066 decompressor kicking off too soon

[Al Smith]

Decomp valve

As I said before,I am not familiar with the 066,I have 3 Stihl's,042 ,2, 048's,none with decomps.The 3 McCullochs 2,125s and 1 105,and the 1 Lombard,all have decomps.This style is a basic poppet valve,with a detent to hold them open.It takes an actual detonation in the cyclinder to kick them out of detent and thus off of decompression.I could pull them over for ever[this is a prevarication,because after about 8 times I have to rest]with the ignition off,and they would not come off of detent.Have you tried pulling the saw through with the ignition off,to see if it trips the valve?If it does,in my opinion,something is wrong with the valve,if not must be too far advanced timing.Okay,Stihl experts,your turn

 

[Dadatwins]

Like I said I would suspect timing is off on flywheel. Would try to reset position of ignition module. The 066 I use have some pullback to them but not to the extent that is descibed.

 

[Crofter]

I pulled the decompressor valve out of the 066 and found that the exhoust port in it was a mere 15 thou. dia. hole in one side. Don't know if it is the right one or if one size fits all. Anyway I drilled the hole out to approx. twice the diameter and it starts like a charm and kicks off nicely. A young boy or an old lady could start it now!

Frank

 

[ccicora]

So..... what does that make you????

Sorry frank I had to ask...

Later,
Chris

 

[Crofter]

"HAPPY"
I figured that might be coming! Lol! Good tip on the reaming Chris.
Am curious as to whether the wrong one was fitted from the factory. You can be just so much more casual now about starting that saw.

Frank

 

[rb_in_va]

Originally posted by Crofter
You can be just so much more casual now about starting that saw.

Is that a good thing?

 

[ccicora]

Frank,
I got the idea from Ed on boring out the valves. It worked really well on the 3120 hotsaw. So nice that when the saw is warm Gretchen can get her started and to the wood in preaty good time.

Later,
Chris

 

[Crofter]

rb_in_va;

Don't be picky now! lol! By more casual I mean that at least now I can start that saw without having to hold it to the ground by the handle, foot in the rear handle, and give a VERY determined pull. I don't like putting a saw in the mud or a foot of snow to start it.
I still find it hard to believe that single .015" diameter hole in the decompressor valve could be expected to bleed off any considerable amount of an 066's displacement in the time available. Doubling the hole diameter gives 4 times the flow. A bit less would have done the trick. It now is as easy to start as an 026 PROVIDING you hit the decompressor, but dont get confused. There may be other issues with timing and an unusually high compression that made this particular saw so mean, but it cuts so well I wouldnt want to mess with that! It is a somewhat tame ?????cat to start now, but as rb hints, it could still scratch you!

Frank

 

[Gypo Logger]

When I was out in the woods cutting some firewood with my son, I thought he said something about premature release.
Being kinda deaf and all I told him he'd go blind if he didn't stop doing that.
"Dad, I'm over here!", is all I heard back.
John

 

[Crofter]

Gypo, I think you need a wax job!

Frank