Strange Leaf Blower Starting Problem

Forums: Spark Plug, Carburetor, Leaf Blower, 2-Stroke, Magneto
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I've got a Ryobi 310 BVR leaf blower, with a 31cc 2-stroke engine, which I bought used ($75) at least 15 years ago and while it's had it's ups and downs, it's been remarkably dependable. I had to replace the carburetor ($15) a couple of years ago, which gave the blower a whole new lease on life.

https://drive.google.com/uc?id=1Grg6kQeLXn8p1Qr-RlswF8jmo0tZziPi

Here more recently, I gradually seemed to have trouble getting the blower started and running - until now it just won't start at all. Thinking that the carburetor was plugged again, I purchased a new one, and this time the "kit" came with a carburetor, new primer bulb, fuel filter, fuel lines and even a new spark plug. All for $14 (not bad).

https://drive.google.com/uc?id=1VBIB8aJkkUe3EzEiPlyRouffVkSBuR3U

I swapped everything out and reassembled the blower - but no luck on getting it started. On the last carburetor swap, the blower started on the second pull.

This problem actually seemed more like an ignition problem. This seemed all the more strange, since I had just installed a new spark plug - although the old spark plug was still in pretty good condition and only showed a little bit of carbon deposits. Regardless, the new spark plug was essentially brand new.

https://drive.google.com/uc?id=1yPQUgBQR6uYLN5mnAnAfKcXAuxPR9dkG

https://drive.google.com/uc?id=1v-ngWkEpzqPflNhBW88VMb5KPF1aDjIG

This blower has a magneto to generate current from the rotation of the flywheel and send power to the spark plug - and to generate a spark to ignite fuel in the cylinder. So, I pulled the spark plug and with it attached to the spark plug wire and rotated the flywheel, but I observed no spark at the plug's tip. I even tried swapping out the old spark plug, which I knew was working the prior week. But nothing. So, using my voltmeter, I checked to see if the magneto was even sending power to the spark plug when the flywheel was rotated. And yes, current was definitely being generated and registering cyclically on the voltmeter.

So, the problem seems clearly attributable just to an issue with ignition, and a lack of spark being generated by the spark plug. I guess I should check the continuity of the spark plug, from the head to the tip. The thing I don't know, is what amount of current should be being generated by the magneto? I can't imagine the magneto would somehow being generating too little current, although I can't say I know that for sure. I think I'll stop there and see what suggestions or questions people recommend. And yes, I know that for my $75 I've probably more than favorably amortized my original investment over the past 20 years. I just like to fix things that are well . . . fixable.

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@CDobyns,

Forgive me if the answer to this question is "Of course." , but thank me if the answer is "Oops." When you checked for a spark with the plug out of the engine, did you ground the plug to the engine?
It may have lost enough compression ( either through the rings or valves) in the last couple of years to affect the starting. When the engine is cold the piston/ rings don't seal like they do after it warms up. I don't know, but that spark gap looks too tight to me. Some plugs are way off out of the box.

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@CDobyns,

If it seems easier to pull the rope, that means it has lost compression.

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@CDobyns,

Oh, about the current- A car engine plug gets about 30-50,000 volts. I figure a plug is a plug regardless of the engine size, so it should require about the same current.

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@Ponderer,

Okay, some good (albeit slightly embarrassing) suggestions from Ponderer.

First off, in response to the initial question - I'm chagrined to admit that I did not ground the spark plug when testing/observing for a spark. It's difficult to categorize how different kinds of "dope" I felt like, when I read that. It was made all the worse, as I was apparently canny enough to know to attach to the spark plug wire and the ground wire when I was successfully testing the output from the magneto with my voltmeter. Clearly I will need to "clip" the spark plug to the engine block and check again for the presence of a spark (which I'm already ashamedly 100% confident I'm going to observe). After that is confirmed, then I think we're back to fuel/carburetor as the problem source.

And no, there is no noticeable difference in the resistance when using the starting cord, so I'm already (a little more) confident that we're getting compression in the cylinder.

More to follow, but thanks for the good (semi-fun) wake-up call on grounding the spark plug . . .

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@CDobyns,

You'll appreciate this. I used to do metalwork/ welding. A guy came in looking for a job and he had to take a welding test. They had a metal table with the ground clamp on it, but he was holding the piece he was trying to weld in his hand. It wouldn't strike an arc, and a coworker told me to tell him to prop his foot on the table.
I appreciate your "Why toss it?"/ " Cheaper to keep 'er" attitude.
Be careful. If you have never experienced a 50,000 volt jolt, it will get your attention.

