Different Shaft Size on MTD B/S Engine

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  #1  
Old 06-24-07, 01:14 PM
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Question Different Shaft Size on MTD B/S Engine

I have a Yardman 21" Push mower that the crank shaft was bent. I purchased the crank shaft and necessary parts to rebuild engine. After I completed the rebuild, I went to put the Drive Pulley and Blade adapter on and the output shaft on the new crank shaft is larger. The old crank shaft tapered down to 7/8", but the new is 1". Has anyone heard of this happening? I'm going to try to contact MTD tomorrow. Here are the part numbers:

Yardman
12A-S569T401
Briggs
123J09-0188

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  #2  
Old 06-24-07, 02:04 PM
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Is the crankshaft part number you purchased 691451? If so, this is the correct crank and I don't understand why the specs would have changed without an update kit to include a new hub/pulley arrangement. If this is not the part number you purchased then you will need to order the correct crank.
 
  #3  
Old 06-24-07, 02:14 PM
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That is the part number. I'm not sure if B&S changed it because of the shaft being too easy or what. Kinda frustrating to rebuild this lawn mower and now it seems to be useless.
 
  #4  
Old 06-24-07, 02:18 PM
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Having been in the business for 25ish years and having replaced numerous crankshafts in rotary mowers over those years I don't ever recall running into a situation that you're in. Did you accurately measure the crank and can say with certainty that the new crank is 1"? As opposed to, the now common, 25mm? I wouldn't write this mower off just yet, post back with the answers to my questions, if you would, and I can likely recommend new, different PTO parts to get this back to useable.
 
  #5  
Old 06-24-07, 02:32 PM
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I don't have a caliper handy, but with a good straight edge, it could pass for 25mm.
 
  #6  
Old 06-24-07, 03:04 PM
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Without firsthand knowledge, you will need to measure to be sure of the exact size. 25mm is equivalent to .984", only 16-thousandths of an inch smaller. So, as you can see, this is extremely close in size and would need to be accurately measured with a dial (thousandths) caliper.
 
  #7  
Old 06-24-07, 08:04 PM
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It is possible that the part you got was not marked correctly. I have on a few rare occasions opened up a box with the correct part number on the box, but the wrong part inside.

My reference for that part number shows 7/8" diameter x 3-5/32" long crankshaft, Full Keyway with 2 woodruff key slots, Drilled & Tapped 3/8-24. You may be able to purchase a new pulley and blade adapter to fit the new crankshaft if it is long enough and keyed correctly for your application.

Best of Luck...
 
  #8  
Old 06-26-07, 05:27 PM
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After talking to MTD, Briggs, and my supplier. I will have to re-order the crank shaft and rebuild the engine...again. Briggs said more than likely it was a parts mix-up, they showed that p/n to be 7/8".

Also, do you think that I need to buy another gasket set, or is one I used on the first rebuild alright to use? They have 0 time on them. Personally I feel it would be fine, but never hurts to get others opinion.

Frank
 
  #9  
Old 06-26-07, 07:09 PM
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You take a chance when you reuse a gasket. I would be fibbing if I said I have never done it, in fact I have done it several times and had it work alright and then there are the ones that leaked.

It does not matter that the engine was never run or not as the gasket has been compressed when you tightened the sump down. You would probably be alright reusing the gasket, but it's your call.

You don't have to purchase an entire gasket set, you can just get the sump gasket and you don't have to pull the head off to replace the crankshaft.
 
  #10  
Old 06-27-07, 02:51 AM
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If you purchased the parts through an authorized Briggs shop and they know of the issue, they should provide you with a new sump gasket at no charge to you, simply out of good-business-practice. But they can - but probably won't - submit a warranty claim for such since the hassle would outweigh the financial loss (cost of the gasket). However, they are likely going to submit a claim for the incorrectly boxed crank and can submit the gasket on the same claim. Moral: Insist on a new sump gasket from the dealer.
 
  #11  
Old 06-28-07, 06:50 AM
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Shaft Size @ 25mm on New Engine

My problem is similar to "fatherof4's." Maybe you can provide some help? I own a 21" self propelled Yard-Man 12A-979L401 model lawn mower. The engine went south and I have replaced it with a new B&S Intek engine of the same size. My problem is that the new engine has a 25mm shaft size while the old B&S had a smaller shaft size. I need a new 25mm blade adapter, pulley assembly, sleeve spacer: upper and lower, wave washer. Is there a 25mm conversion kit available? What part numbers do I need? I just need to know the retrofit part numbers and where to buy them.
 
  #12  
Old 06-28-07, 05:23 PM
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MTD does have a Drive pulley and blade adapter that would fit, but the length of the items total up to 3.8" while the one I have on my mower is almost 5.8". So I would have lost 2" on my cut, and probably would have messed up the output draft for the clippings. But yours might be different. Measure your assembly's and of they are closer to 3.8" I'll give you the part numbers.
 
  #13  
Old 06-28-07, 05:39 PM
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Steve, to answer your question on a conversion kit, no, MTD has no such kit as you need. You would need to purchase individual parts that will make your current engine useable with the driveline. Bear with me a day or so and I'll see if I have a model series, in my shop for repairs, that uses metric specs similar to your model mower. Whoa, hold on a minute, I just looked up your model and this is a six speed transmission, correct? Man, you're going to get banged for some cash to convert all the parts needed over to metric specs, if they're even available. I don't believe that the six speed mowers are made any longer and especially since the popularity of the metric spec'd crankshafts (2004 model year and since). But I'll have a look and get back to you soon.
 
  #14  
Old 06-28-07, 08:37 PM
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Thanks to both of you for the response. Sometimes the knowledge base is hard to tap into. I work hard and even harder to keep my stuff in the best shape possible. Yes it is a six speed transmission; not sure how they derive that...though it does go faster and slower depending on the gear selected. I have the mower operating in push mode right now. Kind of a rigged situation, but something had to cut that bermuda grass, the rain is coming. If I stack everything together the length is 4.0": 2.25" Blade Adapter, 1.25" Pulley Assembly, and .50" Spacer. The engine i have now is a 6.75 Intek off of a Husqvarna. Runs sweet, but i really need that blade adapter for security. Thanks...
 

Last edited by steve900t; 06-28-07 at 08:41 PM. Reason: missed spec on lengths
  #15  
Old 07-11-07, 08:16 PM
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I have been working out of the country for the last few weeks so i'll do some catch up now. I have found that the same mower made by yardman came with a honda engine in later production years. The honda engine had the bigger 25mm crankshaft. The blade adapter will work but i have not found out if the pulley system will fit the the pulley assembly I have. If you know anything let me know. i am sure there will be others like me!!! Thanks for the help to this point...I know we are all busy so any advice is greatly appreciated. The rain in the south has my lawn growing at a rate that requires cutting twice a week.
 
  #16  
Old 07-12-07, 02:31 AM
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Sorry Steve, I can't figure out anything for you to do to get this back up and running and functioning properly. Perhaps if you call the MTD Central Distributor in your region, which you'll be routed to if you call the MTD Factory. The number is 1-800-800-7310. Good luck and let us know how you make out.
 
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