Have I screwed my Dolmar 120si?

[Meteor]

I recently picked up a nice 120si which was running great. I picked up a new bar and chain and the sprocket had to be replaced too. The issue is, after replacing the sprocket, the engine seems to have seized.

I’ve replaced many clutch drums and sprockets and never had an issue before. I used the rope in the cylinder method and a long-handle socket. I didn’t seem to have too much issue getting it off. Pretty standard. Everything was cleaned, new grease and reassembled. Everything seemed to cycle fine when hand turning.

I turned the choke on, gave it a couple of pulls, it kicked over, choke off, went to give another pull to start and the pull start was stuck. In fact the whole engine seems seized. Before I do anything else, I figured I’d ask here. What dumb #%?% thing could have I done?!

 

[alexcagle]

Starter cord spooled incorrectly.

 

[Meteor]

Starter cord spooled incorrectly.

Thanks. I didn’t even consider that. I’ll pull the assembly tomorrow although I suspect given how locked it is, it’s something inside. I hope you’re right though.

 

[alexcagle]

Thanks. I didn’t even consider that. I’ll pull the assembly tomorrow although I suspect given how locked it is, it’s something inside. I hope you’re right though.

Okay, now sleep tight. Lol

 

[alexcagle]

View attachment 1683720430000-1683724402865.mp4
I do some of my best thinking, when I'm asleep.

 

[Meteor]

Okay, now sleep tight. Lol

I had to know so just went out to the workshop to check. It wasn’t that. Flywheel, everything is locked up.

 

[Bob Hedgecutter]

I had to know so just went out to the workshop to check. It wasn’t that. Flywheel, everything is locked up.

Did all the rope you stuffed down the plug hole come back out?

 

[L34]

Pull exhaust and take a peek inside.
+1 on Bob's comment.
Might even see down spark plug hole.

 

[Meteor]

Did all the rope you stuffed down the plug hole come back out?

Yeah every bit of it. Brand new rope and ends sealed too.

Pull exhaust and take a peek inside.
+1 on Bob's comment.
Might even see down spark plug hole.

I’ll pull the exhaust and try and scope the cylinder through the plug hole tomorrow.


I guess my biggest question at this point is whether it’s possible to damage the crank in some way that could cause a lock up like this?

 

[Bob Hedgecutter]

If you used decent rope, if the piston was below the exhaust port- I guess it might be possible when you caught the rope in the port you popped the top off the edge of the piston to ring groove and it has now lodged between piston and cylinder wall.
If you cannot see an obvious and nothing is jamming the flywheel or clutch- then the cylinder kind of has to come off to investigate further.

 

[montana59]

Take chain of the bar, if that doesn’t help,start working backwards with what you changed

 

[cscltd]

I would remove what you did
Take sprocket off and clutch and see if that changes anything

 

[stihltech]

Does the sprocket spin freely?

 

[Woodslasher]

I'll bet clutch drum isn't seated right or rope in the cylinder. I had a 125 snip a piece of rope, it fired up for a few seconds twice then locked up tight. A quick teardown and I pulled the piece of rope out, slapped it together, and it ran again.

 

[Meteor]

Sorry to those who said rope and I said it all came out. I went back to basics and double-checked everything. It’s rope through the exhaust port. It cut so cleanly that the nylon rope appeared burnished at the end and still melted. I pulled most out through the exhaust but it’s still stuck tight. Appears there’s still a little bit caught at the top of the port and the top of the piston.

I’m assuming the best way is to pull the top? Is it possible to turn the engine backwards using the clutch nut or is that a dumb idea?

 

[Bob Hedgecutter]

You could try a wooden dowel down the plug hole and try to tap (not ham fisted Aussie wallop) the piston down with light hammer blows- might come down enough to pull the rest out.

If its stuck tight, if you try to pull the cylinder up and off- you might just stay as stuck as it is now.

 

[Meteor]

You could try a wooden dowel down the plug hole and try to tap (not ham fisted Aussie wallop) the piston down with light hammer blows- might come down enough to pull the rest out.

If its stuck tight, if you try to pull the cylinder up and off- you might just stay as stuck as it is now.

Yeah I tried the wooden dowel trick and unfortunately no go. I gave it a stern tap but not hamfisted as you say. It was as hard as I felt comfortable as I really like this saw. Is it possible to turn the engine backwards using the built in clutch nut? I’ve never even considered if this is possible in a chainsaw so it might be a really dumb idea.

 

[Bob Hedgecutter]

You can turn it any which way you like- its not running so you wont damage anything by reverse rotation.

I dont recommend it, but I have applied turning force to the crank and map gas heat through the exhaust port to dislodge stuck rope before.
Sometimes you do what you gotta- especially when you don't own the machine and the owner is not wanting to take it to a certified shop.

 

[Bob Hedgecutter]

Once you get the piston freed up a bit, I would remove the cylinder and check ALL the rope is out for sure- no wood splinters from your dowel and no damage has been done to the piston like closing/pinching of grooves and stuck rings- before running it again- but thats just me.

 

[Meteor]

Once you get the piston freed up a bit, I would remove the cylinder and check ALL the rope is out for sure- no wood splinters from your dowel and no damage has been done to the piston like closing/pinching of grooves and stuck rings- before running it again- but thats just me.

Thanks. That’s sensible advice.