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Tuning Issue

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Old 10-12-2018, 01:30 PM
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Cool_cris27
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Hello so lets get straight to it, i havent turned on my 1/8 scale nitro buggy OFNA Ultra LX2 for about 8 months i got her running again but obviously not tunned. I understand how the high end needle works but i still cant manage to find the sweet spot, so basically i can go full throttle and it will go some what okay, however if i hit the brake the car shuts off, if i jump the throttle to hard it will bog and shut off (too rich i'm assuming) Another weird thing about it is if i lift the car up while its on the car will accelerate very fast without the throttle moving at all, the servos is completely still, one last thing when ever i take out the the glow plug ignitor it will shut off, i have to give the car a bit of throttle for it to stay on. Any tips on what could be going wrong or how i should try to Re-Tune the engine. Thanks!
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Old 10-13-2018, 04:25 AM
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It sounds like the idle mixture is too rich and the high speed (main needle) is too lean. I would double check that the idle gap is no larger than 0.7mm and set your high speed needle 1 full turn richer and lean the idle speed 1/8 turn. Replace the glow plug with a new one - medium heat range long reach plugs are best. Start the engine, warm it up for one tank of fuel. If it’s real slow to rev and real Smokey, lean the idle needle 1/16 turn at a time until it will drive around cleanly but still a little slow and Smokey. Fill the tank back up and get the high speed set. Do a full throttle pass and note how the engine sounds. If it revs slow and Smokey, lean the high speed 1/16th turn and do another WOT pass. Keep doing this until it revs up and up and up clean and smooth. Once it does, set the idle mixture needle so it will idle for 20 seconds. Now punch it to WOT. It should launch and rev up a little slow at first, real Smokey and burbly, but it should clean out and not flame out. If it flames out (quits), the idle is too rich. Lean 1/16th turn, run a WOT pass, and repeat the idle for 15-20 seconds. Keep doing this until it will rev from idle to WOT without quitting.
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Old 10-13-2018, 05:38 AM
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Thank you so much this is exactly what i was looking for, i'm going to give it a try later today and ill let you know the results!
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Old 10-13-2018, 06:32 AM
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Cool! Good luck!
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Old 10-13-2018, 04:09 PM
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So i ran into a problem lol, My pull start keeps on slipping like it wont hook to the piston and its not turning, it hooks for maybe one spin and the rest is slack and it recoils back in with no spin in the motor, I took the pull start out and changed the nut but same issue happened, i noticed that if the nut slides like 1mm away from the engine it will slip and not grab on to the rod, using different bolts aswell, what could be the issue? i even tried a whole new pull start but it keeps slipping. I checked the crankpin in the piston and it seemed okay to me along with the component that hooks on to the crankpin. I don't know why it keeps slipping.
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Old 10-13-2018, 05:40 PM
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The starter shaft will get glazed over time. When the engine is running, that shaft is spinning with the engine constantly within the one-way clutch bearing. The cure for this is to lightly sand the starter shaft with some fine sandpaper. I use 400-600 grit and sand the starter shaft so the sanding scratches run the length of the shaft, NOT around it. These fine scratches give the one-way clutch bearing something to “grab” on to. The slipping problem is exaggerated when the fuel has a lot of oil in it and/or the fuel mixture is really rich or the crankcase is loaded up with fuel/oil.

What fuel are you using?
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Old 10-14-2018, 06:13 AM
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20% nitro, i'm going to try to sand it and see the results thanks man.
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Old 10-14-2018, 08:31 AM
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Originally Posted by Cool_cris27 View Post
20% nitro, i'm going to try to sand it and see the results thanks man.
As for the fuel - what brand/type? If itís something like backyard basher or Traxxas fuel, it has way too much oil in it and will cause these kinds of problems. Lower oil fuel usually doesnít cause this to happen very often at all (10-12% oil is ideal; I use 11% myself).

Also - what engine is in your buggy?
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