Jasonrj

Savage X RTR 4.6

Here is my problem:

[youtube]http://www.youtube.com/watch?v=oWPO8Yt3Si8[/youtube].

After break-in I adjusted the HSN and had almost a perfect tune and could back-flip with little effort, but could never get the thing to start without turning the idle WAY up, then after a minute of running it would "idle" at like 15mph. So I began playing with the LSN, and have had problems ever since.

Now I don't know what to do, I've returned all the needles to flush and this is how it runs. Those are full throttle bursts and as you can see, it is so weak it can't lift the front wheels at all, and after letting off the throttle it does that sort of weird quick revs sound for several seconds. I still have to adjust the idle a little high to get it to start initially. There is about a 1mm gap in the carb.

Thanks for any assistance.

NOVAMEGA

Your lsn(low speed needle) sounds about a 1/4 turn or more to lean . I would start at your base setting and start over .

pauly187

from what i know and i may be wrong but it sounds like the LSN is to lean you to to richen it
if engine hangs meaning its doing what yours is after u gun it to lean so needs to be richened

NOVAMEGA

The sound in your video is the fuel exploding before your piston gets to the top of the stroke . When that happens it makes that funny sound at idle . Also watch how the engine stoped climbing in rpm when you got on the trottle .... You'll get it... we've all been there

SLAYERDUDE

@ 1:03 it sounds normal, and that is the only time in the vid it seems you are off the throttle.
Sounds like a massive air leak, or you are waay too lean.
My guess is massive air leak causing the lean condition.
If you continue to run it like that, the engine will blow, not a matter of if, but when.
Here's sealing an engine - http://www.savage-central.com/module...Forums&t=54465

Make sure you seal over the ends of the carb pinchbolt, that's a commonly overlooked area.

SLAYERDUDE

Engine tuning info -

Here is some helpful information on engine tuning.

This is an easy to follow tuning guide I wrote up.

To get it tuned, First get the engine fully warmed up!
Never tune a cold engine.
Start from factory settings on all needles. (Maybe 1/8 to 1/4 in on the HSN from factory.)

Be sure to set the idle gap as well as needles to factory settings before retuning from scratch.


Get your HSN set first.
Keep leaning the HSN 1/8 turn in at a time and watch the performance increase.
Making a couple top speed passes each time to let the engine get used to the new setting.
When you see a decrease in performance turn the HSN back out 1/8 to 1/4 turn to richen it back into the safe zone. Keep an eye on temps as well.
Good top speed and good trail of smoke at all speeds is what you want.

Then set the LSN.
You can do the pinch or punch test, or both.

PUNCH TEST-
Once you have the HSN set, engine warmed up.
Make a couple top speed passes and bring it in and let idle for 10- 15 seconds.
Then give it 3/4 to full throttle.
If is slow to take off and smokes alot you are too rich and need to start leaning the LSN.
If it takes off fast, rev's and dies, etc... it is too lean and you need to richen the LSN.

If it smokes and is slow taking off, start turning the LSN in 1/12 to 1/8 turn and again make a few passes to get it used to the new setting in between adjustments.

PINCH TEST-
Make a couple top speed passes, bring it in and pinch off the fuel line near the carb.
Start counting 1...2...3...
It should run for about 3 seconds before it revs and dies.
If it runs longer you need to lean the LSN.
If less than 3 seconds you need to richen the LSN.


Once you have good acceleration and still have smoke at all speeds you are done.
You may need to reset the idle on the carb once you are done tuning.

Weather always plays into your tuning and you will need to adjust the HSN for day to day conditions.
I.E.- colder weather requires more rich settings and vice versa.

I am just a basher and no expert so use this info at your own risk!

SLAYER


__________________________________________________ __________________
Here is a tuning guide from Ron Paris.
Very good reading!

Tuning tech: carb Needle balance

We get dozens of tuning questions from around the world at Paris racing daily, The number one questions is, were do I set my needles on the carb? Unfortunately there is no such thing as a definitive universal setting for any engine!

Every application will have it's own unique requirements, even two IDENTICAL set ups can and most likely will have at least slightly different settings.
Please see tech tips following the article below [from our web site]
I would like to address what seems to be the # 1 mistake we encounter in engine tuning:

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!

CAUTION!!!!

