1997 GTX not reaching 7000 rpm

[vogs77]

I believe 7k rpm is what I should see at WOT, correct. I am only getting 6400 at WOT. So history on this ski is I have everything up to date new lines, filter, fuel selector, and I rebuilt the carbs at the end of the season last year, carb kits form OSD. Jet pump rebuilt with new wear ring and replaced the carbon seal. Both cylinders have 150 psi in them, ski is right around 200 hrs. Fresh plugs installed also. I did get 2 short runs on it last year after carb rebuild and it ran great, jumped right up to 7k from what I remember. Why would I only be getting 6400 at WOT now?

 

[JJinSC]

How are the RAVEs? If they are dirty and not functioning well it will keep you from reaching top RPMs.

 

[vogs77]

I replaced them at the start of last season with used updated ones but have not checked them this year. Can the gaskets be reused or will they tear when removed.

 

[GGuillot]

I believe 7k rpm is what I should see at WOT, correct. I am only getting 6400 at WOT. So history on this ski is I have everything up to date new lines, filter, fuel selector, and I rebuilt the carbs at the end of the season last year, carb kits form OSD. Jet pump rebuilt with new wear ring and replaced the carbon seal. Both cylinders have 150 psi in them, ski is right around 200 hrs. Fresh plugs installed also. I did get 2 short runs on it last year after carb rebuild and it ran great, jumped right up to 7k from what I remember. Why would I only be getting 6400 at WOT now?

I have a 97' GTX, unless you do some significant mods, you won't see 7K at WOT. I see the 6700 range, the HS needles are set at 1/2 turn out on mine, I could possibly squeeze a little more and reach 6800, but I feel it's a safe setting to avoid any leaning out.

Take a look at your water valve on top the muffler, looks like a RAVE valve, that can hold back a few hundred RPM at WOT.

 

[etemplet]

I doubt you'll see 7K RPM unless your wear ring is worn. 6700 is a good number. 48 to 50mph on the GPS. That's all I see on the ones I do in general.

 

[AKnarrowback]

7k, according to the shop manual, is where the rev limiter is set to kick in (+- 50 rpm). You don't want to be right at 7000.

My 97 gtx runs around 6810 to 6850 depending on what mood it is in.

6400 would seem a little low.

From what I have read and learned on this site the rave valves operate at the high 4000 to right at 5000 rpm range. But I have also heard that the water valve on the muffler operates near the top of the rpm range and is responsible for getting that last couple hundred rpms. Anyone with more real life experience please chime in and confirm or correct this please.

Another possibility is if you pulled a rock through the pump and bent the trailing edge of the impeller forward a hair. It doesn't take much to change that top rpm with a little impeller bend. However, you would know you pulled a rock through because the noise is loud and unless you had an "oh dang it" moment in shallow water I doubt this is the problem.

 

[etemplet]

I might need to put some high octane fuel in my skis and see what happens. I"ve seen 68 to 6900 on them but not this year. They are as fast as they were last year but I"m not seeing the RPM up that high. I"ll have to check. I know they are not hitting 6900. I did do the WCV on both skis and they were giving us problems. The Water Control Valve operating properly is the difference between having fun and Oooooo Weeeee !!!! Yikes !!!!

 

[vogs77]

I may be off guessing 7k, I guess a little under is normal but I am still not reaching top rpm I can feel it is slower also.

 

[AKnarrowback]

A good place to start would be to make sure the rave valves are clean and operating smoothly. Since you say it ran good last year and is different now then look at simple things first. It sounds like you have a lot of things already done right. Pull the raves out and clean the up, it's easy to do and only takes half an hour.

Pull the black caps with the red dot off, be careful to catch the spring under the cap. You can move the rave piston by hand at this point to get a quick idea if they move freely. Regardless of how they feel I would remove and clean the off carbon. Rave cleaning is considered a regular maintenance item.

The water valve I do not have a lot if experience with. You can remove the cap and do a movement check and see if any water, corrosion belows damage is present. Be gentle with the movement check, the mechanism is not a valve like on the exhaust and is more fragile.