i can say you will not need a new air filter, the stock one is in my opinion a very good filter, i run 3 of them, two on mach 427's (in my muggy and LST2) and one on my RB TM523 (in my revo).
the last time i posted this tuning guide in here, i got flamed because it had the word "TRX 3.3" in it, hopfully some ertain savage owners can look beyond the fact i'm a traxxas/losi guy and accept that i'm trying to help
, good luck, heres my tuning guide.
THE FACTORY SETTINGS
First things first, you need to set the engine back to factory settings, you will need to find out what these are for your truck, and set the high speed needle, low speed needle, idle screw, and in some cases mid range needle to these setting, although the setting for the idle screw is almost universally sheared between engines at .7-1mm (roughly 7/16th-1/8th of an inch) from the carburettor body to the carb slide.
SETTING THE IDLE
Start the engine and run it around to let it warm up, once you have it warmed up bring it in and let it idle, if it's to high you will need to turn the idle screw out maybe 1/4 or 1/8th of a turn, and see how it's idling then (drive around a bit to clean the engine of fuel before doing this), if you cant get the truck to start, give it a little bit of throttle, now, for the idle being to high or to low, when the engine is warm it should start up very easily, if it doesn’t start when warm, but will when cold you may have some more serious problems including worn out piston and sleeve.
There something to watch for when setting your idle, it is commonly called a “Fake” idle, the characteristics of a fake idle are very similar to those of an air leak, the idle will change erratically without any input from the throttle linkage, the best indication of a fake idle is when you bring the truck in to idle, the idle will initially be high, then drop within a few seconds, the cause of a “Fake” idle is having the idle gap (the gap between the carb slide, and the carb body) to wide, which normally causes a high idle, the user then compensates for the wide idle gap by richening the low speed needle, the engine then loads up on idle which lowers the idle RPM, this can in-fact hide an overly lean high speed needle by burning fuel left in the crankcase at higher RPM, so it is very important to make sure you do not have a “Fake” idle.
The solution to a fake idle is very simple, simply lean off the low speed needle, and reset the idle gap until the idle is down to a suitable RPM again.
ENGINE NOT STARTING?
If the engine will not start, check to see if the glow plugs good, to do that just take the plug out, put it in your glow igniter hold the glow plug up against the cooling head, the coil of wire in the glow plug should glow bright orange, if the wire doesn’t glow at all, or if only a few coils of wire at the bottom of the wire glow then the plug is burned out and needs replacing.
If the glow plug is good, then the engine may be flooded (have that much fuel in the engine that there is not enough oxygen in the air to support combustion), to correct this, take the glow plug out, turn the engine upside down and turn it over a few time, this will clear some of the fuel out and should allow it to start.
There are a few other reason why the engine may not start, one is that the piston and/or piston sleeve may be worn out, or damaged which will low the engines compression enough to not allow the engine to get enough heat to the glow plug to ignite the fuel, another is possibly an air leak, these are usually at the front bearing, the back-plate, the carb pinch bolt, a crack in the carb body or from either the high, or low speed needles, and air leak will characteristically vary your idle erratically, produce high operating temperatures, even with rich needle settings andpoor performance.
To test for an air leak, remove your engine from the car/truck, take the exhaust header off, leave the glow plug in turn the engine until the crank is at bottom dead center and attach some fuel tubing to the fuel nipple on the carby, mix up some soapy water (dishwashing liquid mixed with water) and brush the mixture onto known problem spots for air leaks, then cover the carb opening, and the exhaust port with your fingers, and blow into the fuel tubing, look for bubbles forming anywhere, if you see bubbles, that area of the engine has an air leak.
Other reasons can include, a leaking exhaust or fuel system (causing fuel to back track into the fual tank), a clogged fuel line or carb needles which will start the engine of fuel, or needle setting that rich or lean that combustion of the fuel cannot be supported.
THE HIGH SPEED NEEDLE
Once you have the engine idling properly you can start tuning, when you a tune your engine, turn the fuel needles in very small increments at a time, and ALWAYS tune the high speed needle first, i usually go by 1/12 or 1/16th of a turn at a time, but most guys go 1/8th of a turn, after each adjustment do a few high speed passes to clear any fuel that may be have been left in the crankcase, take very careful note of 3 things while doing these high speed runs.
