Rave Valve Differences

[halomatic]

First, thanks everyone for all the info. I’m learning a lot and starting to do my own maintenance.

I’m rebuilding my RAVE valves on both of my skis (98 GTX Ltd) and so I purchased 4 new Titan guillotines. Question is… why is there such a huge difference in the length and shape? I’m measuring a difference of 3-5mm between the length of the new guillotine and my old ones. Also, one set (top of pic) has a steep angle, which more closely matches the new one, and the other (bottom of pic) is practically 45 degrees. Do these wear down over time? Is it safe to install the new longer one, seeing as how the cylinder bore clearance is NLT .5mm?

I’ve only owned these for a short time and don’t know the maintenance history. Thanks!

 

[burtshaver2021]

those old guillotines have been machined. You would need to double check but I believe factory clearance is .020 and minimum clearance is .015 but you should double check those numbers for your own machine, The guillotines may wear on the sides but not the length. Definitely do not install those new ones and run it or they may catch a ring and cause damage. Did you have the top end apart? There may be markings on the top of the piston that would let you know how many sizes over those bores are. You can machine those new guillotines down. There is a video showing 1 method to take them down and a good thread on this subject. I will try and find both and attach

 

[burtshaver2021]

How much to shave 951 RAVE Valves?

This is a good thread for you to read

 

[burtshaver2021]

See if this link works, if you end up using this method to take down the new guillotines I would use a 1 size under what you have piston. Someone else may have more knowledge, but if it where me I would definitely be rotating that engine by hand before starting it up to be sure they are not hitting

 

[mikidymac]

I would also measure the stems and top as the new ones look smaller in the picture.
Also, Titan has not proven to be a quality brand from what I am seeing here lately.

 

[halomatic]

Damn. Sounds like I have to pull the cylinders. I guess I’ll know more after checking everything out you referenced. The ski with the longer guillotines actually ran pretty good. Maybe I should just put the old ones back in

 

[halomatic]

So I measured the stem (it looks small to me too) and it’s 0.1mm smaller than the existing guillotines. Then I measured from the bottom side of the stem collar to the center of the blade edge. Ski #1 measured 55mm; ski #2 measured 55.5mm; the new Titan measured 56mm. Also, the arc of the Titan blade is equal to ~82mm diameter, whereas skis #1 and #2 are equal to ~88mm (the approximate size of the pistons.
I think if I get the arc right by machining, they should work.
Thoughts?

 

[etemplet]

I use a feeler gauge to measure the clearance on the raves nothing else. (.015" or .020") Doesn't have to be all that close but I try not to be excessive with the clearance. I have fit the valves with the cylinders on the engine but exhaust removed. I cut and bent a pice of .020" shim stock to suit my needs. I have a spare cylinders and pistons normally the size I need and I just fit the rave to those. Good Luck !!

 

[halomatic]

Thanks. I’ll try to find an old piston for milling.

 

[halomatic]

I would also measure the stems and top as the new ones look smaller in the picture.
Also, Titan has not proven to be a quality brand from what I am seeing here lately.

Mikidymac, what brand would you recommend for guillotines? Thanks.