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Old 03-16-2011, 04:38 AM
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Default Masport Ironhorse engines. DiZcuss



I might get one to play with. Gone off the half crank victas...

what do they go like?
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Old 03-16-2011, 04:52 AM
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Good motor design, reed valve, mods up to 10hp ive been told, have three of my own.
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Old 03-16-2011, 01:59 PM
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reed valves? why would you bother on a lawnmower lol. My friend has an old as one. Is there much difference between the old and newer engines? what do your exhaust ports look like? three holes?
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Old 03-16-2011, 02:50 PM
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Originally Posted by sexyvicta View Post
reed valves? why would you bother on a lawnmower lol. My friend has an old as one. Is there much difference between the old and newer engines? what do your exhaust ports look like? three holes?
Engines with reed valves are mechanically simpler because they dont have a valvetrain. More lawnmowers should be 2 strokes, IMO.
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Old 03-16-2011, 05:13 PM
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Here in the states is known as a Lawn-Boy model "D" (possibly a "C").
Spark advance is a somewhat curious design.
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Old 03-17-2011, 02:50 AM
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Yeah, three holes, reed valve more efficient as well??
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Old 03-17-2011, 12:37 PM
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Engines with reed valves are mechanically simpler because they dont have a valvetrain. More lawnmowers should be 2 strokes, IMO.
what? i didnt say why is it a twostroke. I said why reed valves? lol

piston port with no reed valve is simpler.

reeds will make it more efficient i guess and possibly a wider power band but less top end than a straight piston port. Iduno, may have something to do where they put the intake port....yes probably now that i think about it haha.

what're the reeds made out of? pretty high tech for a 1950s spec lawnmower engine lol
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Old 03-17-2011, 12:40 PM
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Here in the states is known as a Lawn-Boy model "D" (possibly a "C").
Spark advance is a somewhat curious design.
is it the same engine?

- who designed it then? I always thought it was a New Zealand design. My mate measured the crank and its metric anyway. Probably those crafty germans are involved.
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Old 03-17-2011, 12:52 PM
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what? i didnt say why is it a twostroke. I said why reed valves? lol

what're the reeds made out of? pretty high tech for a 1950s spec lawnmower engine lol
I've never hear of a 4 stroke with reeds or a 2 stroke with a valvetrain. Asking why they would have reeds on a lawnmower is basically the same as asking why its a 2 stroke. You asked why reed valves and I said because its simpler.

I think some sort of spring steel or the like.
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Old 03-17-2011, 01:04 PM
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I've never hear of a 4 stroke with reeds or a 2 stroke with a valvetrain. Asking why they would have reeds on a lawnmower is basically the same as asking why its a 2 stroke. You asked why reed valves and I said because its simpler.

I think some sort of spring steel or the like.
you are missing my point. A twostroke does not require reed valves edit: and a twostoke with reeds is more complex than one without. they are just a one way valve to stop fuel being blown out the engine back into the intake i belive. Can be steel or plastic or whatever

edit: but i think this engine would require reeds or a disk valve or similar due to the location of the intake. im no scientist lol
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Old 03-17-2011, 01:12 PM
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Right, you don't need a reed valve in a 2 stroke. The fuel mix can get into the crank case by way of a ported crankshaft, as is the case with most RC airplane 2 strokes, or through a port that is uncovered when the piston goes up, which was common in model airplane engines before 1950. A poppet valve directly into the cylinder can also be used, especially in the case of supercharged engines.
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Old 03-17-2011, 02:19 PM
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I think some sort of spring steel or the like.
Reeds can be made out of almost anything. I have seen high performance MB engines with plastic reeds. All reeds will lose their strength to a certain degree as they age, depended on many factors.

Jeremy.
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Old 03-17-2011, 04:37 PM
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Quote:
Originally Posted by sexyvicta View Post
is it the same engine?

- who designed it then? I always thought it was a New Zealand design. My mate measured the crank and its metric anyway. Probably those crafty germans are involved.
Engine design predates Lawn-Boy and was originaly produced by a company called RPM (Rotary Power Mower).
OMC (Outboard Marine Corp.) purchased the rights to RPM engines and thus the Lawn-Boy was born.
Definitely not a New Zealand design.
The reason for a metric sized shaft is unknown to me.
The C and D engines I have worked on were all 7/8" or .875" which works out to 22.225 millimeter.
Reed valves in Lawn-Boy 2 cycle engines have not changed in 50+ years and are completely interchangeable with any other model.
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Old 03-17-2011, 10:13 PM
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cool as. Yeh masport must have bought the plans to the engine early on as they started making it in the 50s also i think. My Grandfathers first motorised lawnmower was an ironhorse Masport

will go see my mate and measure his crankshaft with an electronic vernier caliper lol
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Old 03-17-2011, 10:44 PM
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cool as. Yeh masport must have brought the plans to the engine early on as they started making it in the 50s also i think. My Grandfathers first motorised lawnmower was an ironhorse Masport

will go see my mate and measure his crankshaft with an electronic vernier caliper lol
A vernier wont give you an accurate reading. You really need to use a micrometer. Sure the vernier will give you an idea, but I have seen a brand new Mitutoyo out by .5mm, which when you think about it is quite a bit, lol.

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Old 03-17-2011, 10:58 PM
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stink cos i dont have a micrometer

will have to use the old eye-o-meter. Same as i use for sizing up fish
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Old 03-17-2011, 11:07 PM
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So your the one we see on coast-watch, poaching out of our waterways?

Jeremy.
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Old 03-18-2011, 03:01 AM
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Well if it comes up at something like 25.67 it prolly aint metric, verniers should be accurate enough (if it comes to a rounded figure).
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Old 03-18-2011, 01:58 PM
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Quote:
Originally Posted by Rustydog2010 View Post
A vernier wont give you an accurate reading. You really need to use a micrometer. Sure the vernier will give you an idea, but I have seen a brand new Mitutoyo out by .5mm, which when you think about it is quite a bit, lol.

Jeremy.
do you mean .05mm? because .5mm is a **** of a lot!
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Old 03-18-2011, 02:36 PM
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Verniers and micrometers are of equal quality and precision.
They just do different jobs.
Verniers should always be used to measure diameters.
Quote:
but I have seen a brand new Mitutoyo out by .5mm
Then it needs to be calibrated.
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