Decompression Valve Install

[Captn Jack]

Hi all need some advice and help.
I have a Husqvarna Rancher 55 it's an older one from in the mid-'90s. I always could start but have not used it in a year. I went to start it and I don't seem to be able to pull the rope hard enough to get it to start. I check the pull with the plug out and all seems ok . My problem is I am 69 and it really hurts my arm and shoulder to try and pull it anymore. I had a friend who is a lot younger than me and pulled it and it started and ran like it always has. I bought a factory stock decompression valve (544200001)to install it and I see on the cylinder where there is a place to install one. It looks like I need to tap the hole but I am a little leery about drilling the hole which will go into the cylinder. I heard it should be about 1/8"right or smaller or larger? Also when I do it should I remove the head. I have been a heavy equipment mechanic all my working life so don't see any real problem with the install. Any advice will be appreciated though. Thanks.

 

[Bob Hedgecutter]

It can be done- the hole is pretty small, I believe well less than 1/8"- would have to fish out a cylinder and measure to confirm.
Problems I see- having to buy a tap (if you do not have one already) and it costing more than what a machine shop might charge? Damaging the interior cylinder plating by drilling the hole through, decomp not sealing because exterior face not machined flat (the valve seals on the face not the threads).

You could try a larger squish decomp- thicker gasket between cylinder and crankcase will increase squish and decrease OVERALL compression, so you would loose a little power, but it will become easier to start.
There is also another method of decomp involving cut to the exhaust port to allow gasses to escape.

Everything else on the saw in tip top condition? Does it start on the first or second pull each and every time, or do you have to yank that cord several times for it to fire up?
Good condition carb and ignition settings will help make the saw easier to start.
The odd thing being, a low compression saw (worn rings) will often be harder to start than the same saw with newer correct end gap rings.

 

[calamari]

I have been a heavy equipment mechanic all my working life so don't see any real problem with the install

But you're asking how to drill and tap a small hole in a simple 2 cycle cylinder head?
If it requires a flat surface around the hole for the valve to seal against, take the head to a machine shop. It'll be cheaper than the tools you'd need to buy to do it yourself.