McCulloch 25cc strimmer (curved shaft) screeching

[JKScotland]

Hi folks, I'm looking for some advice.

I've got a curved shaft McCulloch 25cc strimmer - lightweight thing.

It often screeches / nearly seizes when running sometimes - sounds like it's coming from near the bend in the shaft. The drive shaft inside is flexible with square ends and they don't look worn, so I don't think they're slipping. It can sometimes stall the engine. Grease has previously been added at the grease nipple (up near the engine end, nothing near the curve) so I don't think that's the issue.

Is there something that can go wrong with these curved drive shafts to cause it to jam like this?

 

[Burnerman]

I think it would be a good idea to remove the entire drive cable and make sure its greased all the way.....it should be possible to release the spool hub to pull the thing out.
I believe from memory the spool bolt has a left hand thread, but best not quote me!
John

 

[lostinthelight]

I believe from memory the spool bolt has a left hand thread, but best not quote me!
John

What I have generally found found is that if somthing spins, ithe retaining nut or bolt usually undo in the direction in which it spins.
litl

 

[Burnerman]

Yep, that's a pretty good rule of thumb.
Curious though, car wheel nuts near side don't apply yet HGVs do!
John

 

[lostinthelight]

Yep, that's a pretty good rule of thumb.
Curious though, car wheel nuts near side don't apply yet HGVs do!
John

Not quite sure why that is with wheel nuts but I was thinking more on the lines of where the nut was on the centre spindle.
litl

 

[Burnerman]

It's a bit of a different scenario with wheel nuts......they also rely on the taper to lock them, as well as distortion of the rim when they are tightened (steel rims) helping to keep them secure.
Back to the problem.....it's sure to be a left hand bolt, and I've had a couple of strimmers where the drive tube was worn through
John

 

[lostinthelight]

...it's sure to be a left hand bolt, and I've had a couple of strimmers where the drive tube was worn through
John

I didnt know that type ran long enough to wear the tube through
litl

 

[JKScotland]

So I have had the drive shaft out (weeks ago, sorry can't remember whether it was a left hand thread or not!)

I oiled the entire shaft, didn't have grease to hand. Seemed to be a bit worse after that!

John, when you say drive tube, would that be the same tube as the external tube? Or is there an internal insert that the shaft spins inside?

Thanks again.

 

[Burnerman]

Some machines have nylon bushes inside the external tube (drive tube) that help centralise the whizzing shaft within.....whether or not these are available or even removable I don't know. Certainly grease would be a better lubricant for this one!
John