Jump to content

Nominations for Tractor of the Month
Garden Tractors and Parts on eBay



Photo
- - - - -

MF12G re-power


  • Please log in to reply
95 replies to this topic

#1 MFDAC OFFLINE  

MFDAC

    Only member from Western South Dakota!

  • Senior Member
  • -GTt Supporter-
  • Member No: 5815
  • 2,031 Thanks
  • 1,126 posts
  • Location: East of Rapid City, SD in Rapid Valley

Posted June 27, 2015 - 07:57 PM

I have finally worked up the nerve to tell you folks that I'm going to have to re-power my 12G. It is still running well but the smoke has gotten to the point where it is offensive to anyone in the way of where it drifts to, and it gets a little hard to see on my end too! Last weekend my wife and kids had enough and bought a 13hp Predator engine for Father's Day. I had told them a month or so ago I could probably get a different engine cheaper than a .020 piston for an HH120 (if one could even be found) and required machine work to do the job.

 

I am going to approach this with the intent of altering the tractor as little as possible building engine components to fit instead, like a different exhaust and air cleaner setup. It looks like the centerline of the crank will be only about a 1/4 inch higher than the HH120 and I can probably move it back slightly to make up for that. I'm sure holes will need to be drilled but I think the hood and grill will remain stock. I'm hoping to adapt the muffler and chrome shield since the exhaust port is on the same side.

 

My first panic attack happened when i realized the shaft on the HH120 is 1-1/8" and the new engine is 1"! I thought learning more about the lathe and mill at work building a sleeve would be needed then but doing a search, there is exactly what's needed on an ebay store cheap-19 bucks shipped and it is on it's way! Re-using the pulley is required especially with that vari-drive belt groove on it.

 

Anyway, i hope that this doesn't get me shunned away from here, love this site. I just am at a point where something has to be done within our budget and purpose.

 

I will still keep annoying everyone around our neighborhood and buying lots of 30wt in the meantime until it's not necessary to mow twice a week! With my available time I'm hoping that the tractor will be out of service 2 weeks when the grass quits growing so darn fast!

 

DAC

Attached Thumbnails

  • Gravel 6-20-15 003.jpg

  • olcowhand, DH1, Cvans and 2 others have said thanks

#2 DH1 OFFLINE  

DH1

    Electric Tractors

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 62
  • 4,587 Thanks
  • 5,295 posts
  • Location: Markham Ontario Canada

Posted June 27, 2015 - 08:09 PM

I've done 3 of them, all Hydro drive never a gear drive so I'll lean something watching you do yours.

I used the factory mounting holes and found the factory belts both drive and PTO lined up good.

Hope your repower goes well.


  • MFDAC said thank you

#3 MFDAC OFFLINE  

MFDAC

    Only member from Western South Dakota!

  • Senior Member
  • -GTt Supporter-
  • Member No: 5815
  • 2,031 Thanks
  • 1,126 posts
  • Location: East of Rapid City, SD in Rapid Valley

Posted June 27, 2015 - 09:08 PM

Hello Doug, thanks for the comment! Did you use this engine on your hydro re-powers? If you have posts about your experience getting this to work for you, I would love links to learn or will try a search!

 

That is very encouraging that factory holes and belt locations worked for you! When I did the standard size piston overhaul a couple years ago it was done in frame so the engine never was out of the tractor. I felt the valves and guides needed no service then but the piston was badly scuffed. I hoped it was a collapsing skirt rather than too much taper but it must have been the latter. I didn't have the tools to measure that, but for 50 bucks I figured it was worth a try.

 

DAC


  • DH1 said thank you

#4 DH1 OFFLINE  

DH1

    Electric Tractors

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 62
  • 4,587 Thanks
  • 5,295 posts
  • Location: Markham Ontario Canada

Posted June 27, 2015 - 09:25 PM

I think I used the same engine, up here there sold by Princes Auto and called "powerfist"

 

Here's an article I did on a MF12H repower.

http://gardentractor...r-mf12-with-r71

 

-The hard part is the exhaust.

-Choke works backwards if you use the Massey controls.

-The charging circuit not strong enough to run the lights, but there an easy start with the pull starter, 1 or 2 pulls.

-Found that on late models the bottom of the battery box hits the engine, need to grind away 1/2" of new engines fuel tank mounting bracket. I think it's better/easier to use the Massey fuel tank. 

- The air cleaner hits the hood support rod bracket on the grill, if you remove the outer housing of the air cleaner there is enough room for it to fit. 

- The belt guard for the drive pulley needs to be modified to fit, you don't really need it on the Hydros but the gear drives you need that guard in place, or it's harder to shift gears because the belt won't stop turning.

- And as you already know the drive pulley needs to be shimmed to fit the crank.

 

When it's done you'll love the smooth steady power a NEW engine delivers.


  • MFDAC said thank you

#5 glgrumpy OFFLINE  

glgrumpy

    Getting Out!

