660 starting issue- super hard pull.

[spindrift7mm]

has the compression been checked ?

 

[scallywag]

Have you got the correct lenght bolt in here?

 

[latunxitom]

You need to haul off and pull that thing all the way through.

 

[one2tree]

half pull the cord up softly till its ready to turn over keep yr thumb on decompresion switch then give it what for???

 

[towingace]

If I'm a late-comer to a thread, as I am here, I read every previous post to gain all the info I can so as to hopefully contribute a useful statement and also not repeat what has already been asked or suggested. At first, I thought the starting technique was suspect. Further reading dispelled that for the most part, especially when a vital clue that wasn't mentioned for nearly 1 1/2 pages was revealed. Had we all known, from the start, that this problem persisted WITH THE PLUG OUT, it would have eliminated a lot of the guesswork. That being said, that saw needs to be dissected and thoroughly inspected with each step. There are several useful suggestions posted here that should help the untrained eye from missing something. Once the clutch, loose parts in the flywheel, starter assy., etc. have been eliminated, I'm thinkin' it's time to get that jug off there.

 

[woodeneye]

As stated above don't overlook a full clutch disassembly. I did this once and it solved the very problem you stated, though I swept a lot of crud up in a vacuum and never really found the culprit, it did indeed solve the problem once reinstalled.

 

[Cedar Row]

I had a similar problem with an 041; when pulling to start, the saw would seem to lock up. If I pulled the cord easy and moved the piston to a different position, it would pull ok and start ok. No problems once it was running. A Stihl mechanic told me it was carbon buildup on the piston, and to try using seafoam. I did and it fixed the problem. Now I am working on a MS290 that is doing the same thing. It will hang up and not pull, and moving the piston by pulling easy will eventually allow easy pull and start. Saw then runs fine. This saw's hard pull feels like a timing problem, but it is intermittent. I am going to try the seafoam trick today to see if it helps. The flywheel key is ok, magneto gapped by business card. I just finished cleaning the saw, so crud probably isn't the problem.

 

[woodeneye]

I already suggested that cedar, so it must not be that.

 

[jughead500]

Like giffonks says check for hydrolock.could possibly be full enough to start locking on the down stroke also with the plug out.should hear squishing of the gas in the bottom end though.
If it has Hydrolocked before you could be looking at bent connecting rod syndrome.

 

[tacomatrd98]

OP says it does it with the plug OUT. it cannot be hydro locked with a hole in the top of the combustion chamber

Like giffonks says check for hydrolock.could possibly be full enough to start locking on the down stroke also with the plug out.should hear squishing of the gas in the bottom end though.
If it has Hydrolocked before you could be looking at bent connecting rod syndrome.

Not trying to start an argument but how would something with transfer ports hydro lock on the down stroke?

 

[VinceGU05]

Then my honest opinion, no matter how much its not liked is that the internal bearings are ready to take a walk ............. Crank or connecting rod

its time to stop guessing what it maybe and start stripping the saw down and carefully inspect all key parts of the saw. i am sure all shall be revealed. gotta say the OP was a bit misleading with key observations missing which were later mentioned.. bit of a moving target. i am keen to see the results of the autopsy opcorn:

 

[burnses]

lets just all relax and start and oil thread as therapy...i'm real curious to find out what the problem is. I am clinging to the "does it with the plug out" might as well take the bar and chain off and check out a clutch issue could it be a loose oil pump bolt jamming he back of the clutch....

good luck
the can

 

[towingace]

Pretty much what we been sayin', dissect and carefully inspect, taking into account all of the meaningful suggestions.

 

[treesmith]

You'll have to excuse all the "pull harder" comments but fact is if you pull half assed you'll hurt yourself.
From what others have said, you'll need to strip and check, dont run it till you know its good

 

[Four Paws]

Not trying to start an argument but how would something with transfer ports hydro lock on the down stroke?

There is a period of time that the intake and transfer ports are both closed. Leaking case gasket fills your case with bar oil and then you give that starter rope a tug.

 

[griffonks]

Yes, the saw needs to be stripped down to the case. It could be a number of things and it's probably going to get worse.

Bearings, crank shaft, Journals, FW, Clutch, etc. Check it all.

 

[cutforfun]

Did this ever get figured out???

 

[MervMaster]

Will update when I have the answer.

 

[Big_Wood]

i watch that vid and my first impression is that mervmaster is joking with us. you just gotta be guy. heck i don't even use the decomp with any of my saws. a 660 is ***** **** compared to a 395. have you ever started one of those? i'd like to request another vid but i wanna see you give it your all. if the thing still locks up and don't wanna start then i'll be on your side. i had one 660 break a cage and spin a main but you wouldn't even get that saw to pull out an inch after the starter pawls engaged.

 

[ckelp]

try to light off a sp81 (with a decomp) after that everything seems like a weedeater (includeing mw 394)
that saw almost broke my wrist, pulls the knot though the handle

food for thought, i had a demo saw with a main bearing let go and the saw ran good just was a pain to start