Ryobi Chainsaw - Tough Cord Pull

[PM1035]

I took another look at it and there’s nothing cracked or broken. The plastic pulley teeth that engages the flywheel looks chewed up. But is always in contact with the flywheel. Why is this plastic?-cheap garbage to me.
I didn’t notice that when the piston travels to the bottom point is when it sticks and is hard to pull. Once past that point you can feel that ok, this is the normal feel when pulling the cord. Here’s some pics....

Chewed up plastic.....

Nothing cracked...

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[Ronie]

Even some of the pro saws have plastic pulleys. When you looked at the piston did you pull the muffler and look at it or did you look in the plug hole? If you didn't pull the muffler You should and see what the piston skirt looks like.

 

[PM1035]

Ok not sure how to pull the muffler but I’ll do it.
I’ll take some pics.....


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[Mauser]

That pulley is SHOT. And it is your problem. I have seen this exact problem on cheap plastic Poulans. When the teeth get that badly damaged, the pawls cannot stay engaged when you pull the cord, so the engine does not pull through after the motion starts. What you are feeling is the starter pulley jumping from one tooth to the other, and each time that happens, the motion of the engine stops (and it happens at the peak of the compression stroke), so the sudden engagement on the next tooth has to overcome the inertia and compression of the engine each time.

And the guy in that video that said it was some sort of vapor lock is a total IDIOT. Vapor lock is in the fuel system, NOT in the engine, and it could NEVER cause an engine to stop turning over. HYDRAULIC lock, from a liquid (NOT a vapor) inside the cylinder would stop the engine from moving completely, so even that cannot be happening is his stupid video clip. And besides, ANY engine in good shape without a compression release will have that same type of slow compression resistance when pulled over slowly!

 

[Ronie]

That pulley is SHOT. And it is your problem. I have seen this exact problem on cheap plastic Poulans. When the teeth get that badly damaged, the pauls cannot stay engaged when you pull the cord, so the engine does not pull through after the motion starts. What you are feeling is the starter pulley jumping from one tooth to the other, and each time that happens, the motion of the engine stops (and it happens at the peak of the compression stroke), so the sudden engagement on the next tooth has to overcome the inertia and compression of the engine each time.

And the guy in that video that said it was some sort of vapor lock is a total IDIOT. Vapor lock is in the fuel system, NOT in the engine, and it could NEVER cause an engine to stop turning over. HYDRAULIC lock, from a liquid (NOT a vapor) inside the cylinder would stop the engine from moving completely, so even that cannot be happening is his stupid video clip.

I agree that the pulley is shot but he says that it gets harder to pull over at the bottom of the stroke.

 

[Mauser]

... but he says that it gets harder to pull over at the bottom of the stroke.

How would he know? He said it pulls over just fine with the spark plug out!

 

[Ronie]

I forgot he had said that.

 

[PM1035]

Yes it does get harder when the piston reaches the bottom. I wanted to see the piston travel when I put my thumb over the SP port. It always got harder at that bottom point. I just don’t feel the plastic gear skipping but I’ll check it out again.


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[Mauser]

Yes it does get harder when the piston reaches the bottom. I wanted to see the piston travel when I put my thumb over the SP port. It always got harder at that bottom point.

You have an interesting way to "see" inside the engine. Do you have a transparent thumb?

And frankly, your words do not make much sense. The intake port on a 2-stroke engine opens up way before the "bottom" of the stroke; the motion of the piston moving down is what causes the fuel vapor to be pushed/sucked into the cylinder above the piston. So even if you had excessive liquid inside the case, it would not be binding at the "bottom". AND, in that case, you would NEVER had been able to start it while it was still hard to pull over - liquid gas does not burn!.

 

[Ronie]

Mouser is probable right and all you need is to replace the the recoil but it cost nothing to remove the muffler and check out the piston. To remove the muffler, remove the top cover then remove the two nuts or bolts on the front of the muffler.