  • Senior Member
  • -GTt Supporter-
  • Member No: 8360
  • 6,661 Thanks
  • 6,475 posts
  • Location: Huntington, IN 46750 North East in State

Posted June 28, 2015 - 09:56 AM

Just wondering how you changed a piston with engine still in tractor????  You would have to remove the bottom base, so engineis all free then and could be on bench?  OR, just hit me, maybe side comes off these engines and can access??  Still seems like the hard way. 

     Guy's on those sleeves for crank, how does one tighten that and what about any keyway that would be too deep then? Seems the pulley set-screw would not be good enough to push all that metal down and be tight on the crank is what I"m getting at. You have to drill hole in sleeve and longer screw to get to solid crank metal? Is there a split in the sleeve then for the key? Have to make an extra deep key somehow?  I don't get how the sleeve can work, fill me in here.


  • MFDAC said thank you

#6 Cvans ONLINE  

Cvans

    Tractorholic

  • Senior Member
  • -GTt Supporter-
  • Member No: 5412
  • 4,486 Thanks
  • 5,014 posts
  • Location: Eastern SD.

Posted June 28, 2015 - 10:09 AM

You might find that you enjoy this project more than you would think. If I remember correctly the MF's are belt drive which makes the swap easier. Have fun and keep us informed. 


  • MFDAC said thank you

#7 MFDAC OFFLINE  

MFDAC

    Only member from Western South Dakota!

  • Senior Member
  • -GTt Supporter-
  • Member No: 5815
  • 2,031 Thanks
  • 1,126 posts
  • Location: East of Rapid City, SD in Rapid Valley

Posted June 28, 2015 - 01:59 PM

I think I used the same engine, up here there sold by Princes Auto and called "powerfist"

 

Here's an article I did on a MF12H repower.

http://gardentractor...r-mf12-with-r71

 

-The hard part is the exhaust.

-Choke works backwards if you use the Massey controls.

-The charging circuit not strong enough to run the lights, but there an easy start with the pull starter, 1 or 2 pulls.

-Found that on late models the bottom of the battery box hits the engine, need to grind away 1/2" of new engines fuel tank mounting bracket. I think it's better/easier to use the Massey fuel tank. 

- The air cleaner hits the hood support rod bracket on the grill, if you remove the outer housing of the air cleaner there is enough room for it to fit. 

- The belt guard for the drive pulley needs to be modified to fit, you don't really need it on the Hydros but the gear drives you need that guard in place, or it's harder to shift gears because the belt won't stop turning.

- And as you already know the drive pulley needs to be shimmed to fit the crank.

 

When it's done you'll love the smooth steady power a NEW engine delivers.

I will study your thread when I get some time later today! Thanks for the link. I haven't seen a provision to hook up a cable to the choke, but there are provisions already in place for the throttle. This engine has electric or pull start and it appears there is enough rolled up wire to moved the switch box to the dash or maybe even install it in the original holes. I was kind of planning to use the MF fuel tank, and not moving the battery location, just need to make more time to study what's there and what I have. My 12G never had any lighting so I would think the engine has enough to keep the battery charged at least since it has electric start.

 

Just wondering how you changed a piston with engine still in tractor????  You would have to remove the bottom base, so engineis all free then and could be on bench?  OR, just hit me, maybe side comes off these engines and can access??  Still seems like the hard way. 

     Guy's on those sleeves for crank, how does one tighten that and what about any keyway that would be too deep then? Seems the pulley set-screw would not be good enough to push all that metal down and be tight on the crank is what I"m getting at. You have to drill hole in sleeve and longer screw to get to solid crank metal? Is there a split in the sleeve then for the key? Have to make an extra deep key somehow?  I don't get how the sleeve can work, fill me in here.

Hi GL, It was pretty easy to do the piston swap in frame and with the block still bolted down it was nice and solid for honing. As you suspected the side cover on the pto drive side comes off and of course with the head off, the piston comes right out of the top. I also had to remove the flywheel obviously to pull the crank but no big deal there either. The machined shim is slotted and it comes with a rectangular key to make up the extra thickness of the sleeve. The pic is very small but it may help.

 

You might find that you enjoy this project more than you would think. If I remember correctly the MF's are belt drive which makes the swap easier. Have fun and keep us informed. 

Thanks Chris, I am looking forward to going on this but I don't have an extra tractor to mow with right now, so it will have to be in the planning stages for awhile!

 

DAC

Attached Thumbnails

  • crank sleeve.jpg

Edited by MFDAC, June 28, 2015 - 02:06 PM.

  • DH1, limebuzz, MH81 and 2 others have said thanks

#8 MFDAC OFFLINE  

MFDAC

    Only member from Western South Dakota!

  • Senior Member
  • -GTt Supporter-
  • Member No: 5815
  • 2,031 Thanks
  • 1,126 posts
  • Location: East of Rapid City, SD in Rapid Valley

Posted July 02, 2015 - 05:33 PM

We are going to be gone for 8 days so no updates will be happening for awhile. Got the new vari-drive belt, but the pto shaft sleeve hasn't arrived yet. I have to go get one more mowing in yet tonight before we leave. I will report back in when we get home!

