Starter clutch — check, service & the three types

Starter clutch — check, service & the three types

Watch the walkthrough

Watch on YouTube ↗ · Jetboard Australia — "Jetsurf Main Gear, Starter Clutch Service" (~23 min). Timestamps below follow the video's own time. Filmed on an engine out of the board (for carbon repairs) — the job can also be done in the board.

The starter clutch — a one-way (sprag) bearing behind the main gear — lets the starter turn the engine one way and freewheel the other. When it fails, the board won't start or the crank locks up. This covers testing it, servicing it, and the three different clutch types JetSurf has used, because the parts and tools differ for each.

Tools & supplies

• EP2 water-resistant marine grease (Rod uses Suzuki EP2) — the grease grade matters here
• 2.5 mm Allen key (cover), 3.5 mm Allen key (retaining screw)
• Loctite 243 (blue)
• 32 mm socket, 1/2" drive (end cap)
• JetSurf coupling-holding tool — or a large square-blade screwdriver / bar
• Screwdriver to work grease in; parts washer / solvent
• Lanox / Inox spray (gear-assembly external)
• The type-specific clutch alignment tool if you're fitting a new one-way bearing

Test the clutch first — 2:34

1. 2:42 — Turn the main gear by hand. It should freewheel smoothly one way and lock the other (locking positively, "really wide").
2. 3:06 — Bad signs: it freewheels both ways, or it locks both ways (the crank turns with it in both directions). Either means the clutch is done.

Remove the cover & idler gear — 1:03

3. 1:06 — 2.5 mm Allen key, cover off. (Late-model plastic covers have captive screws.)
4. 1:29 — Inside: the main gear (one-way bearing / starter clutch), the idler gear, and the starter motor + gear.
5. 1:45 — Jam a second Allen key between the gears to stop them turning, undo the idler-gear Allen bolt, and wriggle the idler gear off its square drive.

Remove the main gear assembly — 2:24

6. 3:33 — Remove the end cap — it's on an O-ring, not tight, usually hand-undo (32 mm socket if needed). There should be grease in it; watch for the O-ring. A cap that's black and nasty inside means trouble.
7. 4:11 — Fit the JetSurf tool (or square-blade screwdriver) on the crank, press down hard on the bench, and undo the retaining screw with a 3.5 mm Allen key. On reassembly this screw gets Loctite — it must not back out.
8. 4:52 — Slide the main gear off.

Inspect the crank & main bearing — 4:58

• 5:19 — Run a finger over the crankshaft — no grooves or gouges, dead smooth.
• 5:36 — Look through the gap at the main bearing and rotate it — the balls and cages must all be present and in place.
• 5:49 — Known failure: the seal at the back of the clutch breaks up, gets into the main bearing, destroys the plastic race, the balls come loose, and the bearing fails.

Clean & grease — 6:23

9. 6:23 — Wash the old grease out. Check the seal, that the clutch bearing is one piece, and the small end bearing.
10. 6:41 — Use EP2 water-resistant marine grease. Squirt it around the seal and the bearing, then work it right into the bearing with a screwdriver.
11. 7:29 — Pack grease around the seal lip. This rear seal separates the crankcase from the clutch — if it fails, grease is pushed out into the engine, out the exhaust, and the clutch runs dry. Pack it full.
12. 8:34 — Put a little grease on the inboard (crank-side) seal and the shaft — too much ends up in the engine and can foul a plug.

Reassemble — 9:12

13. 9:14 — Slide the gear back on; wipe the excess grease.
14. 9:25 — Clean the retaining bolt, apply Loctite 243, fit it. Hold the crank with the tool (other way round now) and tighten — not super tight, but it must not come undone.
15. 10:43 — Wipe the cap, check its O-ring, fit it. As the bearing warms, the grease and cap flow into the bearings and keep them fed.
16. 11:17 — Refit the idler gear (back where it was — you can see the wear mark), line up the square, a little Loctite on its bolt, jam the gears, tighten.
17. 12:02 — Re-test: freewheels one way, clutch locks the other. Light Lanox spray over the gear assembly (grease would fling off), cover back on.

The three clutch types — 14:31

• 14:38 · Current (DFI era) — the big one-way bearing, pressed in. JetSurf don't sell a rebuild kit — officially you buy the complete gear assembly; Rod can press new bearings and seals into your old one. If you do fit a new assembly, first confirm the crankshaft is undamaged.
• 15:50 · 2016–2017 (short run) — identifiable by a very large end cap and a big end bearing. JetSurf changed the crankshaft journal size around here, so an old clutch won't fit a new crank. Greased (EP2). Rebuildable — bearing & seal kits available from JetSurf.
• 17:24 · Early boards — oiled, not greased. Held on with a nut on a thread (the identifier — pull the front cover, see a nut = the early one). Lubricated by undoing the end Allen screw, screwing in the supplied syringe fitting, and squirting in a very light oil (ATF / hydraulic fluid grade); it feeds through a drilling in the crank, sealed by two O-rings. Kits available directly from JetSurf.

Fitting a new one-way bearing — 19:52

18. 19:59 — The one-way bearing goes in one way only. Wrong way and the starter just spins — no start. Fit it the same way the old one came out.
19. 20:20 — Test the direction: on this motor it freewheels anti-clockwise and locks clockwise. The sprags lean at an angle. On the pressed-in type, the printed face of the bearing faces the seal.
20. 21:05 — The bearing assembly is spring-loaded and won't compress by hand once in the clutch. Use the type-specific alignment tool (from Rod or JetSurf) that screws into the crank end and guides the clutch on — "almost impossible without it." The early-model crank (thread + taper) needs its own different tool. Order the tool with the kit.