Now that you have the idle set correctly the top end may be too lean!!!
Keep in mind the fuel does not directly enter the cylinder area like a 4 stroke engine, it enters the crankcase area first then is transferred or pumped up to the cylinder area by the piston movement.
Simply put, the crank case volume can hold much more capacity than the cylinder so it takes some time to burn off the residual fuel.

In other words if the bottom end is to rich the engine will be supplied by this residual fuel briefly and depending on the demand you may be actually be experiencing a lean condition on the top end that can range from:
1. Seems to run well but engine life is short
2. Seems to run well but car continues to get hotter the longer you run to the point of overheat!
3. Seems to run ok on the bottom but sputters starves or strains to gain rpm
4. Seems to run ok on the bottom but when I give full throttle it cuts out or stalls
[An overly rich top end can act the same as 3 & 4 but excessive smoke and oil are usually present with a distinct blubbering sound]

There is no reason for an engine to continually get hotter unless the tune is wrong [classic #2. symptom] or there is a mechanical problem causing more load or drag on the engine as the run continues.
Exception Note: if the weather or track conditions change DRAMATICL Y. {Examples}
A light drizzle starts and the off road track goes from a very dry loose to high traction condition, or during a race a rapid weather front like a ten degree change! It is very important to fully warm up your engine, clutch and chassis before making finale adjustments.
The chassis in most applications also works like a heat sink to the engine so it is important to fully saturate the chassis!!!

I like to start the engine at least 3 or 4 minutes before our qualifier to get some heat in the engine.
[Operate the throttle by hand until you have radio frequency clearance]
It still takes at least 2 to 3 minutes of hard running on the track to fully saturate the chassis!

There is a series of restrictions to control fuel flow at different throttle/air flow positions called needles These are the five basic parts of the carb to concern yourself with:

1.The slide or barrel [regulates the amount of air to enter the engine controlled by the servo]
It simply blocks off the airflow to the engine proportional to how far it is open or closed.
2. The idle/air speed screw [sets the absolute minimum air the barrel/slide can control to maintain idle speed]
It simply is an adjustment screw that comes in contact with the side at the nearly closed/idle position.
3. The high speed needle [regulates maximum fuel flow allowed to enter engine at any throttle position]
It simply is a tapered needle that screws into the fuel flow orifice [an adjustable restriction] .
This maximum fuel flow ideally is adjusted to the correct mixture ratio for the surrounding conditions at WIDE OPEN THROTTLE or WOT
There are two more devices' the low speed or minimum spray bar and the mid range needle that restrict or control the fuel further at less than full throttle.
4. The low speed needle [regulates fuel to engine at idle]
The low speed adjustment simply restricts the flow at idle speed.
If you look down the bore of the carb you will see a long tapered needle [except for Picco torque carbs]
When the carb barrel/slide is closed the larger part or diameter portion of the long tapered needle is inserted into the spray bar, this is what's adjusted when you turn the low speed/minimum adjustment.
It literally moves either the tapered needle OR spray bar farther in or out changing the restriction independent of the barrel/side position.
This leans [more restriction] or richens [less restriction] the flow from the spray bar at idle.
NOTE: some carbs the spray bar is moved and others the needle assembly is moved, both have the same effect.
5. The mid range needle [regulates fuel to engine after idle and before full fuel position.
Notice as you open and close the carb the tapered needle [mentioned above in item 4.] enters into a small tube this is called the spray bar/jet.
This spray bar is were ALL the fuel enters the airflow stream regulated by the high speed, mid range and idle/minimum adjustments!
Normally somewhere between Y2 and % throttle open position the needle is completely out of the spray bar, This is what is called full fuel position or FFP [at this point 100% of the mixture is controlled by the high speed needle.
On many carbs the low speed and midrange are not independently adjustable so the mid rage is a factor of the needle taper and is engineered by the
factory. On some SLIDE carbs there is both independent spray bar and mid range needle adjustments. CAUTION: be very careful with these type carbs!!!
You can identify them easily because there are four adjusting screws!
0ne each for the:
High speed/top end [normally sticks up some what vertical]
Idle/air speed [normally a much smaller screw entering the carb at an angle]
Low speed/minimum [located in the end of the slide OR on the opposite end of the carb body]
Midrange [also located in the end of the slide OR on the opposite end of the carb body]
Note: if there are adjustments on both the slide and the carb body one is an adjustable mid range and the other the low speed!!! Check with the engine manufacture before attempting to adjust these types of carbs!