 

[Ronie]

When he said it was harder at the bottom of the stroke, I was thinking that it might have some transfer below the exhaust and it was creating a drag on the the piston. If so that may have been what messed up the pulley.

 

[Mauser]

By the way, when I said the jump happens at the "peak" of the compression stroke, that does NOT mean at the top, it means some point BEFORE TDC after both the exhaust and intake ports have been closed during the upstroke. Perhaps my use of the work "peak" can be quibbled with, but I was trying to convey the idea that the increasing resistance of the compression as the piston was moving up eventually causes enough resistance that the starter pulley could no longer stay engaged on those chewed up plastic teeth.

 

[Mauser]

Two things to consider besides just replacing the plastic pulley -

First, make sure those two metal pawls on the flywheel are moving totally freely, so that they quickly drop down into the base of the teeth on the starter pulley. Shoot some WD40 or something under them and wiggle them back and forth to clean it out under there.

Secondly, when you go to start the saw, do not just grab the handle and jerk. Start just slowly enough that you can feel the fist compression stroke against the cord, then give it the good pull; that will ensure the pawls are well seated against the teeth and not jump over the top, chipping them, when you start that first jerk.

 

[PM1035]

You guys are incredibly helpful and it’s a great learning experience for me. Here’s two videos. First one I turn the flywheel by hand with no pull cord and felt that binding up in the same piston position.There’s free movement for about 180 degrees and then I feel the binding.

The next video is observing the plastic gear engaged with the flywheel and it just doesn’t seem like it’s slipping. I will change it though since it’s a cheap fix and per your advice and also I will remove the muffler and observe. What ya think?

Turning Flywheel by hand...


Observing plastic gear.....



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[grizz55chev]

You guys are incredibly helpful and it’s a great learning experience for me. Here’s two videos. First one I turn the flywheel by hand with no pull cord and felt that binding up in the same piston position.There’s free movement for about 180 degrees and then I feel the binding.

The next video is observing the plastic gear engaged with the flywheel and it just doesn’t seem like it’s slipping. I will change it though since it’s a cheap fix and per your advice and also I will remove the muffler and observe. What ya think?

Turning Flywheel by hand...


Observing plastic gear.....



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Magnets passing the coil at TDC.

 

[Ronie]

make sure your magnet is not touching the coil

 

[Mauser]

Your videos simply show that your engine has normal compression. If it did NOT do that with the spark plug in, it would not run at all. Just to try and convince you that what you are showing is totally normal, consider that one of the simple tests to check decent compression is to lift the saw by the cord and see if it turns over just from its own weight - if it does not at least stop in jerks as it hits each compression stroke (like yours is doing), then you can be pretty sure the p&c is toast.

Turning the engine over slowly proves NOTHING for your problem. The issue is how the starter pulley stays engaged when the cord is pulled FAST, so that it hits a quick compression pulse that tries to stop the engine from turning - THAT is what causes the pawls to jump those damaged teeth.

When you start a saw in good condition, the greatest resistance is when the engine first starts to turn and hits that first compression stroke, but then the momentum of the spinning engine and the pull on the starter cord causes it to turn past each subsequent up-stroke fairly easily, and you do not feel each pulse of resistance. But when your damaged pulley skips on those teeth, that lets the engine STOP turning instantly, so that when the pawls slam into the next tooth, you feel like the engine just locked up. That sensation is worse than when you first start pulling the cord because your arm already has momentum, and the inertia of the engine combined with the peak of the compression stroke is hard to overcome.

 

[PM1035]

Got ya. Thanks! I’m going to order that new pull cord gear. Curious to see how it does.


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[PM1035]

If the recoil is the problem they are pretty cheap.

View attachment 717426

Thanks for the info Ronie. Can’t beat the price at $9.


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[Okie294life]

My 038 was doing that and it needed a carby kit. If the carb is crapola it will dump fuel and be a beeotch to start, may even lock up. May try kitting it or buying one of those cheap 5$ carbs from China. Since your saws from China it won’t hate on you too bad.