How to Choose Your Kart Motor Mount Size: Tube Diameter, Rail Spacing & I vs K Type Explained
Choosing the right motor mount for a 4-cycle kart is not about brand loyalty - it is about geometry. Once you know two numbers about your chassis, the right Odenthal mount, clamp pair, and bolt pack falls out automatically. This guide walks through the exact measurements, decodes I-Type vs K-Type, and gives you a kart-by-kart cheat sheet for Briggs LO206, World Formula, GX200 clone, and shifter classes.
If you have not yet, start with our overview of the new Odenthal lineup at Swift Karting. It groups every motor mount, clamp, and bolt pack we currently stock so you can see the full set side by side.
The Two Measurements That Matter
Every kart motor mount sits on a pair of parallel rail tubes near the rear axle on the driver's right side. To pick a clamp size you need:
- Tube diameter - the outer diameter of one frame rail tube. Most karts run 28mm, 30mm, or 32mm tubing.
- Rail spacing (I or K) - the center-to-center distance between the two rails. There are only two common values: 92mm (I-Type) or 90mm (K-Type, used by CRG-derived chassis).
The clamp guide below shows both measurements visually. Total outside-to-outside width minus one tube diameter equals the center-to-center spacing.
Worked example: outer-to-outer = 122mm, tube = 30mm, so 122 - 30 = 92mm = I-Type. Order a 30mm I-Type clamp.
How to Measure Your Chassis (Calipers, No Calipers, or by Brand)
With calipers (most accurate): open the calipers across one tube to read the outer diameter. Then measure outside-edge to outside-edge across both rails at the engine pad area. Subtract the tube diameter. Done.
Without calipers: wrap a strip of paper around one tube, mark where it overlaps, then measure the marked length and divide by 3.14 (pi). That gives you the outer diameter. Then use a tape measure across the rails. Less accurate, but it gets you within 1mm.
By brand and model - this chart covers the most common kart chassis we ship to. If your chassis is on this list and you do not feel like measuring, this is what we recommend.
| Chassis | Typical Size | Notes |
|---|---|---|
| Birel AM29 | I28 | 28mm tube, 92mm center-to-center |
| Tony Kart Racer | I30 or I32 | Measure to confirm year |
| Kosmic Kart | I28 or I30 | Measure to confirm year |
| FA Kart | I30 or I32 | Measure to confirm year |
| Top Kart | I30 or I32 | Measure to confirm year |
| Margay Ignite | I30 | Standard rail spec |
| Coyote | I30 | Standard rail spec |
| VLR | I28 | Cadet-style rail spec |
| MGM | I32 | Senior rail spec |
| CRG (all models) | K Type (90mm) | Measure tube for 28/30/32 |
| All Cadet karts | I28 | Unless CRG-based |
| Swift Kart A Flyer | I30 | Perfect fit for Pro Series 0 deg low profile |
| Eagle (American-made) | I30 | Same as Margay/Coyote spec |
Sizing reference adapted from Odenthal Racing's published clamp size guide and our own fitment notes from karts we have built and shipped.
Two-Piece vs One-Piece Mounts: Which to Pick
Odenthal offers both two-piece (base plate plus upper plate) and one-piece designs. They are not interchangeable - they target different setup goals.
Two-Piece (EZ-Set Series)
Two-piece mounts give you adjustability. The base plate clamps to the chassis and stays put, while the upper plate (the "EZ-Set" piece) lets you swap engine angles by changing only the top half. We carry two angle options:
- EZ-Set 8 Degree Upper Mount for 4-Stroke Motors - the most common LO206 angle.
- EZ-Set Upper Mount Only 10 Degree - 10 degree variant for chassis that need more clearance.
If you race classes that periodically swap motor type (LO206 in spring, Animal in summer) the EZ-Set lets you change angle without ever loosening the clamps that hold to the chassis. You will need the matching Bolt Pack for EZ-Set Base Plates for the lower mounting hardware.
One-Piece (Pro Series & Code Red)
One-piece mounts give you weight savings and a lower engine center of gravity. Because there is no separate plate stacked on top of the base, the engine sits roughly 1.5 inches lower than an equivalent two-piece setup. That is a real aero gain - 1.5 inches times the width of your engine in reduced frontal area drag.
