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Discussion Starter #1
Hit a chunk of wood last month with my D400 series bricktop engine. Stopped the motor dead from max rpm, had to get the chunk of wood out with a pry bar from between the blade end and body.

Since then its gutless and virtually impossible to start, looked under the cover and the aluminum piece with the small spring which wraps round the crankshaft has obviously moved.Not easy like the four strokes which have a key, can't figure out how to get this one sorted out.

Threw another D500 motor in in the meantime to use but want this one sorted out to put back on.

Anyone have a link to instructions, or video? The engine was mint before this, so well worth saving..does not vibrate or anything since this episode but is nigh on impossible to start..it does eventually but seems to flood in the process.

Cheers!
 

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D engines do have a keyed crank pull the flywheel and check it I bet you sheared the key.
 

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Discussion Starter #5
Hi guys, will tear it down this morning after breakfast and have a closer look, but when I took it apart after I hit it, the flywheel key was in perfect shape. That's why I tore it down.
I will try to find a pic of the part which does look as though it has shifted and post it up.

Thanks all
 

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Discussion Starter #6
This pic is from a friend of mine who lives in NZ, pcamore..the piece by his thumb is the piece on mine which looks to have moved, and that's timing related I'm sure?

If so I need to find out how to get it back in its proper position.

Cheers
 

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The hairpin has to be inside the advance weight. Make sure the closed end is leading and the tangs are horizontal, not pointing down toward the engine. Walt, unfortunately, is correct, the expensive flywheel will protect the cheap key. Years ago in my rental business when we used to rent LB mowers, I had some aluminum keys made just for this issue.
 

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Discussion Starter #9
Thanks guys, well, have been out and stripped it down.
Flywheel looks perfect, as is the key, not even deformed.

Thought I'd try another carb, since there is fuel leaking from exhaust gasket..and cleaned the points and gapped correctly.

Threw a new plug in, fresh fuel mix, and pulled the cord, and hey presto...nothing! Good spark off lead too.

Been pulling for a half hour trying new plugs, throttle adjustments etc but not even one single fire.
There's obviously something wrong,but I'm too dumb to figure it out.

So I did the standard man thing...pushed it in the garage and slammed the door after it muttering bad things....lol

But the worst of all is now I have to go and get the new mower out to do the lawns....with a bland, boring, cheaply made, mass produced 4 cycle mower with no character....**** it!
 

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Discussion Starter #10
oh, and yep the flywheel weight looks to be in order...I have an electronic ingition unit here, might try and fit that up and see what it does.
 

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Crank might be twisted, I'd regap the coil to, the trauma of striking the object might of moved the coil enough to effect timing. I'm still thinking that the flywheel maybe hiding a crack from you to. I think I would probably swap the flywheel out just for good measure. It may look good, but who really knows just how weak, or distorted that chunk of aluminum is now, or just how long it will go before letting go. I don't know how abundant flywheels are over where you are, but here in the states a decent used one is fairly easy to get and really not that expensive. I probably have one that would work for ya, but the shipping would be outrageous.
 

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Discussion Starter #12
Thanks lawnboy77, I have heaps of spare motors here, so I'll try another flywheel out of desperation!

Its run since this, just hard to start, and it ran normally, no vibes, just nigh on impossible to start, and maybe didn't rev as hard.

Now I've been thinking I'm the main mechanic and playing, it won't start at all...ha ha

I think the blade carrier may have saved the engine actually. Its a tapered end where the blade carrier sits on the crank, so it may have simply "spun" the blade carrier on the end of the crank, almost looks like it has to me.

I'll maybe try again tomorrow, its dark here now and I'm too busy sulking!!
Thanks guys for all the helpful replies, much appreciated!
 

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The crankshaft of D400 LBs is VERY tough, doubt it is twisted or bent, once bent, I have found them impossible to straighten because of their toughness.

Walt Conner
 

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Its run since this, just hard to start, and it ran normally, no vibes, just nigh on impossible to start, and maybe didn't rev as hard.

Okay well that's good news, sounds like to me it has to be in the spark advance system, maybe for whatever reason the flyweight and cam are stuck in the run position. That should be an easy fix then, and alot cheaper than a crank or flywheel. Should be just a matter of getting it freed up maybe replacing the pin, since it could have gotten bent and is now binding. Should be able to grab with fingers and move it back and forth from the start to run postion without binding.

