First ride on new DOO, with a D'oH! ending....

[AKnarrowback]

I had some friends of my Cousin give me their 97 GTX a couple of weeks ago. It has 97 hours on it, is in near perfect condition, runs as good as the day it was pulled from the crate, but has a failing RV resevoir seal on the crankshaft so it smokes a bit when you first start it.

Today was the first chance to take it out. Water temp was 44F, air was 52F, sunny with yellow leaves on the trees and Geese flying south overhead.

I see what everyone is talking about with the 3k to 4500 stumble in these machines. It's interesting how the carbed, rave equiped motors in PWC's react the way they do when compared to how smooth the rave valves transition on the carbed snowmobiles. With so many more variables in clutching, gearing, altitude and air density that a sled can encounter it seems like the lack of fine tuning that can be done in the PWC carb is one main contributor to this stumble. There are so many more components in a Mikuni round slide that can tune out running problems.

Does anyone know the rpm range where the 787 motor is designed to transition from a low port to high port? What rpm the carb transitions (roughly)? What rpm the water valve is supposed to operate at? Many overlaping actions, there has to be a way to smooth things out a little. The rave transition rpm on sleds is higher than it is on PWC's, what will it hurt to increase rave spring tension to delay the transition until after the carbs have moved further into the high speed circuit? Lots of carb theory - vs - engine rpm can be applied here. Things were engineered to prevent burn downs, but the engineering was also done to accomodate a wide range of riding styles. Too bad the season is almost over, I really want to go experiment on this......

Anyhow, it was an awesome ride until I came back up river to the park/launch area where a group of people were standing in a half circle on the grassy river bank, playing an acoustic guitar, some were holding a single flower. I thought "hippies" and parked my Doo about 75 feet down stream, backed the trailer in and loaded my ride. The tie down strap for the machine had fallen in the water so I hopped off and reached in to retrieve it, and noticed a flower float by next to me, then another flower and a strange looking, grayish, pollen looking something floating on the water all around me. I looked around and see the people up stream, one at a time, reaching into a big zip lock bag full of dust, take a hand full and throw it into the river.....
They were spreading the ashes of someone..... well...... being a man of God I did what I thought would be best at the moment, I said a short prayer, unloaded my ride, found some clean water, washed myself and the Doo clean, waited for the ceremony to end, loaded up, waived good by to those watching and left. Mark that one up to "akward moments"......

 

[GGuillot]

I have a 97' GTX, great ski, you could tweak the springs on the RAVE valves and see how it works for you. You should note a slight change in the transition when they open. Usually this range is 4500 -5000. Yes, normal on the roughness in the 3000 - 4500 range on these 787 engines, it's been discussed at length in the forum. I'm told the water valve works in 6000+ range, if it's not working at this rpm the engine falls flat and you won't reach top rpm at WOT.

Cool story on the hippies, and it looks like it's cold already in Alaska, while most of us are still enjoying 80 degree water temps down South, in Alaska you guys are seeing 44 water temps. Don't fall off!!! that's cold..

 

[Mekanix]

The raves open more in the 5700-6500 range.
The main jet transition from the pilot jet is what your feeling around 4500.
My rave caps have holes in the top I can watch this happen.
However if you mash the throttle they will open as soon as you hit 4500 and the main jet really starts to flow. It's more pressure driven than an rpm thing. The rpms mentioned above would be if you smoothly pushed the throttle and watched it happen.

The 34-4500 roughness is a lean condition.

1 from a lean pilot circuit. As in pilot jet too small or pop off pressure set too high.
Or other worn components that limit the amount of fuel flowing at that throttle opening. ( worn or clogged carbs, throttle valves leaking air, throttle plates too worn on top and bottom allowing air to pass by)
Either way the pilot circuit runs out by 3400. A way to notice this is to hold that rpm and wait. You'll notice it works great then starts to fade. This is the running out of fuel. A quick blip of the throttle momentarily opens the main jet and it transitions to above 4000 and after 4500 the main jet is flowing enough to make it seem good.

My best running engine had a 23 psi pop off and 75 pilot jets and 147.5 mains. (New build, no accell pump )

I've been fighting that midrange crap for over two years and only recently started upping pilot jets to compensate for clogged carbs that cant be cleaned.

I've tried full cans of carb cleaner through the pilot circuits with the jet removed and ls screw closed and although it may make a difference it doesn't fix it. So by going with a much larger pilot jet I managed to flow enough fuel to make the midrange smooth.
Another interesting fact is that with really worn raves that also smoothed out the midrange but with new ones installed it behaved rougher in midrange but also gave more punch to get to the higher ranges quicker ...


I'm going to start experimenting with this stuff again to see what can be done to affect midrange only. So far pop off has to stay between 23 and 38 psi and pilots start at 70 and I'll go up.
I have tried going down and that results in it falling on its quickly in the mid range. As in hold 3400 and it dies in 3 seconds from literally running out of fuel.

 

[AKnarrowback]

Thanks for all the good info. I double checked all three red button settings, all were turned in all the way. I set the raves flush and water valve out 3 turns as per the manual. After messing with my 94 xp for the last year I just happen to have a set of 72.5 low end jets, the 97 gtx has 70's. So it looks like a test ride to see how things are running with the caps set properly then a rejet to richen the low end a hair and see what happens.

Yes, the water is a bit more chilly on the rivers where I do most of my riding. Summers are short with maybe a stretch of five weeks where things get HOT (maybe 80). The near 24 hour summer daylight makes up for a lot, I was riding the Chena on june 21st at 2am with the sun just under the horizon. We parked the sleds in mid April and will be getting them out again in 4ish weeks. If anyone is planning on getting up here in the summer and wants to Sea-Doo under the Midnight Sun shoot me a message and we'll try to set something up.

A shot of our last ride, 51 degrees and raining, borderline hypothermic with 8 more miles till we get back to the truck. My Son and I sort of dared each other to go riding, once we did neither one wanted to chicken out and we both ended up freezing. Good times.

 

[benjilafouine]

At that temperature, my ski is usually already winterized... But maybe you can beat this taken this spring:

 

[AKnarrowback]

First ride this year. Had to push the XP over a few feet of ice to get to the water, dodged ice chunks floating down stream.

I spent a lot of time dialing my XP in on the Chena River. I'm not sure of the water temps, but you only want to fall in during the hottest days and even then you don't spend much time in it. When I got it to the lake, warmer water, I noticed a significant tendancy to "bog out" at times. It didn't run as well on an 80 degree day in that warm water. The people I trust to do any machine work for me (Darbys) bore outboards and PWC's, anything cooling with the water they run in, .001" over the suggested bore to compensate for the cooler temps the motor runs at.

Tomorrow will be 55 degrees, sunny, fall colors and a beautiful ride, just at 32 degrees at night so we are getting our end of the season rides in.

 

[AKnarrowback]

Upping the low speed jet, from 70 to 72.5, improved the mid range roughness a bit, but not enough to call it fixed. After getting the rave and water valve caps set to spec, vs all the way in on all three, there is a little improvement. Slow application of throttle results in a increase in power with throttle, until 5200ish, where extra throttle provides no more extra power until the throttle travels almost 1/4 travel more then the power kicks in. I'm going back into the raves to clean them again and double check for smooth operation.

We have very high water on the rivers right now and my Son and I went up a slough we never explored before. Some areas were grassy sand bars two weeks ago, today they had a foot of water over them. We idled in and back out. See the picture for how much grass got sucked into the intake on my Son's SP. There was almost as much wrapped around the drive shaft. It took 15 minutes with a long blade screwdriver to clean the shaft off.