I just finished installing the "fix Kit" into a friends 2008 Dragon 800. I tried starting it back up and I get nothing but a huge backfire. I am not familiar with fuel injected sleds so I am wondering if I need to bleed the fuel system or something before starting it up? Any info would be most appreciated
back fire after top end rebuild
- Thread starter 660canuck
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channonmanuel
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Fuel injectors plugged in backwards?
Or spark plug wires backwards?
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Or spark plug wires backwards?
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- #3
both are correct, I pulled the plugs and turned the motor over to clear out the crankcase. Threw in a new set of plugs and that cured the backfire. Still wont start though
channonmanuel
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Do you have the sled fully put backtogether like the exhaust? What about exhaust valves are they installed correctly?
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- #6
Sled is fully back together, exhaust valves installed properly. I just checked to see if it was getting spark and found that it sparks for a quick second and then stops when you turn it over. It does this everytime I turn the key, sparks for 1 sec and then nothing as the engine is still turning over. Does this on both cylinders. Any insight into this? Looks like I will be spending some time with my multi meter
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Rhodesie
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how much throttle cable freeplay do you have. if the throttle safety switch is active and the tps is reading a higher than idle voltage it will kill the spark. if you had the throttle bodies off make sure you did not reinstall them with a twist in the cable. just a thought.
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- #8
Never had the throttle bodies off, and the throttle cable has not changed since before the new top end. I adjusted the cable to have a little more free play but it still wont start. I have no idea what is killing the spark. I'm not familiar with polaris so I'm totally lost now
Rhodesie
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was it running ok prior to rebuild? acting like the voltage reg screwed up and fried the ecu trick. that was common.
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channonmanuel
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Did you remove any wiring? Maybe double check your grounds
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moto5151
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Check the mag pickup on the stator. If they have come loose they might only pick up every second tab...
I had a similar issue with my pro.
I had a similar issue with my pro.
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- #12
It was running but it had gone into limp mode.
The wiring removed was the two plugs into the ecu, sensor on the pipe, temp sensor in the head, and air box sensor, all of which are plugged back in.
I'll check the mag pick ups
channonmanuel
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Are both plugs doing the exact same thing as video?
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007sevens
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He said it did this on both cylinders when he posted the video.
I would unplug the ECU and plug it back in again. might not be making a good connection. check all connections really close.
moto5151
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Sometimes when the machine goes into limp mode, for various reasons, it will stay derated. Are there any faults, or eng lights? It's possible it needs to be cleared.
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- #16
Found one of the plugs for the ecu was ever so slightly loose. Now I have spark and I am back to my original problem. Sled sputters briefly, lights on the gauges come on. After turning it over several times I get a huge backfire. The plugs are brand new and the fuel is fresh premium from Shell
moto5151
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Are the plugs wet when you pull them? Is it getting air? Is the pipe plugged with a mouse nest or something? Start from scratch, air, fuel, compression, exhaust. Might be worth pulling head to see if pistons were put in right
CrankShop910
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You don't need to pull the head to see if the pistons are install right.. Take off the Y pipe and see if the ring gap is in the port.. The ring gap should be facing the intake side.
channonmanuel
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Did you plug anything with a rag?
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- #20
I decided to take moto's advise and start from scratch. Both cylinders have 125 psi compression cold. It is getting fuel, the plugs are wet. Nothing is plugged with rags, throttle bodies and exhaust are clear. Pistons are installed correctly, arrows facing to the exhaust side, ring gaps are to the intake. I decided to check spark again and its back to sparking for a half second and then nothing. I'm thinking its gonna half to go the a dealer and get the computer reflashed or check out the ecu. I wish we had another Dragon in our group so I could swap out the ecu and try that
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