MS650 idles fishy. Need help!

[Wonkydonkey]

When you come to put the clutch back on, your ment to put a piston stop in and then tighten the clutch, I use a bit of old starter rope. Just put it in when the piston is above the exhaust. If you don’t put enough in when you tighten the clutch it will compress the rope and turn over. I just put a bit more in if this happens.
I’ve never had a clutch come off, except then I was in arb school and someone didn’t put in on tight enough and when I slapped the break on it undid it self to the drum and was a fecker to get the c clip off

 

[Wonkydonkey]

And looking at your piston, Looks like someone has been using a metal screw in piston stop. That’s why I don’t use them for anything else other than getting tdc when port timing a saw

 

[popopboat]

And looking at your piston, Looks like someone has been using a metal screw in piston stop. That’s why I don’t use them for anything else other than getting tdc when port timing a saw

Yeah, thats my artwork.
Made a "stop" from an old sparkplug and a screw... as i didnt really care for the piston, it had to be replaced anyways.

After closer "investigation" , cant really find any threadlocker residue, appears like i never used it

Not entirely sure what happened overhere.
Usually when im assembing clutch, i give a few light taps with screwdriver&hammer combo, and then few revs with brake engaged, and it usually worked.
Maybe as an old carb was defective, saw was jumping around while idling, probably causing the clutch to come of.

After all, im suprised that everything else held up well, as i was extremely inpatient while assembling to get my first Stihl working.

This was probably causing an air leak too.

 

[BuckthornBonnie]

Every used saw that ends up on my bench gets the crank wiggle test before almost anything else. It can tell you a lot immediately. Some bearing/crank failures can slip by, but it’s similar to pulling the muffler on any engine; eliminate the easy/obvious first and then go from there.

Stihl 1122s, Husky 372, and smaller Husky homeowner saws tend to give me the most positive crank wiggles. Those are distantly followed by Stihl 1128s, 1125s, and Dolmar 6400/7900. In just my own experience, Stihl 1118 (028) have the fewest bearing or bottom end issues on any series I have wrenched on.

 

[popopboat]

Alright, replaced bearings, new gaskets and oil seals.
Guess what, NOTHING CHANGED, i mean atleast it doesnt rattle, but problem still persists.

Id doesnt die after WOT or cutting or whatever, rpm changes a bit but nothing too noticeable.

If it idles longer than 5-10 seconds and i blip the throttle real fast, rpm drops and/or acceleration is delayed.
Tends to die if i richen L or H , and its already on the edge of being lean.

 

[popopboat]

How "normal" is to have to use choke for restarting the saw if it has been shut for 2 mins or so?

 

[Cooper264]

How "normal" is to have to use choke for restarting the saw if it has been shut for 2 mins or so?

I read a few of the first post on here and then skipped to the end, but I was out cutting with a 066 that I just got done rebuilding and once it warmed up, it would idle fine fore a sec, and then when I came out of the cut to adjust the wedges, it would die as soon as I sat it down. Then I would have to Put her on high idle to start back and then it would idle fine. A small like 1/4 turn on the carb cleared that up

 

[Wonkydonkey]

I do find tuning Carbs one of the hardest things to do..
I’ve a few saws and everyone I’ve had problems with, sometimes you think it’s down to other problems, and sometimes it is, most times it’s the carb..

My 044 would idle all day long, but if I picked it up from the floor quick it dies. The low was 1.1/4 but turning it in a 1/4 fixed it and a slight tweak on the la.
Then I just checked the H to be sure it wasn’t a bit lean.

some saws need the fast idle (aka hot start) when hot and been left for a few mins
if you switch them off and start it immediately it’s not a problem,

 

[popopboat]

But the problem is that ive never had problems with carb adjustments.
This is the only saw that i cant get it "perfect"

If i lean L aymore chain spins (rpm goes above 3000), if i richen it anymore chainsaw dies after quick throttle blip, worsens the main problem.

If i lean H, it wont fourstroke, if i richen it dies after wot.

Im kinda stuck like this, i ordered new carb kit, maybe....

 

[smokey7]

When you lean the low out you must back the la screw out to bring the idle back down to normal.

 

[popopboat]

When you lean the low out you must back the la screw out to bring the idle back down to normal.

Unfortunately, it is already almost all the way out.

Pump diaphragm seems a little bit "stretched" so it maybe pushes a bit too much fuel in the carb.
It runs smooth in the cut, so ill leave it for now until new kit comes.

 

[Vintage Engine Repairs]

Stick it in some wood to clear the crank case out of the loaded fuel. Tune the H in the cut to only
Just clear up with good load. See if problem persists. A video speaks a gazillion words.

 

[Wonkydonkey]

When you lean the low out you must back the la screw out to bring the idle back down to normal.

Unfortunately, it is already almost all the way out.

Pump diaphragm seems a little bit "stretched" so it maybe pushes a bit too much fuel in the carb.
It runs smooth in the cut, so ill leave it for now until new kit comes.

I thought and are probably wrong... you lean the L (screw it in) you screwed the LA in to bring the revs down (open the butterfly)
Although maybe you didn’t have the butterfly open enough in the first instance .

but if I’m wrong on this assumption.
what’s wrong in starting again, as it says the stihl manual. although I can’t find it at the mo
here’s two ways, from the net, I,m sure there’s others and maybe someone else will chime in.

https://chainsaw-workshop-manual.com/how-to-adjust-a-stihl-chainsaw-carburetor/
not saying this is the best vid but it may help

 

[Lightning Performance]

If you did not not test the carb for vac and pressure your wasting time.

Have you even unloaded the shafts from the springs and checked the throttle shafts for play?

Could be a leaking welch plug. Very likely with the adjustment you described and the manners it presents plus poor hot starts.

All that should have been checked before messing with a carb kit or the diaphragm. Sometimes you never see the micro-holes in those places.

The basics first on the carb.

Was the saw pressure and vac tested to rule that out first?

Doc was here and asked some of these question but got no answer or did I miss that part?

 

[popopboat]

Alright, alright...
I want to punch myself in the head.

Ive checked the carb inlet and welch plugs, and it held lot more than 15psi, but ive never bothered checking from impulse line, now ive connected syringe to impulse line and applied pressure, some quite severe hissing..... appears like leaking occurs between fuel delivery line and pump part...

 

[Wonkydonkey]

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[popopboat]

.... Found one more bad-ish pump diaphragm and placed together with this one... doesnt leak anymore ... idle problem is pretty much non-existent even when too rich

 

[Wonkydonkey]

 

[popopboat]

OKAY, problem STILL persists
BUT, i found the "cause" ------- muffler mod, i removed baffle(for sound mainly) and opened muffler slightly, and when i for whatever reason blocked one of the outlets (had dual port muffler) , idle rpm dropped from 2800 to 2200ish, now i closed one of the ports, problem still persists but slightly less noticeable

(richening the L causes it to die after throttle blip)

it looks like it has too much suction is it even possible?
any ideas?

 

[kneedeepinsaws]

Anything extraordinary here?
View attachment 278367 View attachment 278368

See those marks on the butterfly? They look like they are out. The butterfly to me looks like it’s not sitting right.