A true 7/8-inch engine-shaft bore measures 22.225 mm, and the product list includes one 7/8-inch-bore option: a 40 Series torque converter driven clutch, not a conventional shoe-style centrifugal clutch. The other listings use 20 mm or 3/4-inch bores, which are not interchangeable with 7/8 inch. The options below are best suited to buyers who can match the bore and clutch type to their setup.
| Product | Listed bore | Best suited for |
|---|---|---|
| 40 Series Torque Converter Driven Clutch | 7/8 inch | Buyers needing a 40 Series driven clutch |
| WPHMOTO 12T Centrifugal Clutch | 20 mm | Compatible 20 mm-shaft engines |
| 20 mm 12T Centrifugal Clutch | 20 mm | Small-engine builds with a 20 mm shaft |
| ILONPA 12T Centrifugal Clutch | 3/4 inch | 2–7 HP projects using a 3/4-inch shaft |
| Predator 212 Clutch Kit | 3/4 inch | Buyers seeking a clutch and chain kit |
40 Series 7/8-Inch Bore Driven Clutch
This is the closest match for a buyer specifically searching for a 7/8-inch bore. The listing describes it as a 40 Series torque converter driven clutch and gives replacement part number 209139A. It is intended for 8–18 HP go-kart applications, according to the product information.
Best for: Buyers who need a 7/8-inch-bore driven clutch for a compatible 40 Series torque converter system. It is selected because it is the only listed product explicitly described with a 7/8-inch bore.
Check before choosing: This is a driven clutch, not a standard centrifugal shoe clutch. Confirm that the required component is the driven side and that the torque-converter series and part number match your setup. The listing does not specify tooth count or chain size.
WPHMOTO 20 mm 12T Centrifugal Clutch
This conventional centrifugal clutch has a 20 mm bore, 12 teeth, and a stated engagement speed of 2,000 ±100 RPM. The listing names several engines, including GX160, GX200, Predator 212, GC160, and GC190, and identifies it for a #35 chain setup.
Best for: Buyers whose measured engine shaft is 20 mm and whose drivetrain uses the listed 12T/#35 configuration. Its stated engagement speed and engine examples make it a useful comparison for small-engine projects.
Limitation: A 20 mm bore is approximately 0.787 inch, not 7/8 inch. Do not select it based only on a broad “7/8 clutch” search; verify the shaft measurement first.
20 mm 12T Clutch For #35 Chain
This 12-tooth centrifugal clutch is listed with a 20 mm bore and an engagement speed of 2,000 ±100 RPM. Its engine examples include GC160, GC190, GX120, GX140, GX160, GX200, and a Predator 212 engine with a 20 mm shaft.
Best for: Buyers who have confirmed a 20 mm shaft and want a clutch listing that names several small-engine families. It offers a straightforward 20 mm alternative to the 3/4-inch options below.
Limitation: The product information does not state that it fits a 7/8-inch shaft. Engine model names alone do not establish shaft compatibility, so check the actual shaft diameter and drivetrain requirements.
ILONPA 3/4-Inch 12T Clutch
The ILONPA clutch has a 3/4-inch bore, 12 teeth, and is specified for #35 chain with a 9.525 mm pitch. Its listed engagement speed is 2,300 ±300 RPM. The product information includes Honda GX-series engines and certain 196cc applications.
Best for: Buyers who need a conventional clutch for a verified 3/4-inch shaft and a #35 chain. The listing provides a specific shaft-size exclusion that helps prevent a common fitment error.
Limitation: The listing says it is not for 20 mm-bore versions of Briggs & Stratton or Tecumseh engines. A 3/4-inch bore is also smaller than both 20 mm and 7/8 inch.
Predator 212 3/4-Inch Clutch Kit
This kit combines a 12-tooth, 3/4-inch-bore centrifugal clutch with #35 chain, screws, and a connecting link. The product description names Predator 212 and compatible GX160/GX200-style small-engine projects.
Best for: Buyers who have a 3/4-inch shaft and want the clutch and chain components together. The included parts can simplify sourcing compared with buying a clutch alone.
Limitation: The stated 3/4-inch bore does not match a 7/8-inch shaft. Confirm the shaft diameter and chain specifications before ordering.
Buying Guide: How To Choose The Right Bore And Clutch
Does 7/8 inch mean the same as 20 mm?
No. A 7/8-inch shaft measures 22.225 mm. A 20 mm shaft is about 0.787 inch, while a 3/4-inch shaft is 19.05 mm. These are distinct sizes. Measure the shaft diameter rather than relying on the engine’s displacement or model name.
Do you need a centrifugal clutch or a driven clutch?
A centrifugal clutch and a torque-converter driven clutch serve different positions and functions in a drivetrain. The 40 Series listing is a driven clutch; the other four products are described as centrifugal clutches. Identify the component you are replacing before comparing bore sizes.
What chain details should you compare?
Match the clutch sprocket tooth count and chain type to your existing drivetrain. Several options list 12 teeth and #35 chain. For the ILONPA model, the listed #35 chain pitch is 9.525 mm, or 3/8 inch. Do not assume a chain fits just because the bore matches.
Which engagement speed matters?
Engagement speed indicates when a centrifugal clutch begins to engage as engine speed rises. The listed 20 mm WPHMOTO and 20 mm clutch options state 2,000 ±100 RPM; ILONPA states 2,300 ±300 RPM. Compare these figures with your project requirements, and avoid assuming that one setting suits every engine or vehicle.
Can an engine name confirm fitment?
No. The same engine family may be sold with different shaft diameters or configurations. Check the measured shaft, bore, chain size, tooth count, and clutch type against the product details before buying.
Frequently Asked Questions
Is a 20 mm clutch a 7/8-inch clutch?
No. A 20 mm bore is about 0.787 inch; 7/8 inch is 22.225 mm.
Which listed product has a 7/8-inch bore?
The 40 Series torque converter driven clutch is listed with a 7/8-inch bore. It is a driven clutch, not a conventional shoe-style centrifugal clutch.
Is a 3/4-inch clutch interchangeable with a 20 mm clutch?
No. Their bore dimensions differ. Use the size that matches the measured engine shaft.
What does 12T mean?
12T means the clutch sprocket has 12 teeth. The chain must also match the sprocket’s specified chain type.
What should I measure before ordering?
Measure the engine shaft diameter and verify the required clutch type, chain size, tooth count, and drivetrain position.