Magnum 20 Rebuild

This is where we can discuss all the stuff made after IH's sale to MTD.
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dag1450
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Magnum 20 Rebuild

Post by dag1450 »

Ok..well im finally going to do it. Let me start by saying I'm pretty nervous about the whole process but if I take one step at a time...and your guys help .....it might run again. :? I have done a couple car engines years ago so I'm not a complete stranger to this type of stuff. I plan to mostly post pictures with little dialogue. Feel free to comment or ask questions.... as I will also b asking some from time to time. I'm already into it but I see this taking a couple months to finish.
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

I forgot to mention that this was a good running engine w about 1700 hours. It did burn a little oil ,was hard starter when hot, fuel pump was shot, and starter would not throw out too well below 40°.
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duke
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Re: Magnum 20 Rebuild

Post by duke »

Looking forward to following this thread :beer:

PTWannaHave
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Re: Magnum 20 Rebuild

Post by PTWannaHave »

dag1450 wrote:Ok..well im finally going to do it. Let me start by saying I'm pretty nervous about the whole process but if I take one step at a time...and your guys help .....it might run again. :? I have done a couple car engines years ago so I'm not a complete stranger to this type of stuff. ...
I am confident you'll do just fine!!

Not being in a rush is a good policy...

Cheers,
PTWannaHave

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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Thanks guys. The engine was greasey and dirty but not too bad. I was thinking the cooling fins on the cylinders would b somewhat full as the screen under the steering column has never been on....but they were clear. Took off the flywheel and checked the magnets...only one loose. Ok first question right here. Best method for reattachment.
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BigMike
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Re: Magnum 20 Rebuild

Post by BigMike »

Dave, you are going to do juuuuust fine :beer:
Slow and steady wins the race. As has already been said, clean, clean, clean......then clean it some more.
Brace yourself for parts prices......I did not find aftermarket stuff and used all Kohler but I made a commitment to build it the best I could and have a great running engine that makes loads of power.

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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Yea Mike I have been looking for aftermarket to no avail. I'm good w the real stuff. I found a pretty complete kit...pistons seals and gaskets. Like said before I also need a fuel pump, starter, governor gear and im sure other stuff. Talking to a local machine shop....ouch!
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BigMike
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Re: Magnum 20 Rebuild

Post by BigMike »

Well, if I don't have complete faith in a machine shop I am not leaving parts with them.....period.
You are not all that far from Engine Mike are you? UPS the stuff to him or Kevin at Pipestone Small Engine near me.

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Re: Magnum 20 Rebuild

Post by JMotuzick »

mike and I where just texting about him doing a batch of kohler cranks real soon.... get some mesuments and yours will get added to the stack!

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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Thanks Joe. Yes the machine work has been one thing I have been stuglin with. I called around to several and out of the six I called one guy said..." Yea bring it in..and I might b able to do it". So then I called the shop that I used 30 yrs ago( I thought they were out of business) when I asked if he does lawnmower engines he said no but gave me a name of a shop close by. I went up to the shop and it is full of crankshafts, heads, flywheels, and really all kinds of stuff. It seems to b a very busy shop. He seemed willing and gave me the time of day. I thought about shipping it somewhere... And that would b fine I guess when u get good recommendations w history ..thanks BigMike. Its hard making a new contacts... But at some point there has to b a first time.....sometime. :? I will talk prices when I get further along.
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Dave C
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Re: Magnum 20 Rebuild

Post by Dave C »

I plan on sending at least 2 magnum cranks to mike also.... they like to group their work up there... if your gonna set the machine up for 1 crank you can do 10 just as easy.
Trying to save cubs... one at a time.......

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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

What size magnums Dave? Is it wishful thinking that I won't need crank work? I sure hope not but will have to check somehow. I could have my nephew bring over his mics. I saw undersized rods..for an arm and a leg...bearings were just as much. Please tell me some cranks don't need work. :shock:
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Re: Magnum 20 Rebuild

Post by JMotuzick »

Sadly most do....

Get that mic set and measure mesure again just to be sure. Then mesure again!

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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

I'm about as far as I can go on this until I firm up some details w shop....I hope this week.
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Pistons skirts looked good and the bore has no lip i can feel....but the pistons had some small chipping on the top edge...only thing I can think this is from the carbon. Have u guys seen this? Valve clearance to tappits....way to tight. I guess as the seat wears the valve sinks. I did some reading and this seems to cause my hard hot restarts.
Oh...and intake valve seal...Hahaha. They were toast! :x
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

ok guys....If u have not figured out im on somewhat of a budget. Tom Scott contacted me once he saw my thread and talked to me about doing some of the machine work myself. Needless to say i am a little apprehensive about the whole idea....he seems to think no problem. He put me in touch w this video laying out the boring measuring and honing process for the do it yourself er. Im just not sure i have the right tools....https://www.youtube.com/watch?v=bT1nRq-cM7M
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Tom Scott
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Re: Magnum 20 Rebuild

Post by Tom Scott »

Dave - I'm really disappointed that you shared that; this was going to be our new business venture, and now everybody knows the secrets to proper machining!

