Repowering My MTD
Printed From: Unofficial Allis
Category: Other Topics
Forum Name: Shops, Barns, Varmints, and Trucks
Forum Description: anything you want to talk about except politics
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=210332
Printed Date: 07 Mar 2026 at 1:09am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Repowering My MTD
Posted By: Dave H
Subject: Repowering My MTD
Date Posted: 06 Mar 2026 at 7:04pm
No need to get into why the current engine is toast.  Anyhow I really like this lawn tractor. It came with the twin cylinder opposed motor. Finding a replacement motor of that vintage has proven like impossible so far. Does anyone know of a replacement engine chart that says what else besides my dinasour cousin will fit the mounting, shaft, ect. I don't care about the motor fitting under the sheet metal. This thing has beening running around naked for some time. thanx
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Replies:
Posted By: jaybmiller
Date Posted: 06 Mar 2026 at 8:03pm
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Assuming it's a B&S , drop in a V-twin ! , they run smoother than the opposed, should fit fine.Wiring is the same. LOTS of 'dead ' riders with vtrins in them for sale, anything from 16 to 24 HP will work for you. ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: Dave H
Date Posted: 06 Mar 2026 at 8:44pm
Jay, Thanks for the reply, are you indicating that the crank shaft diameter and length are about all the same. That is what has me befuddled. Like I indicated fitment on the deck of the chassis and crank has me in a tissy. 
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Posted By: AllisFreak MN
Date Posted: 06 Mar 2026 at 9:13pm
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This thing has beening running around naked for some time. thanx Sounds like a girl I once knew... ------------- '49 A-C WD, '51 A-C WD, '63 A-C D17 Series III, 1968 A-C One-Seventy, '82 A-C 6060, '75 A-C 7040, A-C #3 sickle mower, 2 A-C 701 wagons, '78 Gleaner M2 |
Posted By: Dave H
Date Posted: 06 Mar 2026 at 9:59pm
Allis, you lucky dog. 
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Posted By: steve(ill)
Date Posted: 06 Mar 2026 at 11:55pm
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Dave... you can find the shaft dia and length on line.. I assume you have the old 18 HP opposed 180 degree twin.. The came in a vertical and horizontal option... The newer engines are the same, both options...(Remember, some of the HORIZONTAL shaft engines have a shaft sticking out both ends for the DRIVE on one end and the PTO / mower belt on the other...) They also advertise the shaft diameter and length.. I have found most are comparable, as long as you dont try to put a 25 HP motor in a 18 HP tractor..... Jus compare what you have now to the new.. I know you want a YES- NO answer, but some of this depends on what engine you chooses..
this is what GOOGLE says......... Briggs & Stratton 18HP Opposed Twin Engine Crankshaft Specs422707 model often faces engine replacement challenges and crankshaft compatibility issues during upgrades. The Briggs & Stratton 18HP opposed twin engine (model 422707) typically has a crankshaft diameter of 1 inch and a length around 3.5 inches. When replacing the engine, matching these dimensions is crucial for proper fitment with the mower deck and transmission. Measure the existing crankshaft carefully, including keyway size and position. Also, verify mounting bolt patterns to ensure compatibility. Proper alignment prevents premature wear and ensures smooth operation after replacement. ------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date Posted: 06 Mar 2026 at 11:57pm
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NOTE the SPEC ... gives shaft size... the new engines will all be overhead cam and have oil filters .. both improvements over the old 160 18 HP opposed twins.  ------------- Like them all, but love the "B"s. |
Posted By: steve(ill)
Date Posted: 07 Mar 2026 at 12:09am
here is another version... NOTE the shaft is 1-1/8 instead of 1 inch... so you have to VERIFY as they make a couple different sizes.. ------------- Like them all, but love the "B"s. |