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Old 08-23-2010, 03:27 PM   #1
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Default Idle hangs high and surges?

I am not new to R/Cs but I am new to nitro. I have a Losi 8ight-T with the 454 engine. I have been trying to tune it and I can't get it to idle right. When I start it, it will idle but when I rev it up, the idle stays high and surges. Can anybody give me an idea of what I am doing wrong?
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Old 08-23-2010, 03:32 PM   #2
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I am not new to R/Cs but I am new to nitro. I have a Losi 8ight-T with the 454 engine. I have been trying to tune it and I can't get it to idle right. When I start it, it will idle but when I rev it up, the idle stays high and surges. Can anybody give me an idea of what I am doing wrong?
Surging is caused by inconsistent fuel pressures , check all fuel lines , pipe , tank and such . Try richening both needles a little to see if you can get a consistent idle before changing everything

Hope this helps ,
Monty
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Old 08-23-2010, 03:35 PM   #3
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I wonder if by surging he means the noise and pulsating you get when the LSN is too lean? Or Maybe it's high enough to be engaging and releasing the clutch?
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Old 08-23-2010, 03:53 PM   #4
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first things first check your idle gap it should be around .7 to 1mm max any larger than that and you'll end up with a false tune. sounds like your idle is to high and your LSN is rich and what is happening is when you clear out your engine with a full throttle run your high idle is causing your throttle to run on until the bottom end loads up again.

check out the tuning bible at the top of the nitro off road forum page the first post will help you out
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Old 08-23-2010, 04:05 PM   #5
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first things first check your idle gap it should be around .7 to 1mm max any larger than that and you'll end up with a false tune. sounds like your idle is to high and your LSN is rich and what is happening is when you clear out your engine with a full throttle run your high idle is causing your throttle to run on until the bottom end loads up again.

check out the tuning bible at the top of the nitro off road forum page the first post will help you out



i had a similar problem, with too wide of a gap on the idle and just enough and it wouldnt idle right and would load up on the low end. and i keep on leaning the low end, out little by little and the main needle a little and it would flame out on the track .

well all it was is, the glow plug was bad and i stuck a new one in and problem sloved i keep on idleing with a light smoke coming out the pipe when i hit the throttle, but i probety need to richen the low end a little and turn the idle down a bit or so.

that could be one of his problems.
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Old 08-23-2010, 04:39 PM   #6
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You're lost in the tune.... Setting your idle gap proper and going back to factory needle settings should get you in the ballpark, tweak from there.
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Old 08-23-2010, 05:21 PM   #7
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Set gap first then don't touch it. Go back to factory needle settings and tune the HSN then the LSN. If your still having issues there is an air leak.
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Old 08-23-2010, 06:10 PM   #8
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I've got a problem close to yours. Mine idles very high when first started. After it warms up the idle drops down really low and it won't hold it for more then 5 or 6 seconds without dying. The buggy runs great, all kinds of power from top to bottom, and the temp was around 135 when I checked it.
Any idea what I might be doing wrong?
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Old 08-23-2010, 06:16 PM   #9
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Originally Posted by bevofrancis View Post
I've got a problem close to yours. Mine idles very high when first started. After it warms up the idle drops down really low and it won't hold it for more then 5 or 6 seconds without dying. The buggy runs great, all kinds of power from top to bottom, and the temp was around 135 when I checked it.
Any idea what I might be doing wrong?


change the plug if it wont hold a idle right thats what i did.
and 135 is way too cool for, the engine lean the main needle and run it on the track and take it off and have it running arond 235.
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Old 08-23-2010, 06:43 PM   #10
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change the plug if it wont hold a idle right thats what i did.
and 135 is way too cool for, the engine lean the main needle and run it on the track and take it off and have it running arond 235.
I meant 235, don't know why I put 135.
I don't know why I didn't try a new plug. That's always the first thing I do when I start to have a tuning problem. Hopefully that will fix it. thanks.
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Old 08-23-2010, 07:03 PM   #11
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Originally Posted by bevofrancis View Post
I've got a problem close to yours. Mine idles very high when first started. After it warms up the idle drops down really low and it won't hold it for more then 5 or 6 seconds without dying. The buggy runs great, all kinds of power from top to bottom, and the temp was around 135 when I checked it.
Any idea what I might be doing wrong?
How much fuel has been thru motor? If its getting old and when the motor gets to temp and it flames alot the motor could be wore out. Of course try a new plug and retune before coming to that conclusion.
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Old 08-23-2010, 07:54 PM   #12
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Maybe idle gap to large low end to rich.
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Old 08-23-2010, 08:38 PM   #13
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I meant 235, don't know why I put 135.
I don't know why I didn't try a new plug. That's always the first thing I do when I start to have a tuning problem. Hopefully that will fix it. thanks.

+1 theres nothing, more agerateing than messing with needles and flameing out on the track and all it was is a plug.
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Old 08-24-2010, 07:03 AM   #14
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Set your idle gap, control your idle with your lsn and tune for power on the top
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Old 08-24-2010, 07:41 AM   #15
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That losi 454, is a decent engine but I will be surprised if you ever get it to idle smooth. I had one for about a week and it ran like it had a wicked air leak, I tried sealing everything up with no luck. I think it is pretty tipical for these engines to run like this.
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