It is very important not to use the mid screw to adjust the low end by mistake; it is very easy to get the carb way out of sync.

Normally I recommend not attempting to adjust the mid range even if your carb is so equipped, the gains are VERY small and mostly limited to minute midrange drivability/economy changes that only the most sophisticated driver will recognize!

The negative is a carb that is so screwed up only an expert can get it back in tune!
Please note the above descriptions will apply to 99% of the modern car carbs being manufactured as of this writing with the exception of the Picco TORQUE carb that use's no mid range needle at all.
It utilizes a fuel management ramp built into the slide; the carb also has two completely independent fuel delivery spray bars/jets.

I wish I could tell every one exactly how to tune their engine but I cannot!
My hope with this article is if I can help racers to more understand How your carb works, all the other instructions and guides will make more sense!
Best Regards,
Ron


More from Ron Paris.
http://www.mnnitroseries.com/files/P...ngTechTips.pdf


Another tuning guide from ERCM -

This is the way that I tune engines, there are many other ways to tune but I figured this is the most simple way to do it so I will share my info. This technique is for a fully broken in engine that is ready for a full performance tune. This tuning procedure will set your needles where they need to be for optimum performance, a temp gun is not required (other then high temp safety check) because there is no guessing, the engine will tell you.

For this to work the engine has to be at running temps (or as close to it as possible) as well as having the standard 1mm gap for the carb opening.

#1) High Speed Needle.
Pull a wot pass a couple times and listen what the engine does when you let off the throttle. As long as the rpm drops right to idle, the HSN is either good or on the rich side. At this point you can lean the HSN in 1/12 increments until the idle seems to hang a little after a wot pass, when it starts to idle high after a pass it is just on the lean side of a perfect tune. Back the HSN out 1/12 turn at a time after a wot pass until the engine drops right to idle after a pass. Now your HSN is set.

To give an explanation to what is happening is simple. If your HSN is too lean, after a wot pass when you let off the throttle the engine is still lean causing the idle to hang and idle high until the LSN has a chance to take over and meter the right amount of fuel to bring the idle down to normal running speed (given the LSN is set correctly)

Now if the opposite happens, after a wot pass when you let off the throttle, if it drops to a good idle right away and then starts to idle back up too high, this is a sign that the LSN is too lean. If it comes off wot with a good tune and will drop rpm nicely then the HSN is metering the fuel properly but once it hits idle the LSN being too lean will quickly take over causing the rpm to go back up.

#2) Low Speed Needle
Most of this setting was explained above but there are a few little tricks you can use to make sure the LSN is adjusted perfectly. We all know that you don't tune for temps but a temp gun is very handy for this part. After some wot passes with the engine good and warm, bring it in and let it sit for about 10 seconds. At this point take your temp gauge and hold it as steady as possible on the head, what you want to see is the temp dropping a degree every 4-5 seconds. You want the temp to drop very slightly at idle because when your off throttle the engine should be cooling, if not, the temps will keep pushing higher with on and off throttle running and will cause temp issues.

This is how I do it and I have tuned a lot of engines for people whether bashing or racing. I have seen across the board from beginners to veterans that when they hear the high idle after a pull, the first thing they go for is the LSN when in fact it is the HSN causing the issue. The veterans are surprised when we richen the HSN an hour or two and the problem goes away. I hope it's not too hard to understand as typing it out is much harder then explaining it to someone first hand, if you have any questions feel free to ask.

Robin

NOVAMEGA

Nice !!!!! You rocked it [X(]

SLAYERDUDE

I can't link threads from my forums, so the only option is copy/pasting a giant post.[:-]

Sounded to me that it idled okay @ 1:03 or whaterver., which leads me to think the LSN is closer than the HSN on the tune.
But I say seal the engine first and foremost, which will make for a much simpler tune.

mileslong

check this out.. i bought this for my son and all my friends that are new to the hobby have read it as well... its full of all kinds of info not just engine problems.. http://www.rcplanet.com/Air_Age_How_..._p/aap1014.htm just about any issue you'll have in the fisld you can find in this book