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088 hydrolocking

Raj

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I've mentioned before how my one 088 with kick back and pull the starter cord out of my hand, tearing my shoulder and to ad insult to injury the handle will smash my other hand.

Coil and flywheel are good. Carb rebuilt tuned to factory settings. New decomp. Still did the same. Usually when cold. Once I get over the kick back it'll start. I thought it was a cold weather issue. Nope. Does the same in the hot weather. Only when first starting for the day.

I thought it might be an issue with my 088 but it does the same on the second 088 I have.

I'm thinking hydro lock.

Any input?
 

Nutball

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Sounds too rich when starting? Use less choke or no choke. I had a wood splitter do that a lot, and what I found was that it was loading up on fuel, and I had to start it with no choke or as little as I could or I wouldn't get it started for a week. Not hydro locking, which literally locks the piston so you either can't turn the engine, or it bangs to an immediate stop right after it tries to fire up. But, it seemed to be getting too much fuel to start. I can't imagine, though, how that would happen to cause it to kick back as if the fuel burned so slow it smolders the first stroke, then flares up during the second with a fresh charge of air. I learned before stopping the engine I'd have to bring it to an idle first instead of the usual shutting it off from full throttle. The spark plug eventually got changed which had a huge gap, so I don't know if that was the problem, but it made starting easier.

I used to have a problem with starting a 661. I can't remember if it would ever kick back, or if it simply flooded, but I tried to use the choke as little as possible on it even if it meant more pulls.

Maybe try holding the decomp valve down while pulling or during half of the pull?
 

Magnus

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You mean its so wet inside it can't compress it?
If so I bet plug get wet..

If not I think it ignites, perhaps a bit early.

Turn it of one and pull once, then try start it.
If its flooded and plug is wet after one pull you know...
 

Marc-Antoine

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With an hydro lock, you can't pass the first comp, even move at all, it's a dead stop. I just got that on an engine, carb valve didn't work apparently and flooded the air filter and the cylinder with gas.

With an ignition too early, you can pull slowly the starter chord all the way out, no problem, just feel the successive compressions. But if you pull it to start, the engine turns a little and Bam, takes out the handle off your hand. The piston doesn't have the time to pass the top dead center before the full development of the explosion, so it takes a full hit and inverts its rotation. Painful.
My big franken saw was a 065 with a 066 cylinder and did exactly that. It ran good but was painful to start. The problem came from the fact that the previous owner (or repair tech) put a 066 coil in it too. It isn't exactly the same coil's mounting points and the same flywheel setting. The ignition came too early. I had to pull really fast and strong to make it pass this bad point. Decomp valve didn't help a bit. It really hurts, I wrecked my right biceps with that (so, since this time, about 11 years ago, I always start my chaisaws with the left hand). After a few ouch, I was scarred in advance and can't pull it fast enough any more (more ouchys but still no start !). It took me a while to figure it out.
I took out the woodruff key of the shaft and move the setting of the flywheel a bit (half the thickness of the key in my case to be precise). Not too much, otherwise it's easy to start but you loose a lot of power.
 

Raj

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Great info.

I tried a different method. The saw travelled with the fuel cap loose. Decomp pressed in and the switch set to run. A few pulls on the cord. Switch to choke and start as usual. No issues today.

I'm thinking a partial hydro lock. I've noticed it only happens after the saw sits for a while. Fuel leaking into crank? Then sucked into cylinder? I've tried to hold decomp down before but it would still pop closed much to the discomfort of my finger.
 

Raj

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Both of them don't!

Edit: Sometimes, ok, often, I will store the 088 on the mill standing up. I wonder if that would cause my issue?
 

SeanKroll

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What about emptying the fuel after use, idling it dry, then storing it. Test afterward.

IDK, just guessing at options. Since it's only the first run of the day, it might be a stop-gap measure.
 

