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How To Replace The Engine On Your Garden Tiller

Updated on July 7, 2014

Why Change Tiller Engines?

Ordinarily you should never have to change the engine on your garden tiller. But, there are rare occasions when the tiller engine may fail prior to the expiration of the entire unit. Such is the case with my tiller. The Briggs and Stratton engine has spun a bearing and thrown a connecting rod right through the side of the engine block. Why this happened I do not know, but the damage to the engine is very extensive and repair costs for the engine will be too expensive to justify fixing it. The more economical solution when a small engine suffers major damage is usually to replace the entire engine with a comparable unit.

Garden Tiller Motor Replacement

8HP Briggs & Stratton Engine

The original tiller engine is 30 years old and warn out.
The original tiller engine is 30 years old and warn out.

The Problem

The piston connecting rod has broken and punctured a hole in the side of the engine block.
The piston connecting rod has broken and punctured a hole in the side of the engine block.

Identifying The Problem

Sometimes an engine problem can be difficult to identify. Small engine operating issues can usually be repaired without a huge expense for parts, but those little problems can be very time consuming to isolate. Major engine problems are very expensive to fix, but also very easy to identify. This Briggs & Stratton 8 horsepower engine is the original tiller engine which is 30 years old. 30 years is a long lifetime for a small 4 stroke engine and because of its age experiencing a failure was inevitable and only a matter of time. Usually when a rod is thrown through the side of the engine block it is an indicator that the bearing between the crankshaft and the connecting rod was in poor condition. This scenario can develop from normal wear and tare over hours of engine operation. When the connecting rod breaks free of the crankshaft while the engine is running the rod often gets hammered through the block wall totally destroying the engine and rendering it worthless. It will be cheaper to buy a replacement engine than to repair this blown motor.

Unbolting The Engine

Only a few bolts to remove and the old engine is ready to take off the tiller structure base mount.
Only a few bolts to remove and the old engine is ready to take off the tiller structure base mount.

Remove The Engine

Tillers are usually manufactured with an engine base mount configuration that will accept many universal style engines from different engine manufacturers. This tiller as 4 bolts that secure the Briggs & Stratton engine base to a corresponding base mount on the tiller structure. When I remove nuts from those 4 bolts the engine will lift straight up and off of the bolts that held it tightly to the structure. Once I unhook the throttle cable from the carburettor and the drive belt guard and the V-belts from the chive on the engine output shaft I can completely remove the engine and set it aside. Because this engine is blown and will not likely ever run again I am draining the gasoline out of the tank and I will put it in the Honda engine that I will be installing.

8 HP Honda Engine

This engine is the same horsepower rating as the Briggs & Stratton engine and also has the same size output shaft.
This engine is the same horsepower rating as the Briggs & Stratton engine and also has the same size output shaft.

Finding A Replacement Engine

It is very important that the replacement engine be the same horsepower as the original engine. If you use an engine with less horsepower, the tiller will not have the power to do its job effectively. Problems will also arise when you use an engine that has more horsepower than the original engine. Too much power will allow the replacement engine to over work the tiller and probably break components like the tangs that till the dirt or the gears that drive the rotating tangs.

It is always better to replace the damaged engine with an engine of the same HP rating. Usually the engine output shaft will be the same size also when HP ratings are identical. Many universal style engines have a base design and bolt pattern that will interchange with each other. It is not imperative, however, that the replacement engine always have a matching base bolt pattern because new holes can be drilled in the tiller base mount structure for bolts to fasten the replacement engine down.

Bolting It All Together

This Honda engine is universal and bolts to the existing base mount bolts.
This Honda engine is universal and bolts to the existing base mount bolts.

Replacing The Engine

I was fortunate to find a used Honda engine that is 8 horsepower the same HP as the damaged engine. Though this Honda was used on a small power generator it is a universal engine and it will bolt to my tiller base mount exactly as the old engine did. The engine output shaft is also the exact same size which will allow the existing drive belt chive to slide right on and lock and will not need replacing. The output shaft is a few inches longer though than the old engine and the V-belt guard will need to be modified to slide over the shaft to completely cover the chive and V-belt. The throttle wire hooks directly to the carburettor just as it did on the old engine. I bolt the engine down to the tiller base mount, put the chive on the output shaft, mount the modified belt guard, hook up the throttle cable and add some gasoline and crankcase oil. Now I will attempt to start the engine and see how it runs.

Gas And Oil

I put the gasoline that I took out of the old engine into the replacement  engine and check the engine oil by removing the 3/8" plug in the bottom of the engine crankcase.
I put the gasoline that I took out of the old engine into the replacement engine and check the engine oil by removing the 3/8" plug in the bottom of the engine crankcase.

Final Maintenance Check

With everything bolted back together tightly I am almost ready to start the engine and see how the tiller works. Before I can attempt to run the engine I need to add the gasoline that I took out of the damaged engine and then check the fuel lines from the gas tank to the carburettor to make certain that the engine is getting gasoline. I will also remove the oil level check plug in the lower part of the engine block or crankcase and make sure that the engine oil level is sufficient. After I am satisfied that the gas and oil are fine I can give the pull rope a few pulls to turn the engine over and the engine should start.

Off To Till The Garden

The tiller engine blew up while I was tilling my garden so now that I have the tiller running again I am off to finish the work.
The tiller engine blew up while I was tilling my garden so now that I have the tiller running again I am off to finish the work.

Questions or Comments?

I welcome all your questions and comments as well as any suggestions or ideas of your own. Please contact me through any of my links with any input that you desire to contribute. I enjoy hearing from everyone.

Thank you

How To Pam

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