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Mf 12 Rebirthed


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#91 Gabriel OFFLINE  

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Posted May 10, 2014 - 09:04 PM

Gabriel I believe the correct part name is the piston cylinder block that the wear is on. The wear is on the opposite side of the pistons. Like I mentioned I'm not sure if I can or should do anything for this because it works fine. My concern is what caused this. If a worn bearing that would have some slop in it cause this or did some foreign material get trapped in there????

 

With much needed sleeping in & a late breakfast at Crackle Barrel along with the grandsons ball games today not much GT time. I was able to get the pump drive shaft out so I can install a speedi sleeve on that. I took some measurements of the shaft & my smallest was near the shaft seal as expected & it was .747 & the largest was .749. The speedi sleeve from Napa fits between .748-.752 I'm not sure now this one will work. I'm going to search & see if someone else has a smaller size. I guess I could apply some sealant on the shaft before installing the sleeve to make up the difference between the shaft size of .747 & the sleeve .748 any suggestions would be helpful. I wasn't too happy to find out someone filled the seal housing area with what looks like hardened gasket sealer  :mad2: . 

 

Pump drive shaft 

attachicon.gifoutput shaft1.jpg

 

Pump housing with the hardened sealer, what a mess.

attachicon.gifoutput shaft2.jpg

 

No sizes found for a 3/4" shaft other than the one I mentioned. I did find the same SK sleeve on Ebay for half the price. I'll get that one & try it. If anyone has any suggestions on the best sealer to put on the shaft before sliding the sleeve on I would appreciate it. Thanks

Is the part deeply scarred?



#92 Gabriel OFFLINE  

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Posted May 10, 2014 - 09:08 PM

It does make you wonder what caused it.



#93 IamSherwood OFFLINE  

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Posted May 14, 2014 - 05:50 AM

Gabriel I believe the correct part name is the piston cylinder block that the wear is on. The wear is on the opposite side of the pistons. Like I mentioned I'm not sure if I can or should do anything for this because it works fine. My concern is what caused this. If a worn bearing that would have some slop in it cause this or did some foreign material get trapped in there????

 

With much needed sleeping in & a late breakfast at Crackle Barrel along with the grandsons ball games today not much GT time. I was able to get the pump drive shaft out so I can install a speedi sleeve on that. I took some measurements of the shaft & my smallest was near the shaft seal as expected & it was .747 & the largest was .749. The speedi sleeve from Napa fits between .748-.752 I'm not sure now this one will work. I'm going to search & see if someone else has a smaller size. I guess I could apply some sealant on the shaft before installing the sleeve to make up the difference between the shaft size of .747 & the sleeve .748 any suggestions would be helpful. I wasn't too happy to find out someone filled the seal housing area with what looks like hardened gasket sealer  :mad2: . 

 

Pump drive shaft 

attachicon.gifoutput shaft1.jpg

 

Pump housing with the hardened sealer, what a mess.

attachicon.gifoutput shaft2.jpg

 

No sizes found for a 3/4" shaft other than the one I mentioned. I did find the same SK sleeve on Ebay for half the price. I'll get that one & try it. If anyone has any suggestions on the best sealer to put on the shaft before sliding the sleeve on I would appreciate it. Thanks

 

Jim, sorry but I can't shed any light on this situation, as I've never had to go

inside one of these units. If you're interested, I do have 2 sitting around, doing

nothing, and I'll be heading to NW Pa. in mid June.


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#94 Sawdust OFFLINE  

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Posted May 15, 2014 - 08:16 PM

Thanks Will. I've been searching for days & found out a fellow had an antique farm tractor & had the same problem I have, his shaft was in between the speedi sleeve sizes because of wear. He bought the sleeve recommended & also used Loctite 620 Retaining compound. He spread-ed a layer of this sealer on the shaft before installing the sleeve. I ordered my sleeve & some Loctite so when this comes in I'll be posting my results.


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#95 Sawdust OFFLINE  

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Posted June 10, 2014 - 02:11 PM

I put my Speedi Sleeve on today went real well. It fit tighter than I expected since mine was a little worn near the seal area. While tapping it on I could feel the resistance was less near the bearing area as expected but still fit tight. It's critical in my case because of the room between the shaft bearing & seal. The sleeve has a ring around it near the flange which is a break away point if you need to remove the flange, it's not in my way so I'm going to leave it. The crown of the seal will ride about 3/16" away from the ring. I may not seat the seal all the way to give me a little more room for the seal to ride on.

 

Here is the loctite I used on the shaft. I drove the sleeve down just shy of where it needed to be then I spread a coat before driving it home. This stuff is extremely expensive $5.28 for .5ml

loctite 620.jpg speedisleeve1.jpg speedisleeve2.jpg speedisleeve4.jpg

 

If you remember in my early post someone put some kind of sealer inside where the bearing seats. This stuff looked like the old Permatex that hardens. I experimented with a few different solvents & found out Mek will dissolve this stuff. I filled an old glass bowl & set the housing in it for a few hours. I took a soft brass brush & just basically wiped  the residue out. Mek can be very dangerous read the label before using. The black ring is just a shadow.

