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Old 12-28-2014, 07:36 PM   #1
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Default nitro engine tuning. air bubbles in fuel line etc...

hey guys, i recently bought a novarossi .12 flash engine for my xray nt1. during my 4th ish tank in break in i noticed the engine would act erratic after it finally warmed up. i found that there were air bubbles in the fuel line. now i changed the fuel tank, fuel lines, glow plugs and inspected the engine for any visible problems. after non of that worked i tried to manage and finish breaking it in. during one of the runs i noticed the air bubbles would pop out of the carb into the fuel line, then get sucked back in causing the engine to act crazy lean and even cut out sometimes. if anyone knows why this could be happening it would be aprricated . im running odonalds 20% race fuel and i believe a"hot" glow plug
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Old 12-28-2014, 08:28 PM   #2
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Check the grommets that the tank sits on and make sure the tank isn't too tight. I have bubbles in the fuel lines on my 2014 but hasn't effected engine performance.
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Old 12-28-2014, 08:35 PM   #3
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I checked that a while back even changed the fuel tank.
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Old 12-28-2014, 08:36 PM   #4
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Originally Posted by Bundy_Bear View Post
Check the grommets that the tank sits on and make sure the tank isn't too tight. I have bubbles in the fuel lines on my 2014 but hasn't effected engine performance.
I'm thinking of just buying a used motor
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Old 12-28-2014, 08:58 PM   #5
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Otherwise check carby is tight and HSN is down tight.
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Old 12-28-2014, 09:06 PM   #6
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Otherwise check carby is tight and HSN is down tight.
You mean where the hsn and the fuel intel screws into carb?
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Old 12-28-2014, 09:06 PM   #7
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Otherwise check carby is tight and HSN is down tight.
Could this be from bad fuel?
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Old 12-28-2014, 09:13 PM   #8
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No from adjusting when installing engine and it will create an air leak.
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Old 12-28-2014, 09:17 PM   #9
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Originally Posted by Bundy_Bear View Post
No form adjusting when installing engine and it will create an air leak.
I will checj it out, it only happens when the engine finally warms up,the tube will be perfect but once the air bubbles pop up all hell breaks loosr
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Old 12-29-2014, 08:01 AM   #10
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Seal the fuel line from tank to carb. You can seal around banjo fitting and inlet to carb housing. Cushion the tank with 'O'-rings. And tune the engine. Small bubbles will dissipate.
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Old 12-29-2014, 11:23 AM   #11
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If it only does this after the engine is warm, you may be a bit lean on your needles.
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Old 12-29-2014, 12:20 PM   #12
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If it only does this after the engine is warm, you may be a bit lean on your needles.
I figured that but the majority of the run the engine is turned properly but it will act erratic and Leann for about 30 seconds or so , then back to normal. That's if it doesn't cut out from no fuel
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Old 12-29-2014, 02:21 PM   #13
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A large bubble? or small bubbles like fish eggs? What width the Throttle air gap?
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Old 12-29-2014, 08:18 PM   #14
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A large bubble? or small bubbles like fish eggs? What width the Throttle air gap?
Tiny tiny tiny bubbles, almost like dots. There could be like 100 in half the fuel line. And tbh I don't know, it may be to large. Could that cause the bubbles
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Old 12-29-2014, 10:22 PM   #15
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Tiny tiny tiny bubbles, almost like dots. There could be like 100 in half the fuel line. And tbh I don't know, it may be to large. Could that cause the bubbles
Did you seal the fuel line, tank to carb? This line should be the shortest as possible. Have to know the air gap of throttle. Small bubbles may be easy by leaning or richening. There is only one way air is being formed, if fuel line is sealed. Maybe you can answer it yourself!! Can you guess???
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