Will this piston still work ? ( husqvarna 445 x-torq chainsaw )

[naimc]

My brother gave me his husqvarna 445 x-torq chainsaw. it was running at full RPM hit the gound, brake bar got engaged flywheel broke off apparently.

He had a local shop put on a new flywheel, but the saw still had issues when warm it would refuse the started. It was assumed the piston was scored or other internal damage.

After having the thing sitting around for 2 years I finally took it apart. expecting to find major damage I was not to careful during disassembly, omitting to remove the clutch and flywheel.

Piston and the cylinder did have any visible scoring, that's when I realized I should just clean everything up and re-assemble it, fuel it and fire it up.

But my mistake I should have put the cylinder back on to get the cloth off, I rapped the piston in rag and braced it against the case but while removing the clutch, with dead blow, the fragile piston broke, or rather a chunk of the side skirt came off.

Too bad as the piston looked good, ring in good condition. I thought why not carve out a notch on the other side but I guess that the lengh of the skits is important and it controls the intake and exhaust exits ?

Also having a hard time trying to find a replacement piston for this :

On the top of the piston, there is stamped mark 43.95 . On Amazon / Ebay all the kits for 445 chainsaws list a 42 mm piston, and few 44 mm but nothing 43.95 Also I can't find an official parts list for this model. they all appear to be pre- 2011 models.

 

[Fordiesel69]

That piston will not work. You have greatly changed the port timing on the intake side. Use a 44mm piston or get a used oem one. Replace the ring. Use your finger with some 320 grit and deglaze the cylinder wall.

I recommend removing the crank assy and doing a very close inspection of the plastic case where Tha ball bearings sit. The clutch side can crack.

 

[Fordiesel69]

 

[jeepman3071]

View attachment 267681

+1

I'd at least get a good condition used piston if I'm going through all that work.

 

[Fordiesel69]

Forgot to mention, if you removed the crankshaft which it looks like you already did, you must put on new crank seals. They will never go back in perfectly the same way and will leak.

 

[naimc]

+1

I'd at least get a good condition used piston if I'm going through all that work.

Yeah I figured, my 1st mod piston would not work but I had fun with my dremel grinding out the other side to "balance" the damaged piston.

I got my cheap replacement from Amazon today and size if fine but bottom of skirt is scratched and I know that will damage the cylinder wall. If just sand and buff out the scratch should be OK thinking that would be good enough and simpler that dealing with a return and possible getting one in worse shape.

..

 

[naimc]

Forgot to mention, if you removed the crankshaft which it looks like you already did, you must put on new crank seals. They will never go back in perfectly the same way and will leak.

I don't even know what is wrong this chainsaw. Before taking it apart I checked compression and it at 120 psi.

Without knowing the real issue I was just trying to get it back on and running with minimal expense. I was planning to coat the bottom end with a this gasket maker in the green areas

I did check the case as you mentioned and it has no cracks.

 

[jeepman3071]

I'd just give that area of the piston a good polishing to remove any burrs. I would also replace the crank seals. They are a known issue on these saws anyway. Once back together it will be a good saw though, those 445s are nice little saws and good power to weight ratio.

 

[Fordiesel69]

As Jeepman3071 has stated a little emery cloth will fix those gouges. Shouldnt hurt the longevity especially with modern FD oils today.

You must replace the crankshaft seals. These fail often and may have been part of your issue. I did use sealer on my 450 and I think it helps improve issues with crankcase leaks. Moto seal will not work on plastic-to-metal mating sufaces. I had to take my 450 back apart and re- acetone all the surfaces a second time. Use that black stuff the permatex has. I think it is called optimum max flex. It has a gold stipe on the tube. Some will hate that recommendation but on a strato port saws, not a ton of fuel puddling will be occuring in the bottom end so the sealer should be exposed to oil more than anything. It should hold up fairly well.

Also if we forgot to mention it above, go thru the carburetor. Properly clean the microscreen even if it looks good, and make sure fuel can pass thru it. It can look spotless but fail to pass fuel. Also the metering diaphram will most likely be aged out. Good to swap that as preventive maint.

 

[naimc]

@Fordiesel69 , thank you very much for all the tip's. My stubbornness has dissolved.

I found a amazon kit that fits, won't be OEM but better than the old ones I hope.

And I will use the permatex max flex.

 

[Fordiesel69]

So the amazon seals will certainly work, and most likely they will be an improvement over the old ones. The clutch side one has the high failure rate as it gets blistering hot.

