Brian Scott
Husqvarna
AA Class
What do you think? Time for a new piston? I discovered this carnage tonight after pulling the reed block out to check for cracks because my top end has been flat for the last 6 rides/weeks (but the bottom and mid has been killer) despite changing mains richer and leaner and repacking the silencer. This is a Vertex B size cast piston. Not sure how this happened. I checked compression 4 rides/weeks ago and it was at 198 psi, then looked up the exhaust port and the piston looked pretty good despite having nearly 3,400 miles and almost 300 hrs (180 hrs/2,300 miles since last top end). I'm not particularly hard on the engine. I ride single track in the woods in Western Washington usually lugging in 3rd gear just under the pipe, and I keep the jetting a tad on the rich side. The last few rides have been very wet and I drowned the engine twice in deep puddles requiring trail side triage to purge H20 from the cylinder and crank.
So here are my questions:
1. How did this happen/what are the suspected causes?
2. Where did the fragments go? The upper half of the cylinder and head look ok, but the piston is heavily gouged below the rings, but only on the intake side. No signs of cylinder or head gouging.
3. Do I need to spilt the cases to inspect the crank and look for fragments?
4. Could this possibly be the source, or a contributor to, the lazy top end I've been experiencing?
5. Can this happen to a forged piston, or be less likely to happen?
Thanks!
Intake side = not so good

Exhaust side = looks good.

Top = not bad for 180 hrs (I use Motorex full synthetic at 50:1 w/92 octane non-ethanol)

So here are my questions:
1. How did this happen/what are the suspected causes?
2. Where did the fragments go? The upper half of the cylinder and head look ok, but the piston is heavily gouged below the rings, but only on the intake side. No signs of cylinder or head gouging.
3. Do I need to spilt the cases to inspect the crank and look for fragments?
4. Could this possibly be the source, or a contributor to, the lazy top end I've been experiencing?
5. Can this happen to a forged piston, or be less likely to happen?
Thanks!
Intake side = not so good

Exhaust side = looks good.

Top = not bad for 180 hrs (I use Motorex full synthetic at 50:1 w/92 octane non-ethanol)
