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97 polaris slx 780 bogging after rebuild

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brock1

brock1

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Ok i decided to start a threa on this issue since dr. honda and i have been trying to figure this out by messaging and i still cant get it... Here it goes... I picked up 2 97 polaris slx 780's with the BULE FUJI engine in them... neither of them ran and were in pieces so i constructed 1 engine out of all the parts and put it together.. tested the compression after the rebuild and its 125 across the board.... it fires up great and idles beautifully.. but as soon as i hit the gas it will rev to around 4000 rpms and stay there and just make a boggging noise and the engine will rock back and forth and it wont go any higher than 4000 it just makes like a wah wah wah wah wah wah noise any time after 4000... I cannot for the life of me figure this out i have fresh fuel...(by the way doc i got rid of the premix i was talking about and just ran straight gas with oil injection and it didnt help) ... i originally thought that the plugs were fouling but that is not the case now... I have spark BUT.... it does seem kind of weak to me but then again i have never dealt with this kind of engine before.... the plugs are a little wet when i pull them out but not crazy wet just a little... if anyone has any idea let me no :thumbsup:
 
no sad faces needed.


OK... does it sound like it's bouncing off a rev-limiter? Or is it just a hollow bog?

There are a few things that can put a Polaris CDI into low RPM mode. Low oil... low fuel... over temp... and if it thinks the reverse gate is down.
 
9 views and no opinions...... wow this is gonna take a while LOL ........................maybe ill become a premium member
 
of course as soon as i write that last comment someone replys...LOL Ok ummm no it dosent sound like its bouncing off the rev limiter it is just a hollow bog.... But i should mention that it is showing low oil and low fuel since i just put enough in to start it and run it for a few min.... no reverse gate though on it so cross that off...
 
GEEEEEEEEEEEEZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ !!!!!!!!!!!!!!!!!!!!!


Some of us have to work for a living ! (j/k) Also... the 9 views could be you refreshing your browser. (lol)


OK... I would put enough fuel and oil in it, to get rid of that possibillity. Then... let us know what happens.

Question... you have the digital display... right?
 
yes i do have the digital display and im sure you are gonna aks...yes the red light is flashing
 
HA HA good one ya prick LOL...... this thing has me at my wits end...guess ill tryt o fill it with oil and see what happends...is there any way to disconnect the display temporarily to get rid of the warnings and see if that makes a diff
 
brock1 said:
HA HA good one ya prick LOL...... this thing has me at my wits end...guess ill tryt o fill it with oil and see what happends...is there any way to disconnect the display temporarily to get rid of the warnings and see if that makes a diff
Click to expand...


What' ya call me???? BANNED !!!!!!!!!!!!!!!!!

Seriously though... take care of the light, and it's probably going to be just fine. BUT... if it doesn't... just post up. :cheers:
 
ok sounds good thanks for the help but as far as unhooking the light can it be done or should i just drive an hour to get the oil LOL
 
The sender in the oil tank isn't a simple unit. (like in a seadoo) You could take it out, and turn it upside-down. Personally... I would just put oil in it.

On that note... you can use a TC-w3 oil in that ski (the original recommended oil)... but Polaris did change their stance on oil, in 2000. They also recommend an API-TC oil (like seadoo) I personally run XPS semi-synth in my Genesis.
 
ok thank you very much good thing i have 2 of the same ski's looks like im gonna be robbing parts cuz my baffle is bad i think in my fuel tank
 
UPDATE------ Went home and filled the oil almost to full and the warning light is still flashing saying low oil and im still having the bogging issue... i took a video of it but i cant get the dang thing to load so that wasnt much help...its so wiered because its acting like fouled plugs but it will idle PERFECT...... it sounds beautiful when it idleing but anytime after that it is bogging .....any suggestions would be great
 
will do ready to put this thing out to the road in the shape its in..... tryin to fix it and hopefully sell it on a trailer for 1200.00 think its worth it...verified last night that the ski has only 20 total hours on it
 
The only thing that i an think could be wrong would be my FUEL PUMP... i think it may only be getting enough fuel to idle and that would explain why when i take the plugs out and crank it for a sec. then put flugs back in it will run fine for like 5 seconds since it has enough fuel...i have an extra fuel pump gonna switch it out tonight when i get home
 
If that was the case... pulling the choke a little would bring it to life.

