787/800 Rotary Valve clearance

[CRei]

If the clearance on my RFI rotary valve is excessive what the best way to correct the problem? Thanks guys

 

[rcr1978]

New or machined RV cover

 

[CRei]

Used RV cover in good shape be ok? Can I get one on ski now machined??

 

[mikidymac]

SBT sells resurfaced ones and some have local machine shops do it.

 

[CRei]

If the timing was off would I still get 6900 rpm at WOT?

 

[mikidymac]

Possibly, the excessive clearance typically causes hard starting.

 

[CRei]

Your right !! Very hard too start in water, so am I better off getting a new one?? Or an SBT one??

 

[CRei]

Check clearance it’s within tolerances with feeler blades. Going to do the solder test next. If this passes what else can it be??

 

[etemplet]

First verify the clearance is excessive. Hard starting on the water could be compression. I think it is best to buy a good part as opposed to machining unless you know someone that has access to a lathe. 3 Surfaces will need to be machined. As you can see this one was REALLY bad even after the first cut. The edges around the ports are worn excessively yet the ski started and ran fine which was surprising. When I do these things I get pretty anal with anything out of spec. On this one it I took more than .020" off the face to get a flat surface. Get some .032" solder material for testing your clearance. Good Luck .

 

[etemplet]

Can getting water in the engine cause the rotary valve to distort? I got one here that is pitiful. Lots of wear and the valve plate looks like a "V" in the middle. No gouges. I machined another plate to get everything on spec. This thing is gonna start so much better. I wonder if a severely worn valve section would affect overall performance?. I enjoy machining these worn parts because I can see the degree of wear as I am cutting the surface and it helps let me know what is critical and what can be gotten way with. Gonna find out tomorrow if the valve affected the full range of engine performance.