Scratching on rotary valve case and crank case side

[niccompisi]

My 97 spx was running good until one day it refused to start. It would start occasionally, but eventually it would only crank. has good compression and spark, and the carbs were just fully rebuilt. I took off the rotary valve cover and found scratching all over both the cover and where the valve rests against the crank case. What I am wondering is would this be a good explanation as to why my ski stopped starting and would only crank? Is there any repair aside from swapping in a new crank case, rotary valve and cover?

 

[mikidymac]

You had something metal go through that rotary valve, either something fell in when you had the airbox off or a piston pin bearing let go. Either way those cases are junk and the reason it won't start.

 

[niccompisi]

i thought so, thanks

 

[etemplet]

Since you're gonna replace the cases and possibly rebuild the engine would you like to try to fix that groove? I think it can be done. I'd sure play with it and give it a try. That surface doesn't have to be perfect there just has to be a barrier separating the ports.

I'd pull the engine and get it on the bench. Then using a die grinder with aluminum bits, you'd need something pointy. I'd grind into the groove and make a dove tail on each side. You don't have to go the entire length. Stay about an inch away from the ports. Take the width of the groove completely out and make the dove tail. That will hold the JB weld in place and not rely on adhesion alone. There are much more expensive products than JB but what the hey. Fill the groove and make it as smooth and as level as you can. Leave it raised up a bit for sanding if you like. I think that would work as a long term fix. As long as you prepped the surface properly. It'd be a cheap fix that is for sure.

Just a note you'll need to grind deep enough for the material be a certain thickness. The groove can be ugly and crooked and different depths. No need to get it perfect. Just no feathered edges. The edges must be deep and dovetailed. I'd bet I could make that work. You could even cheat and only do half the groove. Sometihng to think about.