 

Before & After

output shaft2.jpg output shaft3.jpg

 


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#96 olcowhand ONLINE  

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Posted June 10, 2014 - 02:21 PM

Jim, the wear on the barrel end & face are likely from either contamination, or the hydro was ran too hot until the oil lost it's lubricity, or of course it could have been ran low on oil.

I have done about 3 similar, but in worse shape.  I turn the barrel a new face on my lathe, then machine the face plate to a new surface on my end mill.   If she still works fine, you may just leave it as-is.  


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#97 IamSherwood OFFLINE  

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Posted June 10, 2014 - 07:02 PM

thanks for the fine tutorial Jim.

I hope the fix is good for you.

looking forward to seeing it up and running.


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#98 Sawdust OFFLINE  

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Posted June 10, 2014 - 08:48 PM

Jim, the wear on the barrel end & face are likely from either contamination, or the hydro was ran too hot until the oil lost it's lubricity, or of course it could have been ran low on oil.

I have done about 3 similar, but in worse shape.  I turn the barrel a new face on my lathe, then machine the face plate to a new surface on my end mill.   If she still works fine, you may just leave it as-is.  

Daniel my guess would be contamination due to the hardened sealer I removed. There were some small pieces inside the housing loose. The filter would have never picked this up in this area. Since it ran fine before other than the leak I'm going to clean & reassemble.


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#99 Sawdust OFFLINE  

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Posted April 11, 2015 - 05:19 PM

Well after rebuilding my MTD 990 & tweaking out my Bolens H16 I'm back to working on what my wife has claimed her "Miss Massey". While waiting until the weather warms up so I can do some painting I started doing the very dreadful job of rebuilding the engine. I have looked at this thing all winter knowing this day was coming. Just a little update the last time this engine ran was about 18 years ago & it ran rough with a little smoking on start up but ran well with plenty of power.

 

My valve gap before I took it apart was exhaust .009 good but intake .022 not good. My camshaft's intake lobe has a flat spot which explains the large gap of .022.  Also the intake lifter has a worn line across the top due to the before & after flat spot striking it. The cylinder wall has a mirror finish with no lip at the top or scouring anywhere. Connecting rod has a little wear look but I will replace regardless.  I have a std piston with a small imprint of a tiny screw on top & the head imprint to match. No other damage because of the screw. Both valves look good with typical oil burnt deposits in the head. The crank looks good but it could use some polishing. My battery is dead on my digital caliper so I need to measure that for wear hopefully this won't be a surprise. I'm really pleased with what I found so I'm really happy. 

 

I'll be cleaning & prepping for a few days & I'll get a parts needed list together along with some paint soon I hope. 

Just some pics on how ugly this was
Engine rebuild 2.jpg Engine rebuild 3.jpg Engine rebuild 4.jpg Engine rebuild 5.jpg Engine rebuild 6.jpg Engine rebuild 7.jpg Engine rebuild 8.jpg
 
My camshaft with the flat lobe 
Cam shaft2.jpg

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#100 olcowhand ONLINE  

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Posted April 11, 2015 - 05:43 PM

I have a 1968 MF12 with a Sundstrand Hydrostatic tranny. Model # 902050. Everything works well with the exception of the seal leaking around the output shaft. I have replaced this seal once but it still leaks. The PO had replaced it prior to me getting it but did a bad job of doing it. My plan was to install a quick shaft repair sleeve thinking maybe the shaft was slightly worn. When I started to take the pump apart I found something that doesn't look good. Is this wear normal because of the age & should I not be concerned because it works well. If this will be a problem what would be the result later if I don't address it now. Thanks

 

This is showing I can only come out of the shaft a 1/4" with the quick sleeve because of the pulley.

attachicon.gifpump shaft.jpg

 

This is the damage. I'm sorry I don't remember what this part is called.

attachicon.gifpump damage1.jpg

 

Here is the mating surface showing no wear or damage.

attachicon.gifpump damage2.jpg

 

That really needs to be refaced.  It might well work for a long time, but maybe not.  While out I'd have someone face it on a lathe.  Very little will have to come off & it won't affect anything except to improve performance.


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#101 MFDAC OFFLINE  

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Posted April 12, 2015 - 09:10 PM

 

Well after rebuilding my MTD 990 & tweaking out my Bolens H16 I'm back to working on what my wife has claimed her "Miss Massey". While waiting until the weather warms up so I can do some painting I started doing the very dreadful job of rebuilding the engine. I have looked at this thing all winter knowing this day was coming. Just a little update the last time this engine ran was about 18 years ago & it ran rough with a little smoking on start up but ran well with plenty of power.

