Power then bogging?

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May 30, 2019
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#1
Bought a 92 750sx have been having a ton of trouble with everything originally was in limp mode so I disconnected the temp sensor by going into the Ebox and disconnecting the leads and bypassed the water flow entirely straight from the stinger to the pisser.... gave me full rpm so that’s fixed (I think) then it was getting really hot and not pissing much out so I did all new gaskets and new rings cylinders/head/pistons look good so that’s fixed (I think)

Current problem... when I first get it started and into the water it’ll have decent power for 5 seconds or so then it just dogs out to a crawl if I pull it out of water and give it some rev’s and put it in I get power for a few more seconds then it’s gone again I rebuilt the carb and cleaned the jets changed plugs and that hasn’t helped me I also noticed the hose going from the water box to the exhaust hole seems to have melted? My dad seems to think it’s supposed to be like that but I think it could be a part of the problem maybe causing too much back pressure? I’ve been reading online non stop trying to find a solution but no luck quite yet
 

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Joined
Jan 26, 2014
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#2
That Hose has cancer. Replace it asap.

Or is it oily sludge? If the Hose feels dried out, crunchy and is not pliable when you squeeze it, then it's definitely bad.

Also, the Waterbox may be clogged up. Inspect and clean it. Check the entire Exhaust System all the way to the Outlet too.

Make sure all the Cooling Lines are clear. Check starting from the Pump Tap to the Exhaust Manifold plus all the other associated Cooling Hoses.

There may be Mud Daubers, Rats Nests, God knows what packed in there...
 
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#4
Also, tell us what the compression readings are in each Cylinder.
130 in each I don’t think the rings have fully set yet as I only rode for about 3 minutes before giving up for the day. Also have the carb set at what it says in the oem manual and have stock jets in it
 
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Jan 26, 2014
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#5
Kawi 750SX Service Manual says acceptable Compression range is 121 psi to 187psi.

OEM Jetting: Main Jet #140, Pilot Jet #75. Both Low and High Speed Screws set at 7/8th open.

It helps if you spell out what you have to make sure nothing is missed and it's also for the benefit of anybody else that has a stock single-carbed 750 that comes across this Thread...
 
Joined
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#7
That Hose has cancer. Replace it asap.

Or is it oily sludge? If the Hose feels dried out, crunchy and is not pliable when you squeeze it, then it's definitely bad.

Also, the Waterbox may be clogged up. Inspect and clean it. Check the entire Exhaust System all the way to the Outlet too.

Make sure all the Cooling Lines are clear. Check starting from the Pump Tap to the Exhaust Manifold plus all the other associated Cooling Hoses.

There may be Mud Daubers, Rats Nests, God knows what packed in there...
I’ll give the exhaust a good look again today and see if that could be the culprit the hose felt alright except for a few soft spots but I would assume all those *tumors* growing in it wouldn’t be from the factory so I’m gonna replace it either way I’m just seeing where I can find one other than a used one on eBay. Would taking a video of it on the river help diagnose a problem like this maybe someone would hear something I’m not?
 
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Jan 26, 2014
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#8
Photos and Videos always help. Video the engine running on the trailer. Have you back-flushed the ski off the garden hose yet? Start the engine, turn on the water, let it idle, rev it a few times, then shut off water and lastly, shut down the engine. A video of that would be helpful.
 
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