Just how "governed" are 2-cycle engines?

[JHZR2]

Hello,

As I recently bought a house, I bought a husquvarna 323L straight shaft weedwacker.

It is a great unit, with a LOT of power and nice smooth running. Im like echo typically, but got a *** deal on the 323L... and Im happy for the most part.

My one issue is that this is the first time Ive used a clutched trimmer. I thought that due to the fence and driveway layout of my property, it would be nice to have, but I dont have enough big stuff to cut to make good use of it. The top-quality string they put on there takes everything out first pass, and so I barely need to give it gas to move the head and then my trimming is done... I only trim what the mower misses, so its not HD cutting.

So in reality, my only peeve is that I wish that it didnt have the clutch. Oh well, its a nice machine, and Ill make do.

However, I think Ill switch to a much thinner string. Even if the head does not feed properly, its OK, for what I do.

But it makes me wonder... the engine will rev a lot easier when there is a lighter load on it, due to a lighter string. Will it have the ability to rev higher compared to a heavier load/thicker string? Will it be able to over rev?

How wel governed are these 2-cycle engines? if I use a light string to not cut everything with such a vengance... will i be doing no favors to my engine and drivetrain, in the instances where I do rev it up high, etc?

I hope this makes sense...

Thanks!

JMH

 

[80caprice]

When my string gets worn down, mine will rev alot higher... this is with .65 on my weedeater brand one... They have no governor, they do have a idle speed adjustment stop.
Same with my clutched trimmer, using the .105 line its ok, use the brushcutter blade.. it revs alot faster.... just less load will do it. I've reved my weedeater full throttle, couple inches of line out on purpose to get some tight spots for several minutes..... no harm at all.... great compression and all, still a easy starter.

 

[GT Mike]

I put together a Ryobi 2-cycle 31cc trimmer that actually did have a rev limiter on it. First time I ever heard of such, but at about 6000 RPM, it would just "chatter" and "float". Sort of like the rev controller on an MSD box in a dragster. It had to be something built into the CDI pack, as there was nothing else that looked out of the ordinary.

 

[Craig in Canada]

My 2003 Echo SRM-210 indicates in the manual that you should not exceed 10,000rpm and that it can happen if your string load is insufficient (ie. very short or none).

 

[Slick 55]

Run it 'till she blows.

 

[GT Mike]

quote:

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Originally posted by Brett Miller:
Run it 'till she blows.

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Best advice yet!

 

[MN Driver]

Sometimes the carbs are adjusted a little rich on the H side to prevent this. I know that with chainsaws some service manuals recommend that the engine be connected to a tachometer and be tuned until they don't go over a certain RPM under no load. If it is a fixed jet carb(no 'H adjustment', only an idle speed adjustment and idle or 'L' adjustment), then it is probably jetted to prevent overspeed. Or it could be detuned by means of air intake restriction.

 

[Master ACiD]

usually the engines are restricted by their wimpy ports, intake and exhaust.

 

[Slick 55]

I have a cheap Homelite that I bought at Home Depot which is a piece of crap (I should have known better and bought an Echo). One of these days, I'm going to cut off the string and tape the throttle wide open and see how long it runs. With my luck the dang thing won't blow up

 

[GT Mike]

quote:

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Originally posted by Master ACiD:
usually the engines are restricted by their wimpy ports, intake and exhaust.

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Not my Ryobi! Since it was free, I tore into it and did some port work to it. Maybe a little too much...It has such a kick now that if you don't have a good grip on the starter, it'll snap back right out of your hand! Crack the throttle, and it wants to twist right out of your hand! I lent it to a buddy, and he gave it back after darn near breaking his wrist starting it and asked me if I had a stock one that he could use instead.

The exhaust has been modified a little too...It's one of those "**** off the neighbors" machines now! Think of a very tiny snowmobile engine with aftermarket pipes on it. Brrrrraaaaaaapppppppoppoppopopop!!

 

[GT Mike]

quote:

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Originally posted by Brett Miller:
I have a cheap Homelite that I bought at Home Depot which is a piece of crap (I should have known better and bought an Echo). One of these days, I'm going to cut off the string and tape the throttle wide open and see how long it runs. With my luck the dang thing won't blow up

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If you hate it that much, just run straight gas thru it.

Otherwise, send it to me and I'll build another hotrod out of it!

 

[Cujet]

As a general rule, the nature of a 2 stroke engine will not allow excessive overev. A good example of this is the 125cc motocross bike starting line. Riders hold the bikes at full throttle to clear the carbon out (so to speak).

I would guess that the Husky trimmer will reach an RPM ceiling that is well within the structural limits of the internal parts.

This does not mean that prolonged use of High RPM will result in longer engine life