My Lawnmower Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
My B+S mower made a small bang the other day while mowing, the revs dropped low for a minute, the engine out.
Now when I pull the cord to try start it there ain't much resistance, the flywheel spins freely and the blade, a lot more than normal.
And no hint of it starting.
Anyone have any ideas?
 

·
Registered
Joined
·
473 Posts
Welcome to MLF. It sounds like you may have broken the piston connecting rod. Remove the spark plug, insert a pencil into the cylinder until it stops and slowly pull the starter rope to see if the pencil moves in and out. If it moves, you have a different problem, if it don't move, you need a new motor or major repairs.
 
  • Like
Reactions: Brad

·
Registered
Joined
·
6 Posts
Discussion Starter · #3 ·
Thanks.
I inserted a pencil in the spark plug hole.
Going straight in, it didn't go in far, inch and a half maybe and no movement when I pull the cord.
Then I tried inserting the pencil at an angle and when I pull the cord, the pencil kinda bobbed in and out a bit, I could feel and see the movement on the pencil.
 

·
Registered
Joined
·
473 Posts
If the pencil doesn't move an inch or two, you found the problem. You could pull the cylinder head off and look into the cylinder.
 

·
Registered
Joined
·
473 Posts
I believe you have a flat head motor and that is why you have to insert it at an angle in order to reach the piston. Do you hear or feel and kind of knocking noise when pulling the rope ? What brand and model number engine do you have?motor
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #7 ·
I believe you have a flat head motor and that is why you have to insert it at an angle in order to reach the piston. Do you hear or feel and kind of knocking noise when pulling the rope ? What brand and model number engine do you have?motor
I believe you have a flat head motor and that is why you have to insert it at an angle in order to reach the piston. Do you hear or feel and kind of knocking noise when pulling the rope ? What brand and model number engine do you have?motor
On side of the fuel tank is, Family YBSXS 1901VC 27466
Sigma brand, made in Italy.
The noise I hear when I pull the cord, mostly just sounds like the flywheel and blade spinning, no real knocking as such. It spins freely for a few seconds on each pull.
 

·
Founding Administrator
Joined
·
1,269 Posts
As stated earlier, sounds like a connecting rod or possibly hole in the piston. Probably no compression. Any way, it's a substantial repair. Not totally out of the a home-owner repair if mechanically inclined. If not, maybe a local mower shop can check it out or replace the motor with a used one?
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #10 ·
Thanks. I suspected from the start it may be a major issue.
The mower is fairly old. I have nursed her over the last few years.
I think the value of repair may outweigh the value of the mower.
But, I may try to repair it as a project, progress my learning a little bit more.
I would love to see it running again.
I really appreciate the help and advice given.
Thank you.
 

·
Registered
Joined
·
12 Posts
If you want to play with a possible repair, you might be able to find a comparable mower someone is throwing into the recycle pile. Might or might not have usable parts but its 'fun' to take stuff apart and if you can cobble together something that works from parts, all the better. With all the videos available, you can almost always find a how to video
 

·
Registered
Joined
·
293 Posts
I think the value of repair may outweigh the value of the mower.
But, I may try to repair it as a project, progress my learning a little bit more.
If the crankcase is not holed, replacing the connecting rod, cleaning up the crankshaft with acid and rebuilding is a fairly easy job. Patience and step-by-step diligence it all it takes.
 

·
Registered
Joined
·
8 Posts
Thanks. I suspected from the start it may be a major issue.
The mower is fairly old. I have nursed her over the last few years.
I think the value of repair may outweigh the value of the mower.
But, I may try to repair it as a project, progress my learning a little bit more.
I would love to see it running again.
I really appreciate the help and advice given.
Thank you.
A good source of info is on Youtube under Mustie1 and another Chikanic they tear down everything and Terrylfixesall or something like that
 
1 - 13 of 13 Posts
Top