Why is my Rotary Valve still scrubbing?!

[kleary]

Help! Late last year, my rotary valve seized due to oil starvation. I pulled the shaft and replaced the brass gear, cleaned up all the parts as best I could and reassembled. It scrubbed again . . . no surprise. So over the winter, I did a full teardown:

- Cleaned all the brass shavings out
- Made sure the RV block face was flat (some remaining grooves and dings but surface is flat and smooth)
- Cleaned up the RV cover (a couple of small grooves but very flat and smooth)
- Bought a new OEM Rotary Valve
- RV Shaft Spline had the usual groove at the plate location, but not deep.
- Oil flow from the Mikuni pump looked fine. Oil lines were primed with oil before starting

The rebuild looked real good . . . everything turning smoothly. Once in the water, the engine started and idled fine. I got on plane easily. After only a couple minutes above idle though, it started losing power again. After cooldown, it started and idled, but I did notice an occasional misfire or predetonation that was never there before. Cooling flow out the stern fitting was pretty good, but not great. I removed the RV cover and found that the RV had scrubbed again! All the parts were plenty oily. The scrubbing happened only on the outside . . . on the RV Cover, not the block.

I’m at a loss. By only hypothesis is that the plate position is more sensitive to the spline grooving than I thought, and that I did not seat the RV shaft far enough into the block - which may tend to center the RV too close to the RV Cover?. The snap ring went on fine, but it is touching the seal.

Any thoughts would be greatly appreciated. I think the engine rebuild is still fine. But I don’t know how to get the RV to run free again. Thanks,

Kevin
1999 SeaDoo GTX-RFI

 

[mikidymac]

THe rotary shafts can bend when the brass gear goes. I would order a complete shaft from SBT and give it a try. Make sure the shaft and seal are fully seated in the case.

 

[donkey]

had 2 brass gears stripped(diff engines) both had bent shafts.replace it n be done.

 

[kleary]

OK, here's the wrap-up. I bought both a new Rotary Valve (OEM) and Shaft (SBT). Install went smoothly, optimism high. Then I killed about three summer weekends with an endless cycle of assemble, start, run, bog, pull intake, inspect, notice valve scubbing, , repeat.

Then one day I found an ultralight aircraft site with a nice photo sequence for a Rotax rebuild. His rotary valve surfaces looked horrible compared to mine! Scratches and dings on valve, cover and block. And to him, it seemed like a total non-issue. Slam together - motor ready to put back in an airplane!!! So I stopped worrying about the d*mned rotary valve. Some small amount of scrubbing must be a fact of life. After moving on, it didn't take long to realize that I was fouling plugs like crazy. In previous years, I had no fouling. I was running synth oil in injector tank, and about 60:1 premix (just to be sure!). Engine ran like a dream. This year:

1) switched to Quicksilver dino oil (still good, but a little cheaper - grrr)
2) bumped the premix up to 45:1 because of the recent rebuild (just to be sure!)
3) slathered oil over all intake parts during every rotary valve reassembly
4) and of course the injector was still doing its job pouring oil in there

Oil, oil, everywhere. So, to recover, I added raw gas to the tank and ran BR7ES (hotter) plugs. Now I'm back to synthetic oil, very light premix, and standard BR8ES plugs. All good for 3 or 4 weekends. I'm not sure there's a moral here. Just a case of a DIY-er that was totally un-calibrated regarding what normal rotary valve parts should look like. Thank you for the help mikidymac, donkey, and everyone. Enjoy the rest of the summer,

Kevin

 

[mikidymac]

Is this the 99' GTX RFI ski in your member info? It is is you should not be premixing in a fuel injected ski.