97 GSX First Trip out, is this normal?

[97gsxmt]

First off let me apologize for my lack of knowledge on PWC's firstly, first time owner here, this was our first trip out so here goes. 97 GSX 787 2 stroke oil injected. Machine will run ok but seems to lack any punch, at wide open throttle it will consistently get 48-4900 RPMs.. at first i thought man this is running like crap, Initially if you'd let off the gas briefly at wot and pin it again you could definitely feel the difference in top speed etc and the rpm's would go to 6100, throughout the day this method no longer worked, so in order to get her up to speed you'd have to catch some air, and while in the air hopping across the waves it would gradually build up rpms, until wala it would attain 6100 rpms, as long as you kept her pinned it would sustain 6100 rpms with good power, also the speedo would not function at all when in this 4800 rpm funk, but when the engine got to full power the speedo would start working? any suggestions, the speedo thing doesn't really bother me, but i'd like to get the machine running right as i suspect this is not normal. Thanks in advance for any ideas on resolving this problem.

 

[Dr Honda]

Sounds like you have 2 probs.

First… your speedo is dieing. It’s normal for the older skis. The gauge gets water in it… and they give up. It could be a loose wire… but probably not.

Second… your engine should be running up to 7000 RPM’s. If it seems like its running OK… but just not reving out… I would say your RAVE valves are sticking closed. There could be other problems… but most of them would be fuel supply… and if it was running good enough for you to stay out on the water… it’s your raves. (or you have very low compression) A compression test is quick… but I bet you will find your vales are stuck.

Good luck

 

[97gsxmt]

i did a lil reading.. the rave valves are the two caps on top of the carbs correct? how does one know if they are sticking? Do you simply remove them and clean them? Also how does one check the fuel filters on this? The unit does not have the crappy grey fuel lines, and the plugs look good, was a lil tuff to start also sometimes. thinking i will start with the obvious but like i said this being my first pwc I am not familiar with how they are designed. So any help in these two areas would be greatly appreciated.Thanks for your reply and hope I can figure this out.. I had a blast on the ski and like i said i got it up to 50 mph with my chubby butt on it.. and it was doing i think 6100 rpms... if it has more in it yet that would even be better.

 

[cmeseadoin]

i did a lil reading.. the rave valves are the two caps on top of the carbs correct? how does one know if they are sticking? Do you simply remove them and clean them? Also how does one check the fuel filters on this? The unit does not have the crappy grey fuel lines, and the plugs look good, was a lil tuff to start also sometimes. thinking i will start with the obvious but like i said this being my first pwc I am not familiar with how they are designed. So any help in these two areas would be greatly appreciated.Thanks for your reply and hope I can figure this out.. I had a blast on the ski and like i said i got it up to 50 mph with my chubby butt on it.. and it was doing i think 6100 rpms... if it has more in it yet that would even be better.

Your raves are NOT on top of the carbs, they are the black circular bulbs sitting on top of each cylinder jug behind the exhaust manifold just off the engine and they have a red center cap with a retaining pull over sping device to hold the cap on. You prolly have another one on the exhaust water box....dont mess with that one. I dont even know what that one does but it looks JUST like a RAVE to me....anyone know what that does on the exhaust?

These valves are easy to clean. What they do is run off of engine pressure and open up as the engine speeds increase thus increasing the size of the exhaust ports thus changing the horsepower and torque curves thus impacting top end and low end torque. Your symptoms seem as though they def. are at least one problem you have. They need to be cleaned frequently as you have a 2 stroke engine and the junk that builds up in there is amazing from the oil that is burned in the fuel.

Take the retainer clip spring off holding the cap down...remove the cap and there will be a cylindrical spring in there which holds tension on the diaphram which controls the valve's up and down motion. You'll need to remove the two allen screws that fix the rave assy to the engine as well....total of 4. Then, there is a sping that goes around the diaphram, remove that. Separate the diaphram from the black circular housing it is hooked to and unscrew the black circular part from the rave valve. Once that is off, you'll be left with the rave valve down in the engine and the black oring on top of that. Remove all this stuff making sure you dont drop parts into the slit of the engine. It ALL need to be cleaned VERY well. It is a FILTHY job. PLENTY of carb cleaner is needed. buy the cheap stuff because you're just using it to just clean. Get two bran new RAVE valve kits from SBT for the 787 and they are like 25 a piece....you get a new diaphram and oring and gasket.....clean it up really good and then put it all back together. If you are mechanical like me, you'll figure it out as you go. Its hard to type an exact step by step but I think someone else has on this site......maybe even with pics. Good luck. Those valves HAVE to be working or else you wont get to the upper RPMS.

I have a 1996 GSX 787 and I just did my carbs too....you might want to replace your fuel filters at the very lease and check fuel lines for degradation. I have the grey lines but they are all in great shape at 287 hours so I did and no no and stuck them back in. Any issues, will replace no big deal but for now, going to continue using.

Any questions, ask away

 

[Petron]

It might be a good idea to inspect and or change out your wear ring. I had a similar problem, once I changed out my wear ring she ran like a rocket. Just a thought.

 

[97gsxmt]

k i got the rave valves out of it.. and got em all cleaned up... took forever i couldn't get them back in, seemed like the bolts were crossthreading... but got it back together finally. they were black and had a bit of crusty crud on em but overall i would say they were not that bad... I never checked it out of the water to see what the rpms would do.. but now that i got it back together out of the water it revs up to the 7000's didn't wanna damage it so i didn't do it but real quickly.. also checked the plugs they were a lil black so I put in a new set of plugs. Beings I am over an hour away from the nearest water I will have to drag it out there on my day off next week and see if the problem is solved.. or if we are back to square one. Thanks for the advice guys, will let u know what/how it turns out.

 

[cmeseadoin]

k i got the rave valves out of it.. and got em all cleaned up... took forever i couldn't get them back in, seemed like the bolts were crossthreading... but got it back together finally. they were black and had a bit of crusty crud on em but overall i would say they were not that bad... I never checked it out of the water to see what the rpms would do.. but now that i got it back together out of the water it revs up to the 7000's didn't wanna damage it so i didn't do it but real quickly.. also checked the plugs they were a lil black so I put in a new set of plugs. Beings I am over an hour away from the nearest water I will have to drag it out there on my day off next week and see if the problem is solved.. or if we are back to square one. Thanks for the advice guys, will let u know what/how it turns out.

Good deal, you might want to pick up a rebuild kit and stick all new parts in those raves eventually.....if that diaphragm is not sealed 100% it will not operate the rave correctly.....cleaning them is good for now though as a test. If your plugs are good and gapped right and you have no ignition issues, you "should" be good. you might have a carb issue(s) as well though...that might be the next thing to target depending on the next ride and the data you get from it. See how she does and let us know. :cheers:

 

[97gsxmt]

thanks for the input, how hard is it to change the internal fuel filters? And also what is the procedure for checking for a worn wear ring?