How to discern *and* do a timing advance? And...what of plugging a decomp-valve with a LONGER bolt, to boost compression?

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arborjunky
Joined
Jun 25, 2019
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Tampa-Area
Will start with the latter item (these are in-relation to my 590's "hot woods-port" project but also just to understand!) Decomp valves are often removed, am uncertain if the chief reason is their potential to fail, or their OEM characteristics (my understanding is they ALL cause some compression loss?)
I'd learned of filling-in the valve's hole with JB Weld, but then was shown a better, purpose-built plug for decomp's but it made me think "Why bother ordering&waiting for a bolt? I'll just go to Ace with my cylinder and get it there....but wait, if plugging that hole/recess boosts compression, and people have spoken of welding-in a dot of 4130 into the comb.chamber to reduce volume/increase compression, so what if I got a bolt that was longer-than-necessary, and let it stick-into the combustion chamber a couple millimeters?? Would use JB Weld 'as Loctite' when doing this, of course (would've done that when installing a purpose-made plug, anyways!)


Timing....I know the 590's(and many newer models?) are sensitive here, and that it may not even need it, and that before I'd even go do it I'd need to somehow measure to know IF, and HOW MUCH, to shave off the keyway on the flywheel.... ANY insight into how to measure/determine timing here would be incredibly appreciated, as would guides on doing a perfect job of the filing (I know how, but haven't found a guide that's taught me a way I'd feel confident "I'm doing this 100% properly"!)
/Saw a youtuber('mweba1') using this timing-gun, if that kinda tool is the only means then my question would be "Where are these guns, is it something I rent, is it something I go to an auto-repair-shop and offer them $$ to do the timing-test for me?" :)

Thanks a ton for any insight on these two, am doing a "2nd round" of work to my new 590 that I did a VERY mild woods-port on recently, goal is making it "as hot as possible for a work-saw", it won't be used all day for bucking in fact for a majority of my jobs I don't need the 590 my lil 355t is all I need to get through like 90% of my work...the 590 makes some of it easier but my 355t can do all I need to the smaller trees here in FL, heck 50-55' is the tallest tree I've done/been on this year!!
 
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arborjunky
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Jun 25, 2019
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Tampa-Area
Hate to jam-in a Q like this but expect anyone who can answer ^ my OP could answer this and this doesn't deserve a thread..What is the norm for oil% for you guys? I'd gone to 40:1, then 45:1 which is where I am now...Donny Walker says to go by the label (50:1) and I put weight on his opinions (should I be doing this or his he considered more like iron horse/tinman?) so it has me 2nd-guessing the "add extra oil" thing (40:1 is a big jump in oil%!!!)
 
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lostone
Joined
Jul 20, 2002
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Salt Lake, Ut.
One thing a lot of people don't talk about on the 590 is the under square design Echo implemented into the engine design. This design was setup for torque and most people that have this saw, If it's tuned correctly, will say it's a torque saw rather than a high rpm saw. I did some mild work on the one I did but not much more than taking the squish from .040+ to .022 and raising the upper transfers a bit, cleaning up the exhaust port some, the rest of my port timings where pretty much where I wanted them but I don't port for a race saw I'm just looking for a decent woods port on them.

Obviously doing the muffler mod, carb jet bypass as well. I had considered checking the timing and doing a timing advance if needed but even at 8K+ elevation it is running good so I haven't bothered with timing advance, pop up piston or going to a 620 coil. I use 88 octane, ethanol free gas and I don't want to have to deal with advancing it to much and end up having to run a higher octane fuel.
 

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