Sounds like a common MS270 issue “found” and quite likely a dumb question to go with it.

[skids-stihls]

Hi there Arb team.

So after finishing my tacho mounting mission Featured here https://www.arboristsite.com/threads/my-easy-tacho-mount-“i’ll-show-you-mine-even-if-you-haven’t-shown-me-yours”.361956/

I was going over the MS270 again to write down some reference rpm and screw turns after the muff mod. I’d also had enough of a break in the weather to bring a ring of wood into the barn so I can tune in the cut regardless of weather and time of day.
I was able to (several times) have it idling ok, great response (no bog) from idle to WOT, and had it sounding pretty good in the cut around 9500-10000, which gave a max rpm of around 13,600-13,700 without load.
However the idle kept changing and with each adjustment I had to change the H screw too if keeping to similar rpm and good response.
I also thought that the L adjustment seemed to alter the speed at a slower rate than I’d have expected. Eg turn a little, then wait for reaction rather than slowly turning and listening/watching. Then after a cut, it would change again. I topped up fuel once warm as I hadn’t checked the fuel hose for leaks in the tank end yet, still the same. I also thought it was taking a while to get back to idle after WOT or a cut, (slowing down but not instant).

Anyway, I got it to a stage where I was happy enough to put it into Dads box of tricks for his task tomorrow, so he can blunt his 026, then my 270 and I’ll sharpen both at lunch time, more cut time for him. But then I decided to do one more rip(with the grain) on the bluegum ring, plenty of grated cheese coming out and still around 9500-10,000 rpm in the cut, lift a little and 4 stroke, into it again and cleared up, cut well.
Then I backed up ready for a brief idle down before refuel and into the toolbox, “CLICK, CLACK, CLUNK, and STALL”
I couldn’t move the pull cord
I was sure revs were low enough to not be too lean, so back to the workshop and pull plug, looked as ok as I could tell since it’s not new or just been set for a read. Pulled the muffler, piston up position but oily enough and no scoring, pulled starter cover and moved flywheel by hand, it only moved a knats kiss each way, but the piston moved with it. So off with the flywheel and thank goodness, problem found, (the dreaded loose bolt hitting the flywheel) pretty pleased it happened at idle rather than WOT,
The other 2 were still tight but the one that hit the Flywheel had a bend in it. Not bad but enough to not reuse it, not now that I’m all the way in here anyway.

Now for my dumb question, the hole is very deep compared to the bolt, does this go right through to the crank case? or would the air leak symptoms be from the case not being clamped together with only one bolt missing? The only reason it matters is because while replacing the bolt, I plan to locktite them and need to know just how careful I need to be with the locktite, obviously if a drip could make it to the crank case then I’ll need to be more sparing with the locktite and probably sit the saw on its bum while fastening them just to be safe.
Or if the locktite is just a bad idea in that area and occasional flywheel removal to check them is better, then I’m ok with that, just seems this is the most likely place to find someone who knows that.

Anyway hopefully once together this sorts the L speed issues, sorry for the long explanation, but sometimes more is more.
Be safe out there folks.

 

[Fatherwheels]

You have found the source of your slightly altering tune,
with the bolt loose there could indeed be an air leak,
that would cause your saw not to return to idle in the correct
manner, as you mentioned it not doing so.
You could put in a new bolt, torque up all the bots and try
the saw, ideally you should pressure and vacuum test the saw.
Yes, use thread lock, not a lot, put on a dot or two and let it
run around the clean threads of the bolt, that way it wont be in
one spot and drip into the case.
best to get a small torque wrench and find the correct spec
and make sure you torque the bolt down, not too tight to strip
the case threads.
You can put a small dot of thread lock on the nut that holds the flywheel
on just to be safe.


At least no damage is done, and if the worst happens, you can put
new seals and sealant around the case joint and have the saw right.

