Symptoms of too much timing advance

[Magic_Man]

What I'm getting at is even on a stock vehicle it's best to set at full advance and then check the timing at idle. You'll find a lot of mechanical advances that are stuck or improperly functioning. If you would set the distributor where it idles best and leave it you may have too much timing to start due to a stuck advance. Or the springs could be weak or broke and the late timing will cause excessive exhaust temps which will crack exhaust manifolds and intakes near the egr port. Or the advance could have too much range and have too much timing at full advance and you'll detonate or burn pistons.

Also, it's good to look at the timing through a sweep of RPM, at idle a loose distributor gear or timing chain will usually not show up. If either are worn the timing can be erratic at certain rpms and steady at others.

Agreed

 

[Al Smith]

Just a note which may or may not have a thing to do with timing .If you walk up on a saw with a D-handle it's telling something ,pull that SOB over like you mean it or it will try to pull your arm off.I fractured a bone in my hand from an 084 by not paying attention .Took six months before it quit hurting .

 

[Keith Gandy]

Just a note which may or may not have a thing to do with timing .If you walk up on a saw with a D-handle it's telling something ,pull that SOB over like you mean it or it will try to pull your arm off.I fractured a bone in my hand from an 084 by not paying attention .Took six months before it quit hurting .

I think I may have the same behind my right thumb from my 064

 

[Terry Syd]

Once I learned how to start one I haven't had one kick,give a half ass pull and it will kick everytime. A 064 is a good example,they have more timing and they are notorious for kicking but there notorious good runners too.

Start it like it owes you money and it won't kick.

My mate likes me to start his 064, I know the drill about bringing it over TDC and then pulling like you mean it. However, I didn't want to have to go through a starting drill with a little 029/390 every time I wanted to use it. I just wanted to grab the saw, pull and then start cutting. The 4 degree retard for starting in the coil allows me that freedom and helps protect the lightweight starting mechanism. The coil will go on a number of the Stihls.

 

[Terry Syd]

Question: I have an MS390(bought new) from the change over from the 039. No decompression valve, or such as the newer version. Since day one, my saw is such that it will snap back, and make you check your fingertips if you don't have the starter handle deep enough in your hand. Is this just variation in set up from the factory, or do earlier models in a model line tend to be slightly advanced in respect to timing?

The factory specs for the 029 have a 5 degree spread because of manufacturing tolerances. It can be anywhere from 23.5 to 28.5 degrees. I got that information right out of the Stihl shop manual. I couldn't believe it when I read it - 5 degrees! I expect that all the saws of that line have the same tolerances as the components are all the same. I've read of guys adjusting their ignition timing and adding as much as 8 degrees to one of these saws. I added about 6 degrees to my saw.

My saw also has a compression release, so with the ignition retard, the saw is a very easy starter. Just pull and go.

 

[CR888]

Performance and easy starting can work against each other, but engineers are at least on to it with some of the clever ignition modules today. Easy starting vs a modified advanced ignition can make a saw something that you give to your gorilla size mate to start. When working with saws and timber each day you get tired and learn to continue working under fatigue, it is just part of that work. Under those conditions a saw that behaves and starts consistently easy is important. Also as Terry mentions the starter pawls and mechanisms these days are often shared among models with varying displacement so can be adequate or small in instances. The components are more plastic today compared with years past and probably come from China. I have a 'D' handle for a ported 660 with a bit over 200 psi and it certainly helps when they bite, to me on a go-2 worksaw ease of starting is important.

 

[jmssaws]

When I cut timber I run a mild ported 395xp simply because I start it 50 times a day. Nothing worse than being a mile from the truck and your starter brakes.

 

[Moparmyway]

My 661 with the key filed a ton loved to run with both the 4700 and the 4701 mtronic coils. When I installed the European, non-mtronic coil, at mid throttle, or backing off the throttle in a cut, it started sounding like the chain was slapping something, a hammer like strike.
I had to file another key with less advance and that got rid of my little hammer wielding gremlins

 

[Keith Gandy]

My 661 with the key filed a ton loved to run with both the 4700 and the 4701 mtronic coils. When I installed the European, non-mtronic coil, at mid throttle, or backing off the throttle in a cut, it started sounding like the chain was slapping something, a hammer like strike.
I had to file another key with less advance and that got rid of my little hammer wielding gremlins

Pre ignition?

 

[Moparmyway]

Pre ignition?

I'm smart enough to know that I'm too dumb to be sure ..............
but ................
I believe it wasnt pre-ignition.
I believe it wasnt detonation either.
I think it was just too much advance

 

[smokey7]

Too much advance causes popping like a miss fire.

 

[Moparmyway]

Too much advance causes popping like a miss fire.

I hear you, but it didnt misfire or pop, it just did a little metal to metal hammering mid throttle.
Filing less off of a new key cured the problem

 

[Keith Gandy]

I hear you, but it didnt misfire or pop, it just did a little metal to metal hammering mid throttle.
Filing less off of a new key cured the problem

Thats odd. Maybe piston slap?

 

[Moparmyway]

Thats odd. Maybe piston slap?

Why would a less filed key eliminate the problem ?

 

[mdavlee]

I've advanced them too much and got a bad popping noise. Sometimes that tiny bit farther is just too much.

 

[Keith Gandy]

I've advanced them too much and got a bad popping noise. Sometimes that tiny bit farther is just too much.

Now my 241c did that after I ported it and advanced it too much. Popped or missed on topend in cut. Retared it and it stopped

 

[Keith Gandy]

Why would a less filed key eliminate the problem ?

Im out on a limb and gonna say too much transfer flow after ignition ?

 

[Moparmyway]

Im out on a limb and gonna say too much transfer flow after ignition ?

Huhh ?
Whatchoo talkin bout willis ?

 

[Keith Gandy]

Huhh ?
Whatchoo talkin bout willis ?

Just guessing!! Lol! Is it possible to have too much raw fuel in and not be able to combust it because of the advanced timing and cause the piston to slap the skirt?

 

[Lone Wolf]

I've never had a stihl pop but have had plenty of huskys do it.

My 288 did it all the time.