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Discussion Starter · #1 ·
Okay, it's not a bike...it's a VFR800-powered minibuggy. This thing was running perfectly until I decided to sell it (to build another one with more oomph). I drove it into the driveway, parked it, shut down, and the only things I did here were move a light bar from the front of the buggy to the roof and pulled the ground from the fan off the frame and back to the fan switch.

Immediately there after she's broken. When cold she idles and revs great, fast as shit...once she's warm she starts misfiring, backfiring, won't idle, no power, stalls. Obviously I moved my ground and lights back, but the problem persisted.

I have tested and tried lots of things but the problem persists. New fuel filters and lines, new plugs, ran new grounds to EVERYTHING (000000 ohms everywhere), no FI codes, MAP is getting voltage, gone over all the connectors I can find in the harness, no fuel leaking from vac port on fuel rail, 36~40psi fuel everywhere, 20+psi vac at idle, 13.4vdc at idle, it doesn't even get hot enough to open the thermostat.

I'm stumped and am looking for new ideas and possibilities. Any help would be appreciated!
 

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Discussion Starter · #5 ·
Yeah it gets warm, but not really operating temp. Never gets warm enough to open the thermostat...right side coolant lines get pretty warm to the touch and pressure builds in the system, but the left side of the engine never gets much above ambient temps.

I've had some suggestions that possibly either the thermostat isn't opening or the impeller is bad, which is causing the engine to overheat while the lines never really get hot. I don't have the factory dash so I'm not sure what temps the ECM is seeing. The FI light comes on while the thing is acting up...I've been trying to sort out if the FI lights on if the temps are too high.

It's all from a '98.
 

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Discussion Starter · #7 ·
Yeah I've got the manual and no, there's no codes stored. The FI lights on when it's acting up but it doesn't store any codes.
 

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Discussion Starter · #8 ·
Okay so I'm no longer convinced it's temperature related. I just went out to move the buggy and it was acting up almost immediately. Plus, it's 40*f out so if it were overheating I should have had more time than that.

It wasn't backfiring so much this time as it was just not idling, low power, and stalls. FI light was when it started struggling, but if I gassed it the light would go off. Still no codes.
 

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sickboy
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you sure its firing on all cylinders? check for spark or at least check the temp of each header?
 

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Discussion Starter · #11 ·
I think the immediately acting up thing earlier was my fuel pump vapor locking. I looked at it tonight hoping for some inspiration and saw that have the pre-filter was empty. After I bled the air out of it the thing fired and idled just fine for about 10 minutes....then same story. I'm pulling the wiring harness off tomorrow to go over it and trim it down.
 
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