Chainsaw Repair
Husqvarna - Stihl - Poulan - Jonsered - Dolmar chainsaws and more => Husqvarna => Topic started by: waynec on December 21, 2015, 10:25:36 pm
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I'm working on a Husqvarna 51 chainsaw. Replaced the piston/cylinder 5 years ago with aftermarket parts - worked great for 5 years.
Recently lost compression
replaced piston/cylinder/ring/bearing with another aftermarket kit.
Compression good - saw started up, ran for 1 minutes, jammed/seized.
Ordered another piston/ring - saw started up, ran for 1 minute, jammed/seized.
I'm a glutton for punishment so ordered a full replacement kit piston/cylinder/ring - and again after 10 seconds of running jammed/seized
Went back to look at the current/previous pistons and the scoring is the same location on all. Assuming there's something breaking apart and causing the similar damage:
Inspected the ring, looks correctly orientated.
Inspected the retaining clips, look good, in place, no damage.
Inspected upper bearings, look good, no damage
I don't see any inside damage that is throwing metal to cause the scoring.
I'm having 1 last kit sent to replace the last one - any thoughts on what could cause this similar problem?
Do these cheap kits need to be honed/polished in any way - they come together smoothly and look ready to install.
Keep in mind the cylinder/ring/piston were replaced as a set and took on similar damage without heating up.
Plenty of oil left behind, lubed it up and pulled it 20-30 times before starting and did not feel any issue when pulling.
Pictures attached to show location of damage. Thanks for any help before I give it a last try with the replacement parts.
-wayne
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First guess would have been cir-clip. Next crank bearing good? Cage broken etc.
You are smoothing out the previous damage in cylinder?
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Check crankshaft bearings and rod bearing. That looks like damage from foreign material. Bearing are probably coming apart.
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thanks for the feedback. Smoothed out damage when replacing just piston, but last replacement included both piston/cylinder. Upper bearing (that lives inside piston), looks good. Will pull the lower bearing and check for damage in the lower camshaft area under the piston. I think that's the only area that wasn't replaced.
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Big end rod bearing and crank bearing cages etc. Look at them closer.
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Is that a decomp hole that lines up with where the damage is?
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Yes. Decomp hole is lined up with score.
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Same decomp on all cylinders?
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the original cylinder did not have the decomp hole. The 1st aftermarket cyclinder (which is made for 51/55) and all subsequent ones have the same hole / same location. I've been capping the hole with external bolt that was included with original replacement cylinder.