 

DAC


  • MH81, KennyP and Cvans have said thanks

#9 MH81 ONLINE  

MH81

    Proud to be Deplorable

  • Staff Admin
  • Staff
  • -GTt Supporter-
  • Contributor
  • Member No: 802
  • 27,292 Thanks
  • 28,623 posts
  • Location: N. W. PA

Posted July 02, 2015 - 08:37 PM

Safe travels and happy 4th
  • MFDAC said thank you

#10 MFDAC OFFLINE  

MFDAC

    Only member from Western South Dakota!

  • Senior Member
  • -GTt Supporter-
  • Member No: 5815
  • 2,031 Thanks
  • 1,126 posts
  • Location: East of Rapid City, SD in Rapid Valley

Posted July 13, 2015 - 09:54 PM

Hello, GTT! Had a great vacation even though a lot of it was chores for one of my sisters. Back to the job tomorrow at 5am. Started getting mail service today and the pto sleeve adapter was here and looks like a very nice quality piece. Mowed the ENTIRE acre today without running through mud and standing water, with the old smoker! 12 days growth. Standing water sure killed some grass though.

 

Here's a couple of pics of the sleeve and key. Need to shorten them a bit but that's no problem. It measures 1.126" diameter but it still has a smidgen of crush so it will fall into the 1.1249ish area like the HH120 shaft measures.

 

If the weather pattern continues like it has been while we were gone, I'm pretty confident in about a month it will be ok for the tractor to be down for a couple weeks. Seems the rains followed us to Denver, CO as it dumped every afternoon and a couple days it rained all day. So far it didn't follow us back!

 

Going to try to do a little preparation for exhaust and air cleaner in the meantime although it will he hard to fabricate anything substantial until the engine can be plopped into position. Sorry the second pic sucks but you get the idea.

 

Later---DAC

Attached Thumbnails

  • crank shim 001.jpg
  • crank shim 002.jpg

  • olcowhand, DH1, MH81 and 3 others have said thanks

#11 MFDAC OFFLINE  

MFDAC

    Only member from Western South Dakota!

  • Senior Member
  • -GTt Supporter-
  • Member No: 5815
  • 2,031 Thanks
  • 1,126 posts
  • Location: East of Rapid City, SD in Rapid Valley

Posted July 15, 2015 - 09:51 PM

So much for the weather pattern, 1.5" of rain today and still coming down. The rain followed us to Denver and has evidently followed us back!

 

DAC


Edited by MFDAC, July 16, 2015 - 06:36 PM.

  • MH81 said thank you

#12 Cvans ONLINE  

Cvans

    Tractorholic

  • Senior Member
  • -GTt Supporter-
  • Member No: 5412
  • 4,486 Thanks
  • 5,014 posts
  • Location: Eastern SD.

Posted July 15, 2015 - 10:47 PM

Posted Today, 09:51 PM

So much for the weather pattern, 1.5" of rain today and still coming down. Te rain followed us to Denver and has evidently followed us back!

 

 

 

That's a bummer. We had just a sprinkle but it sure has been humid. 


  • MFDAC said thank you

#13 wvbuzzmaster OFFLINE  

wvbuzzmaster

    Squeaky Wheel

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 1792
  • 4,492 Thanks
  • 7,341 posts
  • Location: West Virginia

Posted July 16, 2015 - 01:55 AM

Don't just shorten the key, relieve the engine side of the key to allow it to fit the contour (somewhat) of the key way in the crank. It is a bigger PITA but it will make for a better result in the end.
  • MFDAC said thank you

#14 MFDAC OFFLINE  

MFDAC

    Only member from Western South Dakota!

  • Senior Member
  • -GTt Supporter-
  • Member No: 5815
  • 2,031 Thanks
  • 1,126 posts
  • Location: East of Rapid City, SD in Rapid Valley

Posted July 16, 2015 - 06:44 PM

That's a bummer. We had just a sprinkle but it sure has been humid. 

The wind must have blown a good bit of the rain past my gauge as the 10 o'clock new said last night that the airport got 2.7" of rain yesterday. That is 2 miles from where we live and as much standing water as we have again, that sounds more realistic! Humid as heck here too obviously!

 

Don't just shorten the key, relieve the engine side of the key to allow it to fit the contour (somewhat) of the key way in the crank. It is a bigger PITA but it will make for a better result in the end.

That's a great tip Casey! I will contour the engine end of the key to to fit that!

 

DAC


  • wvbuzzmaster and Cvans have said thanks

#15 FirefyterEmt OFFLINE  

FirefyterEmt

    Tractorholic

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 610
  • 425 Thanks
  • 849 posts
  • Location: Northeast Connecticut

Posted July 21, 2015 - 10:14 PM

Looks like a fun conversion!  My son is going on a good 4 years on his 6hp conversion of a little MF8.   Keep in mind, that a lot of cart racers use these engines (granted, moreso the 6hp ones) but there are quite a few preformance items and air clearners made for them.


  • MH81 and MFDAC have said thanks




Top