Mp9 Tki3 Problems

[Jase125]

Hi people! Been a while since I've been on here, cut long story short took the carb of my tki3 and cleaned everything. Went to put the carb back together broke it so bought a new carb fitted it got it running but sometimes it won't idle for that long and when applying throttle it bogs and cuts out? I've checked the gap on carb its about 1/1.5mm. The hsn I've put back to factory settings or as good as i can! and lsn flush with the edge of the side. Could it be something ro do with the idle screw or throttle trim on the control? I have no idea. So of someone has better knowledge then me on these engines please let me know what the best thing to do is or where to start! Thanks.

 

[Tzicul]

Try to lean LSN. Flush is so... unclear It happened to me also

 

[Jase125]

When you say lean do you mean turn in a bit or out?

 

[D3MON]

to lean is to tighten, think of the needles like a garden hose, tightening the spigot closes water off, loosening allows more to come through. go in 1/16 turn increments, full 360 turn of the screw is 1 turn. to make sure the throttle trim is correct (while not running preferably inside) turn car and controller on, press on the brake slowly, the carb should not close anymore than when statically on with no input. if it closes a bit when you do this you need to adjust trim. it does sound like either lean or rich LSN, are you getting smoke out of the exhaust low RPM to mid RPM (half throttle)? if lots of smoke or oil blowing out exhaust, then its a bit rich.

 

[Jase125]

I will check the throttle trim, i can't even rev to half throttle cus it just starts bogging out then cuts out. Like its starving itself with to much fuel? I'm getting plenty of smoke while idling tho?

 

[D3MON]

factory settings are very rich, very rich, i wouldnt be suprised if you have to lean it 1 turn, but do not go that far, maybe start with 1/4 turn max! it has to much fuel and not enough air so the mixture can't burn very well not very much combustion making it cut out and die, lots of smoke means lots of fuel, no smoke mean not enough fuel.

 

[Tzicul]

As D3MON says

 

[Jase125]

Thanks for the help guys, ill be back if still having problems ?

 

[cbaker65]

Thanks for the help guys, ill be back if still having problems ?

Also ,if you have set the needles to factory ,then you may have your HSN set too rich!

Try leaning the Hsn in about a 1/2 turn first ,warm the engine up ,an then adjust your Lsn while
running the car.
Do quick stabs at the throttle ,if the engine bogs at the stabs ,then lean the LSN in as said!

 

[Tzicul]

Performance Tuning Guide
There are many ways to tune a nitro engine but I figure this is the simplest way to do it. This technique is for a fully broken in engine that is ready for a full performance tune. This tuning procedure will set your needles to where they need to be for optimum performance, the engine will tell you all you need to know.
For this method to work the engine has to be at running temperature (or as close to it as possible) as well as having the standard 1mm gap for the carburetor opening.
High Speed Needle
Pull a full throttle pass a couple of times and listen to what the engine does when you let off the throttle. If the it 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 turn increments until the idle seems to hang a little after a full throttle pass. If 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.
An explanation to what is happening is simple - if your HSN is too lean, after a full throttle 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).
If the opposite happens, after a full throttle pass when you let off the throttle 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 full throttle 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.
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 temperatures, but a temperature gun is very handy for this part. After some full throttle passes with the engine good and warm, bring it in and let it sit for about 10 seconds. At this point take your temperature 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 during on and off throttle running and will cause temperature 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. If you have any questions feel to contact me at [email protected] .

 

[Tzicul]

In addition, this is how I adjust LSN: let the engine idle for 20-30 seconds, then apply full throttle. If the car hesitates with a lot of smoke, LSN is too rich, but if the same happens without the smoke, you are too lean. You have to learn to listen to the engine, a high pitch means lean, low pitch means rich

Nitro Engine Tuning Basics:

NOTE: ALL TUNING MUST BE DONE AT OPERATING TEMPERATURE

Rich: An excessive amount of fuel entering the engine, more fuel means more oil, which
typically lowers the operating temperature. Rich=counterclockwise

Lean: An insufficient amount of fuel entering the engine, less fuel means less oil, this
causes more friction, higher temperatures, and engine damage. Lean=clockwise

High Speed Needle:

The High Speed Needle (HSN) valve is the tall valve that sticks out from the top of your carburetor. Its job is to control the main flow of fuel to the carburetor. If you lean out the HSN, the LSN (Low Speed Needle) will be automatically leaned too (think of it this way, the HSN is the garden hose faucet which controls all of what goes in, the LSN is the nozzle which controls the exact amount that comes out). The HSN mainly effects the top speed of the car. If your HSN is set too rich, the engine will typically not reach its full RPM potential. If the HSN is too lean, you can experience hesitation, overheating and flameouts (engine instantly shutting off at random or at higher RPM’s). WARNING!!!! The HSN IS NOT to be used as a thermostat. Yes tuning effects running temperature, but only half of it. In the cold, you will typically have to set your needles richer because cold air carries more oxygen, therefore with the previous settings you will be running too lean.

Low Speed Needle:

The Low Speed Needle (LSN) is used for fine adjusting the rate of fuel flowing into the engine from the HSN. If your LSN is too lean then you will have erratic idling, it might want to drive off without you, and it can suddenly shut off (flame out). A characteristic of an overly lean LSN will be a random surging and sound “angry” so to speak. It also will have sporadic RPM increases. Too rich of a LSN will make the idle sound deep and rough, at idle the RPM will slowly decrease and then shut off due to the excess fuel building up, it will also cause consistent sluggish acceleration all the way up the RPM range, and this is what makes it different from a lean bog.

The best way to test your LSN is to get your engine running at normal operating temperature, drive it around, and then let it sit and idle for 30 seconds. Once 30 seconds is over, apply a lot of throttle, if it is rich you will notice slow, gurgly acceleration, if this happens, lean the LSN out by 1/8th of a turn and then test it again, if it is lean, chances are it will flame out or have random surges. In this case you would richen the LSN up by 1/8th of a turn at a time. Your LSN will be set near optimum position when you have little to no hesitation after 30 seconds of idling.

Keep in mind that an engines tune changes day by day, every time you get our your engine and run it, you should tweak the needles a little bit (typically). One day your engine can run fine, the next day it can be running extremely lean.
NOTE: Tune the HSN first because it controls the full amount of fuel entering the carburetor, and then tune the LSN because it is a fine adjustment screw.

As a side note, if you do a lot of wide open running at WOT (Wide Open Throttle, a.k.a. full throttle) your engine will need extra lubrication and it could need to be set 1/4th turn rich to ensure proper lubrication to your engine at high RPM’s.

Here is a good little graphic that for the record I did not make, I simply found it very helpful.