- Pro Series 8 Degree One-Piece Motor Mount - the rigid 8 degree LO206 setup, drop-in for most international rail karts.
- Pro Series Low Profile One-Piece Motor Mount 0 Degree - 0 degree flat variant for level engine pad chassis.
The one-piece weighs about 2.6 lbs less than a slider mount with the same fitment. For LO206 and Animal racers this is the most-asked-about upgrade we carry. Pair it with the matching Bolt Pack for Pro Series Mounts and your choice of clamps below.
Wedge vs Euro Cradling Clamps: When to Pick Each
Once you know your tube size and I/K type, you still have to pick the clamp body style. Both Odenthal options bolt to any of the mounts above, but they grip the rail differently.
- Wedge Style Motor Mount Clamps - older sprint chassis, classic 4-cycle setups, and any rail tube that has a flat seating surface for the clamp. The wedge is the original Odenthal style.
- Euro Style Cradling Motor Mount Clamps - modern Tony Kart, Kosmic, FA Kart, Margay Ignite, and most current sprint chassis. The cradling design wraps further around the tube for a more secure grip on round-profile rails.
If you are unsure, the cradling Euro style is the safe modern default for any 28mm or 30mm rail you can wrap your hand around. Older fabricated frames (mostly oval and dirt karts) often need the wedge.
Special Cases: Shifters, Kid Karts, and 2-Cycle
Not every motor is a Briggs flathead. Three special cases come up enough that we stock dedicated mounts:
- Daytona 190 shifter: the Daytona 190 Shifter Motor Mount Plate Only is sized for the Daytona 190 cc shifter case bolt pattern - it is the engine plate only, you supply your own clamps to match your chassis.
- Honda GXH50 kid kart: the Honda GXH50 Motor Mount is the cadet-class mount sized for the small Honda GXH50 used in most kid kart classes.
- Yamaha KT100 2-cycle: the Yamaha KT100 Third Bearing Style Motor Mount includes the integrated third-bearing upright that 2-cycle classes require. You will also need a Snap Ring for Third Bearing EN Upright for the upright assembly.
Hardware You Should Always Have on Hand
The hardware that holds the engine to the mount is technically a consumable. Studs, bolts, and washers are the things you find missing the night before a race. Keep at least one full set in your trailer:
- Engine Stud Kit for 4-Cycle Motor Mount - the threaded studs that go into the engine case.
- Bolt Pack for EZ-Set Base Plates - everything below the upper plate.
- Bolt Pack for Pro Series Mounts - one-piece mount hardware kit.
- 8mm Low Profile Seat Washer - thin profile washer for tight clearance against engine mounting tabs.
Frequently Asked Questions
What if my chassis isn't on the brand chart?
Measure tube diameter with calipers and outer-to-outer with a tape, then subtract. If you get within 1mm of 90mm or 92mm, that is your I-Type or K-Type answer. If you measure something exotic (98mm, 88mm) email us a photo and we can usually identify the chassis.
Can I run an LO206 mount on an Animal or World Formula?
Yes, the bolt pattern on the engine case is the same across the Briggs LO206, Animal, and World Formula. The Pro Series and EZ-Set mounts are designed around that shared bolt pattern, plus they fit clones, flatheads, and Honda 4-cycle engines too.
How much weight do I save going from a slider mount to a one-piece?
About 2.6 lbs from the engine area, plus you lower the engine center of gravity by roughly 1.5 inches. That combination tightens the kart noticeably in transitions.
Is the bolt pack included with the mount?
Yes - both the EZ-Set and Pro Series mount listings include the matching bolt pack. The standalone bolt pack listings are for replacement or extras.
What's Next
You picked your motor mount. Now mount a camera so you can see what you fixed. Day 4 of this series is How to Mount a Camera on Your Go-Kart with the EZGP System, and Day 6 covers universal mounting hardware for the airbox, exhaust pipe, and frame accessories on your kart. Bookmark the main Odenthal lineup post as the hub.
Questions about your specific chassis? Email support@swiftkarting.com or call 317-494-8791 and we will confirm sizing before you order.