EDIT: The more I think about it, the more I'm convinced that the spark advance pin is your trouble, it probably got joggled and will require replacement.
 

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The spark advance is very likely your trouble as I indicated before. When the spark is advanced, it becomes weaker than the starting spark. It will be impossible to start with the spark advance in the advanced position.
 

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Since then its gutless and virtually impossible to start, looked under the cover and the aluminum piece with the small spring which wraps round the crankshaft has obviously moved.

I think what was throwing me on it initially was the fact that you said it was gutless once you got it started, but now that you say it runs normal, just hard to start then yeah I agree with Red, almost has to be the spark advance.


EDIT; one other thing to add...my recommendation of replacing the flywheel still stands, not necessarily for reliability reasons, but for safety reasons. I think that flywheel needs to be inspected for cracks using good inspection techniques, like dye penetrant, eddie current, x-ray, ultra-sound or whatever the crack experts recommend. Like I said earlier a crack could lead to chunks of aluminum being hurled when it hits the next object, or sooner.
 

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Discussion Starter #17 (Edited)
Thank you very much guys, for all your replies and advice, much appreciated.

If I get time today, I'll pull it down again and see if I can replace the flywheel and advance mechanism, and see if that helps, I guess its just a case of pulling it off and replacing with another? No marks which have to line up etc?

I'm reasonably capable mechanically, but have never played with timing on the Iron Horse motors.

I got a couple of D500 motors off the scrap man a while ago, put them on a chassis yesterday and they both run, but one sounds like it has a worn top end bush and the other just sounds "tired".. but I couldn't bear to see them being smashed for scrap so I bought them for $10 a piece. He now calls me if any more turn up.

Thanks again for your time and efforts guys.
 

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Do the top ends of the D500's in New Zealand have bushings or bearings? A bearing would be pretty easy to replace. Good to hear that you're saving these from being scrapped.
 

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Discussion Starter #19
I have been told the D500 series was a more resilient motor due to having bearings instead of bushings, but haven't pulled one down to see.

problem here is us NZer's like to muck around with things, so have seen these motors with the D500 tags on the cylinder, but the older D400 series tops (Flywheel/alloys covers etc) fitted, so I can never be too sure what it actually is.

The one I am trying to sort out is a genuine D500 throughout, and is a low mileage motor I think. The one with the rattly top bearing is a D400 series so they still had bronze bushings "I think".

Got a couple more last weekend, both D500 series and they both run...BUT....you can flop the crank round in these with huge movement..amazing how they actually still ran! I'll be using them for parts I guess, although the fuel tank is probably the only bit that's not shagged!
 

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Discussion Starter #20
Well, went out and stripped it down again, the spark advance weight (if that's the right term) looked okay, but I stripped it out. Not bent, everything moved freely and clean.

So I wondered if it had a dud condenser..do I stripped the points right out and got another condenser off a running motor, and got another coil as well. Then I remembered one of the runners I got the other day had an electronic ignition module on it..yep, bolted to the outside of the shroud..lol

So I got that, undid the rough connections (wires were just tied together, no insulation) and soldered up new connections.
Fitted that...and well well...it fired first pull, and runs nicer than it ever has!
Seems more responsive, only problem is I can't shut it off..don't know how, as the original off knob was connected to the condenser.

So I'll just have to choke it to shut it down.

Got one wire (white) going to coil from the elec ign unit, and the other wire just bolted to the engine (blue)
Have tried connecting the "off wire" which is original to mower to both those wires but it still gives out a fat blue spark when I use the off knob.
It's an Australian "Atom" ign unit, tiny, I easily fitted it there the points sat, can't see it there and it's out of the weather.

Proud of that...never done one before, but disappointed I can't use the original "off" button.

But she runs again, so many thanks again to all who wrote down their ideas, much appreciated. From the way this runs now, it would be well worth replacing all points with these (depending on price of course).

Motor has a slight vibration, I'll swap out the blade just in case it's that..but can't remember it vibrating much earlier...unless I'm only just noticing it, because it runs nicer now?
 
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