Holzfforma G660 Stihl MS660

[huramentzefix]

I am glad that I came across this forum, it looks like a lot is going on here and that there is a good set of very knowledgeable people here.

I recently bought a G660 and was milling for the first time the other day. It was very hard wood and I was cutting with a 36" bar. The trunk was about 28" I would guess.
I spilled some bar oil which was sitting on the crank case and I saw this oil bubbling from the heat on the crankcase, so the saw was indeed working hard.
I was wondering if that could do any damage and if I should let it cool a bit but decided to keep going.
The idea was that if something fails I will replace it with better quality parts.

And here I am ...

3/4 down the way the saw stopped working.
1.) compression is good
2.) there is a spark and I changed the spark plug
3.) the spark plug is fairly dry even when I pull it various times with the choke
4.) sometimes it fires out of the crankcase
5.) seldom it lifts the decompression valve
6.) I have de-assembled the carburettor and blown it through with compressed air.
.... still no joy

I have ordered a new carburettor, a new ignition coil and I am going to order crankshaft seals.
What should the compression be, I will check that later then?

any recommendation what I should inspect and how so that I can get the saw back up running?

thanks a lot!

 

[J D]

Compression should be around 150psi give or take a bit. If you're unsure about that pull the muffler & look for any scoring on the piston.
Sounds like the saw was getting pretty warm, first rule of using a chainsaw (after all the safety stuff) is if something doesn't seem right stop & work out why!
It could have been hot enough the fuel was boiling but that would've come right once the saw cooled down.
Have to be careful blowing the carb out with compressed air as it can damage the nozzle check valve.
If your replacement carb is a Chinese one be aware some have issues & don't work right from new.
I wouldn't go replacing the seals on a relatively new saw just because... if you suspect something like that then a leak test is in order

 

[Mad Professor]

Pull the muffler to see the scored piston and stuck rings.

Ah.......Chinesium!!!

 

[irhunter]

Pull the muffler to see the scored piston and stuck rings.

^^^^^^^^^^^+1

To the OP...in the future, it is better to ask for help here before ordering parts.

Roy

 

[huramentzefix]

OK thanks for your help guys.
I will weld some adapter tomorrow so that I can connect air to an old spark-plug.
Then I will do a compression test and take the muffler off to see for scoring.

Thanks for the hint with the check valve I have to be careful.

where should one order a carb from then in case? I was looking on the hyway website but couldn't find any.
So I just went with a cheap Chinese one to see if it makes a difference.
But I will further investigate tomorrow and if lucky then I will get a Christmas tree this year.

 

[ballisticdoughnut]

I wouldn’t order any parts until you pull the muffler and inspect the piston. If it’s scored up you’ll need a piston and cylinder.

 

[Mad Professor]

I wouldn’t order any parts until you pull the muffler and inspect the piston. If it’s scored up you’ll need a piston and cylinder.

Better to start out with a real Stihl 066/660, with a scored P/C..........

 

[singinwoodwackr]

 

[huramentzefix]

for the ones that helped me here and that are curious of what it looks like
here some photos of the C A R N A G E

 

[ballisticdoughnut]

Better to start out with a real Stihl 066/660, with a scored P/C..........

I’d have to agree.

 

[singinwoodwackr]

for the ones that helped me here and that are curious of what it looks like
here some photos of the C A R N A G E

Ho…Lee…****…

 

[Mad Professor]

for the ones that helped me here and that are curious of what it looks like
here some photos of the C A R N A G E

Seized up good. Maybe some detonation as part of piston crown is missing, maybe not caught ex port? Looks WAY lean.

What is the circular thing in between the spark plug and decomp?

 

[ballisticdoughnut]

Seized up good. Maybe some detonation as part of piston crown is missing, maybe not caught ex port? Looks WAY lean.

What is the circular thing in between the spark plug and decomp?

That circle appears to be a result of the low quality chicom mold their using to cast the cylinders. Attention to detail isn’t something they seem to care about. You can also see raised lines in the squish band at 12, 3, 6, and 9 o’clock.

 

[Mad Professor]

That circle appears to be a result of the low quality chicom mold their using to cast the cylinders. Attention to detail isn’t something they seem to care about. You can also see raised lines in the squish band at 12, 3, 6, and 9 o’clock.

Ah, Chinesium!!!

Did not see any machining in squish area.

Here's a tecomec, they machined the casting in the squish area, that was still not uniform

 

[huramentzefix]

that I was running it lean is a possibility.
when I was half way through the trunk I remembered that I didn't had it dialed in properly, but it was running great so I kept going.
I will adjust it properly with the new cylinder.
should I go from 1:40 to 1:33?
It didn't seem and oil issue to me though, it looks like the piston wanted to melt away?

Also I will remove the baffle in the exhaust I think that thing is probably not good for the saw.
I have seen videos and everyone removes that for performance but I didn't want it because the saw had more than enough power and I thought the fuel consumption might increase. I wasn't looking for extra power but I think it might actually be better to remove it for longevity?
That trunk is extremely hard but the saw was chewing through it like a beast! But it was drinking fuel like a V8. 3/4 of the way through that trunk and the tank was empty!

 

[a. palmer jr.]

You probably shouldn't run the same fuel mix in the Chinese saw that you would in a Stihl. Try it at around 35:1 on the China saw. Also, carb adjustment shouldn't be on the lean side, maybe toward the middle.

 

[Mad Professor]

that I was running it lean is a possibility.
when I was half way through the trunk I remembered that I didn't had it dialed in properly, but it was running great so I kept going.
I will adjust it properly with the new cylinder.
should I go from 1:40 to 1:33?
It didn't seem and oil issue to me though, it looks like the piston wanted to melt away?

Also I will remove the baffle in the exhaust I think that thing is probably not good for the saw.
I have seen videos and everyone removes that for performance but I didn't want it because the saw had more than enough power and I thought the fuel consumption might increase. I wasn't looking for extra power but I think it might actually be better to remove it for longevity?
That trunk is extremely hard but the saw was chewing through it like a beast! But it was drinking fuel like a V8. 3/4 of the way through that trunk and the tank was empty!

See post #7......you'll be ahead of $$$

 

[burnses]

more fuel...less heat

 

[RedneckChainsawRepair]

Besides all the rest going on in top of that cylinder. Anyone else notice the sparkplug? Did you tune for milling? Most guys I know that mill 32:1 good FD oils and rich tune milling.

 

[fields_mj]

Don't feel too bad. I've got an 064 with an OEM piston and cylinder that's in the same condition, and likely for a similar reason. I will be rebuilding it, but I was working on an +60" oak at the time and needed a saw immediately. That's how I wound up with my G660.

Honestly, if you were running it lean with that mix, it's probably best that you trashed the top end of a $300 saw instead of a $1500 saw. I'd look at this as a blessing in disguise and say that you made a wise purchase to begin with. No disrespect intended or implied.