Choose the right crankshaft bolt size for your Predator engine

Last Updated on August 17, 2023 by Pittalks

Are you working on installing a torque converter or centrifugal clutch onto your Predator engine? If so, you’ll need to make sure you have the correct size bolts for the job.

Keep reading to learn what size crankshaft and mounting bolts you need for your Predator engine.

Predator engines crankshaft bolt size chart

Note: Predator engines are designed for the North America market, that’s why they all use SAE standard. Do NOT try to replace them with a similar metric bolt, it will strip the holes out.

Engine displacement	Crankshaft bolt size	Buy it on Amazon
Predator 79cc	5/16″-24	79cc’s clutch bolt kit
Predator 212cc	5/16″-24	212cc’s clutch bolt kit
Predator 301cc	7/16″-20	301cc’s clutch bolt kit
Predator 346cc	3/8″-24	346cc’s clutch bolt kit
Predator 420cc	3/8″-24	420cc’s clutch bolt kit
Predator 670cc	3/8″-24	670cc’s clutch bolt kit

Predator 212cc shaft bolt size

Predator 212cc engines use a 5/16”-24 bolt for the crankshaft. 5/16” is the size of the bolt’s hex head, the number 24 is the number of threads per inch.

Make sure you count the threads on the crankshaft bolt before you try to put it on. Any number other than 24 (fine thread) is not the correct bolt and could damage your engine.

Many people have made this mistake by using a 5/16”-20 bolt, which is a coarse thread.

You can easily buy this clutch bolt kit for Predator 212cc on Amazon, the kit also includes a washer.  

Other 212cc Predator Info:
5 Dreaded Problems With Predator Engines
212cc Predator Engine Top Speed: Stock? Governor? Stage 2?
Predator 212 Oil Change: Parts, Process and More [Guide]
Best Clutch for Predator 212: Can It Be Just One? [Review]

Predator 301cc shaft bolt size

Unlike any other predator engine in this article, predator 301cc uses a 7/16″-20 bolt, which is a coarse threaded one.

This type of bolt is pretty hard to find if you plan to buy it at your local store. But you can order it online very easily.

Predator 420cc shaft bolt size

The crankshaft bolt for a Predator 420cc engine is a 3/8″-24. This is also a fine threaded bolt. This clutch bolt is also used in Predator 346cc and 670cc.

You can order this kit online and it’ll have everything you need.

Other Predator engines

Small Predator 79cc use a 5/16″-24 shaft bolt, just like 212cc.

Bigger Predator engines (346, 420, 670) use 3/8″-24 bolts as they have similar crankshaft sizes.

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Why it’s easy to thread at first, but it gets hard later?

As mentioned above, make sure you have the correct number of threads per inch. If you have already checked it, there are three possibilities:

• You were having difficulty hand threading the bolt because it was clogged with gunk.
• The bolt’s threads were knicked, in this case, get a new one.
• Cross threading – this is very likely to happen if you are using an impact wrench or electric ratchet, use your hands instead.

Engine for North America market >>SAE standard (don’t try to find similar metric bolts). Predators don’t use metric bolts on the side cover or the crankshaft. If you try and use the metric bolts it will strip the holes out.

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Mounting bolt size chart for different types of Predator engines

Engine displacement	Mounting bolt size
Predator 79cc	5/16″-24 (6 pieces)
Predator 212cc	5/16″-24 (5 pieces)
Predator 301cc	3/8”-16 (4 pieces), 5/16″-24 (8 pieces), 3/8”-16 (1 piece)
Predator 346cc	3/8”-16 (4 pieces), 5/16″-24 (8 pieces)
Predator 420cc	3/8”-16 (4 pieces), 5/16″-24 (8 pieces)
Predator 670cc	5/16″-24 (4 pieces), 3/8”-16 (4 pieces), 7/16”-14 (4 pieces)

References:

• https://manuals.harborfreight.com/manuals/69000-69999/69733.pdf
• https://manuals.harborfreight.com/manuals/69000-69999/69730.pdf
• https://manuals.harborfreight.com/manuals/62000-62999/62554.pdf
• https://www.manualslib.com/manual/674471/Predator-Engines-346cc.html
• https://manuals.harborfreight.com/manuals/69000-69999/69736.pdf
• https://manuals.harborfreight.com/manuals/61000-61999/61614.pdf

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