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Changing push mower flywheel to cast iron?


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#1 dmorrill22 OFFLINE  

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Posted March 09, 2015 - 01:50 PM

I am working on a mower engine which will be used in a non-mower application. As it was designed exclusively for mowing, it originally had an aluminum flywheel. I want to fit a cast flywheel on it instead.

The original flywheel keyway was pointing towards the magnet. From all of the pictures I found online, a comparably sized Briggs cast flywheel has the keyway located much farther from the magnet.

I am assuming that this will drastically affect the timing of the engine. Assuming I cannot find a suitable cast flywheel with the keyway indexed the same as the aluminum flywheel, what can I do to make one work? Would I have to have a new keyway machined into the flywheel?
 
The engine would be used to run a centrifugal clutch powering a transaxle. For what it's worth, the engine is a Briggs 12V802/2376-A1.

Thanks.
-Doug

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#2 tater195 ONLINE  

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Posted March 09, 2015 - 01:59 PM

I have never tried it, so I aint much help there. I get a chuckle from the CL ads for a push mower engine saying it would make a great gocart engine. They do make a blade simulator for safe bench testing of mower engines. They basically ad weight to the pto side to make up for the missing blade weight


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#3 petrj6 ONLINE  

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Posted March 09, 2015 - 02:35 PM

     the flywheel that you want to convert over to would have to be very close to the original, same od same thickness and the same shaft taper. the magnets would need to be in the same location of the flywheel.  after you have found a flywheel that will work all you would need to do is map out where you want the key-way cut and go for it.  it may be a difficult thing to get correct, most key braches are made for straight holes so you would need to have a new broach collar made to fit the tapered hole so your new keyway would be correct and straight.

    I you got all your ducks in a row I see no reason why you could not do this but you need to be very careful about cutting the new key, even a little of and it will not run correct.

                Pete 


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#4 superaben OFFLINE  

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Posted March 09, 2015 - 10:01 PM

Doug, you will need to have a cast flywheel from an engine using the same or similar ignition so that the magnets are the right strengths, sizes, and spaces so you will have spark.  You will need to take it and your old one over to a machine shop and make them cut you the new keyway exactly the same going by the magnet's position.  Then make sure they rebalance the flywheel to prevent vibrations.

 

I have seen this done before for some racing guys (they change cast to aluminum) or some pullers, too. 

 

Personally I would leave a push mower engine running a pushmower.  They are disposable engines. 

 

If you are looking for a cheap small HP vertical crank engine, most areas have the old Snapper RER's running around or any old ride on lawn tractor that you can buy for peanuts and save yourself the pain of converting the push mower engine.  They will last 10 times longer, too.

 

I'm not trying to be a wet blanket on your project, I'm just giving a different idea that might save you some time. 

 

Ben W.


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#5 dmorrill22 OFFLINE  

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Posted March 09, 2015 - 10:46 PM

Doug, you will need to have a cast flywheel from an engine using the same or similar ignition so that the magnets are the right strengths, sizes, and spaces so you will have spark.  You will need to take it and your old one over to a machine shop and make them cut you the new keyway exactly the same going by the magnet's position.  Then make sure they rebalance the flywheel to prevent vibrations.

 

I have seen this done before for some racing guys (they change cast to aluminum) or some pullers, too. 

 

Personally I would leave a push mower engine running a pushmower.  They are disposable engines. 

 

If you are looking for a cheap small HP vertical crank engine, most areas have the old Snapper RER's running around or any old ride on lawn tractor that you can buy for peanuts and save yourself the pain of converting the push mower engine.  They will last 10 times longer, too.

 

I'm not trying to be a wet blanket on your project, I'm just giving a different idea that might save you some time. 

 

Ben W.

 

I should mention this engine was to replace a Tecumseh vertical shaft of similar HP.  Because Tecumseh no longer makes engines/parts, and Briggs has excellent parts availability and support, I was hoping to make this engine work for my application.  It helps that I got it for free.  Also, I like the carburetor on the Briggs engine as it is not a plastic-bodied carb like the Tecumseh (I always have trouble with those).

 

Thank you for the insight Ben - most topic's I've read on this issue online have mentioned to just "swap the flywheel for a cast one," but it seems like all the people who have suggested this have never done it before.  I am going to continue looking for cast flywheels that may work, but certainly am not getting my hopes up.


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#6 toomanytoys84 OFFLINE  

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Posted April 06, 2015 - 08:49 PM

I have never tried it, so I aint much help there. I get a chuckle from the CL ads for a push mower engine saying it would make a great gocart engine.

I have put probably used 50 plus old horizontal shaft engines. Briggs and tecumseh from edgers , tillers, snow blowers ect and never had a single problem. I have a bike now run a huge hm100 big block tecumseh that came off a sears suburban.

what are your thoughts on how it would be a problem?

the honda engines I use for race motors I use the lightest billet aluminum fly wheels I can find. Those things Rev super quick and hum at 9k rpm all day long.

I can understand the issue of it being a vertical shaft engine for a go kart.

Edited by toomanytoys84, April 06, 2015 - 08:50 PM.

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#7 tater195 ONLINE  

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Posted April 06, 2015 - 08:57 PM

I have tried to use push mower engines for other applications and damn near got my arm broke from kick back. If you can get them started, they dont run right,


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#8 holdenboy1960 ONLINE  

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Posted May 10, 2015 - 09:16 AM

if it is a push mower engine only you will have problems when you start it 

reason 1 being ,the cutter disc acts like a fly wheel & removing it will result in havoc

when you pull to start the engine it will kick back Sooooooo hard & nearly tear ya fingers of on back lash 

simply because the timing is advanced to much for non cutter disc operation , unless you fabricate a fly wheel of sorts 



#9 bbuckler OFFLINE  

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Posted May 10, 2015 - 12:01 PM

I have tried to use push mower engines for other applications and damn near got my arm broke from kick back. If you can get them started, they dont run right,

I had the same thing happen to me 6 years back my wrist hurt for a week.


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