letting off throttle very high idle sound

[f1n3sse]

Fired the truck up today after a month sit, its a picco .28, new clutch and some other parts and after running it for half tank temps steadily at 220 after wot passes let off throttle and it idles super high then falls back down to normal idle after about 5-6 seconds. It has always done this from the gate, I thought I had my carb open too much for idle setting so I closed it to what I believe is 1mm. It fires up after about 1-2 pulls from a 125 preheat, idles great, and runs great but I'm concerned about this a bit. any suggestions? I have no air leaks.

 

[Pope]

sounds like you fixed it that is what i was messing with yesterday. also make sure your servo is pushing the carb all the way closed when you let off the gas mine was keeping it open just a hair.

 

[f1n3sse]

servo is closing carb 100% epa set thats all good, I think I know what it is. I think my lsn is leaned a bit too much, gonna richen it a bit tomorrow and find out, now that I think about it I'm almost positive thats what it is. Alex lets shoot for next weekend. I want to bring my buddy iacco down with his lst2 to bash with us.

 

[Pope]

sounds great man we have to make him regret buying a lst2 over a savage lol:violent-smiley-087:

 

[f1n3sse]

he has 2 savages also. He bought a new lst2 because he liked the shocks lol, this is the buddy of mine that runs his trucks until they break and thinks they are broken for good.

 

[windjammr]

mine did that till i leaned the lsn out a bit good luck

 

[Fx]

You need to richen you idle up. Read this.

Carburetor Needle balance:

It has come to our attention some racers are making the mistake of setting the idle speed opening to wide [high idle] and setting the bottom end too rich! This will give a false normal idle speed even though the speed is set to high because it "loads up" the engine with excess fuel causing the idle to be lower than set!
The end result is a very unstable idling engine that surges and may cut out as full throttle is applied because the over rich bottom end can disguise a too lean TOP end setting!!!

Let's address this a little more in depth! Idle speed opining set too wide: It is possible too set the idle screw adjustment in to far but yet the idle speed is not high! Even though the air regulation [carb barrel or slide] may be set to a position that would normally equal a vary fast idle, the idle is low because the low speed mixture adjustment is set so rich that the engine loads up with excess fuel and the engine goes into what's commonly called a four cycle idle. One tell tail sign of this is if after reving up the completely warmed up engine it tends to idle fast for a few seconds then drops to lower idle speed.

[Here we go again with the written sound effects ]
Something like da..da..da..da..da..da..da..da then it drops to da da da da [if it were sheet music it would be like dropping from 8 beats per measure to 4
beats per measure]

If you start leaning the bottom end a little at a time [then repeat the reving up and idle test] and it takes longer before the idle drops your going in the right direction! Eventually as you keep leaning the bottom the idle will stay to high, now it is time to lower the idle to were it belongs by re adjusting the idle screw!

Source- http://www.serdarevic.net/manuals/paris-racing-tuning-guide.html

 

[noogie]

I had a hanging idle after a WOT pass and I use this to correct the issue. Hope it helps.

https://www.hpisavageforum.com/forums/showthread.php?t=12260

 

[Purenitro]

Your LSN sounds fine, no need to play with it if it idles fine after a few seconds. If it runs on like you describe, that would tell me it's the HSN, try and richen it up some. Read this link, you will understand why it's idling high after wot.

https://www.hpisavageforum.com/forums/showthread.php?t=12260

 

[f1n3sse]

thanks robin