Originally Posted by
Gsnow39
Ok I have been trying to tune my idle using the methods in this forum. I broke in my engine. Got it tuned pretty good. Runs good it idles. it will idle about 15 to 20 seconds befor dropping to a lower idle. But the idle seems very unstable. It never consistent I can make a lap come in may drop sooner or take longer. Some times it will idle back up some times it won't. I sealed up the engine. With rtv, carb back plate pinch bolts. The engine I am trying to tuneis a dynamite .21 platinum xp. I also have a Orion jtb addition that is acting similar to this one. My sons losi 350 was a snap got it diled in the first round. any ideas? 20% nitro also on all engines
Ive written many posts regarding the subject of a faux idle. As another member posted, too much idle gap with a rich lsn compensating.
the indicators for a faux idle are a overunning idle after wide open throttle. and a dropping idle at rest.
the key is to understand that the IDLE screw and LSN must be tuned in unison. increasing the idle gap will richen the mixture as well. when you increase the gap, in effect the lsn is opening as well, the needle moves out from the seat.
best practice I find is to ensure all leaks, hoses and gaskets are good. then use a spring or rubber band between the hsn and carbt to hold the idle back to prevent chattering idle gap.
then richen the top needle 1 or two turns, it doesnt matter how many turns, the objective is to allow maximum fuel pressure.
then I set the idle gap at 1mm as a starting point and when I do, I ensure my bottom needle lsn is not pushing hard against the seat and ensure it's not too lean. I open the lsn to begin with.
Without using the throttle, its a matter of attempting a start, removing the plug and seeing if the mixture is too rich (spray of fuel versus mist) clear the crank and keep repeating the process of clearing the crank, attempting a start until the engine fires first time. If the engine iss too rich I lean the LSN incrementally. If too lean I richen it.
from there I know my bottom mixture is somewhere in the ballpark. I then give it 1/8th throttle to see if I am in a state of faux idle. the engine usually over runs if I am too rich with too much idle gap. So I then reduce the idle, this by default leans the low speed mixture. if I stall, I lean the bottom.
All the time flushing the crank by removing the glow plug to be sure.
So I begin to lean the lsn until I reach a happy idle. In race tuned I wont get a continuous idle either, it will be slightly rich.
Once Ive setup my LSN with a very rich HSN, I roughly tune the HSN on the rich side and put the car on track and complete the tuning under load and once engine is up to temps.
hope this helps.