Huztl / Farmertec ms 440

[TimTaylor]

No the piston and bore look good. Bit confused if the piston was in backwards I remember checking twice that I had I correct. Also when I put it together I remember how impressed I was with the bearings and how smooth it all felt.
It did get a rough life for a start though, with the carb issues.It is possible that it got slightly hydraulic ed perhaps...with the raw fuel..? Wouldn't have thought that would do it but it might have contributed. Also possible that it was shocked in shipping.

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[tbohn]

I would think it would not fire if it was flooded enough to create an incompressible fluid situation. Mine floods with one extra pull on choke. My guess would be a defective bearing or a loose chunk of carbon. How many tanks have you put through it? Looks like a lot of buildup on the top of the piston.

 

[BuckthornBonnie]

Curious failure--- flywheel side bearing went first? I've had two Chinese 6203s that were "rough" and not used. Plus another that I thought was ok that ended up failing in an 029. I'm running two others with no problems yet. They were noticeably better than the aforementioned junk ones.
China is a nuclear nation; they can make a bearing. The quality control and consistency is the issue.

 

[BuckthornBonnie]

Both 6202 and 6203

 

[TimTaylor]

I would think it would not fire if it was flooded enough to create an incompressible fluid situation. Mine floods with one extra pull on choke. My guess would be a defective bearing or a loose chunk of carbon. How many tanks have you put through it? Looks like a lot of buildup on the top of the piston.

That was my thinking as well. The bearings looked and felt very good. It has had ten or twelve tanks through it. I was just thinking that I had sorted all of the niggles.

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[TimTaylor]

Curious failure--- flywheel side bearing went first? I've had two Chinese 6203s that were "rough" and not used. Plus another that I thought was ok that ended up failing in an 029. I'm running two others with no problems yet. They were noticeably better than the aforementioned junk ones.
China is a nuclear nation; they can make a bearing. The quality control and consistency is the issue.

Does anybody think that fuel quality could have contributed? I would have expected the piston to show first effects of any fuel quality issues but I did hear yesterday that the place I buy fuel from has had some quality issues.

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[davhul]

My 660 bearings felt a little crunchy when spinning them by hand. I washed them out with carb cleaner until I felt good about it then lubed them. I already had the seals popped out at the time. Then put the cases together relieved the preload on the bearings, then installed the seals. I haven't had any problems with that one and it has maybe 10 gallons through it last I checked with no problems other than it has frayed 2 oem elasto ropes. So I plan on installing a oem rope bushing 1110 084 9102 and see if it helps.
Did you relieve the preload in your bearings after the case was together? Not sure if that could have been your problem but could have it they were tight.

 

[TimTaylor]

I did relieve the preload, but didn't actually measure any backlash in the crank,I thought because the bearings were tight and new. I'm second guessing everything, and now I'm wondering if maybe you are right. Also wondering if maybe I didn't center the crank exactly. These are all things I have done before and although I have had engines fail it's mostly been because I've reused something well past it's use by rather than installation error but a bad day can still happen I guess. I have ordered another crank and bearings so I can have another go.

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[davhul]

The sideload is important. But Being perfectly centered isn't as important as long as it's not rubbing the case.

 

[TimTaylor]

No rubbing marks in the case. I'm working at the moment but next time I get a chance I will split the case and have a really good look at it all because it looks like ground up metal and oil splashed around the crankcase.The failure has been happening for a while and the bearing obviously put up a fight and that makes me think more and more that it wasn't the bearing itself at fault. Built it on a clean bench on an old table cloth but it might get rebuilt on the kitchen table.I think this failure will have to go down as assembly error. Somehow.

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[Bedford T]

A suggestion you might rinse it out well before you crack it. Might give you needed perspective.

 

[TimTaylor]

A suggestion you might rinse it out well before you crack it. Might give you needed perspective.

I thought that too but I also thought that I might rinse out any clues. I have an old dishwasher in my workshop that works well with water based degreaser so it will be very clean before it goes back together

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[Stihlofadeal64]

Curious failure--- flywheel side bearing went first? I've had two Chinese 6203s that were "rough" and not used. Plus another that I thought was ok that ended up failing in an 029. I'm running two others with no problems yet. They were noticeably better than the aforementioned junk ones.
China is a nuclear nation; they can make a bearing. The quality control and consistency is the issue.

I've not had good fortune with the chinese bearings. My MS390 kit had bearing failure after around 5 tanks. For me these bearings will always be replaced with better quality bearings.

 

[TimTaylor]

Well i think I have it figured out. When I cleaned the piston I saw a ring just in from the edge. Under a magnifying glass that ring is beaten into the piston. The same ring appears in the jug. And under a magnifying glass you can see detonation damage outside of that ring on the outer circle of the piston. Someone else mentioned it as well but I guess I didn't see it at the time but the squish is fine at the edges of the piston and the combustion area slopes the wrong way from there in towards the centre, it actually gets lower and its been hitting the piston. Which pretty obviously sorted the crank bearings out .

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[TimTaylor]

My question is can I hone that raised bit out and put in a new piston and go again or does the hard bore extend into the combustion area?

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[Bedford T]

you dont want to damage the cylinder coating. its hard to be certain but a new piston and gasket would be the first step and assume its the path of least resistance. i cant remember but the 440 kit might have been the one with the piston with the arrow pointing the wrong way. i am using that piston with it turned. send them photos and ask for some love, but go ahead and order it. not worth a wait.

did you mill any on the cylinder base before you got started?

 

[TimTaylor]

you dont want to damage the cylinder coating. its hard to be certain but a new piston and gasket would be the first step and assume its the path of least resistance. i cant remember but the 440 kit might have been the one with the piston with the arrow pointing the wrong way. i am using that piston with it turned. send them photos and ask for some love, but go ahead and order it. not worth a wait.

did you mill any on the cylinder base before you got started?

No I didn't have to mill the cylinder and the squish measured about as low as I would want to go with the gasket in place (020 squish) . I do still have the original jug and piston(50mm) so I might use that to run in the new crank until I'm sure I have it all right.

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[TimTaylor]

And yeah I've already ordered the bits and more.I'm not really someone who argues over a few dollars especially when I'm not sure whose fault it is

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[Bedford T]

And yeah I've already ordered the bits and more.I'm not really someone who argues over a few dollars especially when I'm not sure whose fault it is

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I was talking about waiting, but you are not.

 

[tbohn]

My question is can I hone that raised bit out and put in a new piston and go again or does the hard bore extend into the combustion area?

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I had the same raised ring on the squish band on a ms440 52mm cylinder. I swapped it out with a 50mm.
There are people that do turn the squish band to square it up.

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