Top loader rpm question

[Bigredram87]

Hi guys I have been having a little trouble with my ski, I have a 787 97 gsx . Compression about 150 each cylinder grey lines changed out also working pretty flawlessly. This year I got a couple chances to race my friends 98 gts with a 720 motor. He pulled on me high speed and beat me a few times which made me start to notice something must be wrong. Now initially I tore apart my water regulated valve and realized the bellow was ripped. I replaced it with another random model used 787 wr valve and I thought it helped a bit but I am still maxing out gps at 50.7mph . The last time I was in flat water was 2 years ago and I was hitting 57 ish gps. The thing is since my last 57 mph run I have put a top loader in. I realize that should affect top speed a little but this seems intense. Right now my max rpm are about 6400-6600 (hard to tell water was choppy and pulling pump out of water at times. Wear ring was just checked and perfectly in spec. Any other ideas would be awesome . I am using 87 octane btw which after reading a bunch of threads and manual seems to be correct. I can't keep letting this 720 beat me lol

 

[LouDoo]

I don't know what your friend told you but a 98GTX has a 951 it stands to reason he would beat you in a race.

Lou

 

[Matt Braley]

Haha true.

I would check your rave valves on that 787 and make sure they slide up and down easily.

 

[Bigredram87]

I don't know what your friend told you but a 98GTX has a 951 it stands to reason he would beat you in a race
Lou

I screwed up Lou it was a 98 gts that was typo

 

[Dr Honda]

Well....


Along with your top-loader... what other mods? Do you have an aftermarket impeller? if so... what one, and what pitch?


His ski is an old-style, and is long an narrow. (high aspect ratio) in turn... it takes less power to push. Also... does his ski have any mods?


There are a lot of mods that people do, that in reality, slow a ski down. A top loader, extended ride plate, "Swirl" impellers... and so on. But, all those mods are great for getting you out of the hole, or staying loaded in rough water. SO... when racing a buoy course, they help maintain top speed.


With all that said... your RPM's are a little low up top. I would suspect that your regulator is leaking. (unless you are over-propped)

 

[Strizzo]

In heavy chop, I couldn't keep up with my 95 gtx on my 97 xp. Too much time out of the water and bouncing while the gtx just plowed through the waves.

 

[Bigredram87]

Well....


Along with your top-loader... what other mods? Do you have an aftermarket impeller? if so... what one, and what pitch?


His ski is an old-style, and is long an narrow. (high aspect ratio) in turn... it takes less power to push. Also... does his ski have any mods?


There are a lot of mods that people do, that in reality, slow a ski down. A top loader, extended ride plate, "Swirl" impellers... and so on. But, all those mods are great for getting you out of the hole, or staying loaded in rough water. SO... when racing a buoy course, they help maintain top speed.


With all that said... your RPM's are a little low up top. I would suspect that your regulator is leaking. (unless you are over-propped)

I am going to have to try peak up there look at the pitch numbers again (hopefully I can see it) I can't recall, when you say regulater leaking do you mean internally like the bellow? And as far as checking if I pop the plastic cap on the wr it should be dry inside correct? Until I pull the bellow off of course I am also going to check my raves later just to verify they are clean moving freely. Also neither ski has any performance mods except for mine with the top loader . I sent my stock impeller to sbt a couple years ago for them refurbish and I just assumed they sent me the same impeller back I should really double check that

 

[Bigredram87]

[video=youtube_share;JGjL3aa4F04]http://youtu.be/JGjL3aa4F04[/video]

So I just checked my rave valve and this is the result check out the pto side. I am obviously going to tear them apart and clean them curious if you think this could be my loss of a few hundred rpm, I kinda feel like it may affect performance going from high to low but wouldn't affect top end cause it's getting stuck open

 

[soccerdad]

They look like they are dirty but the spring that holds them down is pretty strong, so they are not hung open. I don't think that is your problem. I am curious myself on this. I have two skis with the same symptoms. About 6500 rpm and 50ish MPH. Please post back and let us know what solves it. I just ran my 96 GSX for the first time this week with a top loader. LOVED it in choppy water. Did not do GPS though this time. But this is one of the 6500 RPM skis so I am guessing still around 50.

Question to the ace team out there. If you do not see any leaks in the water valve, and it all moves freely, can it still have problems that would cause a loss of RPMs? Assuming good compression and fuel supply, what else can hold the revs down a little? (total stock pump and motor component setup)

 

[Bigredram87]

Opened up my wr valve and it does look wet I'm assuming this should be completely dry in there