Nitro engine tuning

[Eddie168]

im using a HPI nitro star 21 in my Trohpy 3.5, i followed the manual but not sure if i tuned it right or not, the car seems quite slow and sometimes hesitates when full throttle, please help

[mark christopher]

Setting up and running your engine
Once a nitro engine has been run through several tanks during break-in process, it¡¦s

finally time to tune the engine for racing. Here are some tips when tuning engines.

Raise the idle about 1/2 a turn from where it was previously run. This is just to keep the

engine from stalling when I start going through my routine. Next, will fire up the engine ¡

§blipping¡¨ the throttle a few times until the engine is up to a reasonable temperature.

Some where in the 150 degrees
range. Now, richen the top end up a full turn. Holding the carburetor wide open and continue

to richen it up till the engine nearly stalls. If it does stall that is ok, just lean the

engine back in slightly so you can get it to re-start. Reason for doing this is to help

flush out any dirt or residue
(or after run oil) out of the carb and engine. Now that things are cleaned out and now can

begin to tune the engine to race trim.

First off, is to set the bottom end. To do this, carefully listen to the idle. If the idle

slows down and the engine stalls, lean out the bottom end needle.
If the idle speeds up then, richen up the bottom end needle. as much as possible until it

stalls.

From that point raise it back about 1/8 of a turn. The lower you can set the idle means

lower engine temperatures, better fuel mileage and better operation of your clutch since a

high rpm idle can slightly engage the clutch causing excessive heat and wear. Overall, your

engine should idle nice and consistent for at least 45+ seconds.

Next it¡¦s time for the fun part! The top end needle, where all that straight away speed and

power comes from. This is more of an adjustment for out on the race track but here¡¦s a way

to get it close on the bench.

Listen to the engine and lean it out until it sounds like it is achieving a nice clean

sound. This is a critical adjustment that will greatly decrease the life of your engine if

you get in a
hurry here so take your time. Once you get it to where you think it is close you have to

make sure that the engine won¡¦t lean bog or hesitate (say after a long straight, hard

braking and then hard acceleration to the next corner). Open the carb to full throttle for

2-3 seconds, then close the carb for 2-3 seconds, then back to full throttle for 2-3

seconds. Your engine should rev nice and clean through the 2nd full throttle blast. If it

hesitates at all then your engine is too lean and must be richened up on the top end needle.

Most importantly, listen to your engines. A lot of people fall into just watching the smoke

that comes from the exhaust and tuning the engines that way. This way is ok but if for some

reason you use different fuel (with different oil content
or mixtures) it becomes much more difficult to make your engines perform consistently from

race to race and in different weather conditions from just the sight of smoke. Learn how

your engine sounds and responds to your throttle input.

Good luck and have
fun!!!

[Eddie168]

i tried to set up my LSN before using this video http://www.youtube.com/watch?v=Y8T8S...e=channel_page but i just can't get the engine to raise RPM when i pinch the fuel line wat have i done wrong?