stihl 441 carnage twice what am i doing wrong?

[ericm979]

It's pretty clearly a ring getting snagged in a port. I have seen engines with many transfer/boost ports run safely with a ring gap crossing a port, but they're small ports. Not an exhaust port or the large transfer ports in a 046.

When you assemble an engine, turn it over a few times gently by hand with the plug out and feel for anything that's sticky. Just in case the manufacturer puts the arrow on the wrong side of the piston or you made an assembly mistake.

I try to check everything even when the manufacturer is known to make quality parts. I have had rings from a Japanese motorcycle company come with insufficient ring gap. That will blow up the engine pretty quick.

 

[CAMike]

Check the piston arrow on next cylinder/piston installation -check. To be safe I'd pull the flywheel and verify the key way is still in the correct orientation. Trust but verify.

 

[Rooster1956]

Make sure there’s no debris in muffler.

 

[sawmill sam]

hi everyone long time lurker and reader of this site. i have a 441 that i've been working on its blown up twice in short order, second time about 15 seconds. Now i've been using the very cheap cylinders and pistons from fleabay,but still think they should last longer than 15 seconds. It looks like the rings are breaking and get wedged in exhaust port. Yesterday it broke the top of the piston off. i checked the intake boot and it is good shape. nothing in my no so good eyes jumps out at me. Can a connecting rod get bent on these? it was a very sudden stop yesterday. i would send pictures but dont think i can with no posts. Also now you know why I am only lurking on here by my typing skills and abuse of the english language. This little paragragh took 15 minutes.

Next time order parts from Wolf Creek Saw Shop in Colorado!! They have a great selection and they STAND BEHIND WHAT THEY SELL. Check them out on their website or on ebay. They are the best! This is an unsolicited plug!

 

[Bob Hedgecutter]

We do it nice because we do it thrice?

 

[ballisticdoughnut]

I can't see an arrow on what should be the exhaust side of that piston so if there was one it's gone with chip off the top & that would mean it was on what should've bèn the intake side to start with

If you look closely at the broken piston you can see what looks like a triangle (maybe an arrow missing it’s tail?) pointing opposite of the locating pin bore in the top ring groove. If that is in fact the case, which I believe it is, the piston was most certainly installed incorrectly.

 

[ballisticdoughnut]

We do it nice because we do it thrice?

I have to wonder. How many times would someone have to buy aftermarket parts, have them fail, and only then realize they should have bought OEM to begin with? Even if you could buy three top ends at half the price of OEM, what’s your time worth? Frustration? Stress?

 

[J D]

If you look closely at the broken piston you can see what looks like a triangle (maybe an arrow missing it’s tail?) pointing opposite of the locating pin bore in the top ring groove. If that is in fact the case, which I believe it is, the piston was most certainly installed incorrectly.

I'm not seeing it...
OP, can we get a pic of the top of the piston missing a chunk, & a pic of the top of the missing chunk if you have it.
Cheers

 

[ZeroJunk]

Well, if you buy a cheap cylinder take your finger and feel the edges of the ports and transfers. I f they are sharp you can take something as cheap as a Dremel Tool with a round stone and chamfer them yourself .

 

[Ed Penney]

hi everyone long time lurker and reader of this site. i have a 441 that i've been working on its blown up twice in short order, second time about 15 seconds. Now i've been using the very cheap cylinders and pistons from fleabay,but still think they should last longer than 15 seconds. It looks like the rings are breaking and get wedged in exhaust port. Yesterday it broke the top of the piston off. i checked the intake boot and it is good shape. nothing in my no so good eyes jumps out at me. Can a connecting rod get bent on these? it was a very sudden stop yesterday. i would send pictures but dont think i can with no posts. Also now you know why I am only lurking on here by my typing skills and abuse of the english language. This little paragragh took 15 minutes.

If you use the Chinese stuff you need to triple check everything. bevel and chamfer all the ports. mount the assembled engine on your workbench and turn it over with a drill slow and with a lot of oil. You don't need to seal it up tight on the first test run leave the plug out. after turning it for a good length of time disassemble it and check it good, focus on ring lands and ports. If there is any excess movement in the ring lands you got a dud, if there are any scrapes or scratches where the end gaps of the ring contact the cylinder you gotta hanger. 1 outta 5 clone cylinders will survive a quarter of the lifespan of a Mahle or Comet, your getting what you pay for. There are a few companies that buy Chinese cylinders and pistons in bulk. They run them thru extensive quality control and have them coated or plated (piston and cylinder sets) they offer 30 day warranties and keep the prices low. I won't tag the companies, but it's obvious when you look for parts. Buy from American distributors on American soil that offer warranties

 

[NSEric]

You are going to have to get a different kit or a different piston at least. The ring locating pins are in the wrong spot on the piston and are hitting the exhaust port.
You cant put that piston in backwards like you can in most saws, the intake skirt is much longer than the exhaust skirt so it only goes one way.

 

[huntdiamondjim]

hi and thank you for the comments will check out everything very good ordered a meteor jug and piston, the piston from both cylinders seems to caught on the exhaust ports. i have learned my lesson on the 45.00 jug and piston trick. hopefully i can let you all know how it works out. thank you again

 

[Ed Penney]

the condition of those piston is disastrous, I think personally I would change the crank, rod and bearings also, just for reassurance. sometimes damage isn't visual

 

[Chevboy0167]

^^^^^ At the very minimum, remove crank and flush it in a parts cleaner bath along with new outer bearings and seals. All the metal flakes can and will chew up parts fast!

 

[huntdiamondjim]

hi guys just a little follow up on this saw . took advise from all involved in this thread bought a meteor jug and piston from wolf creek very fast shipping and service highly recommended, cleaned out crankcase and everything real well and saw runs great. the difference between parts was amazing. the ring locating pins were in the spots they were supposed to be,didnt have to dremel anything in the jug. the chinese jug looked like they used a drill bit to machine it. like most people have said be very careful with the chinese route or dont waste your time. must admit taking it apart and putting it together multiple times has improved my skills with the stihl 441. thanks again to all

 

[ballisticdoughnut]

Glad to hear you got it sorted out.

 

[Bob Hedgecutter]

Cool you got it sorted and learned some stuff along the way.
It is still one of my least favourite Stihls- but it goes!
Not my saw, so not mine to point sticks at- long may it continue to treat you well.

Nice you noticed the quality differences- there seems to be huge variations of quality in the Asian aftermarket stuff- Meteor has made a name over time and is fairly well recognised as near good as OEM for a lot less $ when it comes to Stihl parts- not so much of a difference with Husqvarna parts- least for you guys over there.

 

[steele_109]

Did you figure out what caused it to blow the first time?If you didn't it will ruin all your work and possible do it again.I hope you put new rubber and seals and flushed it out really good and as stated in the above post the arrow on the piston goes toward the exhaust port.Oh and good luck.

 

[J D]

Original failures were almost certainly due to rings hanging in the exhaust port because the manufacturer put the locating pins on the wrong side of the piston.
I would encourage the OP to seek a refund for the chinese kits, if for no other reason than to make the seller aware they need to address the issue with their kit.
To give some assurance of future reliability a pressure/vac test should be done on the saw if one hasn't been already

 

[steele_109]

What caused the original oem cylinder and piston to fail.If the oem cylinder failed for the same reason,then fixing this time bomb is a waste of time.Giving enough time heat and friction will eventually cause it to happen again.