How To Restore An Old 12P Mighty Mac?

hejerry(9A)January 3, 2013

I inherited my dad's 1984 MacKissic 12P Mighty Mac chipper/shredder and I would like to restore it to use. Dad always stored the machine in his weather proof garden shed when it was not in use and it has been stored there for the past 20 years or so. It has a 7 HP Briggs and Stratton engine which I would like to get in running order before I tackle the shredder part of the machine. However, I have never attempted anything like this and I need some advice. Can anyone give me detailed advice or tell me a book I can obtain or where on line I can find detailed information on what needs to be done to a 30 year old 7 HP Briggs and Stratton engine that has been in storage 20+ years to get it into running order?

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Try youtube on starting old Briggs engines at the site below and there must be more and listed info.

Good Luck!

    Bookmark   January 3, 2013 at 2:26PM
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I had to do a similar restoration on my 12P Mighty Mac. I did it by replacing pieces as needed and found Mackissic to be extremely helpful. Try giving them a call and/or getting onto their website for assistance and parts diagrams. Those chippers have changed very little over the years, other than the HP of the engines and minor part design updates.

    Bookmark   January 3, 2013 at 10:43PM
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Thanks loger and hellyeahitis! I e-mailed MacKissic and they confirmed that parts are available for the machine and attached a PDF owners/operators manual that includes parts breakdown. I want to get the engine started first before I tackle the chipper/shredder mechanism. The centrifugal clutch is old, rusty and I need to remove it so that I can examine and service it. However, I'm having difficulty removing the retaining bolt which is probably all rusted up and frozen to the shaft. It's too close to the gas tank for me to heat it with a torch but I have been applying Liquid Wrench to it several times a day. Anyone have any tips on how to unscrew the retaining bolt?

    Bookmark   January 9, 2013 at 9:55AM
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Please post a picture or link showing the bolt. Sounds like a job for an air impact or hand impact wrench to give it a shock treatment along with the penetrating oil. This will help w/o holding the flywheel w/o the proper tool.

Plus, more pics if possible and tell me the process of more than one pic per post. Thanks In Advance!!

    Bookmark   January 9, 2013 at 11:18AM
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Loger -

Here's a photo of the retaining bolt -- circled in red:

After I remove the stuck bolt, I'll loosen the set screws, remove the retaining ring then keys from the keyways. Then hopefully the rusty clutch will slip off. I'll probably replace it once I get it off because as you can see it has been repaired (welded) and I expect the springs inside are a rusty mess.

Here's a photo of the motor with the frozen bolt circled again in red:

In order to post multiple photos on GardenWeb, you must first upload them to a photo sharing site on the WWW. There are several such sites -- I used PhotoBucket to post these. After the photos are uploaded to a place like PhotoBucket, you then copy and paste the HTML link into the post where you want them to appear.

    Bookmark   January 9, 2013 at 5:03PM
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Thanks! Good pics of problems and good tips on uploading multiple pics. I think I see the weld with a little light added on the outside of the pulley (correct)? I'll hope you can salvage some of the clutch but you have a part source. Good Luck with the carb and cyl if the carb was not run dry and the cyl w/n lubricated. Does the eng turn over w/o feeling locked and a compression "kick-back? Light oil and checking for approx 100 lbs or not holding with your thumb will give an indication.

I kept a spare Briggs about 10 yrs stored after putting and turning the crank with about an ounce of oil in the cyl and a dry carb. The monster started on 2-3 pulls after the years.

I use a free ver of PhotoBucket and feel I can copy past the HTMLs as needed vs url addressed below to view when I study PB a little.

    Bookmark   January 9, 2013 at 9:46PM
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txtom50(8a texas)

You should be able to remove the spark plug and stuff a piece of soft rope down in the cylinder to lock the piston while trying to break the bolt loose. I'm thinking you may be able to use a gear puller once you get the outer hub off.

    Bookmark   January 10, 2013 at 6:06AM
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A sample of sharing multiple Pictures using the two url links that exist.

