400c Rumors… or just internet trolls.

[Lightning Performance]

Side note. I don't have a 400 piston and package to weight it.

They said the weight was reduced. So, the way I interpreted the weight was compared to the average 50mm piston not made of mag from a strato engine. Could be wrong and it's compared directly to the 362 piston. It should be compared to the 441 piston. I might be getting the weight on that if I decide to tare that down although it doesn't need to be. Porting would definitely help it. Feels all pent up with a long blowdown I'd suspect. Never timed it. Never timed one period. Never did a top end on that or a 400. Likely Kevin has all that stuff written down by now for weights.

 

[WI_Hedgehog]

It's exceedingly hard to burn up an air cooled motor due to improper warm up.

Tree service, concrete boring, and concrete cutting saws tell a different story during Wisconsin winters. Probably different in Texas.

 

[bwalker]

Side note. I don't have a 400 piston and package to weight it.

They said the weight was reduced. So, the way I interpreted the weight was compared to the average 50mm piston not made of mag from a strato engine. Could be wrong and it's compared directly to the 362 piston. It should be compared to the 441 piston. I might be getting the weight on that if I decide to tare that down although it doesn't need to be. Porting would definitely help it. Feels all pent up with a long blowdown I'd suspect. Never timed it. Never timed one period. Never did a top end on that or a 400. Likely Kevin has all that stuff written down by now for weights.

The 400C piston is 11g lighter than the 362 piston.

 

[sean donato]

Side note. I don't have a 400 piston and package to weight it.

They said the weight was reduced. So, the way I interpreted the weight was compared to the average 50mm piston not made of mag from a strato engine. Could be wrong and it's compared directly to the 362 piston. It should be compared to the 441 piston. I might be getting the weight on that if I decide to tare that down although it doesn't need to be. Porting would definitely help it. Feels all pent up with a long blowdown I'd suspect. Never timed it. Never timed one period. Never did a top end on that or a 400. Likely Kevin has all that stuff written down by now for weights.

The 400 piston is lighter then the 362 piston, it's definatly lighter then a 440/1 piston.

 

[bwalker]

Tree service, concrete boring, and concrete cutting saws tell a different story during Wisconsin winters. Probably different in Texas.

Never seen it in saws and lived in Upper MI for years.
I have seen it happen in snowmobiles and have seen guys blame just about every failure they have on it...

 

[bwalker]

I'm going with overheated, pinched rings that forced up the ring and broke the piston. If they don't find bearing cages or chunk of something in there or missing throttle shaft screws it's unlikely it ate something.

Sure would like to see that cylinder and the whole piston. It shouldn't have soot above the rings or below them. Dome or top side definitely carbon and soot there. The fuel normally washes away soot unless it was already running very lean.

If that happens the ring land is broken and in this case it's clearly intact.

 

[WI_Hedgehog]

Has anyone heard anything negative about the 400c? Someone on a fb chainsaw repair page was claiming that he knows of several 400c’s with pistons melted down on fairly new machines. Not sure if this guy is just a hater or is there some truth to these claims?

You asked, and that's how we learn.

Here's @Juliana Wolf's MS 400 piston looking through the exhaust port, probably not going to melt down any time soon. STIHL Ultra (silver bottle) at 50:1, non-ethanol premium pump fuel. Looks to me like it's getting lubed start to finish, (it's "a little wet" inside the muffler) carbon buildup looks fine, plug looks great, everything looks great.

 

[Jason Pitcher]

I actually saw that picture on Facebook. Now I am no means an expert nor do I claim to be one. When I saw that, my first thought was something worked losse and cooked that piston. I am in a few of those groups and for the most part, I wouldn't trust most of those people with a toy chInsaw.

 

[huskihl]

You asked, and that's how we learn.

