Stihl 461 kicking back

[Old2stroke]

Because the handle either stops dead or more frequently pulls back, right out of your hand with incredible force. Feels like it's gonna break your finger. That thing hit my leg once and left a big bruise, even thru my insulated pants. The top of the saw has black marks on it from the rubber striking it. Until you have it happen to you, you can't imagine it. I have a bud at work with a 261 that is shelved for the same reason. Another has a 361 also shelved. Both of them are waiting on my fix, for theirs. Mine is a "home saw". There's is a work saw for the fire department. It HAS TO WORK when needed.

The only way to really determine what is going on is to use a timing light and find out where the spark is occurring with respect to TDC (spin engine with drill method). If the coil is one that has retard for easy starting, the spark should occur at 10-20deg BTDC, if it has fixed timing the spark should never be more than 30deg BTDC. This will confirm if coil timing is correct and FW has not rotated on the crank. If timing seems right, you might be having a detonation issue. In a normal spark/fire event, when the spark occurs and ignites the fuel, the flame front expands at a known "slow" rate and the timing is set so that maximum pressure occurs just as the piston goes over TDC. With detonation, when the ignition occurs, the whole fuel charge explodes at once (no regular burn) and exerts extreme pressure on the piston and can drive it backwards if it occurs slightly BTDC . Detonation is normally found in a hot engine running on a lean fuel mix with fuel that is too low in octane. Saws that have had a lot of use can have a significant buildup of carbon which will effectively increase the compression, and detonation is a function of compression ratio and the octane rating of the fuel so if the "rip it out of your hands starting" has gradually been getting worse, it could be a carbon issue. Inspect the top of the piston for buildup, maybe try a higher octane fuel? Set the tune as rich as possible. If carbon is an issue, it's tear down time.

 

[ZeroJunk]

Because the handle either stops dead or more frequently pulls back, right out of your hand with incredible force. Feels like it's gonna break your finger. That thing hit my leg once and left a big bruise, even thru my insulated pants. The top of the saw has black marks on it from the rubber striking it. Until you have it happen to you, you can't imagine it. I have a bud at work with a 261 that is shelved for the same reason. Another has a 361 also shelved. Both of them are waiting on my fix, for theirs. Mine is a "home saw". There's is a work saw for the fire department. It HAS TO WORK when needed.

I am talking about the normal compression of the saw is enough to push the decomp out even though it does not fire
If it is a Stihl you take your left thumb and push it back in. Or, I do anyway.

Kick back is something else.

 

[lone wolf]

Sorry if I used the wrong terminology. When I attempt to start the saw, she locks up and pulls the starter cable out of my hand. The saw is a few years old with VERY low hours.
The decomp button pops up every pull.

Those who have experienced this know it's NO FUN.

TomJV

Is the original Stihl Elastostart handle on there, or has it been replaced with a solid plastic one? I just fixed a saw for my buddy just now, and that was the problem. If you don't know what I mean, take a pic of the handle from above, facing down so I can see the top.

 

[Lightning Performance]

The needle valve holds pressure. Could you explain what is happening?

Slow leaks sometimes take a day to load the crank case. Fuel will cook in the sun and push it by or in a heated building.

 

[Lightning Performance]

The best way to test an ignition lead time is to shut off the switch. It will hydrolock without spark.

K.I.S.S.

 

[ZeroJunk]

Pretty sure this is a timing issue. If it is hydrolocked it is like you hit a solid wall. There is no kick back. The rope just stops. Had one the other day and I thought something had broken in the saw since it is rare in a chainsaw by comparison to blowers for whatever reason.
A MS461 has retarded timing at start. That may have failed.
The decomp kicking out is meaningless. All larger saws do that as often as not without firing at all.

I used 066 and 064's for years with no decomp.
You have to understand that it is going to fire before the piston reaches top dead center.
And, if you get lazy they will jerk the rope out of your hands every time.
When you get ready to start those things you have to GO.

And, unfortunately I have to tell people more often than I like that they just can't start one anymore.

 

[Old2stroke]

We seem to have trouble distinguishing between hydro lock and vicious kickback. If it's hydro locked, you won't be able to rotate the engine a whole revolution, it will come to a DEAD stop without any sign of ignition or pull back on the cord and if you drain the fuel from the spark plug hole there will be a lot. If the engine turns over, coughs and tries to jerk the cord out of your hand, THAT IS NOT HYDRO LOCK, usually a timing issue due to a rotated flywheel (stripped key), defective coil, etc. or could just be normal for some saws with a lot of fixed advance timing.