Still not getting top speed

[jjsinaz]

So, I finally got all of the kinks worked out, that last one being the bad ignition relay. Had it out today and is ran great. Only thing is I'm still not getting top speed. It only hits about 45 MPH/6600 RPM. From all the posts I've read, this should be a 50-55 MPH ski.

It's had all of the things done to it you'd normally do. All new fuel lines, new fuel selector new plugs, carbs rebuilt.

I had the adjustments on the RAVEs wound all the way down, as I had read that is where they should be. Tried backing them out about three "clicks" but still doesn't seem to make much difference. Where should the RAVE adjustment be set at? Is there a real noticeable difference when they open.

It has RD flame arrestors on it. They were on it when I bought it so I don't have the stock air box. I've also read that it is difficult to tune these things with those on there. It does not seem to be running lean. I did a plug chop a while back and they looked good. Could it be that the main adjustments need to be opened up just a tad to compensate for those RDs

It does not seem to pick up any more speed between 3/4 and full throttle. Makes a little more noise but does not seem to go any faster.

Other than this it seems to run fine. No bogs or hesitation or surging. It does seem to have some pump cavitation on take off, but if the pump-wear ring clearance was off, wouldn't it tend to want to turn at a higher RPM than 6600?

Any suggestions appreciated

 

[jjsinaz]

Well, I think I found the problem, or at least part of the problem. Pulled the RAVE caps off today and found the PTO RAVE had pulled the threads out of the piston, must have gotten hot and melted the threads I guess. So, the piston was moving, but the valve was not. On the Mag cylinder the piston still seems to be attached to the valve stem.

I rebuilt the RAVEs last fall after melting a piston and hoped all would be well, but I guess not. I'm thinking that the valve stems and/or housings may be worn to the point where I need to replace them. The valve stems are worn about .004 when comparing measurments between the contact vs. non contact areas. Ski has 280 Hrs on the clock but the engine has been replaced. I'm thinking that the RAVEs have also been replaced at some point because it has the newer design with the slots cut in them.

These things seem to be VERY problematic and I just want to be sure I do everything I can to get them working again and that they last for a while. I'm thinking of just buying a good used set of assemblies and just swapping them out. Also can't understand why the hell they would make the pistons out of plastic such that they melt so easily.

Any feedback is appreciated.

Thanks, Jim

 

[jjsinaz]

Okay, so I got a good set of used RAVEs. Big thanks to the folks on this site because after reading many posts on the subject, I had the forethought to check to see if they made contact with the pistons before I just slapped them in and started it and destroyed the top end THANKS GUYS!!

So I took my dremel with a sanding drum on it and filed them down to the point where I can install them and rotate the engine by hand and verify that they don't contact the pistons anymore. However, I am now concerned that even though I know there is clearance between the valve and the piston, I don't know how much clearance. I am afraid that whenever they heat up and expand, there might be contact. How could I check this?

 

[soccerdad]

I am sure you are on to the problem with the RAVES. You may also the water regulator. It has to work to get those final revs and more top end. The adjustment on the raves has nothing to do with top end. They only control when the open. Once they are open, that is all they do.

 

[jjsinaz]

Finally got back out on the water today since replacing the RAVEs. Runs like a dream now 54mph and nothing melted

 

[Bills86e]

You deserve a big "ATTABOY", and congrats on Success! Have a great summer. Grease is your friend, so do all your zerks and also your trailor.