(Turning the tuning needles in a clockwise direction will lean (provide less fuel) the engine, and tuning the needles counter-clockwise will richen (provide more fuel) the engine.)
1. The PERFORMANCE, has it gotten better or worse? when you start getting the rpm up does it sound like it's cutting out? if it sounds like it's cutting out then you are to lean and need to richen the HSN, if it is loading up and the performance is very sluggish then it is rich and you can go a little leaner
2. The SMOKE TRAIL, there should always be a nice, clearly visible trail of blue smoke coming from he exhaust, always, if you cannot see a good trail of smoke, it is another sign of being to lean, if you see a lot of smoke at all rpms then you can go a little leaner
3. The TEMPERATURE, (the temperature of the engine should always be taken at the glow plug, not the top of the cooling head or the crankcase, the glow plug) personally, I believe that to an advanced tuner, temperature is an irrelevant tuning guide, as the temperature of the engine has to many variable to put a label on a correct temperature, but very high or low temperature can and will cause a lot of damage to an engine, after a while you will be able to pick an overly lean or rich running condition by the performance and smoke trail alone, only at that time will temperature become an obsolete tuning tool, until then a good, reliable temperature gauge is recommended for any novice, the optimal operating temps are around 230-280 degrees Fahrenheit as a rough guide, any higher can cause heat damage to the engine by softening the component to the point that they ware away very quickly, and any lower will not allow the components inside the engine to expand enough, so the piston and sleeve especially will run against each other and wear out very quickly.
A last note on the high speed needle is, never tune by one symptom alone, never tune just by performance, or smoke trail or temp, use at least two, so if you lean the engine by 1/8th of a turn on the high speed needle, and the tempurature at the glow plug go from 230 to 240, and you notes it's a little more powerful and go a little leaner, the only time you should ever tune by using just one symptom is when:
A: you run to lean and the engine start to hesitating and/or cutting out (you give it gas but it will not accelerate or gain RPM, but instead stutters) at high rpm
B: the temp go above 290 degrees F
In both cases you need to richen the HSN by at least an 1/8th of a turn if not more.
THE LOW SPEED NEEDLE
Once the high speed needle is set to where you want it, you can start with the low speed, start off at the factory setting on the low speed needle, and just like the HSN tune in small increments of at most 1/8th of a turn, if not smaller, when tuning the low speed needle you are aiming for a nice crisp throttle response, if you run the low speed needle to lean you will burn through glow plugs very quickly and it can damage your engine, particularly if you are on and off the throttle a lot.
Once you get it so as soon as you touch the throttle the engine start revving up and doesn't bog down at all, so as soon as you hit the gas, the truck takes off, once you get to that point do not lean it any further, and for a safe guard i like to richen it by 1/16 of a turn.
You can test to see if the low speed needle is set to rich or to lean one of two way, I find it best to use both tests in unison.
1. The idle test
warm the engine up by running the truck around, make sure the engine is full warmed up and heat as saturated the entire block and cooling head, once warmed up, bring the truck in and let it idle for 30 seconds.
After 30 second take off at full throttle, the engine should take of strait away, and in the 30 seconds the idle should stay very consistent, if the idle drops off, or the truck bogs down when you hit the throttle the low speed needle is to rich, in overly rich conditions the engine may die as soon as you hit the throttle, if the idle increases during the 30 seconds, or the engine hesitates (similar to an overly lean high speed needle) the engine is to lean
2. The pinch test
Warm the engine up just as you did for the idle test, once warm all you do is pinch the fuel line, and count how many seconds it takes for the engine to die, when you pinch the fuel line, the engine should idle normally for a second or two, then just before it dies it should rev up a few hundred rpm, then die on the count of 3.
If the engine die's in 2 seconds or less, or does not rev up at all, you are to lean and need to richen the low speed needle, if the engine takes more then 3 or 4 seconds to die, you are to rich and can lean the engine out a bit more.
Once you have done all your tuning you might have to set the idle again, if you do have to set the idle again, just follow the steps i posted at the top of the page, you should never have to touch the idle screw unless the truck is idles high enough for the clutch to engage, or that low that the engine wont start.
This tuning guide was last updated at 9:09 pm (21:09) Eastern Australian standard time on the 5th of September 2007 (05/03/07)
(I don’t mind if people use this guide to help people out, as long as I, Ttoks get credited as the author as I have put many hours into writing, and perfecting the guide for the sole purpose of helping others)