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0:00 - Setup
0:50 - Exhaust Deflector
2:18 - Engine Mounting
7:49 - Clutch Body Assembly
It's time to give this mower some power! Today we're installing a brand new 3.5HP 550-Series Briggs and Stratton engine.
🎬 Watch the unboxing video
• Unboxing a Briggs & St...
Before we start, find the exhaust deflector as it will need to be installed. It's normally in the plastic bag containing the instruction manual. The deflector directs the engine exhaust at the desired angle. Position it however you like using the pre-drilled mounting holes on the side of the exhaust. Two screws are used to hold it in place.
In this video we show the cutter clutch already mounted on the engine shaft. Don't forget to slip the clutch spring into place on the PTO shaft (inside the clutch cone) before bolting everything together.
🎬 Watch the engine-side clutch installation
• Scott Bonnar 45 Rebuil...
If you prefer, the clutch body can be fully assembled and the engine shaft then inserted into the clutch.
Orient the engine above the four engine mounting holes in the mower deck. We place a soft rag or cloth under the engine to do this without scratching the paintwork but it's not necessary.
The engine is secured using four bolts, each with a washer and a shakeproof washer. The bolts are threaded directly into the deck or rails. It's a good idea to ensure the threads of these holes are clear of debris before getting started (run in an old bolt or use a tap). A liberal coating of anti-seize or grease will help these bolts tighten up easily, especially if using stainless steel fasteners.
This newer-style of B&S engine has two circular mounting holes at the back and two elongated holes on the "front" side of the engine base. Use this to your advantage for fine-tuning the position of the engine (or, specifically, the engine shaft) and only lock down all four bolts once satisfied.
Unfortunately the shape of the engine housing makes it awkward to use a socket or even a ring spanner to tighten these bolts so it's a slow process with an open spanner. Take your time.
Ensure all four bolts are snug but don't overtighten them to avoid stripping the threads. If these bolts are not tight (and not kept tight), engine vibration can crack the deck or rails over time.
If you're mounting a used engine filled with oil, be careful to keep it level during installation. Some engine designs will hydrolock or foul the spark plug if tipped.
Finish by bolting together the two halves of the cutter clutch. Three bolts and Nyloc nuts are used here, with the bolt heads sitting in the countersunk holes of the clutch. To avoid mangling the bolt heads, use a large driver to hold the bolt steady while tightening the nut.
If you're keen to start the engine at this stage, don't forget to add oil!
🎬 Watch all the rebuild videos here
• Scott Bonnar 45 Rebuild
🎬 Watch all the teardown videos here
• Scott Bonnar 45 Teardown
🎬 Check out the SB 45 walkthrough videos if you're new to cylinder mowers and Scott Bonnars
• Scott Bonnar 45 Walkth...
⚠️ Your safety is your responsibility. Don't forget to disconnect your spark plug before starting work on your machine and always read and follow the instructions/labels on your equipment, tools and chemicals. ⚠️
#ScottBonnar #Engine #Clutch
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Additional Resources
🌐 Scott Bonnar Restorations FB Group
/ 1801521490103765
🌐 Scott Bonnar - Buy, Sell, Swap Australia FB marketplace
/ 1207116562722291
🌐 Scott Bonnar Addicts FB Group
/ 791569104336316
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About me and this channel: I'm Michael, a homeowner and aspiring lawn addict. I make these videos to share as much as I can, as best I can, from my recent experience rebuilding two Scott Bonnar 45 mowers. Although I'm a passionate wood worker and ex-IT guy, I have zero mechanical training. I'm no expert on these subjects but I learn by sharing and it encourages me to grow a better lawn and build a better mower if I know you're watching!
© 2020 Michael Hanes. All rights reserved.