1997 GSX Won't Run up top unless release throttle and then full, RAVE?

[Tfast]

I recently purchased 2 '97 GSX (standard) PWC from a friend. Fairly lightly used and well cared for. He was not mechanically inclined and had a local "lake mechanic" maintain them. When you first ride them after not having being ran for a period of time they seem fine down low but won't clean out and run up on top (full throttle'ish). If you release the throttle and then go right to full throttle they then get full power and run fine for the entire ride. He had no idea why and just lived with it.

I am new to these but have worked on lost of 2 strokes, mostly motocross bikes and standup skis. While what the RAVES on it confused me when I first looked at them (I asked my friend and he said they were the carburetors, I said those aren't carbs ... he said, yes they are :0) ) I came to the conclusion that they are basically power valves and look to be a pretty slick design. My guess is that when first being ridden the RAVEs are sticking, hence the choked performance due to low flow through the exhaust, and pumping the throttle full off and then on frees them up for the ride and suspect a good cleaning would fix the issue.

I guess my question is, is this (not running up top) a symptom of a RAVE issue and, if so, is it probably sticky (or sticking) and might cleaning them fix it? Or am I just off base on this? Cleaning them does not look difficult, but any input or advice on that other than the obvious would be appreciated.

Thanks!

 

[tobytd]

Yep, disassemble and clean. The assembly under the exhaust requires, the piston screwed off of the guillotine to remove the guillotine (guillotine “power valve“).

 

[Tfast]

Thanks for the reply and information. I pulled them apart, cleaned and reinstalled them this afternoon. There was some carbon build on the guillotine but not excessive. There was more of an accumulation of thick oil gunk, as if there is too much oil mixing with the gas. I know some brands of PWC inject copious amounts of oil that can gum things up a bit. Is that the case with See-Doo or this particular motor (Dual Carb 947 RAVE)? Does switching to premix help with this problem (RAVE not working correctly)? Is the switching to premix difficult on these? When they are switched what ratio is recommended?

Thanks again for the information, it was very helpful. I won't have in in the water for a week or two but when I do I will report back if it fixed the problem or not.

 

[tobytd]

Keep the oil injection..very reliable
API-TC full synthetic oil ONLY,

 

[Tfast]

Will do. When they work well and are reliable oil injectors are nice from the "keep it simple stupid" perspective and with lake beginners using them throwing in as few variables as possible is wise.

Thanks again and I will update how they run once I get them on the water.

 

[JJinSC]

Since you stated slightly used, from a friend, we must ask. What color are the fuel lines?

 

[JJinSC]

Thanks for the reply and information. I pulled them apart, cleaned and reinstalled them this afternoon. There was some carbon build on the guillotine but not excessive. There was more of an accumulation of thick oil gunk, as if there is too much oil mixing with the gas. I know some brands of PWC inject copious amounts of oil that can gum things up a bit. Is that the case with See-Doo or this particular motor (Dual Carb 947 RAVE)? Does switching to premix help with this problem (RAVE not working correctly)? Is the switching to premix difficult on these? When they are switched what ratio is recommended?

Thanks again for the information, it was very helpful. I won't have in in the water for a week or two but when I do I will report back if it fixed the problem or not.

Using the correct oil is imperative for good Rave function.

 

[POPPS]

That symptom/syndrome is often the result of temporary fuel starvation,
I would go through the carbs with a fine toothed comb if you are still having issues.

 

[Tfast]

I did get them down to our lake house but didn't have time to drop them in the water - hope to do that the next trip. What might the fuel line color indicate? I don't recall the fuel line color but will check that next time down.

I think pretty much all two stroke engine oil is API-TC ( (API)-American Petroleum Institute, (TC) the API designation for two stroke oil). In my mind the choice is more in the other 3 options, conventional, semi-Synthetic or full Synthetic, and which work best in a particular application. It sounds like most owners have found the best performance is with Full Synthetic. To me, with the configuration of this engine (rotary valve, RAVE power valve) the one that collects the least carbon and gums surfaces up the least would likely be best. I would guess (and agree with the comments above) that would likely be the full Synthetic. Does anyone know what See-Doo recommends for this engine?

Thanks.

 

[mikidymac]

IF your fuel lines are Grey they are the dreaded Tempo lines and the rot from the inside out leaving green goo to plug up the carbs and fuel system.

Your GSX requires API-TC Full Synthetic. The different oils will not give more or less performance but the full synthetic will burn cleaner keeping the RAVE valves cleaner and provide more engine protection.

 

[Tfast]

That is good to know, I will definitely check them next chance I get and will run a FullSyn API-TC oil via the injector.

An odd thing that I was going to address in another post but might throw it out here. On one of the skis, the mechanic my friend used installed a brass ball valve in the oil line between the tank and the injector. You turn the valve on before starting and off after you shut down. My friend said that, without it, it would gravity feed oil and make a mess in the bottom of the hull, I assume via the injector (an overflow hose or something?). The mechanic suggested to him that switching to premix might be the best fix to eliminate the ball valve. After reading posts on this forum I have decided I far prefer having the injectors.

Is this a common issue and what might be the fix so I can eliminate the ball valve. If feels like a recipe for disaster since it just takes one person forgetting to turn it on to basically destroy the engine.

Thanks very much for the in put. Very helpful!

 

[mikidymac]

No, you should never have any valve installed on the oil line from the tank to the oil pump, your friend is wrong and you need to remove it.

The only oil valve that might be installed is on the 12mm oil line that supplies the rotary valve oil chamber. The only reason you would install this is if your inner crank seals are leaking and the cylinders fill with oil after sitting a few days or weeks.

The only oil injection issues thesk skis have is the small 3/32" oil lines from the oil pump to the intake manifold can get brittle with age and break, thus starving the engine of oil. I always suggest replacing these small oil lines with new Tygon or OEM lines and an new inline filter and you will be good to go for another 15 years.

 

[Tfast]

That's interesting. I'll have to look at it more closely and ask him some specific questions as to why it was installed - leaking oil into the hull or the crank filling with oil. From the parts drawings I see online it looks like there are two oil lines from a fitting at the bottom of the tank - one gravity fed to the rotary valve on the intake side of the engine and the other to the oil pump on the front of the engine. Is that correct?

I definitely need to get more familiar with them.

Again, appreciate the input!

 

[mikidymac]

Yes, you are correct on the oil lines on the tank.

There is no place that a valve would stop oil from "filling the hull with oil".
If oil is getting in the hull there are only 3 causes and none will help with a valve.
1. Cracked oil tank or oil tank seam.
2. Old oil tank grommets that seal the hose elbows.
3. Oil hose cut by hose clamp or loose hose clamp.

 

[Tfast]

At the moment, I am really shooting in the dark. I'll take a better look at it when I have time and see what exactly they did and if I figure out why and hopefully return with knowledge.

Thanks for all the info!