Saw nearly impossible to start when cold!

[samthescam]

Hey there, new to this forum. But I found out about it about a week ago and have been reading a lot even since.

 

Want to see if anyone has any ideas on this. I am a landscape gardener. I have a couple of saws, which I mainly use for cutting sleepers and hedge reductions. Pretty much little jobs that don't require much grunt.

 

I have this old Stihl 021. And it is impossible to start when cold! Once it's warm it's fine and runs happily. By impossible, I mean it literally won't start.

 

 

I've checked the plug and get a spark, i've taken the carb off and it looks fine.

 

Any ideas?

Edited August 5, 2011 by samthescam

[Tom2020]

Wrap a blanket around it and give it a hot water bottle before it starts work

 

Apart from that i ant got a clue

[Chris Sheppard]

Does it fire at all? if not, given that it will run when warm, it must be getting some fuel through, I'd guess at too low compression (worn piston ring maybe) but once warm and everythings expanded a bit there's just enough compression to fire.

[Megatron]

Take off the air filter (top piece) and look down at the choke plate on the carb, put the master control lever on cold start position and see if the choke plate shuts fully. Sometimes the lever which activates the choke plate gets bent resulting in full choke not being achieved.

If not you could try a 1/8th turn anti-clockwise on the L-speed screw.

[samthescam]

Does it fire at all? if not, given that it will run when warm, it must be getting some fuel through, I'd guess at too low compression (worn piston ring maybe) but once warm and everythings expanded a bit there's just enough compression to fire.

 

I thought as much... Basically it will fire under very certain circumstances. However it makes your arms feel like they want to fall off and takes a couple of hours (i'm not taking the mick). You just have to keep cranking it with the throttle open...

 

I've only managed to start it twice, both with help from arborist mates. I have brought a new ms261, but would like to be able to have it as a backup.

 

Any idea how much it would cost to sort the compression out? Don't want to spend a lot as I've got another bigger saw, and in reality it's a bit of a dog anyway.

 

Thanks

[Megatron]

Pick the saw up and then hold only the recoil handle, how fast does it fall?

 

If the saw runs well/normal when you get it to start it would suggest to me that it is not a compression related problem. Usually saws with low compression are hard to start and have noticably low power in use. In severe cases they will only run with the choke on.

 

Does the saw race at idle?

[spudulike]

Does it fire at all? if not, given that it will run when warm, it must be getting some fuel through, I'd guess at too low compression (worn piston ring maybe) but once warm and everythings expanded a bit there's just enough compression to fire.

#

 

Erm - compression is always more on a cold engine due to the fuel/oil coating covering the piston and cylinder being thicker when cold and more liquid when warm.

 

Things I would check - make sure the choke is fully closed when the choke is engaged, make sure the throttle opener for starting the saw is opening the throttle when you take the saw choke lever off full choke and on to the next position.

 

Sometimes sterting the saw whilst holding the throttle wide open will get it going.

Agree with the earlier suggestion that the L screw may be turned in too much, if you undo it a little, the idle will need adjusting.

[samthescam]

Pick the saw up and then hold only the recoil handle, how fast does it fall?

 

If the saw runs well/normal when you get it to start it would suggest to me that it is not a compression related problem. Usually saws with low compression are hard to start and have noticably low power in use. In severe cases they will only run with the choke on.

 

Does the saw race at idle?

 

The saw was fine when it was going. It doesnt race at idle, but sits nicely. It also has plenty of power for a little saw.

[samthescam]

#

 

Erm - compression is always more on a cold engine due to the fuel/oil coating covering the piston and cylinder being thicker when cold and more liquid when warm.

 

Things I would check - make sure the choke is fully closed when the choke is engaged, make sure the throttle opener for starting the saw is opening the throttle when you take the saw choke lever off full choke and on to the next position.

 

Sometimes sterting the saw whilst holding the throttle wide open will get it going.

Agree with the earlier suggestion that the L screw may be turned in too much, if you undo it a little, the idle will need adjusting.

 

 

Checked the choke, its closing tight. infact I took the carb of to check this. And the throttle is opening when trigger pulled. I will try playing with the L screw now. Thanks

[samthescam]

Take off the air filter (top piece) and look down at the choke plate on the carb, put the master control lever on cold start position and see if the choke plate shuts fully. Sometimes the lever which activates the choke plate gets bent resulting in full choke not being achieved.

If not you could try a 1/8th turn anti-clockwise on the L-speed screw.

 

It's not bent. I will attempt to try the L screw.