 

My valve gap before I took it apart was exhaust .009 good but intake .022 not good. My camshaft's intake lobe has a flat spot which explains the large gap of .022.  Also the intake lifter has a worn line across the top due to the before & after flat spot striking it. The cylinder wall has a mirror finish with no lip at the top or scouring anywhere. Connecting rod has a little wear look but I will replace regardless.  I have a std piston with a small imprint of a tiny screw on top & the head imprint to match. No other damage because of the screw. Both valves look good with typical oil burnt deposits in the head. The crank looks good but it could use some polishing. My battery is dead on my digital caliper so I need to measure that for wear hopefully this won't be a surprise. I'm really pleased with what I found so I'm really happy. 

 

I'll be cleaning & prepping for a few days & I'll get a parts needed list together along with some paint soon I hope. 

Just some pics on how ugly this was
 
My camshaft with the flat lobe 

 

Hi Jim, thanks for those detailed pics and info of your teardown. I haven't taken much time to read your thread here as my 12 is a "G" so I assumed they didn't have much in common. Your engine looks like my HH120 though besides the different starter systems.

 

My engine is a smoker once again, using 3/4 quart of oil in the 2 to 2-1/2 hours it takes to mow. Good power still. I put a new standard bore piston and rings in it a couple years ago due to oil consumption and found a pretty bad scuff in the top ring land. I was hoping that the skirt was collapsing so I tried it. Lasted about half the summer and the smoking came back. I am now sure the cylinder has too much taper, but had no way to measure that. Bore and upper piston clearance ring gap all seemed ok. Anyway looks like I will have to overbore or re-power. Here is a pic of the piston scuff so I hope your engine doesn't have it.

 

Since you do so much modeling, if you go to Hobby Lobby sometimes, look for these batteries. They work in my Harbor Freight 6" calipers great and a whole card is cheaper than one battery at most places! The number on the battery is AG13

 

I will follow this from now on!

 

DAC

Attached Thumbnails

  • HH120 piston & valves 019.jpg
  • Caliper & cheap batteries.jpg

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#102 Sawdust OFFLINE  

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Posted April 12, 2015 - 09:51 PM

Dac that's the same calipers I have & the same batteries my wife gets for all her stuff she illuminates. I never thought to use those that she has  :smilewink:

 

It might be difficult to find an over size piston reasonable. The std ones are not too bad. Have you checked with the sponsors on here for an over size piston. I can already see this MF12 is going to be a costly restore compared to my 990 but I want to do it right.


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#103 Sawdust OFFLINE  

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Posted April 12, 2015 - 10:00 PM

That really needs to be refaced.  It might well work for a long time, but maybe not.  While out I'd have someone face it on a lathe.  Very little will have to come off & it won't affect anything except to improve performance.

I agree Daniel that's one reason it's been on the bench for so long trying to decide on the mill work or not. The other reason Daniel is your fault after seeing your Unico. I had to just hang the MF12 up in the garage & let it watch me rebuild the 990 I had to have.  :D  Machinist around here are scarce. I would rather have someone that understands what I need done rather than just calling some one i don't know. I got plenty to do for awhile on this project.

 

When I find someone I'll PM you if you don't mind to get some specs on how much I can take off without damaging it. Thanks again Daniel for your expert opinion.



#104 MFDAC OFFLINE  

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Posted April 13, 2015 - 09:19 PM

Dac that's the same calipers I have & the same batteries my wife gets for all her stuff she illuminates. I never thought to use those that she has  :smilewink:

 

It might be difficult to find an over size piston reasonable. The std ones are not too bad. Have you checked with the sponsors on here for an over size piston. I can already see this MF12 is going to be a costly restore compared to my 990 but I want to do it right.

LOL! I accidentally figured out about those batteries working in the HF calipers. They were in my Mom's belongings when she passed away in '09 and just laid in a drawer here in my shop for awhile. She had illuminated Colorado Rockies baseball cap and sweatshirt the batteries were for. I actually remembered they were here and where they were when my caliper died once as the size looked familiar when I removed the dead one from the caliper. Ain't the same number and no voltage stamped on them but the physical size was the same so I figured what the heck. They work and I'm good with that! Mom's still taking care of her boy!

 

I did buy one of the standard bore piston/ring kits, for 54 bucks, rolling the dice but it didn't pay off. I have done a little online research found very few results and high pricing on overbore slugs. That is only part of the problem though. Seems machine shops around here don't want to mess with little stuff like this unless their crazy prices are ok with the customer.

 

I'll stock up on 30 wt oil for now---LOL!

 

DAC 

 

EDIT- Oh yeah I forgot to say that my wife's uncle had some kind of small engine-wish I could remember what it was--- it was only a couple months ago but--- well back to the story. He is building some weird little front end loader pretty much from scratch and the engine he wanted to use had a flat spot on the cam. He's cheaper than I am and refused to pay what was out there for a replacement. He used some kind of hard welding rod like old school guys used to build up crankshaft journals. His Dad was one of them old school welders. He ground and polished the lobe by eye and it seems to run great. He's retired so has time for this stuff!


Edited by MFDAC, April 13, 2015 - 09:36 PM.

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