any way to measure or figure out idle gap?

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pjoseph

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the manual for my nitro engine say it should be set between .3-.5mm but i have no idea how to confirm what i have it set at.
When i first start the engine i always have to open up the idle gap in order to get it started, usually to the point that the wheels start spinning right away. Once started i lower it back down, if i happen to run out of gas or stall out, it will not start unless i open up the gap again.

Could the above be a result of having the LSN set too rich? I would love to take the idle gap variable out of the equation by confirming what it is set out somehow.

Thanks
 

BamaFan

ROLL TIDE!!
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Sounds like your lsn is too lean and the motor is starving for fuel if it's doing what you say its doing. Richen it up a 1/8 turn and you should be good to go. If it continues go another 1/8 etc.
 

Rolex

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It could, actually, be either way. Too rich or too lean. When you lower the idle to the point where it's still running, slowly lean the LSN and see if it speeds up. If it does, lower your idle a little more. You might have to do that more than once, but eventually the idle will be consistent and the wheels will not spin.
 

pjoseph

RCNT Champion
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studio city CA
had about an hour of daylight left after work and the lsn was too rich for sure. running much better now, not perfect but close

Thanks agian for the replies and enjoy the weekend
 

Rolex

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Make your adjustments when it's warmed up. Drive it around slowly till it comes up to temp, then adjust the LSN and the idle till it will idle smoothly and take off without sputtering or stalling. That's ALL in the LSN adjustment.
When that's right, make any other adjustments on the HSN for WOT. (Wide Open Throttle)
You'll need to tweak the HSN for any changes in outside temp and humidity, but the LSN should remain the same. In very cold weather the entire tune has to change and it's not a good thing to do.
Keep us posted.
 

Paul

RCNT Qualifier
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164
A note on ambient temps. I would say anything below 40F is to cold. Some would argue even that's to cold. I wouldn't go doing any full throttle passes unless I was sure the engine temp was good and always preheat the engine. There are some relatively inexpensive battery powered heat wraps available from various manufactures, maybe look into that. Otherwise a hair dryer will do, works for me.
 

tvjv2009

The dork that asks all the stupid questions...
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When setting the idle gap (which is the first thing I do), I use a drill bit to slide down between the barrel and the slide. I use a 1/64 which will give you 1mm gap. 1mm is what most engines will require.
 

Paul

RCNT Qualifier
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164
Ideally you want the gap to be as small as it can be and still have fuel pass through the carb allowing the engine to idle. Some will say 1mm is spot-on and others will say .5mm is better and some find that 2mm works best for them. To measure the gap you can use calipers, if you can find a pair that will fit into the carb neck well enough to give you an accurate measurement. Personally I just eyeball it for 1mm .. <-- The space between those two periods is about 1mm, works for me. Another thing to set is your throttle end-point on your transmitter. The carburetor barrel slide will move past the venturi/carb neck at WOT if you don't adjust the endpoint to make it stop right at the edge of the venturi. Here's a vid explaining throttle endpoint...Throttle Endpoint.
 

doutrnz

RC Newbie
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4
So no one is going to answer his question? How do you measure the idle gap. Calipers don't fit. If you know of some that do, then that is the answer he is looking for. The drill bit is a nice answer if you are trying to measure for 1mm. What about .475mm, .5mm, and .525mm? I'm surprised how long nitro engines have been around and no company has designed a measuring tool for the idle gap.
 

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