If the saw still does not run right, at least you will know where the problem isn't!

The secret with these clam shell saws is to keep the chains nice and sharp, no heavy pressure during the cut, and keep the fuel mixture on the rich side and not look for absolute optimal peak RPM. This goes a long way to keep the heat down in the engine. You can expect a very long life out of these when they are cared for.

 

[Fordiesel69]

Any updates on this project?

 

[naimc]

Yes I got the parts last week, did 90% of the assembly then had to leave town for week and I have not been able to fire it up yet.

The replacement seals, went on which a much tighter fit , visual both old and new are the same size but the fit is different. I found a video of a 445 rebuild and the creator says the original seals are better than replacement so he rejuvenates them but does not give details , I suspect he transfer the small retaining springs from one set of seals to an other, this saw will seldom be used in suburbia so not that important.

per-assembly got everything clean :

Very light sliver of the gasket maker

Torqued down the cylinder bolts :
followed the values and steps I found here : https://www.hlsproparts.com/v/vspfiles/downloadables/WM_445-445e-450e-2007_1150342-26.pdf

Pretty clean not to much goo from the gasket maker

During the re-assemble I got confused by this extra fuel bulb , took me a while to realized it was just a spare not connected to anything

Now I am waiting for some parts, a new chain plate, and I noticed I lost the chain tension adjustment screw.

I did re-read all your comments, and will be adding more oil in the gas mixture to run it 40:1 instead of the 50:1 and make sure the chain is always sharp and let the thing over head.

 

[Fordiesel69]

Excellent. Can't wait to hear how it turns out.

 

[naimc]

Excellent. Can't wait to hear how it turns out.

Well it start's ! but that that it , after a few seconds it bogs down.

I left the de-compression button alone, primed bulb till I saw fuel it in, then 6 more time ( the chains saw was dry)
I use a 1 quart VP pre-mixed 2 cycle gas 50:1 and I added about 160 ml of 2 cycle oil to make it richer. (Oups major screw-up right here ! that gas is now 5:1, yeah added 160 ml to 1 liter !)

-Then after 1st pop removed choke without touching the gas trigger to leave it in high-idle.
It won't start like this.



I can only start it in full choke, then when I gas it it will start to bog down and stall. Not on the video but I got to run longer by keeping a light squeeze anything more and it bogs down.

Should I just take the carburetor apart or rather start fiddling with the adjustment screws ?

 

[Zaedock]

I’d start with the screws.

 

[naimc]

I id the screw adjustment , Reset both L and H, manual say's turn to 2 turns, Online video's start at 1 1/2 turns.

I Tried both, chainsaw will start on the 6th pull of full choke or the 7 if I drop the full choke, it then rev's very fast as it's still on the fast idle the second I pull the trigger it bogs out.

I don't have a chain on it as I removed all the chain oil and I am waiting for parts.

I don't know if the cold temp here , 0C having something to do with the issues but I think the carburetor might need a clean-up.

the repair manual has a few pages on it full disassembly, for such a small thing it's pretty complex , finishing with a vacuum test underwater.

The T screw is a mystery no indication of how to reset that one.

 

[naimc]

oh boy did I screw-up in the gas mixture math ! I found a gas mixture syringe ( where was this , this morning)

my per-mix fuel was 50:1 to so I wanted to know how much I should add to bring the mixture down to 45:1, just add 5:1 right ! Wrong.

so I added 120 ml of 2 cycle-oil to the existing 1 liter per-mix of 50:1 ! No kidding I am having issues running the saw with a 3:25 oil to fuel ratio.

I will have to re-test with new fuel.

 

[IndyIan]

Well you've learned something without breaking anything, so that's always nice!
The right oil fuel ratio will help for sure. Its a bit beyond my math skills to figure out how lean you were running the air fuel ratio with that mix, but its pretty lean!
Add 4L of straight gas to what you've got, (1L of gas with 140mL of oil),will give you 5L of gas with 140mL oil, or 35:1 which is good enough.
I run around 32:1 with 91 octane in my 372, and then not really worry about which 2 stroke oil it is, as long as its not for watercraft. If happens to sit around for many months, it goes into the atv or car or whatever low hp/L motor needs gas at the time.

 

[Fordiesel69]

I can't do math either so I do 3.2 Oz per 1 gallon of gas many times rather than figure out how to upsize a batch. Reset the needed. Change the fuel and report back. I'm sure we can solve whatever issue you have even. Even Being far away.