Troubleshooting

On carbureted PWC, the needle and seat is the valve that stops fuel from flowing into the float bowl once it reaches the correct level. When that needle or seat wears or takes a set, fuel continues to seep past it while the ski sits — eventually flooding the crankcase. Adding a petcock or shutoff reduces how much fuel can migrate, but it does not fix the underlying leak.

The permanent fix is a carburetor rebuild with new needle and seat(s). When doing the rebuild, note the number stamped on the old seat — that tells you the seat size you need (for example, 1.5 mm is common on many Mikuni SBN carbs used across Sea-Doo, Yamaha, and Kawasaki models). After installing new needle and seats, always check pop-off pressure before closing up the carb to confirm the new seat is sealing correctly.

If the ski still cranks hard after a rebuild, holding the throttle wide open while cranking can help clear excess fuel from a flooded engine. See the product pages on sbt.com for Mikuni SBN needle and seat options compatible with your specific carburetor.

The most common cause is incorrect rotary valve cover clearance. When the gap is too tight, the rotating valve contacts the cover face and scores it. A critical step that is easy to miss: always remove the O-ring from the cover before checking clearance with a feeler gauge or the solder method. Leaving the O-ring in place gives a false reading that can make clearance look acceptable when it is not.

If the cover itself checks out within spec but scratching continues, the mating surface on the engine case may also be out of spec. A worn or damaged case surface will cause a new cover to read incorrectly and will continue to cause contact wear. In that situation, replacing only the cover is unlikely to solve the problem — the case surface needs to be evaluated as well.

SBT's 717 rotary valve covers are manufactured to original OEM specs. The cover part number is cast into the surface located under the oil pump (format XXX-XXX); the intake manifold must be removed to read it. Fitment is determined by that cast number, not by year or model. The O-ring that seals the cover to the case is sold separately (Sea-Doo rotary cover O-ring, part 293300023 / SBT part 41-101-07).