The Buck

[philip_gpr]

I think we need to come up with a forum solution for the buck that we can freely share with everyone.

There was someone on Riva that got bucked off on the weekend at over 60 mph. He had a stage I ski - nowhere near 80 mph. There is another thread on this topic started by another forum member with the buck.

This is safety issue and I think it needs to be dealt with out in the open. There shouldn't be secrets on this one. I would like to see us all take Ben's approach on this one and talk freely and openly on this topic.

I understand the basic premise behind solving the buck is to relieve pump tunnel pressure. I understand Kawi did this several years back on one of their skis by adding some venting holes in the pump shoe area. I have never owned a Kawi and my ski doesn't buck so this is something I have no experience with so I am no help on this one.

It looks like we will have our billet intake grate this year. This leaves the buck as the biggest safety issue left.

Let's get rid of it as well so nobody gets seriously hurt.

[Pistonwash]

RIVA still has a board?

I'm with you Phillip, we need to put the checklist as a sticky for a while since this seems to be a recurring question/issue that is addressed.

[flyboy]

Ben's approach on this one and talk freely and openly on this topic.

Ben, lets hear what you have to say about this issue, since we are laying it all out in the open, and you have stated that you have fixed the bucking issue

[Duke]

Rich and I have developed a way to correctly remove tunnel pressure without any of the side effects. We are still in the development stage so offering any at this point would be a little premature. WFO will be the one doing the mods to the pump and he will be the one to contact on this issue.

After doing the mod to my boat it safely would run 83 without any sign of bucking. It also allowed me to loosen the boat up as much as I wanted. The boat accellerated the same even from a dead stop.

We are not holding secrets here, just not completly done with testing and finding the parts durable enough to wistand constant abuse.

This mod however is really only for people running 80+. If you have a buck below this your boat is not set up properly and will not benefit from this mod. Once again WFO can help you with this and I have no time to work on my skis let alone anyone elses. I have seen Rich's work and the quality is bar none.

[Hydrotoys]

Yup, the speed thing is over for a year, and we need to settle these skis down. Your Riva example is piss poor. The gpr don't buck at 60, unless somebody has a screwed up setting. No pump relief is going to fix stupidity. however, there are a bunch of folks running over 75 who COULD benefit from this.

I've been doing some pressure testing along with this as well.
http://www.greenhulk.net/forums/showthread.php?t=23383

Per suggestions on here, I've set the grate back as far as possible, but I can still get it to jump around 79 on the 800, and as low as 75 on the 1200 grate with no vents and oblonged grate holes.

Running just one jet works valve on the 2" spacer, the pressure spike and buck started after 81 with no speed loss on the 800 and around 76mph on the 1200. It got better, but it wasn't enough. I'll be installing the second one this week, along with another pressure gauge to get some more readings. Once it's working, I'll be glad to throw it all out there.

I'm still not seeing this "sucking down to the water" effect as some might infer...of course I don't run my ski in bouncy-bouncy trim, as most of these smooth water queens do either, so it's a damn good chance, I'm literally "missing the boat" here.

There are at least 3 different techniques being used right now.

-Kerry's original mod.
-The Jetworks in the 2" spacer mod.
-Drilling 2 holes in the shoe, but in the grate area.

Of the three, apparently only Kerry's is well documented and released. The others are pretty much "I'm getting ready to..." stuff, that still hasn't been widely tested by the average mortals.

[mtrager]

My triple has the holes drilled in the shoe.

It does let you loosen the boat way up. I can run a 1200 grate wide open
superman with no fear of a buck, even hitting waves which could not happen with out the holes. I have no cavitation on the bottom even with an 05 pump.

I unloaded at Mud bug at 84.5 on my gps. That is 2.5 miles per hour faster
than I was last year on gps.(81.9) Which was 83.0 on gun Friday night.

I did see Dukes ski with 3 jetworks valves on the side of the pump.
How will you keep the valves from getting banged up from the pump, plate and hull ?

[HopatcongGPR]

flux capacitor

[jeffsntx]

Just to clarify since Duke and WFO arent online right now, Dukes ski only has 2 Jetworks valves, and he had them neatly placed and supported to keep them from "flopping" around and getting damaged.

[Hydrotoys]

Yup,
they just sit there all zip tied up.

[rossnemo]

I mounted my duals this week just as pictured at 10 and 2 oclock.. The motorhead in me wouldnt let me put on just a single.