Well it does look better now lol. Put it back together and let us know how it does.
Ms 180 rebuild with pictures.
- Thread starter Vintage Engine Repairs
- Start date
Help Support Arborist Forum:
Ah, a bit clearer on the picture, before it looked like a jagged hole.
Looks like the center machine mark, thats not really round anymore from adjacent impact damage.
File it with a flat file, you do know about rocking the file as it goes round the curve of the piston so you dont get a flat when filing, sounds odd I know, but if you just hold the file straight, and wipe it across the piston, as its curved, it will file in one spot, and leave a flat filed mark.
Moving the wrist that hods the handle from high up to low as you swipe the file across the curved surface will reduce the effect.
gently, gently gently,take your time, you only need to knock off the high raised bits of the scoring, no more.
Yes that’s exactly what it looks like close up, but it’s all flat so no need to file I don’t think! Right, i’m Going to put it together with some gaskit sealer and update you guys!
Can I put gaskit sealer around the oil seals to make them fit snugger in case there is a slight leak ?
Put a very light smear around the outside ring of the seal where it seats in the cylinder recess, and a little more where the 9 and 3 o clock area where the base cover joins.
Also put some rubber grease on the inner seal and crank as you fit it up.
As you are re using the old seals, you will see how they were shaped when originally fitted and clamped into position, this does deform the seal a small amount, try to put them back in that position, actually dont try to, just refit them in the same position.
At least scotch brite the piston, and make sure the rings are not stuck, it looked like they were a little bit, but photos can be a bit deceiving.
What sealant are you using ?
I use/ reccomend yamabond or equivalent for those type of joins.
Took your advice and followed it bud 
She’s back together now accpect the carb (needs a clean tomorrow) the throttle and choke linkage (because I need to fix the broken plastic clip bit - tomorrow) and the air filter housing!
I need to grab a fuel and oil filter as they needed replacing and a bar, chain two studs, 1 bar rod, a clutch cover, engine cover and a spark arrestor and deflector and she’s put together. I won’t get any of that until I know she at least runs. Compression feels good though! You were right mate, the top ring was scored and bound. I gently sanded it back and they fitted beautifully. I recon it was a quick fail because now I have cleaned the rings, piston and cylinder it’s got twice the compression to what it had before.
Watch this space!
She’s back together now accpect the carb (needs a clean tomorrow) the throttle and choke linkage (because I need to fix the broken plastic clip bit - tomorrow) and the air filter housing!
I need to grab a fuel and oil filter as they needed replacing and a bar, chain two studs, 1 bar rod, a clutch cover, engine cover and a spark arrestor and deflector and she’s put together. I won’t get any of that until I know she at least runs. Compression feels good though! You were right mate, the top ring was scored and bound. I gently sanded it back and they fitted beautifully. I recon it was a quick fail because now I have cleaned the rings, piston and cylinder it’s got twice the compression to what it had before.
Watch this space!
Attachments
Just a quick heads up, regarding the oil pump, you do know they have a particular depth, and orientation in the case so the oil outlet lines up with the oil gallery in the plastic chassis ?
Edited to add.
Depth is 8mm
Edited to add.
Depth is 8mm
I did but wasn’t sure on precisely thr depth, is the 8mm the protrusion at the gear end protruding out of the Oiler shaft? The oiler has a little step (red arrow pointing to it in the picture below) I pushed the Oiler so this was flush with the surface of the clamshell casing as I wasn’t sure but seemed correct
Attachments
No, its measured from the other end, 8mm from the plastic base of the chassis to the flat bottom of the pump, measured from where you press it in, there is a symbol there too that shows where the flat of the pump faces too, so depth and orientation is critical.
look in your service manual I sent, page 30- ish
look in your service manual I sent, page 30- ish
I understand
everything is aligned correctly, I just cant be certain of the depth. Thanks for explaining, however I can’t for the life of me see where it says 8mm in the manual or that other document that the gentleman just sent
It dosent say in the manual the depth, only refers to the special tool.I understand
There is a thread here from a while back that shows the tools pre set depth, use a vernier, toothpick, depth stick of choise.
See here
https://www.arboristsite.com/commun...tic-saw-oil-pump-removal-installation.300051/
Thanks mateIt dosent say in the manual the depth, only refers to the special tool.
There is a thread here from a while back that shows the tools pre set depth, use a vernier, toothpick, depth stick of choise.
See here
https://www.arboristsite.com/commun...tic-saw-oil-pump-removal-installation.300051/
RIGHT!
