97 XP Jetting & Elevations - What elevation range is stock jetting typically set for?

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XPChick

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What elevations is the stock jetting on a seadoo 787 xp with the BN-40i dual carbs rated for? I am trying to figure out where to start on proper jet sizing to get it tuned in.

Compression is good on both cylinders. I'm used to jetting our 2 stroke motocross dirt bikes, this is my first jet ski purchase. The elevation I'm running in is 4200 - 4700 ft at the lakes, is that considered 'high' elevation for my jet ski with stock jetting? What range of elevation is stock jetting generally set for?

Our dirt bikes TYPICALLY run 2 sizes smaller (leaner) than stock from the factory on the main.

Thanks for any help, I have been unable to find any sort of jetting chart/elevations for my Doo!
 
Guess I'm going to try going down 2 sizes on the main like I do all my 2-stroke motocross bikes and see what I get. It's just a pain in the a** to get to these jets, unlike my bikes. Just be nice not to tear the carbs down any more times than I absolutely have to (and drag them to the lake only to find out the jetting is way off).

Most major motocross bike manufacturers have jetting charts which are very helpful. The charts show the starting point for jetting based on altitude, temperature, and humidity. Normally there is a range so you can get CLOSE the first time and then fine tune from there.

Upon purchase of these skis, I was told they were jetted for 5000 feet, but it's obvious they weren't because all the jets are stock size.

It's getting to be winter here in the Cascade mountains of Oregon, I have the lake to myself, but it's not pleasant jetski weather.
 
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I would very seriously think about not touching the jetting.Use the skiis first ,see if they run to spec. and then look for problems.Bikes are much smaller capacity,mostly 1 cyl. and more prone to jetting changes.Is there anything wrong with the skiis now?
Give them a really good run and check them after that.
Racing is a different kettle of fish but they are after a tiny edge in performance and always run the risk of cooking it.There is a huge amount of talent and info here.A lot of guys are out on the skiis.It's the weekend and will give you an answer.
You will only run the skiis to lean once.Hope this helps
 
Yes, we have been out on the water with them many times. Both run fine in the garage. The both 'run' the same on the water. Idle fine and go about 5 mph fine but at about 1/3 throttle they start bogging down and give it a little more throttle and they start to load up and try to WOT and the engine will flubber and die. Pull it out of the water and back on the trailer, run it to clean the water out real quick and they smoke like a mother. Like they were run around fat and need cleaned out. Have been to the lake 5 times now.

Replaced all the Tempo lines with proper lines, checked compression, cleaned out the carbs and rebuilt with all new Mikuni parts, replaced the plug wires, caps and plugs, cleaned the Rave valves, looked at all the wiring trying to find any corrosion, the list goes on, I think we've gone through everything possible... Now we're onto jetting.

We are very rural here. No sea doo dlr. The only 'marine' place here that is supposedly qualified to work on them is a little hole-in-the-wall mechanic. They rented us skis this year, so I figured they would have some idea of what the jetting should be -- Nope. Had no idea. Didn't even know that the BN-40i took different jetting sizes between the PTO and Mag carbs. They were no help. They just said 'you have to tinker with it.'

When I say there is no one on the lake, that means no one. Not a sole this time of year. Just grabbing a wet suit every time I test it. Even on a nice hot summer day there you very rarely see one jet ski on one of the lakes, but then again that's one of the reasons why we choose to live here. There are tons of high mountain lakes within a 50 mile radius here so the odds of seeing another person isn't very high. Let alone anyone that could help out with any information regarding a jet ski. That's why I figured I'd get on here and see if the vast pool of knowledge on here could point me in the right direction.

Worse case scenario top ends are easy to do. Just would really piss me off to run it too lean before having a chance to 'ride' it. But since no one can point me in the right direction, I'll just have to learn by doing and learn by my mistakes. I'm pretty careful and have a pretty good ear for 2-strokes, but the new 'water' load with a jet ski is all new to me. Keep your fingers crossed, the jets come in tomorrow and I'll be able to head back to the lake and run some fuel through it and see what I get.
 
Please.Wait for a few hints.It may save you a lot of time and heartache.Just give it 24hrs please
 
Yes, thank you for the links. I've been reading all over www.seadooforum.com for the past week. Yes, I've read the seadoosource link when I wanted more assurance that there wasn't a typo in my Seadoo shop manual in reference to the stock jetting and settings on my carbs. All good information, for sure. The second link confirms me trying a little leaner main and going from there. So far it's very similar to my bikes. Biggest difference for me is the pumper carb configuration rather than having floats/slides.

I am so anxious to take them out yet again and give them a try. I may be able to today or tomorrow. I'll keep you posted. Thanks for your assistance!
 
Yes, thank you. That one is a good one. I watched that one when I was getting ready to do my rebuild.

It's funny, my biggest hurdle so far during this entire process was trying to find the carb base gaskets of all things! Every online OEM seadoo parts microfiche gave me a part number for my BN-40i, but the gasket they reference for isn't even close to being correct. I finally just went with gasket in hand to my local Auto Parts Mart and I went through gaskets until I found the exact one I needed.
 
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