951 rave valve triming?

[AKnarrowback]

Hi guys.

I'm getting around to rebuilding the 98 xp Ltd I killed last year. This is the second bore over stock and I want to make sure the clearance for the valves is safe.

Right now I do not have any contact of the pistons or rings with the valve assemblies stock and bolted in place. Can you guys give me some insight into how much material should be removed from the valve, any way to really measure it, pictures of cut - vs - uncut valve face. It seems like a tough surface to measure and be sure of how much you have moved things back.

Thanks!

 

[etemplet]

I bent a piece of (.015") shim stock about 5/16" thick and long enough so I could get it in through the exhaust port. I make sure the (,015") shim has clearance enough not to touch anything. I also rock the valve to make sure the corners don't touch. This isn't necessary as the valve cannot rock that much.

I grab the valve in a vise (gently) and us a medium course half-round file to shafe the valve. The material comes off quickly. You can judge how much metal you are removing by looking at the thickness of the flat spot you creat on the valve's edge. Hope this helps.

 

[AKnarrowback]

Thanks!

I ended up using the clean surface of the old piston. I had two different grits of emery cloth and stretched a strip over the face as a template. It took a minute to get a feel for the angle to hold the valve at, but watching where the residue on the cloth built up and listening to the squeak of the valve let me know when things were at the right angle to sand at. When I had the full surface in contact, and at the proper angle, the squeak sound was just like when you chalk a pool stick. I sanded things back about .010", as far as I could tell, making sure I had a constant looking finish surface like a freshly ground valve seat on a 4-stroke.

Got it all together, lots of double checking for contact, never had any before I started but took some material off the valve just to be safe. Finished the top end yesterday and have it running, water levels are wayyyy too low to risk running it right now so the break in will have to wait.

 

[L. Dean Ficarro]

When i punch out on my rebuilds, i as for the milling to be done through the same machinist. That way, they check tolerances and chamfer everything as one job. Totally worth it!

 

[Boyd12]

When i punch out on my rebuilds, i as for the milling to be done through the same machinist. That way, they check tolerances and chamfer everything as one job. Totally worth it!

Who do you use for a machine shop? Thanks!

 

[AKnarrowback]

Got lucky........

Finally got to start the rebuild in the water. Had the machine on the trailer, let it idle for a few to warm up and I started hearing a slight "tick". I shut it off asap and pulled the rave caps, restarted and lightly pushed each rave in by hand. Sure enough, the mag side had some ring to valve contact once things warmed up. Went straight home, pulled the raves, inspected the rings, no obvious damage. Ground both raves down a good amount, put it together and tested. No ticking, machine ran perfect, put two tanks through and only gave it a full throttle shot when I hit reserve on the second tank.

You learn something new every day. The second I heard that tick I thought I had wasted my rebuild. Whew.........

 

[Boyd12]

Wow! You should go buy a lottery ticket!