Sample # one:

Sample # two:

Well it did not work vs Bingo! The free account might not allow this and I can understand or I put in the wrong codes. Enough of this Monster, I need to get busy loading a fresh batch of wood to the patio with this good weather today

Plus, I hope the compression test, carb inspections and clutch inspection all were good. Briggs are good tuff engines if they are serviced or stored properly. When you get to checking the spark it will be interesting if it is electronic ignition or Magneto (with points/condenser). I lost track in the late 70s, early 80s and converted some mag to electronic in that span. Neat, due to the good fire and oil blow-by from wear not affecting the eliminated points.

    Bookmark   January 10, 2013 at 12:17PM
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A sample of sharing multiple Pictures using the two url links that exist.

Sample # one:

Sample # two:

Well it did work Bingo! I put in the wrong codes first.

    Bookmark   January 10, 2013 at 4:57PM
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Logger -

Yep -- you got it! You need to use the one PhotoBucket calls HTML code for GardenWeb posts.

I won't be trying to start the engine until I remove the centrifugal clutch and I'm still unable to remove that retaining bolt/nut. Do you know whether it's a standard or reverse thread?

    Bookmark   January 10, 2013 at 10:35PM
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I d/n know thread dir and hopefully a personally owner will share or ask your Mackissic supplier. Plus, I w/n hesitate to drill a 1/8" hole vertically in the bolt to add oil "if needed" which I doubt vs a good shock. Hopefully you would feel the drill exit the bottom of the bolt. Next, rem the gas tank and use some heat.

How are you restricting the crank from turning? I have read of the rope holding the crank with 2 cycles. I always like to deal ext crank to crank ends. There is a flywheel wrench you should be able to borrow or purchased, large channel locks and strap wrenches have gotten me through these matters. Impact Shock is the easy out. Do you have a local Small Engine Shop? If so lean on them, they are nice people in this area..

    Bookmark   January 11, 2013 at 12:00AM
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Logger -

I'm not impressed with the small engine repair shops near me -- poor workmanship, surly attitudes and overpriced work. I'm in absolutely no hurry to get the machine up and running and I'm confident if it can be done I can do it. In order to get to both ends of the crank shaft, I removed the starter cover - I figured I'll need to replace the rewind starter pull rope anyway. If all else fails I'll get my hands on an impact wrench but first I want to know for sure which way the bolt is threaded.

    Bookmark   January 11, 2013 at 8:53AM
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I totally understand what you are saying about the Challenge, Thread's direction, and Attitudes/Cost. I have seen and worked through much of this. Knowing the thread directions, a short box-end wrench and a hammer should give you the little shock you might need.

Otherwise! A Minimal Hand Impact Tool could be your friend on many tasks if you are not into air impacts. Tight nuts, bolts and screws a good hand twist toward on or off, hold tight and "BANG"!! I hate the blow that bearing, seal, etc can get but most of the force is toward on/off. Air is better but not worth the cost if you are not Really Into Stuff... If I see where I can make a suggestion I'll Jump In. Good Luck!

Northern Tools:

    Bookmark   January 11, 2013 at 11:21AM
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I learned that the bolt is a standard thread -- counter clockwise to remove and I purchased an impact wrench on sale at Tractor Supply for $20. I already had an air compressor. The bolt came off effortlessly with the impact wrench, I loosened the set screws and pulled the clutch off by hand. Surprisingly it doesn't look all that bad, a bit of rust, but I think I can restore it to use. It'll be a few days before I work up the courage to tackle that but it's next on my to do list.

    Bookmark   January 12, 2013 at 10:17PM
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Good News! The Best News IMO will be to hear, "The Briggs Has Fired And Is Running Houston"! I'll be standing by and wish I had the patience you guys have. For some reason and maybe a good one, I like to fire the engines first. In my interest/needs, the engine is the heart for the project to continue vs sentimental values (on donated to be donated projects) or scrap it. Good Luck and keep us posted.

    Bookmark   January 12, 2013 at 10:56PM
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