Magnus

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Water in fuel can cause hydro lock, a significant amount of fuel as well..
There is no partial hydrolock..
If there is anything above piston that can cause hydro lock it can get out thru exoust port or down in crank case.
A pull or two with plug out will let you know (kill switch activated) if you can't see anything on plug or on piston.

Have you checked for carbon buildup in exoust port and piston top?

Opening fuel cap to ease start has quite the opposite affect as you release the pressure needed to help fuel pump.
 

Nutball

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Opening the cap on they way to the job prevents pressure from forcing gas through the carb (probably due to a carb with imperfect seals)

Too much carbon buildup in the cylinder may have increased compression way too much.

Hydro lock would probably not feel like kick back, but just plain locking. 2 strokes tend to empty the cylinder of a hydro lock condition easily until enough rpm is reached to force pooled liquid from the crank case into the cylinder, such rpm is reached while cranking or just after the engine starts firing.
 

Raj

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Good info!

2nd day. Put the saw to run, a bunch of pulls, then choke and start normally. No kick back or piston stop.
 

Nutball

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I'm going to guess the kick back comes from a flooded rich mixture.

1) Piston goes up, fuel ignites and burns very slow as the piston goes down
2) exhaust port and transfer ports open adding more fuel and air, AND disturbing the flame front causing a faster burn
3) Piston goes back up, closes ports, and tries to compress an already burning mixture.

That's one theory, but I'm certain I have felt kick back on the first stroke from a few engines almost like an explosively lean mixture (which contradicts other conditions involved), or early spark which seems impossible.
 

Magnus

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Opening the cap on they way to the job prevents pressure from forcing gas through the carb (probably due to a carb with imperfect seals)
The main inlet valve is what hold pressure as well and most tank vents regulate pressure unless they are one way valved.
Even if it shakes ever so much it will not build more pressure than needed or else every saw riding on a machine would explode!
Hydro lock would probably not feel like kick back, but just plain locking. 2 strokes tend to empty the cylinder of a hydro lock condition easily until enough rpm is reached to force pooled liquid from the crank case into the cylinder, such rpm is reached while cranking or just after the engine starts firing.
Hydro lock feel like you put a M10 nut in cylinder. There is no way around it and it doesn't go away unless the fluid escape to case or muffler. no need for rpm, just back a bit so ports open and down it go...
Rods have bent and busted from hydrolocking...
 

Frankie

I Build and Run Ported Saws !
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D4B089E3-7C4A-4D6B-A465-00D5B9F427E5.jpeg not conducive to performance lol ... hard to fathom a chainsaw hydro locking as per definition ... a vehicle crossing a stream under hard throttle yes !
 

Magnus

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Its rare.. I have seen it a couple times on 15 years repairing and looking at the saws I got. One time from water, one time from oil.
It is needed quite a bit to get enough to fill compressed volume above piston. A squirt from crankcase won't do it and it needs to be running so there is momentum and forces. I doubt you bend rod with puller...

I do get to see a lot of odd stuff. I bought up lots from dealers between 2 saws and 40 cubic meters of saws and parts. Parted out well over 1500 saws now and got 800 in collection, 4-500 or so doubles and "to be parts"..
+ costumer saws...
So I see a bit of odd stuff...
 

Frankie

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800 saws + parts / accessories is A LOT OF GEAR ! A guy could fund a retirement
 

Magnus

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It sounds a lot and looks like a lot, but it really isn't. In the collectors world I am no big fish. There are those with really large collections.
I spend way to much time on chainsaws, that's for sure.

But with collecting and having a saw shop it generates a lot of experience fast. I get to see a lot of saws with in a model. Not just old, although I do enjoy that more.

I have seen stuff on saws I thought was impossible. Saws with electronic ignition run backwards, run without carb, run without piston ring..
Odd stuff...
 

Raj

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I ran my original 088 today. Turn to run, pulled the cord a number of times and then start as usual. Choke, it burps, set to hi idle, start up.
No kick back. What was going on before when it would pull the start handle out of my hand?
 
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