787 Rave Valve Trim

[Jnz]

I have two separate 787 motors, both rebuilt, but the work was done by the previous owner. Motors are together and I am unsure of the piston bore and need to make sure the rave valves are trimmed. Is there anyway to tell how much to take off without pulling apart the top end ?

 

[Dr Honda]

nope.


Pop the head off, and read the tops of the pistons to see what the bore size is.

 

[Jnz]

Easy enough. Now as far as the raves themselves is there a way to tell if they are still stock or have been trimmed down before?

 

[Guest_User]

you`d have to pull the guillotines clean them, look at the part number, if they are OEM look at the curved edge and compare to some pics found here. I would think it would be easy to tell if they were cut by looking at them.
If they were changed to SBT guillotines, then they should already be trimmed and ready to go...

 

[Jnz]

Pictures do any good at helping me?

 

[Jnz]

 

[Guest_User]

first off change all those bellows to the new green ones.
I can not see the edges, but from this view I don`t think they are machined, they could have been ground by hand.
do the edges look fresh as if they were ground or machined?

at least you have the latest edition being 353`s...

 

[Jnz]

They do not appear to be machined or even filed. I pulled the heads now and one motor is .25 and the other is .75. Any advice on how I can go about getting these done correct. I've read you can do it by hand with a half moon file. Two of the bellows are the green already I'll go ahead and add two to my order with the fresh orings.

 

[racerxxx]

I'll assume the ones with the green bellows have been cut, they look like it to me. I'll also assume they came from the engine with the .75 over pistons. The .25 overs do not need to be cut. That is the first over and Seadoo already built the clearance into the valves for the first over pistons--hence the reason on a 787 RAVE engine Doo only offers a first over piston replacement.

 

[Waterluvr]

Got a caliper set handy? Measure the length of the valves on the outside contoured edges between both cylinders it looks like there's quite a bit of difference in them.

 

[Jnz]

I can't say for sure which motor came with what as I got everything in boxes. Are you saying measure between the red lines?

 

[Waterluvr]

I can't say for sure which motor came with what as I got everything in boxes. Are you saying measure between the red lines?

No, the overall length of the valve was more of what I was curious to know. More or less from a position seated against the spring compressed to say the center of the radius and the outside edges. The Rave's with the green bellows appear to be much shorter in overall length.

 

[Jnz]

Your right the ones on the right are filed down. How can I go from here to make sure it's all good?

 

[Waterluvr]

Not sure what the trim specs are for a .75 over piston for Rave clearance, but I suppose you could extrapolate those figures based on the length of a standard rave versus SD's clearance specs for a stock to .25 over piston. You would have to have a known stock dimension Rave to take measurements and remove .500 material for minimum clearance and compare that to the ones you have on hand.

If it were me, I'd be getting back into those engines and having a look at the cranks before you go through all that trouble and expense of installing one. I know you didn't build them but I wouldn't run a top end set up like that, it just wouldn't set well with me at all and who know's what's been overlooked in the bottom end of those motors.

 

[Jnz]

I did actually build the motors. Both original cranks bearings were shot. The boat came with the top ends pulled off and machined already with the pistons. I failed to think about raves and didn't write down what the piston size was. I got the same advice and decided to pull the bottom ends apart and was glad I did. I put the raves into the .75 engine and they do not hit so I'm thinking these were filled down prior with the top end.

 

[racerxxx]

No matter what size piston you use you need at a minimum operating clearance of 0.015". Factory spec on a standard bore is 0.020" clearance.

 

[grinditout]

Dan ,told me he needed the rave valves and jugs there when he did it.