Heavy Porpoising on 96 XP, hesitation off idle, RPM gremlin?

[Spimothy Leary]

After sticking my nose in my buddy's business I talked him into a Rossier pipe & jetworks valve with extended 95 xp tabs, splash guard. had his/my tuner install & rejet. I picked it up yesterday and took it out for final carb/tuning.

I personally have been off of 2 strokes for a couple of years now (3 from my XP) but I know what to expect, and its falling short. I took it home with me because it has needs that should be addressed.

First... started off with a noticable off idle bog and i'm chasing a RPM gremlin Hitting 7500-7600 top speed 54.4. SBT engine flame arrestors I think stock grate and prop (will confirm that) weather was low 90's humidity in the 90's as well, Gotta love Florida summers.

edit: typo... 6500-6600 rpm.

75 lows, 142.5 front, 145 rear LS out 1 1/4 and HS at 1/4 front and 1/2 rear. Popoff is low but I can't remember what he told me it was at.

We slid the HS up to 1/2 and 3/4 during tweaking it felt like it helped a little but at best pushed top rpm up maybe to 7600

what pounds should the jetworks valve be set at? I'm either at 3 or 6

note: I had not ridden this particular ski before so I had no speed/rpm or proposing baselines to work off of and after calling the owner doesn't pay super close attention he just rides.

I think we may have possibly solved the RPM issue which I'll know next time I can dunk it, after pulling it out of the water we checked and the the rave caps were fried. Almost zero thread. I put a set of OEM tops and OEM baffles on when I got home last night. (I didn't pull the blades out but perhaps I should, maybe a little gummed up too. There is still some side to side play on the rave blades, is that typical for sbt? it didn't feel right to me.

2nd issue. the porpoising was the worst, much worse than I remember ever experiencing at virtually every speed/rpm and I was on 3" chop, couldn't shake it on glass either for more than a few seconds. It din't matter if trim up/down, riding over the bars, leaning back.

I know that is scrubbing my speed as well I can't stay hooked.

assuming we have the stock grate & prop, what grates might help to resolve this?

are the 95 tab's somehow a negative contributor? Are other extended tabs different?
I thought they would help

stock nozzle, should we look at extending or aftermarket?

I always ran no grate, stock tabs and r&d extended nozzle and it was fine so I never experimented with tabs/grates.

 

[Matt Braley]

7500 rpm or more is Superstock race rpm territory. If your tach is correct then you must have impeller or wear ring trouble. I'd get a taller impeller and or smaller diameter nozzles to get that rpm down to 7300 tops. Otherwise it will run too hot for pump fuel.

The pump is extended on a 95 but the trim tabs are the same unless that 95 donor had aftermarket tabs on it.

The bog right off idle can likely be adjusted out of the low speed needles. I'd reach down and open each anothe 1/4. If that makes it worse then turn them in past where they were set originally and try again.

I don't measure psi on the flow valve. I back the ski in still tied to the trailer while leaving that hose off. I watch the tach and adjust the valve to where it starts flowing about 3500 rpm.

There are many different scoop grates that will help steady the ride. Jet Dynamics #6, Inventioneering, and Westcoast dovetail are some that do it without rubbing off a lot of speed.

 

[Spimothy Leary]

oops... 2am typing... 6500 RPM, I actually woke up out of a dead sleep 3 minutes ago and said "oh crap, I put 7500 in the thread last night"

low speeds i'll continue to tweak, still missing the sweet spot,

good idea on the valve, first one i've ever seen so I had no idea.

would non functioning raves put me right in the 6500 max territory? Its been a long time for me.

 

[Matt Braley]

Yes I'm hopeful your RAVE repair is gonna wake it up.

 

[Spimothy Leary]

gotcha, i'll get it back in the water mid week hopefully and we'll see where that takes me, i've been off 2 strokes for so long I may have just overlooked the obvious on those dam raves when riding.