Japan os 11k

[tzhaarc]

So the needles are high speed low speed mid speed
But where’s the idle stop screw?

 

[tzhaarc]

Never mind it’s by the high speed screw
So how do I tune the needles? When do I worry about mid range

 

[ohsnap]

TZ - "So how do I tune the needles? When do I worry about mid range"

For the most part, I find that I don't toy around with either the LSN or the Mid-range needles.
Many carburetors don't even offer the ability to change the mid-range setting.

The HSN gets most of my attention and there are also times when you need to adjust/set the idle (screw).
I adjust the HSN according to the cooling head's temperature.
Ambient temperature and the amount of smoke (or more importantly a noticeable lack of smoke) come into play, but I generally shoot for 220-230F just about mid-tank, and that seems to work out to somewhere around 265-270F at the tanks end.

You can run it hotter (leaner) if you want, but I'm generally happy with the performance - but I'm also not out there racing and focused on "the competition". Plus, I feel this helps the engine last longer.

 

[ohsnap]

Oh yeah, HSN - Screwing it in leans out the mixture (runs hotter) and unscrewing it, richens the mixture (helps cool it off).
You generally don't need to make drastic changes - like start with a sixteenth or an eighth or a quarter turn and drive it around and then see how that affected the engine.

 

[tzhaarc]

So it idles perfect
But when I full throttle it’s very slow
When I partial throttle it’s very slow and doesn’t engage immediately when I blip

it’s very rich but it doesn’t cut off and when I let off the throttle it goes back to idle perfectly never had that with the traxxas plastic carb

 

[tzhaarc]

Lean the high speed a bit?

 

[easy rider]

Lean the high speed needle until it runs at wot the way you like.


After tuning the hsn, bring the car in and let it idle setting still for 15 seconds. Accelerate to wot at the end of the wait. If it’s sluggish at all, lean the lsn. Run it clean with a couple high speed pass. Then repeat.

Once you get it accelerating out of the hole after 15 seconds, push it out to 30 seconds. Repeat the acceleration test. Lean it if it’s sluggish.


You can keep going out to 45-60 seconds if you desire. But, it’s not necessary. An OS 11k carb will idle a whole tank as long as the lsn isn’t too rich. Which after passing the 30 second test, it’ll be to close to perfect tuning it’s not needed.


On the os 11k the mid range needle is a half a screw in from flush. Set it there and forget about it. Seriously.

On any adjustment go small changes. This ain’t a Traxxas carb. It’s the pinnacle of precision work. And, it responds very quickly to adjustments on the lsn and idle.

 

[tzhaarc]

so i leaned high speed half turn and its very responsive now BUT after doing some short burst wide open throttle blips it jerks at idle. am i too lean now? is the perfect tune somewhere inbetween the half turn - i have yet to touch the lowspeed

 

[ohsnap]

Don't touch the low-speed needle.
There MAY be a time that you will need to, but not yet - if ever.
Read up on (research) nitro carburetor tuning before you do.

That jerking may mean that you need to lower the idle speed via the idle stop screw (just a smidge).
With the engine running, lift the truck/car off the ground.
Are the wheels turning?
If yes - need to lower the idle.
Turn it counterclockwise (out) about an eighth of a turn and see what happens.
I'm guessing that it's jerking because the engine RPM's are high enough to get the clutch-shoes to engage and you want to slow it down.

Do you have an infrared thermometer?
You will need something like this.
Aim for the area around the glow plug to get your engines temperature and aim for the numbers I mentioned before.
There's also a spit or drop of water test - I'll let someone else describe.

 

[easy rider]

so i leaned high speed half turn and its very responsive now BUT after doing some short burst wide open throttle blips it jerks at idle. am i too lean now? is the perfect tune somewhere inbetween the half turn - i have yet to touch the lowspeed

What’s your idle like now?

 

[tzhaarc]

What’s your idle like now?

the idle is perfect at startup but after high throttle blips it’s like a idle hang will try again today

 

[ohsnap]

Check your linkage too - it may be "hanging up" on you.
When you noticed the "idle hang", does the idle change when you hit the brake?

You can also test this with the engine off.
1. Turn the transmitter and receiver on.
2. Simulate full throttle.
3. Let off the throttle without hitting the brake.
4. Looking at the throttle linkage and/or down the carbs throat - hit the brake.
6. Do you see any movement?
5. If so, your linkage / return spring arrangement / possibly the carbs orientation / even possibly the "uniball" at the end of the carbs slide needs adjustment.

 

[tzhaarc]

Check your linkage too - it may be "hanging up" on you.
When you noticed the "idle hang", does the idle change when you hit the brake?

You can also test this with the engine off.
1. Turn the transmitter and receiver on.
2. Simulate full throttle.
3. Let off the throttle without hitting the brake.
4. Looking at the throttle linkage and/or down the carbs throat - hit the brake.
6. Do you see any movement?
5. If so, your linkage / return spring arrangement / possibly the carbs orientation / even possibly the "uniball" at the end of the carbs slide needs adjustment.

Check your linkage too - it may be "hanging up" on you.
When you noticed the "idle hang", does the idle change when you hit the brake?

You can also test this with the engine off.
1. Turn the transmitter and receiver on.
2. Simulate full throttle.
3. Let off the throttle without hitting the brake.
4. Looking at the throttle linkage and/or down the carbs throat - hit the brake.
6. Do you see any movement?
5. If so, your linkage / return spring arrangement / possibly the carbs orientation / even possibly the "uniball" at the end of the carbs slide needs adjustment.

So when I brake it closes just a tad I think it’s the linkage

 

[tudordewolf]

The idle stop might need to be lowered a little from factory setting once you start leaning out the needles.

 

[ohsnap]

It don't take much to mess up an idle.
Let's say this is your linkage.
1. Turn everybody on.
2. Loosen the red collars grub & assuming your spring offers enough tension - the linkage should move to take up the slack.
3. Retighten the grub and test it.

 

[tzhaarc]

The idle stop might need to be lowered a little from factory setting once you start leaning out the needles.

So I’ve only done this with the new carb
- leaned highspeed half turn richened about a quarter (now it goes into second gear vs rich and rpm die off )

- low speed leaned about quarter (will need to richen when I pinched fuel line shut off in 2 seconds) (too rich it cuts off when i brake)
My only real issue is

It’s jerking when I lay off the throttle at idle - I need to slightly brake for the linkage to properly seat the boot - jerking stops

 

[tzhaarc]

The idle stop might need to be lowered a little from factory setting once you start leaning out the needles.

So I’ve only done this with the new carb
- leaned half turn richened about a quarter
- low speed leaned about quarter (will need to richen when I pinched fuel line shut off in 2 seconds)
My only real issue is
It’s jerking when I lay off the throttle at idle - I need to slightly brake for the linkage to properly seat the boot -

 

[tzhaarc]

At this point I’m thinking 2 things
- compress spring more ( so at idle the spring will force boot closed vs slightly pressing brake )
- tighten the plastic cup that hooks into boot arm ??

 

[tudordewolf]

At this point I’m thinking 2 things
- compress spring more ( so at idle the spring will force boot closed vs slightly pressing brake )
- tighten the plastic cup that hooks into boot arm ??

I think adjusting the collar so the spring is compressed more is the solution - at idle you need some tension keeping it shut, brake should be freewheeling.

 

[tzhaarc]

I think adjusting the collar so the spring is compressed more is the solution - at idle you need some tension keeping it shut, brake should be freewheeling.

Yes good solution will do this and update