GTX RFI Lean issue

[Gritzlor]

Hey all, I’ve been chasing a lean issue on my wifes 787 RFI for a good while. Fried a top end, then again and the crank with it.
This time I installed EGT probes as I rebuilt it to enable troubleshooting.
As we were breaking them in(I always rebuild the pair if I do any significant work on them) hers was way hotter than mine, so halted break-in.
Troubleshooting mode.
Temp sensors OK.
Replaced air intake pressure sensor(old one had given in, got it replaced with one from a 1999 GSX which is a different item but I thought they were interchangeable), got a brand new one from europe with right part#.
Found no obvious issue with the TPS, replaced anyways with an aftermarket one…bad move…old one going back in.
Gage on fuel pressure on the lake. 58psi flat.
Flow tested injectors, they were within 1.5% of each other.
Water tests inbetween changes, the only thing I got to make it run semi okay was replacing the temp sensor with a 4kOhm resistor. Still it ran temps high around 3200RPM and misfired around 4500 but temps were fine over 5000RPM.
Worst I got was 1050+ Fahrenheit under basically no load, still the sucker ran.
Without the EGT’s I wouldn’t have had a clue.

Been crawling the threads everywhere until I came across someone who had a crack in the rotary valve cover causing hard-to-find lean issue on a carbed ski. This lit the bulb.
Tore off the throttle body and inspected the rubber gaskets it sits in. The gaskets are 23 years old and there are tube spacers on the bolts capping the compression to a certain displacement.
Put the throttle body on a spare rotary cover flange I had, blocked the Y holes and blew some compressed air in. WD40 bubbled on the outside of the rubber seal.
Voilá! Vacuum leak!
Ordered a couple on Amazon for $15 each.
Crossing fingers this is all, and that I won’t have to tear the top off to hone it again and put new rings.

This issue has been bothering that ski for a long time now, probably 3 years or more, I hadn’t nailed the issue before but was determined to find it since I got the probes in.
Never rebuilding a 2Stroke again without tapping in probes. It’s less than $100 in parts for 2 probes and a handheld gage, and not a big deal when the exhaust is off.

I hope someone can use this info. I’ve gathered more insight in the RFI fuel system than I ever cared to and then it was a stupid vacuum leak after all…or I think so. Will repost if it wasn’t the answer.

Happy Sea Doo season y’all!

 

[burtshaver2021]

Nice work, hopefully you’ve figured out the problem, not much that I could add here except a little experience I had with injectors. I’ve had injectors that I flow tested myself, tested good. I took them to a professional for cleaning, they flow tested them before and after, very very minimal improvement on the flow rate however the tech said the spray pattern was bad before the cleaning and sure enough the ultrasonic cleaning fixed the issue for me, That bad pattern in the 1 injector caused me to lose a piston, after I rebuilt the engine I couldn’t get it to run on both cylinders consistently until after the cleaning. I’d be interested in seeing some pictures during your work on this machine if you have any

 

[larryb1963]

1050+ Fahrenheit no 2 stroke should see that high of a temp ! you will 100% see a lean condition and will melt the pistons you can also have a run away motor . you clearly have a circulation issue . I would check to rave valves and back flush All the water lines you clearly have a restriction some where .

 

[tomanycars]

1050+ Fahrenheit no 2 stroke should see that high of a temp ! you will 100% see a lean condition and will melt the pistons you can also have a run away motor . you clearly have a circulation issue . I would check to rave valves and back flush All the water lines you clearly have a restriction some where .

RFI dont have rav valves. Rotary valve.

 

[larryb1963]

LOL ... rav valve (aka water regulator valve )

 

[mikidymac]

RFI dont have rav valves. Rotary valve.

Yes, All 787's including RFI's have RAVE Valves.

 

[tomanycars]

Yes, All 787's including RFI's have RAVE Valves.

Do they. I had a guy tell me rotary valve or rav valves. LOL still learning . I still cant get my head around how 2 stroke work but can build a 1000 HP big block.

 

[mikidymac]

Do they. I had a guy tell me rotary valve or rav valves. LOL still learning . I still cant get my head around how 2 stroke work but can build a 1000 HP big block.

All seadoo 587-787's have Rotary valves, this is like an intake valve or reeds. All 787's and 951's have RAVE valves which are on the exhaust side and change the port timing.