Hutzl MS660 failure ~ 20h

[BTarb24]

I built my hutzl around this same time last year. It cut a couple trees and did around 3h of milling. Honestly, it worked surprisingly well. The last time it was used it started to be a little harder to start and seemed generally a bit fussier. Today, it wouldn't pop at all.

Compression check came in at only 105 psi so i figured there may be some scoring. I thought i'd have a look at the exhaust side of the piston. As soon as i pulled the exhaust shell I knew there was a problem. There was quite a pile of metal chips laying in there. Bummer, eh?


I then went to pull the cylinder up a bit to see how things were looking on the other side of the piston. This is where i could see that the other wall was heavily scored and that the skirt of the piston looked like it was broken.


At this point i gave up on it being a quick fix so i pulled the head entirely. It appears that the chunk of the broken piston skirt may have ended up in a port and got slowly chipped into tiny pieces. The top of the piston was just covered in little crush marks. It even still had a couple pieces still squished to the top of it when it was pulled.


A couple of the chips caused some severe gouging to the piston. It actually fused/trapped the ring in these places so that they couldn't spring back out.


I'm not quite sure what to make of the failure. My assumptions are that it was a defective piston that failed and the broken skirt was just chewed to pieces. Or, it may be that a piece of the cylinder chipped and got wedged under the skirt, causing it to break due to the stress. The ports on these hutzl cylinders are rather sloppy and have a good bit of slag. I was foolish and didn't bother cleaning it up. Considering how bad the piston looks, the cylinder really doesn't look too bad. I can only see a few chips near ports, but the scoring is minimal.


I'm a little torn on whether i should try another huztl c+p or if i should get something other brand such as meteor. The hutzl did hold nice compression until the catastrophee. I'm also debating on if i should bother trying for a free replacement from hutzl. It seems rather apparent that something was defective, but being a whole year since my purchase i don't know how much it'll matter.

 

[Ozhoo]

Ouch, I would wager that the piston was hitting the crank. Did you check for that during assembly? At one time it was pretty common on these builds. You can see where the cylinder plating was flaking away so her days were numbered anyway.

Meteor or Hyway would be the way to go. But if you're going to spend that kind of money, be meticulous during assembly.

 

[BTarb24]

No, i don't believe i checked for that explicitly. I do remember rotating the crank quite a number of times with the cylinder on and it didn't make any clacks or have any feeling of interference. Though, i suppose with propulsion from the ignition it could have still made contact. However, even if that were the case.. what would be the remedy? Grinding the skirt on the piston back?

-- edit --

I just went down to have a look. I don't see any evidence of contact with any part of the crank. The short side still has its native rough cast and the counterweight side still has all the nice even machining marks.


A closer look at the piston does show a very small amount of abrasion on the inner wall. I'm not sure that there's enough of a mark on the remaining corners to justify snapping the skirt in half.. but perhaps the broken skirt hung down a little lower or caught more firmly than the others.

 

[Ozhoo]

Yep, that was it. She was hitting pretty hard. Use a burr/dremel to clearance the inside edge of the skirt.



You're gonna wanna be real meticulous cleaning all that metal out of your crankcase. I'd pull the crank seals and get in there with air/mix to flush, clean and repeat several times. Same for the crank bearing.

 

[davhul]

The bottom end looks kinda dry What ratio for milling? Most use 32:1 for the mill.
From the first post it sounds like it died a slow death and the first sign was easy to pull and a bad idle. Hope you get it worked out

 

[BTarb24]

i was just using my normal 50:1. The easy pull was actually prior to any milling. I'm guessing the idle/start problem started forming as more of the metal chips worked their way up into the transfer port and scored the piston further.

I ended up buying a new p/c from huztl and also a whole new 660 kit. I figured that for the price it's worth it to have a backup saw.. plus it gives me a strong saw to to any cleanup while the other one has the milling attachment on it. Or at least that's what i talked myself into

 

[dswensen]

i was just using my normal 50:1. The easy pull was actually prior to any milling. I'm guessing the idle/start problem started forming as more of the metal chips worked their way up into the transfer port and scored the piston further.

I ended up buying a new p/c from huztl and also a whole new 660 kit. I figured that for the price it's worth it to have a backup saw.. plus it gives me a strong saw to to any cleanup while the other one has the milling attachment on it. Or at least that's what i talked myself into

Love it! I can justify just about anything to myself too. Convincing she-who-must-be-obeyed is a bit harder at times.

 

[Mustang71]

I have been trying to decide about buying a farmertec 660 kit in the near future. I asked about them here in the chainsaw forum and didn't get much response. This is some good feedback to me. Sorry about your saw but that issue shouldn't happen and that's my fear about a Chinese saw kit there's no quality control. I got a wrist pin that was to long and I had to modify it to work. Very noticeable issue. This issue wouldn't be noticeable unless you were looking for it.

 

[davhul]

The control issue I've seen is missing parts or wrong parts sometimes thrown in the kit. It's usually small parts though.
On the original thread there was a list of oem parts that was recommend but not always used. The cases and plastic parts look good and the jury is still out on the crank for me but it seems to be holding up so far on the 3 I've built. The one I kept runs 32:1 and the other 2 I gave away runs 40:1. A used oem crank and bearings are a option if worried or have a failure.
On the carbs it seems sometimes there hit and miss but bedford found a few he likes that I might get around to try soon. On mine I went with walbro. A inconsistent or bad tune in mid cut is something I didn't want to chance on a saw I was giving to someone. I ended up setting them around 12,8-13,000 and let it ride. Time will only tell

 

[a. palmer jr.]

