Seadoo XP 787 "flat spot"

[Aquaboy]

Hi Guys,

I have also posted this in Problem Solver, but have some more info.

I have stripped & cleaned the carbs, forgot to check the yet sizes (bought it 2nd hand, so I don't know if somebody else messed with it) but everything looked good inside. It's a 96 XP 787 and according to the specs, it's fitted with duel Mikuni BN-40I Type 2 carb set.
I set the air corrections as follows: Low speed - 1 turn (as per spec), High - 0.

I'm not sure how well the carbs are synchronized, but it starts up first time every time and idle's well. It runs good at full speed and mid range, but it has a very serious hesitation (flat spot) from idle to sudden rev-up. I found this clip on Youtube and this is exactly what my XP sounds like.
http://www.youtube.com/watch?v=f7l9Qi2I51M

Plugs is currently black from all the fiddling, could it be spark? The plugs still looks like new, what should the gap be? in mm please, I'm from SA.:lols:

What can I do and/or check for the problem

Thanks for any help.

 

[Bills86e]

Engine Response

Pluggs .020. Please read the how-to and Snipes corner on ajusting the Carbs.
You do a leak-down test after reassemby, then lake test adjustments. Let us
know if you need some more help.
If it wants to hesitate before accellerating, add more fuel by adjusting the LS adjusters out a bit more, never going much over 1/8th turn at a time until it just quits hesitating upon the initial hit of the throttle.

 

[Aquaboy]

Adjusting the carbs I did: Low = 1 turn (had it between 1 and 1.75) High = 0.

I have them dismantled right now, seems like the needle&seats are leaking through. I'm about to do a pop-off test.

You mention that I must turn out the LS adjuster to make it richer, is it not the other way round?

How do I do a leak down test?

 

[Aquaboy]

OK, I kinda got it fixed for now, it's not perfect, but I'll give it a 95%. I'll take it to the water tomorrow and see how it performs.
I did a pop-off test and both carbs passed. According to spec, the LS should be set to 1 turn on the 96 model, but I had to turn it out to 2,5 turns:blush:. Could this cause any damage :bigear:??
I also checked the jets and they are also std. Plug gaps were little small and I re-adjusted to 0.020 (0.1mm).

My last attempt will be to sync the carbs, have to wait until Monday to get a carb balancer.

May you all have a wonderfull 2011:seeya: