My saw ate its decompression value.

[Treedusty]

While starting my stihl 034super the guts of the decompression valve dropped into the cylinder and picked a fight with the piston.
This happen when I pressed the value down to pull engine it over. Piston came off second best... And is distorted and pinching top piston ring. All will need to be replaced. Valve was AM and cost ten dollars.
Anyone had a similar experience?
How rare is this? And are they generally meant to last as long as a cylinder?
I not keen to put another decompression value on... Do I really need one one a 60cc saw?
Valve, piston and jug all quality AM and done only 8 hours..
Cheers.

 

[cgraham1]

It is completely unnecessary in most 60cc saws. I would put a plug in it, and never worry about it again.

 

[CR888]

I just bought 6 decomp plugs off the bay for about ten bucks delivered from china. They work geat and are one AM product that is just a short bolt with washer so not much can go wrong. D/Dave should have them, sorry to hear about your decomp destruction!! While I'm not douting the damage it caused you should pull the jug and take some pics of the slug and post em up. I bet you may be able to repair the damage with new rings and maybe piston with some crafty advice from the membership.

 

[blsnelling]

I've never seen that happen.

 

[CJ1]

I think the key is the aftermarket decomp valve. Or was. Like Clint said plug it and forget the decomp. CJ

 

[grizz55chev]

Never needed a decomp for my 036, delete it and rebuild. My 036 is my go to for firewood .

 

[LowVolt]

How much is an oem decomposition valve? I honestly could not trust anything aftermarket when it comes to the top end.

 

[Big_Wood]

i plug all my work saws. if it's not there it can't be a problem and a problem on the hill is never good. had a partner have the same thing happen to his 460. luckily i had a plug in my tool kit and the damage wasn't to end his day. a plug fixed it and he's still running it. was a new 460 freshly ported too. dang that would have sucked if it ruined it. not sure what the piston looks like cause in real life people don't remove mufflers to look at pistons lol.

 

[wde_1978]

+1 on deleting the DeCo valve and plugging the DeCo hole.

My Dolmar PS-7900 is the largest saw I own, non of my saws feature DeCo valves nor do I crave any!

Sorry to hear about Your misfortune!

 

[grizz55chev]

My 044 will bite you if you don't decomp. Anything smaller youll be fine without.

 

[cedarshark]

The decomps in Stihl and Huskie are somewhat different. Stihls decomp has direct exposure into the top of the cylinder.If the pin on the decomp valve comes loose,it drops onto the top of the piston and does significant damage. The huskie has a very small hole in the crown of the cylinder that prevents the decomp pin from dropping in to the cylinder. Although I do plug all decomps at 60cc and below, Huskie seems to have a better design.

 

[a. palmer jr.]

I've never had any trouble with de-comps, I use them in all my Husqvarnas except my 346XP came without one and doesn't appear to need it. It does save wear and tear on the plastic starter pawls. Most of the Stihl saws I own don't have one except my 361 and I use it.

 

[cedarshark]

I've never had any trouble with de-comps, I use them in all my Husqvarnas except my 346XP came without one and doesn't appear to need it. It does save wear and tear on the plastic starter pawls. Most of the Stihl saws I own don't have one except my 361 and I use it.

Another "less than desirable" Stihl innovation....plastic starter pawls. And I like Stihl.

 

[Big_Wood]

The decomps in Stihl and Huskie are somewhat different. Stihls decomp has direct exposure into the top of the cylinder.If the pin on the decomp valve comes loose,it drops onto the top of the piston and does significant damage. The huskie has a very small hole in the crown of the cylinder that prevents the decomp pin from dropping in to the cylinder. Although I do plug all decomps at 60cc and below, Huskie seems to have a better design.

All the newer huskies are coming with them in the combustion chamber now. Only benefit I see is they may bleed off compression faster. It has been said that decomps save recoils. This may have some truth but If you start your saw correctly it won't be an issue. Always engage starter pawls before pulling hard.

 

[Definitive Dave]

Just this week I had a customer (pro builder) let me know about a decomp valve (from NWP, so not the cheapest) that dropped the center down into the cylinder on a customers freshly serviced OEM MS441.
Looks like the guts came loose from the cap and just fell into the cylinder above the piston and got hung in a port - not pretty.
I am sending him a nice used OEM jug and a new OEM piston as replacements. I have never seen this before and have sold thousands of AM decomp valves from both farmertec and NWP.
I think the NWP valves look nicer and they are about .26 more per each than the farmertec valves, but......