Wondering if maybe a 42:1 might be a better ratio for the Chinese saws...

 

[davhul]

I think at least 40:1 should be considered. At 32 I have no spooge or smoke pouring out the exhaust with a good tune. The oil that's chosen also has a effect but I don't want to start another oil thread. Each has their favorite. Cheap box store saws seem to recommend more oil.
I'd probably tear it down and put new bearings and another $13 crank in it. Their probably next grinding up that much aluminum.

 

[s sidewall]

To me, you can see where the counter weight was hitting the piston, seen that before on sloppy wrist pin and bearings.

Steve Sidwell, Samsung On5 using Tapatalk

 

[BTarb24]

Love it! I can justify just about anything to myself too. Convincing she-who-must-be-obeyed is a bit harder at times.

My way around this was showing that our husky 450 bought from lowes cost more than 2 of these huztl 660's combined .. and each huztl is 2x the power. I didn't bother explaining how much extra time i'll have to spend tinkering in the garage to get them to work though

I've yet to split a case .. Are the screw-driven tools necessary or could I accomplish the same thing with general applications of leverage in the piston rod opening? Another thought was utilizing one of my bazillion woodworking screw clamps to fashion my own screw-point tool.

 

[a. palmer jr.]

Just don't use a screwdriver to pry the halves apart. I've been lucky on some using a rubber hammer to separate halves but not sure I recommend that either unless the bearings aren't a tight fit.

 

[BTarb24]

I was considering something like a spreader clamp in the top opening to spread the 2 halves.

 

[a. palmer jr.]

The last one I tried was just an old parts saw, tried using a hammer on the end of the (broken) crankshaft, didn't turn out well. It was going in the junk anyway..
I'm thinking that on a new engine it might not be as stuck as this 40 year old parts saw was, might be able to just tap it with rubber hammer and get it to separate..

 

[weimedog]

A pretty common issue as Davhul already mentioned...the piston skirt to crank interference issue. Some cranks are worse than others.. something to check sometimes even assembling the piston and crank outside the cases first to get a good look to see if dremel wonder work is required. I have thee 660's in use by a logger who runs them all day, every day. he's had them for a while. Going to check in and do a video of how they survived.... That also included my slightly modified one for a month or so. I figure no news is good news.... The one used by my firewood producing bud and the one his friend have have survived a year.... Another clearance issue is with the 56mm builds. Check the gasket / piston at BDC for interference. I've stayed away from the 56mm's for a while waiting for a better plating technic to happen. maybe its time to check in and see if they have improved the 56mm cyclinder. My FIRST one (56mm) from 2015 still runs great and a bore scope look into the cylinder shows its wearing as it should. Looks like a saw with two solid years on it...still has x-hatch and no seize marks on the piston either. The "Bling" saw roasted the first top end I had on it, went and put on the earlier version of the 56mm top end on and its still looking OK. It doesn't have enough time to really matter or show a wear trend. All mine eat 32:1. The 038 and 036's are taking run time away from the 660's though. And building a "Ultimate Old Man Saw" out of a Husky 550 which will take even more time. (562 guts & ignition/carb into a 555 cases...with a popup and muffler mods)

 

[davhul]

A pretty common issue as Davhul already mentioned...first the skirt to crank interference. Some cranks are worse than others.. something to check sometimes even assembling the piston and crank outside the saw first to get a good look to see if dremel wonder work is required. I have thee in use buy a logger who runs them all day, every day. he's had them for a while. Going to check in and do a video of how they survived.... He also has had my slightly modified one for a month or so. I figure no news is good news.... The one used by my firewood producing bud and the one his friend have have survived a year.... Another clearance issue is with the 56mm builds. Check the gasket / piston at BDC for interference. I've stayed away from the 56mm's for a while waiting for a better plating technic to happen. maybe its time to check in and see if they have improved the 56mm cyclinder. My FIRST one (56mm) from 2015 still runs great and a bore scope look into the cylinder shows its wearing as it should. Looks like a saw with two solid years on it...still has x-hatch and no seize marks on the piston either. The "Bling" saw roasted the first top end I had on it, when and put on the earlier version and its still looking OK. It doesn't have enough time to really matter or show a wear trend. All mine eat 32:1. The 038 and 036's are taking run time away from the 660's though. And building a "Ultimate Old Man Saw" out of a Husky 550 which will take even more time. (562 guts & ignition/carb into a 555 cases...with a popup and muffler mods)

Was it the 52mm that you got several in a row that had good bevels and plating?

 

[weimedog]

54's, and they do look different. Want to find time to build a "tweaked" one of those...just time is so hard to come by anymore.

 

[altair]

I've just finished a chinese Farmertec big bore MS660 for a mate..I've tried to convince him 32:1 is a great ratio for that saw using Stihl Ultra, just in an effort to try and protect it a little. Vid below is the saw on first tank, after a few heat up/cool down runs... I've tried setting it richer but it just seems to be a revver. It will end up with 40 or even 50:1 as he isn't known to look after his gear..but in my humble opinion (and it is just MY 2c worth) that no big saw should have 50:1, especially in milling conditions.
I'm keen to see how long this one lasts, in this vid is has a dull chain, because I was too lazy to file it first...lol, fresh Old Man Pine in New Zealand..a fairly soft wood.