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Old 01-07-2009, 08:12 PM   #1
dvu
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Default Low Speed Needle or High Speed Needle

Hello,

I was wondering if I could get some help with my nitro car. When i start up my HPI R40, it seems to idle just fine. But after I run it for a while and the engine gets warmed up, it still wants to inch forward when the throttle is in neutral. I figure it's running too rich and so I've turned down my high speed needle, but if i turn it down too much when i lay on the throttle the car dies so I the have to lean out the high speed. Do I need to be tinkering with the low speed needle instead? Any suggestions would be great.

Thanks
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Old 01-08-2009, 12:16 AM   #2
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Is the idle running on higher rpm?

If not then you have to look at your clutch...

If so then use the brake and try to see if the carb does move a tiny bit and the revs go down. If so then you have to set the trim more to the brake.

If not then there is always an idle screw on the engine
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Old 01-08-2009, 12:50 AM   #3
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Originally Posted by dvu View Post
Hello,

I was wondering if I could get some help with my nitro car. When i start up my HPI R40, it seems to idle just fine. But after I run it for a while and the engine gets warmed up, it still wants to inch forward when the throttle is in neutral. I figure it's running too rich and so I've turned down my high speed needle, but if i turn it down too much when i lay on the throttle the car dies so I the have to lean out the high speed. Do I need to be tinkering with the low speed needle instead? Any suggestions would be great.

Thanks
why dont you just trim your throttle down a bit, your clutch is engaging at the higher rpm, spometimes you have to play with your trim to get the right rpm especially when rpm changes during operation.
just retune it and go from there remember get the car operating at its fastest straight line speed with the highset needle and then back it off a touch and then make sure you car is accellerating well off the start with the low set and adjust your idle with your idle screw and watch your smoke and temp. if your not sure about getting your engine tuned there is some info here on rctech.
cheers
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Old 01-08-2009, 06:26 PM   #4
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The high speed needle valve does not control idle!
The low speed needle valve does affect idle mixture. (and low speed)
The idle stop screw and the servo contol idle speed.
But an overly rich or lean idle mixture can cause the idle speed to increase.
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Old 01-08-2009, 08:14 PM   #5
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Originally Posted by wizby View Post
The high speed needle valve does not control idle!
The low speed needle valve does affect idle mixture. (and low speed)
The idle stop screw and the servo contol idle speed.
But an overly rich or lean idle mixture can cause the idle speed to increase.

Thanks
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