1996 GSX Missing at 3200RPM, won't rev

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crazeejames

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Bought a 1996 GSX 787 for a deal figuring I could fix it and have cheap toy........It starts, idle's fine. Hit throttle, starts missing and kind of backfiring......if I slowly open throttle, it goes to approx 3200 and just start missing, almost like it has a rev limiter!
I have pulled and cleaned the carbs(they were pretty clean), changed all the gray fuel lines out........Rave valves cleaned.........not sure where to go with this?
It is consistent......2 beeps, fires right up, idles like a dream, open throttle, its good till about 3200-3400rpm then just starts cutting in and out.........
Any ideas would be greatly appreciated..............
FYI, this is on the hose, not in the water......as its kinda still winter like here ;)
 
Misfire

There is a rectifier in the electrical box that's in the left front area of the ski.
There are 4 wires going to it (3 yellow 1 red). Unplug the red wire. Take the ski out for a short run and see if the problem goes away. A faulty rectifier can cause the engine to run bad.
Good Luck, DAWG
 
Thanks Dennis

I tried unplugging the red wire, no change..........new development........I pulled on plug wire and fired it up on one cylinder, idles fine............moved that same plug wire to the other cylinder(since the wire fire at same time) and it idles fine.........swapped the wires, and it won't idle on the 2nd wire, doesn't matter which cylinder its one, starts.......stalls...........seems kinda odd since they are both supposed to be the "same"! I cut the wire back 1/4 inch at the plug, no change............I can't see it being a the coil since they both run off the same one, but I've seen stranger things! Anyone got any ideas............maybe a bad plug cap? Bad wire?? Its really driving me nutz.............
 
Plug wire

There's always the possibility that the wire or the wire cap is bad. I've seen corrosion build up on the coil where the plug wire is attached and cause a misfire. This corrosion, if present, is caused by water getting into the rear box and then seeping into ports on the coil for the wires. Another thing....... make sure the small ground wire that connects to the ground side of the battery is ok and the eyelett is ok. Check all coil connections.
DAWG
 
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no revs

The plugs look alright, I'll check the gap in the morning...........they are BR9ES, which may be a little cold in heat range, but should still run I would think..........
 
not the plugs

Changed out and gapped new plugs, no change.........starts idles fine, bogs and missfires when opening throttle whether fast or slow..........I'm starting to think maybe its a fuel problem, seems to have consistent spark, what controls the midrange on these carbs.........I come from the sled world, which has a slide/needle combination..........I would like to have it the water so i could hold it WOT and see if it runs on the top end to isolate if it is just a mid throttle issue............
 
A lean condition can cause BF. In your case, I am inclined to think you have small
metal particles interferring in the magnito. Prop the engine to get the cover off to
get in there to see them or a broken bracket. Vacumn them out.
 
fixed yet

I just came off shift, hopefully do some more troubleshooting this week, just waiting for dealer to get new rotary valve o-ring and carb gaskets in, then I'm back to it..........I'll post whenever I get it figured out.
 
still no go......running out of ideas

Sooooo, pulled off the Mag cover and checked the cup. The leading edge of one of the "bumps" is lined up with the hold in the flywheel.....cup was tight. Removed cup, tried various different positions but there is only the one that puts it even close to the hole in the flywheel............pickup is mounted solid, no cracks in ears, nice an clean in here, hardly any metal filings........
Not sure what to check now...........
ANY ideas would be graciously accepted........is it possible that someone connected some wires in the front electric incorrectly.......as they are all just butt connectors, no plugs......all the colors match, but there are lots of wires the same color...........I'm grasping at straws at this point :(
 
So far.....

Here's the story.......come from sleds and bikes, bought this GSX for cheap, has rebuilt engine, starts and idles fine, but as soon as gas is applied it bogs and backfires..........so far this is what I have done:

Changed all tempo fuel lines to new lines.
Clean/lubed fuel selector valve
Verified both hull vents operational(outlet one was plugged)
Cleaned/checked carbs(they were actually quite clean)
Popoff checked, all passages cleaned.
Pulled "red" wire on rectifier.......no change
Changed gapped/plugs
Cut back plug wire 1/4 inch
Di-electric grease on most connections
Pulled rotary cover and verified valve timing.....147/65
Removed MAG cover and checked "cup" position, as well as pickup ears and no metal particles in there either.

Any idea, no matter how wild will be entertained :ack:
 
inspected the woodruff key/flywheel positioning, on the crank?...just throwing a bone now man...:cheers:
 
Key

Well pulled the flywheel, and nope the key is fine! So there goes that idea!
Back to work till mid next week, so won't be tinkering for a bit
 
howd the RV surface look? Is/was there a "groove" going to both ports? Install 2-long screwdrivers into spark plug holes, then rotate the PTO, Your gonna watch the scredrivers to make sure they move ALWAYS in different directions. If not, you got bent crank/rod...
 
RV surface

RV surfaces were fine......no grooves to speak off.........rotary valve itself had a bit of corrosion in the form of circle where it sat exposed, but no holes or anything, I just ran scotchbrite over it and its fine.....
I done the 2 screwdriver thing to check and see if the the crank had twisted/shifted....as soon as one is going down, the other is going up....no delay.....and I wouldn't think it would idle if it was that far out of time......
 
trailer or water

your "3200rpm" then misses, is this on water or trailer? If its trailer, then your problem is your idle set too low. It should be 300rpm on trailer, with load on pump from lake, it then goes to 1500rpm...
 
idle

Its on trailer, I can set the idle at whatever I want 1500-3000, idles alright, but almost sounds like running on one cylinder........anything on the plus of 3Kish and cough, sputter, pop, etc..........
 
Check the voltage, start it & rev to high or 5500, then check voltage there. post results.

you should know that by reversing the inlet fuel line and the fuel return line on the carb fittings will allow it to run at low rpm, but not at high rpm.
I m concerned if you have the lines between carbs directed properly..
 
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rev

I can't rev it.....it misses and backfires thru carbs......I haven't seen it hit above 4K
I've already tried unplugging the red wire on the rectifier.........no change
 
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