Danju

Help me on this: after a high speed run, the engine will rise a bit and then drop to normal idling. is my LSN too lean or rich?

what does it sound like when the LSN is too lean or too rich?

its supposed to be when the LSN is set right, the engine will begin to idle immediately after the throttle is released right?

thanks
dan

Freezetron

Varying of course engine to engine and type of fuel, the LSN should be set so that there is a nice sharp acceleration from a dead stop while allowing enough lubrication into the engine indicated by a exhale of blue smoke. Too rich of LSN will cause the acceleration to suffer and make the engine bog and even flood with fuel, shutting it down. To lean will cause higher running temps. The LSN and IDLE should be set to when the vehicle comes to a stop, it slowly drops down in speed as the fuel amount increases, cooling the engine until it stops.

IOWAREVO

I'm experiencing the same thing. From what I have found, the fast idle to low idle after a high speed run is called "singing" and its a good thing .

How long it "sings" is what I'm investigating.

This is a quote from the Paris racing archieves:

"set the low end or idle:

After getting top end set close, bring model in, listen to the idle. If it is idling fast then it slows down in a few seconds, it is probably too RICH on the bottom (minimum spray bar). In that case, make it more lean (turn clockwise ΒΌ turn), then run another lap and bring the car in again.

Repeat this procedure until the idle stays high for at least 10 to 20 seconds; at this point readjust the aircrew so the idle is at a moderate speed. The wheels should not turn, and the clutch should be fully disengaged. "

I can get a 7 sec "sing" but if I lean the LSN anymore, it won't drop to low idle. So next time I plan on loosing the idle screw to bring it back down.

freeonthree

My Feedback: (1)

Here's how I set my LSN... I warm it up good, then while it's idleing, I pinch the fuel line going to the carb. If it idles about 4 seconds, then speeds up before it dies, it's right on. If it idles longer than about 4 seconds before it speeds up, I lean the LSN 1/8 turn, and try again. If it idles less than 4 seconds, I richen the LSN about 1/8 turn and try again. Also, if you release the fuel line just as it starts to speed up, it should recover and not die. If it doesn't recover and continue to run, it's probably a little too lean. Also, don't try to get a real slow idle... just set the idle so it does not engage the clutch. If the truck doesnt move at all when it's idleing, that slow enough. Keep in mind, if it runs good before it warms up good, it's probably too lean.
Also, keep the HSN slightly on the rich side of peak, and your glow plugs should last a long time. If ya burn out a glow plug, your HSN is probably a bit too lean. If you have one of those little infra red temp guns (very handy for tuning), shoot for an operating temp between 230 and 250. Try to never let the engine get hotter than 270 degree's. Both my TRX .15 and my Picco .26 run between 235 and 250, and I never burn out glow plugs.

Danju

so my engine is too lean right?

freeonthree

My Feedback: (1)

If the low speed needle is too lean, when ya stab the throttle from idle to about half throttle and up, the engine will die, or at least hesitate. Dont confuse that with loading up and dying when ya hit the throttle though. Thats why the pince test is so valuable. Shoot for about 4 seconds before it speeds up when ya pinch the fuel line. That will be close to perfect on the LSN, but always tune the HSN by doing high speed passes first. Do the pinch test, and tell me how ya do.