 

[skids-stihls]

Thanks for that.
Yeah as soon as I found the bolt that stopped the flywheel I figured there would be a correlation with the tuning issues, if the hole goes right to crank case then that’s hopefully the only place air was leaking. As it would have only had a couple of threads holding it when out far enough to hit the flywheel, so would have definitely let air past.
I plan to get a pressure and vacuum tester but don’t have one yet, so with reasonably low hours for it’s age, I’ll go with the locktite and new bolts and check for tunability after that, if still all over the place then I’ll start with brake clean while waiting for a pressure/vac kit.
I’ll be careful with the locktite, that’s the main reason I wanted to check if that hole went right through.
They’re the stupid coarse thread pitch with thin threads (if that makes sense) so I’ve had to order them, not the normal m6*1.0 which can be found on many of the parts saws here.
So I spent the avo getting our compressor up and running again to save multiple trips to the local garage and messing up their forecourt to get clean enough for the new bolts and reassembling.
I have a torque wrench here, will see if it goes light enough for these once I find the specs.

I appreciate the words of advice, thank you, and hopefully it’s the end of the story. I’ll be sure to follow up tho so it can be closed as solved when the time comes.

Cut safe out there guys

 

[skids-stihls]

While we’re torquing about it
Although I’ve not found the spec for these particular bolts on this particular saw yet, I do think that the torque wrench we have here is probably going to be far too Gorilla fisted for most things on a chainsaw.
Again, not these bolts on this saw but some of the lists I’ve found so far range from 3-30nM then the clutch at 50nm.

Then looking on line, there are some 1/4 torque wrenches that go from 3-25nm and the rest have a much smaller range.
Bicycle shops seemed a good look, but just wondering what others have, eg one small then go bigger , or measure small and hand fist the larger?
$89 for one that goes 3-25nm and comes with allen heads and torx heads, possibly not bad, but if there’s a better range in NZ that I’ve not found yet, or eg above XYZ y’all just grunt it tight, be interested to know.

Found the service manual for ms270 when I went back to check the details of the above mentioned wrench,
QUESTION,,,, are the bolts I have this mission with called the “fan housing/crankcase” bolts at 9 nM at the top of this first page? (Marked with yellow) or perhaps the 4nM below it? As I know they’re the same size as the pull cord cover and about 24mm long.

I can’t upload the second page of torque settings, my net seems ok on all other pages, so not sure what’s going on here.
Perhaps a clogged air filter on the url lol

 

[HarleyT]

Here is the service manual.

 

[Wood Doctor]

Thanks, HarleyT, I needed that one also. It's one of the few Stihl SM's I was missing.

 

[HarleyT]

"S M"

I had to google it....

 

[Wood Doctor]

HarleyT, you are correct and I agree. Abbreviations are killing the English language. Service Manual. I don't think IPL is in there either. Indian Premier League and Interstate Power and Light are more common than our Illustrated Parts List. Our work is way out in the tail of the distribution of terms.

 

[HarleyT]

Darn!!

 

[Chevboy0167]

^^^ Is she available and what are her rates??? Aking for...... a friend of course.......

 

[skids-stihls]

Here is the service manual.

Thank you for that. Looks bigger than the 7 page one I found, should be far more use too thanks.
I’m having issues opening it on the phone so I’ll get to the computer and have a look. Stihl waiting on the damn screws anyway so little time up my sleeve still.
Appreciate the help, thank you.

 

[malquid]

Darn!!

View attachment 1009383

I think if I had one of these persuaders I could buck,split and stack 10 cords a day

 

[skids-stihls]

I think if I had one of these persuaders I could buck,split and stack 10 cords a day

Or you’d be at home on your safety chain getting no work done at all lol.

 

[skids-stihls]

I think if I had one of these persuaders I could buck,split and stack 10 cords a day

Or you’d be at home on your safety chain getting no work done at all lol.

