Husky 141 Rebuild - Aftermarket Piston Issue

[rhonddaboy]

Hi all

Just re-stripped down a relatives Husqvarna 141 chainsaw after it stopped working after only 2 fills of petrol - light intermittent work.  Initially I stripped this saw down and rebuilt the engine after piston scoring due to it being run on too lean a petrol/oil mix (or, as I suspect no 2 stroke in the mix!) - dont loan your saws!

 

The piston ring was also seized in the piston ring slot along the scoring mark.  I rebuilt the engine using the original Husky crank case assembly - still a smooth bore suprisingly (no scoring issues - but sanded with 600 grit) but with another aftermarket piston, wrist pin and circlips.  After much head scratching I located the discarded circlips and found one had its 'loop' ends sheared off (photo).  I can only assume that this metal created the linear scoring and obvious loss of compression and failure to run. 

 

I now plan to purchase another aftermarket piston (40mm) but discard the supplied circlips and purchase and install OEM ones.  Maybe I'm just unlucky with the aftermarket circlips but searching the web suggests poor quality materials materials used in these key parts causing catastrophic failures like the one I encountered.

 

Interesting to see if other members have experienced sililar problems with AM kits?  

[spudulike]

Oooh, thats a nice one, whats the bore like? 

The circlip failing is a common issue on cheap no brand pistons. Husqvarna use them and they always seem fine but the aftermarket ones are typically much softer, less springy and the tab can come off like yours.

Best to fit new OEM or re-use the original ones.

[rhonddaboy]

Thanks for your views. The bore is suprisingly smooth to touch despite the piston score marks - suppose the alloy coating within bore is quite hard in relation to piston/circlip. Having said that it did score the piston ring which is brittle and hard cast steel? Sadly I tossed the original OEM circlips - was unaware of their quality. Big regrets now. Saying 'live and learn' applies here.  Now ordered OEM ones, but like most things 'not in stock' - so on back order.

[adw]

That circlip has not lost its end, that is exactly as it should be, the clip with a tail is not standard.

[spudulike]

5 minutes ago, adw said:

That circlip has not lost its end, that is exactly as it should be, the clip with a tail is not standard.

Agree with that, I was just focusing on the damage. Looks like either the saw had a loose bit of debris in it or the big end is spitting out bearing cage white metal.

Very strange that the bore is free of damage. What are the tops of the transfer ports like?

[adw]

I have to confess i use the Stihl circlip fitting tools to fit tailless clips, they work really well.

[spudulike]

Just now, adw said:

I have to confess i use the Stihl circlip fitting tools to fit tailless clips, they work really well.

Who was it you work for

[adw]

I know, but they are a real bitch to fit and these tools are so good, maybe Husqvarna could copy them, have you eve tried them?

[rhonddaboy]

I will try to take shots of the bore/ports tomorrow and take a look at bearings and crankase assembly for debris. 

[spudulike]

29 minutes ago, adw said:

I know, but they are a real bitch to fit and these tools are so good, maybe Husqvarna could copy them, have you eve tried them?

No, I have a favourite pair of pliers that I always use to great success.