If it was my ski... I would be checking 4 things.

1) I would go thought the carbs again, and verify everything. (also the fuel pumps)

2) On Polaris... the return fuel restrictor is in the return hose. Is it there?

3) Are all the reed valves good? (you can check them when the carbs are off)

4) Are you firing on all cyl's? Run it for a minute... then touch the metal base of the spark plug. If one of the cyl's aren't running... the plug will be cold. From that... you will have to figure out if it's the carb, or ignition. FYI... I had an ignition issue with my Genesis.
 
no all plugs are hot after running it i initially thought an ignition issue so i changed all plug boots and still no difference. i do have spark i checked them several times.. to tell you the truth i never popped the choke to see if it brought it to life.. ill check tonight when i get home..i do have another full set of carbs for it so i am going to switch them tonight also and see if it makes a difference... as far as the fuel restrictor i do not know i did not check that.. i will check it when i get home...
 
The fuel restrictor is a big deal. That's how the pump builds pressure in the carbs. In a seadoo... the Mikuni carbs (in most) have the restrictor built into the exit of the carbs. Polaris uses it as a tuning tool... so make sure it's in the return hose.
 
UPDATE-------- Good news got the polaris to run like a raped ape.... problem was simple actually..apparently polaris has somewhat of a fuel saving mode on their ski's. What hapened was tyhe fuel float was bad and it was showing low fuel al the time...i put a new float in and the blinking warning light went off and it runs great now... But i have to say that this is why i ride seadoo and not polaris....what happends if you are out in the ocean with 4 foot waves and you get low on fuel and it goes into this mode.?????? How do you get back to shore in that situation.... If anyone wants this ski its for sale for $1200.00 on a single place SHORELANDER trailer... Ski has about 22 hours on it and about 2 on the new rebuild... Has new fuel pump and a new set of carbs... if interested pm me ... thanks for all the help
 
Any "Warning" situation will put it into low RPM mode. Also... there probably isn't a RES. spot on the fuel valve. Just off/on. So... if you are that far out... and almost out of fuel... low RPM is not your real problem.

As far as the total time... you can't trust the gauge. They are known to randomly reset.

Glad you got it going.
 
If your slx 785 doesnt pass 4000 rpm in the water

brock1 said:
Ok i decided to start a threa on this issue since dr. honda and i have been trying to figure this out by messaging and i still cant get it... Here it goes... I picked up 2 97 polaris slx 780's with the BULE FUJI engine in them... neither of them ran and were in pieces so i constructed 1 engine out of all the parts and put it together.. tested the compression after the rebuild and its 125 across the board.... it fires up great and idles beautifully.. but as soon as i hit the gas it will rev to around 4000 rpms and stay there and just make a boggging noise and the engine will rock back and forth and it wont go any higher than 4000 it just makes like a wah wah wah wah wah wah noise any time after 4000... I cannot for the life of me figure this out i have fresh fuel...(by the way doc i got rid of the premix i was talking about and just ran straight gas with oil injection and it didnt help) ... i originally thought that the plugs were fouling but that is not the case now... I have spark BUT.... it does seem kind of weak to me but then again i have never dealt with this kind of engine before.... the plugs are a little wet when i pull them out but not crazy wet just a little... if anyone has any idea let me no :thumbsup:
Click to expand...


There is a rev limiter for protection out the water so if there is no water coming in the engine is not gonna pass 4000 rpm there is a black box on top of the battery thats where problem is coming from had the same problem but my mechanic fixed it
 
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