rhonddaboy

The piston was an aftermarket Golf piston. There is a difference of c+3mm from the centre of the wrist pin to the top of the piston between OEM and aftermarket version from the supplier! I take the good and obvious point on paper gasket though. Sensible option here to send it back.

Mmm... wish I had your advice before purchase. Anyway, 'compatible' aftermarket piston arrived - 40mm - problem now that piston top hits top of crancase slightly before tdc. Just about to give up! Heres a thought - can I add a crancase gasket (3mm will suffice cut from high temp gasket sheet) to give clearance at the same time ensuring minimum combustion volume? Thinking aloud - this may/will affect porting?

You could be right. Anyway will give it a go - not to prove you guys wrong - but as as a personal challenge. When completed I will upload hopfully a video of it performing, or not. Either way 50/50. If it doesn't suspect I'll get a Farmatech crancase assy since this saw is only used lightly for firewood. I know... few days time I may get: ' I told you so'. 😉

Here's an image showing scoring at the edge of one of the channel ports. The depth of scoring is abot 1mm beyond that - to the top of the cylinder it is smooth despite visible discoloration. Well, have a replacement piston, wrist pin and circlips. Will use some 600 grit on bore and rebuild. Will let ypu know the outcome in the next few days.

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

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.

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?