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Old 03-16-2007, 05:45 AM   #1
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Default Nitro Engine Tuning Problem/Gremlin

Have a New MR Ninja MR21 B01 5 engine and it is running beautiful. Heaps of low end power, winds out nicely (plenty of power for me), idles nicely and takes off cleanly and like a rocket at the start of the race. But Im having one issue that I cant seem to figure out.
As soon as I roll or flip upside down it flames out instantly and I cant figure it out.
Fuel lines are clean, filter is clean, lines are not getting pinched, fuel if fresh, it will run for ever right side up. I cant figure it out.
I know the obvious answer, dont flip I hear you say, I know but not always possible.
Any ideas would be appreciated.
Thanks
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Old 03-16-2007, 10:44 AM   #2
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is your fuel lie pretty long cause fuel wont get fead to the engine if its up side down only what left in the fuel line
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Old 03-16-2007, 02:48 PM   #3
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if it really matters that much then make yourself a small electric fuel pump
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Old 03-16-2007, 05:55 PM   #4
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yeah every one who has looked at it says it is long enough and it is comparable to every one else's at the track. problem is it is flaming out even before that would be a problem, it happens the instant it goes upside down??
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Old 03-16-2007, 06:10 PM   #5
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Could be something else that happens when the car is inverted. Flip it and look from underneath. One of my team mates had a similar issue, but his was two problems deep. For one, his clutch bearings were going out and would stall the motor, but not always. Then his exhaust/fuel pressure line was too short, only about 4 inches.(he'd been trying to tune it for two days!) I handed him about 8 inches of line, he installed it, problem solved...
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Old 03-16-2007, 06:33 PM   #6
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long shot but it could be way too rich on the bottom and splashing the plug when it gets flipped over....
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Old 03-16-2007, 07:10 PM   #7
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Return line is around 6 inches will try longer though see how that goes.
Have also been slowly turning in bottom end with same assumption no joy yet, also though hotter plug may help if that was problem? Have one coming to try?
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Old 03-17-2007, 01:40 AM   #8
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check the whole clutch
and make SURE everything is tight around the engine and that your idel is high enough cause i run the same motor and dont have that problem
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Old 03-17-2007, 06:22 AM   #9
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How long is the feed line, and do you have a loop or two in it? If you have about 10" of fuel line and a fuel filter there should be plenty of fuel in the line to keep it running turtle style. Also when it cuts out after a flip does it have fuel in the line to the carb that you can see. I'll bet its dying out cause of something else, I've had problems like Adam said. Oil/fuel from the crank or pipe could smother out the plug when it turtles.
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Old 03-17-2007, 06:25 AM   #10
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Robert.
Love the Motor, don't you. I have so much power and it has awesome fuel efficiency, just need to get this sorted and Ill be stoked. Clutch is fine bearings good, no binding. Flywheel not touching chassis, nor is center gear. Clutch engages at a nice point so I dont think it is grabbing to early. Pretty sure Idle is right I think it is probably on th e high side a little but will keep tinkering.
Thanks for the ideas.
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Old 03-17-2007, 08:20 AM   #11
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If you have another pipe try it. A few years ago a guy at our track had the same issue and after countless hours of swapping parts on his car we found the pipe to be the problem. When we cut the pipe apart there was a coating inside the pipe that was falling apart and only attached at the bottom and every time he landed upside down it would fall over and cover the outlet of the pipe. I can't remember what pipe it was though.
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Old 03-19-2007, 02:02 PM   #12
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Quote:
Originally Posted by crlytm
Robert.
Love the Motor, don't you. I have so much power and it has awesome fuel efficiency, just need to get this sorted and Ill be stoked. Clutch is fine bearings good, no binding. Flywheel not touching chassis, nor is center gear. Clutch engages at a nice point so I dont think it is grabbing to early. Pretty sure Idle is right I think it is probably on th e high side a little but will keep tinkering.
Thanks for the ideas.

yea the motors alright im switching to Radical (ops) but its a good motor
defenetly lower the idel if it high
and put a new plug in wether you think the one in there is good or not
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