So strange - has compression, holding the pull cord and letting the saw drop, it gradually goes down, has a nice snap.
So I started with choke, fired, then the next switch up and it ran for 4-5 seconds and would die.
I then couldn’t get it started again until I put it back on choke. It burped, then went to fast idle on the selector and it started again for a few seconds and died.
For some reason it doesn’t flood if I keep going back to the full choke to start it but keeps dying...
I’m guessing not enough fuel is getting to the engine
The carb is totally clean, fuel line is clean everything is clean, I fiddled with idle screw but seems ok?
I did hear a little slap of the piston so it could be that it’s not sucking enough fuel in because of the worn piston and cylinder?
Please help!
Hmmm
if it will burp and run for a few seconds I would assume the compression is fine,if it were too low, it would not start at all, yes your on the right track with fuel and carb.
So even if its at rpm, it will just starve out and die, or only down at lower throttle and idle ?
how did you test the main jet venturi nozzle, and did you set the idle adjuster to stock as per the manual ?
Have to ask, are the diphragms and gaskets the correct way around, tho if it dosent flood, they sound ok
heading offline soon, but check those and did you put the spacer in the intake boot under the carb ?
there is a reason the saw was toasted, you need to find out why.
if it will burp and run for a few seconds I would assume the compression is fine,if it were too low, it would not start at all, yes your on the right track with fuel and carb.
So even if its at rpm, it will just starve out and die, or only down at lower throttle and idle ?
how did you test the main jet venturi nozzle, and did you set the idle adjuster to stock as per the manual ?
Have to ask, are the diphragms and gaskets the correct way around, tho if it dosent flood, they sound ok
heading offline soon, but check those and did you put the spacer in the intake boot under the carb ?
there is a reason the saw was toasted, you need to find out why.
Everything is put together correctly so I don’t think that’s a problem. Maybe the pump diaphragm and metering diaphragm are toast? But they both looked ok (although I don’t know what is and isn’t really!) They moved and didn’t have any splits in them basically..
The jets, i unscrewed the jet to clean it (not sure if it’s main jet? Anyway it’s clean and it’s back.
I tried to unscrew the idle screw to clean it but it doesn’t come out so left it. Instructions say to turn counter clockwise until it seats (but it pressed up against the carb body, but kept spinning and never tightened up which was weird?) and then I did two turns clockwise as manual said for starting setting for adjustment?
I hope I didn’t break that screw? Seems fine though it goes in and out, just doesn’t bottom out when I turn to the left (tightening it)
What is the main jet Venturi nozzle? Is that the thing I unscrewed? I pulled the jet and cleaned it all and soaked in carb cleaner
- Joined
- Jul 19, 2019
- Messages
- 4,226
- Reaction score
- 8,459
Are you playing with the main idle screw that works the throttle butterfly (pressed up against the carb body) and treating it like the low idle mixture screw- with the 2 turns out?
Na there is only one screw which is the idle screw.
Sooooo I put a new carb in (from my other 180)
And it RUNS!!!!!!!!!!!!!
However I need to keep the revs up because it dies haha
So my question to you guys is, why would this new carb idle my new saw beautifully, but not idle this one? Maybe I need to crank the idle screw wayyyyyy up on the old carb?
Nope, the idle screw just won’t turn out... comes out half the way compared to my other carb... maybe I need a new carb
- Joined
- Jul 19, 2019
- Messages
- 4,226
- Reaction score
- 8,459
Or maybe there is a good reason this one only cost you $25.
Thats is what I meant by the idle screw and thinking it altered mixtures like a low idle mixture screw on a real chainsaw carb.
Your carb off the other saw is tuned for that saw, take it off the original and set it on another and generally you have o tune it to suit that powerhead, but those non adjustable MS 170-180 carbs can be wee sods- do a search on replacing it with an adjustable Walbro- lots of information on here about that one.
Thats is what I meant by the idle screw and thinking it altered mixtures like a low idle mixture screw on a real chainsaw carb.
Your carb off the other saw is tuned for that saw, take it off the original and set it on another and generally you have o tune it to suit that powerhead, but those non adjustable MS 170-180 carbs can be wee sods- do a search on replacing it with an adjustable Walbro- lots of information on here about that one.
I’ll get a new carb (i’ll Have to learn how to tune them though and I don’t have a tachometer!)
The idle screw looks super chewed up done by the previous owner, I have a feeling the previous guy probably cranked it too hard that’s why I had problems with it earlier...
