Symptoms of too much timing advance

[smokey7]

I have a question..... is the static timing on a saw engine similar to other two strokes in that it likes between 23*-28* btdc of static timing? Atleast in my other world some guys run huge timing advance then have it pull back some at wot. These are like the "epic" ignition systems. There has been major meltdowns bent rods twisted and cranks from them. Atleast when they ingest water with huge compression and advance they make a spectacular show. I have seen many many surf boats sink from engine parts going thru the hull. Timing is something I cautiously play with.

 

[Mastermind]

Remember that on saws like my 064 without a decomp, advanced timing is harder on the starter.

Bingo.

I build just works saws, so useability is my first concern.

 

[Magic_Man]

I wonder if saw timing could be adjusted using the same method as older distributor fired cars. Typically we adjust timing advance to find the highest vacuum at idle witch typically also is the highest idle point.

So, could you hook up a tach, measure idle, and keep advancing until you found the highest idle point ?

 

[MustangMike]

I think we are instead searching for the timing that runs best at WOT, w/o creating major problem with starting the saw.

 

[smokey7]

I understand that. What I am looking to find out is the timing curve of certain coils. Especially aftermarket ones that are the only option sometimes. I'm sure there are some that offer better timing curves.

 

[MustangMike]

The AM coil I got through Huztl for the 044 seems to perform just like the factory OEM.

 

[Jon1212]

Bingo.

I build just works saws, so useability is my first concern.

Well, it's a good thing you aren't starting them using your legs then, huh?

 

[ft. churchill]

My buddy at work was wanting me to port his jonny red 801, and was talking about an adapter to start it with a battery powered impact wrench.

 

[ft. churchill]

I think we are instead searching for the timing that runs best at WOT, w/o creating major problem with starting the saw.

Boy do I agree with you on that point. It's walking the fine line of getting a good balance between starting ease and wot performance.

 

[Terry Syd]

I'm going from memory here, but I recall the 066 coil has a 4 degree retard on starting. When I advanced my 029/390 project saw I had it kick back and ruin the starting pawl. I had to use my back up saw for the day. I bought a Chinese 066 coil (A$20) and never had it kick back again. It was worth every penny, not just for the ease of starting, but also to prevent a repeat of a broken starter.

Perhaps someone remembers the part number for those coils.

 

[Terry Syd]

I went back to AS and it appears the coil number is 1122 400 1314. It is used on a number of bigger saws 461, 066, 660 etc. It also appears to be limited to 13,500. However, it is the 4 degrees retard on starting that is the most interesting aspect of the coil.

The standard unlimited 'dummy' coil number is 000 400 1300.

 

[MustangMike]

Most modern chainsaw coils (OEM & AM) retard on starting (or advance when running, depending on how you look at it). I don't know how much.

 

[Al Smith]

The only saw I've every jacked the timing on is 6-10 McCulloch which is a points type ignition .It's set at around 30 advance .Any more than that is tough on your fingers .That saw BTW runs at around 15,500 rpm WOT no load .Then a larger carb and some die grinder work might have added to that .

 

[srcarr52]

I wonder if saw timing could be adjusted using the same method as older distributor fired cars. Typically we adjust timing advance to find the highest vacuum at idle witch typically also is the highest idle point.

So, could you hook up a tach, measure idle, and keep advancing until you found the highest idle point ?

That's a good way to kick a starter out of the block, melt down an engine or just be missing a lot of power. Always set timing off full advance, what you get at idle needs to be set by limiting or changing the mechanical advance weights. On high performance engines the vacuum advance gets removed and the mechanical advance is limited to about 10 deg with the heaviest weights and lightest springs, basically anything off idle is full advance.

 

[jmssaws]

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.

 

[Magic_Man]

That's a good way to kick a starter out of the block, melt down an engine or just be missing a lot of power. Always set timing off full advance, what you get at idle needs to be set by limiting or changing the mechanical advance weights. On high performance engines the vacuum advance gets removed and the mechanical advance is limited to about 10 deg with the heaviest weights and lightest springs, basically anything off idle is full advance.

I think that all depends on application, and will agree that's how I have set time on a high performance drag car. My Old drag car for example liked 32 degrees total in by 2500 rpm.

In reality we are comparing apples and bananas, I was just thinking out loud on a possible different avenue to set saw timing.

 

[jmssaws]

I've played with timing on a 066/660 more than I care to mention and I've found that one saw is different than the other.

One 66 might like 030 off the key the next 66 might want more or less.

There's a big difference between flywheel key way location and coil pickup location,it's not one size fits all.

 

[jmssaws]

I went back to AS and it appears the coil number is 1122 400 1314. It is used on a number of bigger saws 461, 066, 660 etc. It also appears to be limited to 13,500. However, it is the 4 degrees retard on starting that is the most interesting aspect of the coil.

The standard unlimited 'dummy' coil number is 000 400 1300.

The only limited 066 is a red light saw that I'm aware of, a few 064s were limited but rare.

 

[srcarr52]

I think that all depends on application, and will agree that's how I have set time on a high performance drag car. My Old drag car for example liked 32 degrees total in by 2500 rpm.

In reality we are comparing apples and bananas, I was just thinking out loud on a possible different avenue to set saw timing.

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.

 

[Jon1212]

I'm going from memory here, but I recall the 066 coil has a 4 degree retard on starting. When I advanced my 029/390 project saw I had it kick back and ruin the starting pawl. I had to use my back up saw for the day. I bought a Chinese 066 coil (A$20) and never had it kick back again. It was worth every penny, not just for the ease of starting, but also to prevent a repeat of a broken starter.

Perhaps someone remembers the part number for those coils.

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?