🕹⏱⛓⛓🗝🛏🛏🛏
Just make sure your safe word is Stihl, Pullan could be too confusing, as could johnsred, Echo you’d have to repeat yourself “ECHO ECHo ECho Echo echo “ and all the others just take too long to say for a safe word

 

[skids-stihls]

Ok so it looks like Daddy gets to buy a new tool, Pressure and Vac tester….. got the new screws for the 270, and proceeded to assemble it again, leaving it a day or 2 to be sure the locktite had set in our current damp, and cool conditions.

Reset carb screws to factory turns, including the difference for the removed limiters, started up good, though idled a bit high when cold, let things warm up a bit and after some fiddlers with the LA, I managed to get her somewhat good, (so I thought, more to come)
L screw was more tunable and responsive than prior, got H to piss rev at about 13000-13200,
Had it idling nice, (no chain spin) and great response when pinned, (no bogging or any feathering required) and good max rpm,
Picked it up to put it through a cut and damn it, the revs at idle picked up an extra 500-700 rpm, (from 2800 ish up to 3300-3500) and of course came the chain spin. Gave her a blip and it settled, turned on its side (both sides) and no difference, hung from the rear handle and no difference, but the sit it down and it putts away nice, pick up by both handles and revs go up again.
Did the spray with engine start, as I was closer to that than my brake cleaner, and no difference on clutch side, but with a bit around the flywheel side it putt putt putts down to a stall, I know this isn’t the most accurate, as there’s a good chance the flywheel just blew it out and the carb sucked it in.

So now in the matter of accuracy, and to make $h!( like this easier in the future, I’ll be looking for a pressure vacuum tester. Hopefully I can find a decent one at a decent price here in little old New Zealand,
From what I’ve read here on this site I should be looking for one that does at least 8psi in each direction (or equivalent vacuum reading) but some say 10psi. If I’m going to get one then I only want one, so I want to get the right one the first time, it’ll get plenty of use, but not enough to justify having 2 units cause I was 2psi short on my first purchase.

It’s possible that my engine start spray was an incredibly inaccurate test, which is more reason to have the correct tool for the job, my main girls don’t have too many “hours” on them for their “age” but time will catch up on them, (like it does for us all) plus I’ve got a couple of older ones coming my way for projects/collection/investment/hide them from the wife so the proper tool is worth having for any of those reasons.

Anyway it was dark and I was loosing some attention span when trying to sort this tonight, so I’ll have another (day time) go tomorrow and see if I have any better luck.
In the meantime, any confirmation on recommend units for a suitable pressure and vac level, available from NZ or short ship from Aus would be much appreciated.

Peace out all and stay safe out there. No short cuts on short days.

 

[skids-stihls]

So Okie has given me some good leads for a vac tester, (on another thread we were on)
I have to admit I’ve not got one yet as I’ve been naughty and brought more projects, which once they all arrive in a week or 2, I’ll post a link here to the new thread. I’ve also been cheating on my girls a bit and playing with the neighbours girl, she repeated herself heaps (its and echo) but it may be another good cause for the vac tester when it gets here, (after I order it that is)
Obviously I’m pretty relaxed these days about the saws as I have enough to get something done if needed, and am not relying on them for a paid delivery each day anymore, so when looking for tools and I found projects instead I figured that the used market changes quicker than the vac tester that will still be there. Dads got his 026 and a lil pusqvana so the 270 sitting a little longer is no big deal, plus my 660 is always my go to, ok it’s heavier but with the little 25” bar I don’t have to bend, or change saws as it’ll tackle most things.
Then the neighbours girl can wait as that’s where dads been doing windthrow clean up lately anyway, and he only has a lil saw to prevent calling on us too often, which is irrelevant since dads there each day at the mo.

Anyway that was a pretty unrelated update as far as the 270 goes, but just letting you all know where we up to and it’s not just another abandoned thread with no answer. We will get there.

 

[Patrick1903]

but just letting you all know where we up to and it’s not just another abandoned thread with no answer. We will get there.

Just making sure this wasn’t an abandoned thread. Any update?