I can't believe you turned on me like that... :evil:
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Tom...I told u I was not comfortable with this. I feel we r moving way too fast! It's not u..its me! :oops:
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Re: Magnum 20 Rebuild

Post by bbaker »

Tom Scott wrote:Dave - I'm really disappointed that you shared that; this was going to be our new business venture, and now everybody knows the secrets to proper machining!

I can't believe you turned on me like that... :evil:
I thought you were serious before I watched the video.... lol

Only thing I'm concerned about is he didn't address making the rings bigger? :)
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

:lol: Bryan..... With the "piston shim material" ......no ring work needed! :lol:
This guy is my new go to for how to's :?
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Ok....back to the real show. I hope to pick up the machine work today or tomorrow. I will post as soon as I get.
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dag1450
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Re: Magnum 20 Rebuild

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I found a nice rebuild kit at Pat's small engine warehouse I think was the name. Came with pistons rings seals gaskets. To my door for like $390. No aftermarket parts r available for the mag 20. Not that I could find. I also picked up a governor gear, exhaust valve guides, and a few other goodies from eBay.
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Re: Magnum 20 Rebuild

Post by dag1450 »

I still need to order a new and improved breather and tube....plus that green grass thing inside. I guess I will b buying a micrometer after all to check the crank stuff.
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Re: Magnum 20 Rebuild

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Picked up the cylinders and heads the other day. It looks good but I really have no idea if they did a good job or not. I can only look at it.....it feels nice and looks clean. :lol: Bored, cut seats, installed new exhaust guides, cut heads, decarboned everything too.
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Ok so I'm back at this project...... I failed to update u guys about the prices for the machine work labor only. Cylinders and head work only. Bore, cut heads, cut valves seats, install new guides, hot tank.....all for $400. Ouch! It sounds high i know. The guy has a busy shop so I guess he can set his prices.
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dag1450
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Re: Magnum 20 Rebuild

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Yesterday I split the block. Stinking oil pressure sensor adapter broke off... :roll: I had to drill it out. I guess I should try to chase the threads but its pipe threads...idk. Washed everything today in the old parts washer ( Rubbermaid) with k1.
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Governor was rubbing on retaining screw.....
Governor was rubbing on retaining screw.....
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

So...I see this "10" on the back of the old bearing. It surly looks like an oversized bearing? Can anyone verify how they mark the bearings for size.....thanks
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Tom Scott
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Re: Magnum 20 Rebuild

Post by Tom Scott »

dag - Since pipe threads are tapered you can always just tap a little deeper if the threads were injured by drilling. Just don't go too deep or the fitting will bottom before the threads get tight. Also, must use a pipe thread tap, no other tap will work.

On the bearings, you will have to mic the crank and bearings reinstalled in the block (without the crank) to judge clearance wear, since I know you are hoping to not machine the crank. These should be mic'ed in many spots if you are trying to skip machining these, as they can wear unevenly; they can be egg shaped when worn, have taper from front to rear, etc. And scoring, uneven bearing surface wear, embedded contaminants in the bearing surface, etc.

Also the thrust wear matters too. I haven't rebuilt a Magnum, but one bearing will have a thrust surface to control axial movement of the crank. The bearing in your pic has a thrust bearing surface on each side. With the crank installed in the block with those bearings you can measure how much thrust clearance you have.
I'm sure it is all in the Kohler manual... :beer:
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Thanks Tom. I guess I should look at the book! ;)
Man....that oil reducer fitting is a weird one. Cheapest i could find was $12 for a steel one. Cub wants like $30. 1/16" male x 1/8" female...npt. It seems to b used today for mustang fuel rail something or other.
Washed most parts again today...this time w purple power and hot water. Really blasted oil passages.
Sorry no pics.
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dag1450
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Re: Magnum 20 Rebuild

Post by dag1450 »

Used jb weld. I hope I got it on the right way....I was going to mark the top but in moving it around and washing it did not get done. I was able to use the old glue on the back to tell "North and South" :?
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Trim nails worked good as a straight edge
Trim nails worked good as a straight edge
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