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@Ponderer,

As little as I know about electric arc welding, I do know/have seen that your work material does have to be grounded for the process to work (that's the extent of what I know).

Glad you appreciate the spirit of willingness to fix stuff. My father was an industrial engineer and as a result . . . "the nut doesn't fall from the tree" phrase applies to me in oh-so-many ways. You'll see a familiar theme in many of my posts (https://able2know.org/user/cdobyns/posts/), if you take a couple of minutes to scan a handful of them.

I'm actually still looking for input on a recent posting (https://able2know.org/topic/481004-1), where there hasn't been much feedback forthcoming. Feel free to weigh-in, if you've got an idea or if my preferred solution/option sounds appropriate.

I'll work on the blower carburetor tomorrow, assuming that it's not too cold in the garage.

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@CDobyns,

I remember reading that about the pulley not pulling. Uh...wrap the belt with duct tape? *raises eyebrows* Maybe using 1' pieces lengthwise would be doable. The worst that could happen it that you would ruin the belt because you'd never get the tape off. Sorry, that's all I've got

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@Ponderer,

Yes, on the drive wheel pulley, the duct tape solution was by far a secondary solution.

I still believe the smartest option was to go "off-spec" and just locate a drive belt that is slightly shorter, which would increase the "throw" when engaged and allow more friction and torque to be transferred to the drive wheel pulley.

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@CDobyns,

I knew you had thought of wrapping the pulleys. I thought that was worth trying. It would take up some slack and might even increase the friction. My idea of wrapping the belt was the the same principle. The "uh..." meant
"Searching for idea" and "raises eyebrows" meant "Hey, that might work."
Maybe wrap several layers of friction tape around the pulleys. About electricity being tricky- I am living in my parent's house now. I found a cord that had been cut off of something and I spliced it to a short extension cord to make it longer. When I plugged in my TV, it didn't work.
Evidently my dad threw away something that was good but had a bad cord. Probably the plug.

1 Reply

@Ponderer,

Dang, I've experienced my regular failure - of not reading things thoroughly. I totally missed both the suggestion and the option of wrapping the drive belt. My boss at work always likes to remind me that there's always at least two ways to solve a problem.

Regardless, I've tried the pulley wrap strategy, without too much (any) real success. I can try the alternate belt wrap strategy, but I'm just afraid that no friction/duct tape in the world is going to have the staying power to hold up to the almost constant stresses and friction when the drive wheel is engaged. The shorter drive belt has to be the better long-term solution - and it should only cost about $10.

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@CDobyns,

Hey, wait. Before you toss out a good belt. (I know, only $10, but that would fuel it for 4 years) See if there is a way to modify the mechanism that engages the belt to give the pulleys more distance between each other.

1 Reply

@CDobyns,

Re:"4 years"
Sorry, I was still thinking about the leaf blower. If you did metalwork you could move the front axle forward. (Haha?)

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@Ponderer,

The more we exchange "off-topic" about the other posting (https://able2know.org/topic/481004-1), probably the more confusing this gets for anybody else who might possibly shed light on the leaf blower problem.

That said, there appears to be no way to shorten the drive wheel pulley throw or to increase the spring retraction distance from the engagement bar. And while the suggestion of just moving the drive axle is an interesting idea, it's more than a little outside the scope of practical solutions, to say nothing of being outside the range of my current metalworking/skill level. I think we're back to giving credence to buying a shorter drive belt.

Quote:

My examination of the drive wheel pulley assembly seems to show that there's no way to increase the amount of distance when the assembly is pivoted. You can't shorten the retraction spring (creating more tension), and it appears as though there's hard stop built into the assembly which limits the "travel" distance and the assembly looks like it's already at it's maximum throw distance when it's tensioned right now.

1 Reply

@CDobyns,

Just to maybe try and semi-close out this posting - at least until the weather warms up again, here's an update.

The "numbskull" omission of not grounding the spark plug proved to be oh-so-correct. After I attached an alligator clip to the spark plug and the engine block, there was no question that the spark plug was generating a visible spark. Beyond that, after re-installing the spark plug, no amount of attempts to start the engine showed any promise.

Since by now our yard was literally a "sea of leaves", discretion became the better part of valor - and I opted to purchase a new leaf blower. Will try and revisit the old blower in the spring, when it warms up - and if I can't reincarnate the blower for the third (or maybe fourth) time, I'll figure that I've gotten more than an adequate return on my original $75 investment.

Thanks for the input and suggestions from everyone (I still think the blower is fixable . . .).

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Strange Leaf Blower Starting Problem

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