LSN all the way lean to run

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bomstick

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Hi all. I have a k4.6 that I absolutely cannot get to run unless the LSN is screwed all the way in. It was heat cycled at break in. Last night I tried starting it for an hour at factory settings and all I got was fuel to dribble out of the exhaust. I leaned the lsn way out and got it started then tried to richen the lsn with it running. About a full turn out from bottom and I couldnt keep it running anymore. Factory pipe, with a blue rubber duratrax extender on it. The damn thing has worn blisters on my hand! Help please.
 
Needles all the way in is way to lean. The factory settings are flush with the groove for the HSN, and flush with the housing for the MSN and LSN. If you are having to lean up to the point where you have the needles screwed all the way in, then you are likely getting no air into the engine. Have you adjusted your idle needle? There will be about 1mm gap when looking down your carb.


upload_2014-10-22_8-50-12.webp
 
To clarify, I think I am good on the high speed needle. Get plenty of smoke and speed. I will check my carb opening to verify that I have enough idle set. I assumed an air leak would cause me to have to tune overly rich? I usually open the carb about 1/4 to start when the lsn is cranked way in. Starts every time but I know this cant be right. MSN is untouched and sitting flush.
 
glow plug is pretty new. Nearly a gallon of fuel though it. Fuel was traxxas because of availability issues. Getting ready to crack into a new can of fuel that isnt traxxas. Gonna order a plug too for good measure.
 
I think I partially misread your initial post. Your second post seems to contradict some of the first post though. In the first post you say you set needles to stock settings then adjusted the LSN. Then in the second post you say that you believe the HSN is fine. If the HSN is still at factory setting then it is NOT fine. Always adjust HSN first, then LSN. This may be part of your problem.
 
Sorry for the confusion. I don't get alot of time with my hobby so every few months I get it out and get to fiddle with it. 3 days ago was one such occasion. I remembered that getting it to run during break in was a bastard until screwing in the LSN, so I checked the needle settings and realized I had screwed the LSN way to far in. So I backed it out to flush and decided to try to tune it. I left the HSN alone because I have good top speed. Wouldnt start and kept flooding real bad. Screwed the LSN back in and cleared the flood. got it started and warmed up and started richening the lsn back out. Made it about 1 turn until it was so pig rich it wouldnt stay running. LOTS of smoke to get it rolling, super sluggish but top speed was still fine. HSN has remained turned leaner than stock
 
One question I have is, do you always run all the fuel out of the engine and tank, if not the alcohol in the fuel will evaporate and leave the oil sludge in the lines and carburetor and cause just such issues you are talking about, I would suggest a good cleaning of the fuel system and carb and start again to see if that helps any, also seal up the engine while ya have it all out....
 
Thank you for the clarification. I still believe that the HSN tune is atleast partially at fault here. The HSN tune affects the LSN tune. If you are very rich on the HSN then the LSN compensates (badly) by being set lean.

BTW, I totally sympathize with the not enough time with the hobby sentiment. There is never enough time in the day.
 
I am guilty of not running the fuel out of the tank and engine. so I will break the carb down and clean it out. I thought maybe the HSN was an issue so I did mess with it the other day only to return it to where I had it. If I try to lean it out much I will get this weird surging once I hit second gear. At full throttle from stop it will accel good, shift, then the rpm drops way off and it surges up and down a few 100 rpm until I let off the throttle from full. Fatten it up a bit and this goes away and I get good performance.
 
When you were adjusting the HSN and got the surging, was this with the LSN tuned very lean as you described before?

I would completely start over personally. Tune the idle needle, then HSN, then LSN.
 
I seriously doubt that the exhaust deflector would cause any problem at all, I use them on most all my nitro rigs without trouble
 
No way will it start what so ever with all needles in factory settings. Just floods, wont hit a single time. Even with throttle manipulated anywhere between shut and 1/2 open.
 
I know, you have to start adjusting before the first start. Set to stock settings, then lean both HSN and LSN maybe half to a full turn unti it starts. Then when it's running tune the HSN first, then LSN.

Make sure that when you are tuning that you are at full operating temperature. Atleast 200-220 degrees. If you don't then you will be just chasing your tail with the tune.
 
always remember to only tune the setting when the engine is at operating temps , usually above 200 degrees, and turn the needles hsn first in 1 hour increments until it starts running good, I still think you have crap in the system causing your problems....
 
Okay X. I will give that a try but I have my doubts. I will start with my fresh can of fuel too. Really appreciate all the help guys. Gonna be a few days until my new spur gear gets here so I will update you. Might try and grab a few pics.
 
Jam, in the meantime I will pull the carb and go over it. Also going to check the pipe for any obstructions causing high fuel pressure.
 
For reference, how old is the truck? You say you've been through break in, when was that? I ask because "gunk" in the system is really only going to be an issue if there are large periods of time between running it. If you are only capable of running it once a month or even less then I would look into some after run oil for the engine.

This is what I use:
http://rbmods.net/rbshop/index.php?target=products&product_id=59
 
I put the k4.6 in it some time around last thanksgiving. the chassis is an original x I got off a friend for 50 bucks.
 
X, when I try retuning from factory, should I leave the throttle closed at 1mm when attempting to start?
 
bomstick said:
X, when I try retuning from factory, should I leave the throttle closed at 1mm when attempting to start?
Click to expand...

As Jam already said, yes. Keep in mind that 1mm is a reference setting, you may need to tune accordingly. If you cannot get the engine to start well without opening the throttle then it is a sign that adjustment is needed.
 
Pulled the carb off and took the slide out, mid needle, low needle all looked clean. May have had an air leak around the carb. Put it all back together and tested for leaks...found one at base of carb and reseated it so all is good on that front. Spur should be here Saturday or Monday. For now I gotta get my big bores, dual brake conversion done.
 
The saga continues. With the needle settings all flushed, I turned the hsn in one turn. Got it started(throttle closed) and running around really rich. Warmed it up and turned the hsn in a bit. Got to a point that I had great take off and starting to wheely a bit with alot of smoke, but as soon as it shifts the engine sorta sputters as long as I hold the throttle open until it does. Now as it shifts and starts sputtering all smoke goes away. IT sounds like someone turning the ignition off with the clutch still engaged. I can richen it literally 1/8 and its nearly so rich it wont shift. Another 1/8 and it absolutely wont shift. I am beginning to think I need some glow plugs and maybe the shift point is set to high? 16/47 with a k4.6 I should expect atleast a wheelie take off right? I would pull my hair out but I am bald.
 
sounds to me as if the glow plug is bad causing it to sputter, get a good medium plug and try that....
 
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