Here's @Juliana Wolf's MS 400 piston looking through the exhaust port, probably not going to melt down any time soon. STIHL Ultra (silver bottle) at 50:1, non-ethanol premium pump fuel. Looks to me like it's getting lubed start to finish, (it's "a little wet" inside the muffler) carbon buildup looks fine, plug looks great, everything looks great.

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Doesn’t have enough run time. Vegetable oil at 100:1 would leave similar results.

But again, for most casual users, 200 to 300 hours of run time is 30 years and that will make most people happy. Unfortunately it’s only a couple months for people that use them every day

 

[RedneckChainsawRepair]

I actually saw that picture on Facebook. Now I am no means an expert nor do I claim to be one. When I saw that, my first thought was something worked losse and cooked that piston. I am in a few of those groups and for the most part, I wouldn't trust most of those people with a toy chInsaw.

But yet you ask alot questions in the groups.

I got a kick out of the one where you pulled the p+c off the 394 before you took the clutch off and then ask how do I get it off now. That was just common sense how to do it if make a mistake like that. But you learned from it.

 

[Jason Pitcher]

But yet you ask alot questions in the groups.

I got a kick out of the one where you pulled the p+c off the 394 before you took the clutch off and then ask how do I get it off now. That was just common sense how to do it if make a mistake like that. But you learned from it.

Actually I still haven't gotten it off. It is to the point I have put it on the shelf. I have partially shaved off the nut that holds it on. Maybe the Para cord I have stuffed in it isn't stopping it enough.

 

[RedneckChainsawRepair]

Actually I still haven't gotten it off. It is to the point I have put it on the shelf. I have partially shaved off the nut that holds it on. Maybe the Para cord I have stuffed in it isn't stopping it enough.

I had to do a parts saw the other day with p+c off to get a flywheel nut off one. Shoved rags in front of crank throws to hold it and then removed nut and fw. GL

 

[Jason Pitcher]

That I will try. Thanks

 

[huskihl]

That I will try. Thanks

Clockwise to get it off. Top to the right

 

[Lightning Performance]

If that happens the ring land is broken and in this case it's clearly intact.

Not always.

 

[North by Northwest]

Doesn’t have enough run time. Vegetable oil at 100:1 would leave similar results.

But again, for most casual users, 200 to 300 hours of run time is 30 years and that will make most people happy. Unfortunately it’s only a couple months for people that use them every day

Absolutely Kevin . P.S. The 7900 is running flawlessly brother !

 

[JKendrick87]

You asked, and that's how we learn.

Here's @Juliana Wolf's MS 400 piston looking through the exhaust port, probably not going to melt down any time soon. STIHL Ultra (silver bottle) at 50:1, non-ethanol premium pump fuel. Looks to me like it's getting lubed start to finish, (it's "a little wet" inside the muffler) carbon buildup looks fine, plug looks great, everything looks great.

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Thank you! I really appreciate the info everyone! Learning a lot about these saws.

 

[JKendrick87]

Doesn’t have enough run time. Vegetable oil at 100:1 would leave similar results.

But again, for most casual users, 200 to 300 hours of run time is 30 years and that will make most people happy. Unfortunately it’s only a couple months for people that use them every day

Mine is definitely not in that every day use category, and is an investment for me and I hope to have this saw along time.

 

[bwalker]

Not always.

Maybe not, but it's an extremely high percentage.
It's also rare for the rings to knock out a pin. The gap at the pin is wider than the gap that dictates ring gap at the cylinder wall.

 

[olgrowth]

When a PTO side bearing fails its almost always from some sort of abuse. Especially given low hours as @PV Hiker alluded to.
And yes running less oil than 50:1 is abuse for all those Amsoil zealots.
A fact lost on or not considered by many is that a strato charge saw not only runs hotter, but they also have much less oil going through them.

ive been sawing in the pnw for over 30 years using 100 to 1 amsoil and never lost a powerhead....low octane gas is what hammers the bearings out from pre-ignition which in turn chips a bearing and sends it up top through mixing chambers