly, just came across it, should have posted it earlier. Don't forget to reinstall the rubber when you get this back together, then the screw. You can wait if you want, there's plenty of room to sneak it in later.



So pop the crankcase assembly back onto the fuel tank assembly - making sure to pass the fuel lines through before you get everything back and lined up (saves some hassle of doing it after) - And reinstall the AV mount screws.

 

TK

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Route the fuel lines properly and install them. Double check for kinked lines, don't need to be tearing you hair out later wondering why the thing don't run..... :thumbsup:



Start popping the outer necessities back on - peel off that stupid Lowe's sticker while you're at it :lol: - and you've got a freshly rebuilt saw.





I pull it over a few times slowly to work the oil in everywhere. Then refuel and oil it up, crank her over, and off you go! Always double check your carb settings before putting the hammer down. It's probably worth while to clean the carb while you have it apart. I skipped that in this session as I didn't feel it was necessary.

Hope this helps out at least one person :smoking:
 

TK

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I should add a few things here. I didn't include the 455 Rancher in this clamshell listing as it is setup a tad differently. The crankcase has the fuel tank combined as a single unit, with just the rear/wrap handle attached seperately.

And on another note - this entire process required extremely few tools.

4mm allen wrench - T-Handle preferred - used for nearly everything
5mm allen wrench - used only for muffler
Slotted screwdriver - used for prying, and for one screw holding oil pump cover on
Clutch tool, flywheel knocker, coil gap insert, 13mm socket for bar nut and flywheel nut, spark plug socket
A couple rags, air compressor with blow gun attachment

And another FYI, a P/C kit for a saw such as this one sells for less that $50....... Get your rebuild on!
 

mweba

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Nice work, TK. Never had the pleasure with the 435 but have had the misfortune with the 455 several time:D
 

TK

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Nice work, TK. Never had the pleasure with the 435 but have had the misfortune with the 455 several time:D

I've never had the cylinder off a 455, would like to just for the heck of it though. I want to compare it to the nightmare of an MS290. I can only hope it's not as bad! :lol: The Husky I can tear down no problem, Stihl I think I need the WM!!!
 

mweba

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The 290 is a PITA, 455 is just unpleasant. The intake design on the 290 is what erks me.

The only real pain to a 455 is the cylinder. It has a metal lower crank case/cap that has no assembly bolts. You have to hold it all together, being careful not to separate the fresh seal while lowering it down into its cradle. At that point the bolts go through the plastic case and sandwich the engine together. Three hands would be the ticket :yup:
 

TK

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Thats the same with the 290..... At least the one I tore down. 4 bolts though the case, bottom crankcase cup, and into the cylinder. Unless I missed something lol what holds the engine in the case?
 

Denis Gionet

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Awesome teardown pics !!! Mine blew up just like this one ! I don't like how lean it runs, scary...

What's the deal with the mixture screws ? Are they actually adjustable, and how ? Looks like a little cover over each screw in one of your pics. I won't run mine (once I get it back) until its adjusted a bit more rich. Any special tools required for the mixture screws ?

Thanks in advance ;-)
 

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