Checking Rotary Valve Clearance Procedure

[nb141fd]

I know it's here somewhere, but I've been unable to find it. I've found the technical articles on how to time the motor, and how to ID the valve cover. Can someone please post the link to "how to check Rotary Valve Clearance"? I have a 92 SP and am having some problems determining the cause of hard warm starting. I have rebuilt the carbs, replaced the needle and seat valve, replaced all fuel lines and checked all fuel filters. I have a new fuel valve on order "just-in-case", and would like to check the RV clearance. Thanks

[Bill O'Neal2]

Re: Checking Rotary Valve Clearance Procedure

Place a piece of modeling clay between the rv cover and the rotary valve and bolt the cover back on. Take it back off and measure the thickness of the clay.

A more difficult method is to use a feeler guage between the rv and the cover. But, that requires disassembly of the oil pump and the carbs and intake manifold from the rv cover.

For good starting, you need between .010 and .025 clearance.

[nb141fd]

Re: Checking Rotary Valve Clearance Procedure

Thanks Bill, appreciate the advice. Using the clay method can I just unbolt the RV cover with carb and oil pump still attached? I'm also assuming that I leave the O ring on the cover, when I bolt it back on, since we're trying to get the actual distance between the cover and the rotary valve? Tony

[Bill O'Neal1]

Re: Checking Rotary Valve Clearance Procedure

Yes leave all of it intact. When measuring, I remove the oring.

[nb141fd]

Re: Checking Rotary Valve Clearance Procedure

Bill, I finally got around to checking the rotary valve clearance on my hard-to-start-when-warm 92 SP. I used the solder method (only because I had some handy) outlined in the manual. My reading was 0.014". The book says 0.009-0.014" is within tolerance. I think I read somewhere that anything under 0.020" should be ok. I'm going to try to upload a couple of pictures of the cover and the rotary valve itself.

The cover has very fine grooves that can be felt as your finger nail runs across the surface. The valve itself has incredibly fine lines across the surface that can barely be felt when using your finger nail. My question: even though the clearance seems to be within spec, does the condition of the cover and valve contribute to my having problems starting the ski when warm. As you may or not recall, the SP starts great when cold (it has a primer) and will run as long as you want, but shut it down and it takes forever to restart. Initially you suggested rebuilding the carb and replacing the needle valve and seat, which I did. No help, so we thought for sure it would be a sloppy rotary valve. Do you have any suggestions? Could the pop-off be too high? I had it checked and was told it was fine although the carb has the 115 gram spring in it. Thanks for any additional advice you might have. Tony

[Bill O'Neal2]

Re: Checking Rotary Valve Clearance Procedure

As long as the clearances are within the toleraces ( yours is excellent at .014 ) I wouldn't worry about the rv cover scratches, All of those old motors have scratches on them. Same goses for the valve.

Have you tried the very basic step of opening the low speed adjuster a little to give it more fuel when trying to start the motor?

You could try a 95 gram spring in the carb.

[nb141fd]

Re: Checking Rotary Valve Clearance Procedure

Thanks Bill, I'll try a 95 gram spring and I'll keep in mind the low speed adjuster, it's currently set at 1 1/4 turns out. I'm also going to try a ODYSSEY DRYCELL battery. My Yuasa checks out fine and starts the SP easily but I don't have the capability to load test it and I'm running out of suspects. Tony

[IDoSeaDoo]

Re: Checking Rotary Valve Clearance Procedure

Would be great if people actually concluded their posts once in a while. I'd love to know what fixed it for him. I have the same issue and have tried EVERYTHING. I'm literally out of options.