Tillotson HW-27A carburettor settings

Hi! I have a Tillotson HW-27A carburettor. When i was at my track. And pressed full throttle i was maxing at 88 kph. And when i let it go a cuple mm it went faster. I wounder how im supposed to tune it. I have a app for x30 carby settings and it says 19/16 high and 16/11 Low how do i do to adjust it to the right place. And how do i know when its 19. And i dont know what the numbers mean. Talk to me like noob.

That’s an interesting issue. I wonder if you have an air leak.

The numbers are fractions of a full turn OUT for that particular screw.

So you would screw it in (clockwise) SLOWLY and gently until it stops. Do not force it. then screw it out by that amount.

One rule of thumb when you are having jetting questions is to richen up first, vs lean. It’s hard to break something by running a little richer, but too lean can cause engine seizures. In the case of the screws, out will richen. Basically the screws are a tap. Another thing you can try is a quick choke/tap on the airbox to see how the engine reacts.

There is another setting that is crucial for these type of carbs called pop off. If this is not correct then the screw settings will appear to be off. I think pop off for the HW27 is usually about 11PSI as a starting point. Please verify this. A lower pop off number delivers more fuel, while higher delivers less.

In any case, when you are comparing screw settings between carbs or drivers it’s crucial that pop off, fuel and oil % are as close as possible or you are introducing variables that might cause headaches.

The carb is pretty new. Only 3 weeks old. And how do i check the pop off.

How mutch is an fraction of the screw in case of 19/16

Which app are you using? I find it much easier when the numbers are in minutes, consider the screw like a clock face and turn it the desired minutes out.

I use this one, never lets me down

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I guess you think of it as sixteenth’s of a turn. So one full turn plus 3/16ths

Or, divide the numbers and you get 1.2 turns ish.

19/16 I believe you should be reading 1-9/16 ie one full turn plus 9/16.

19/16 isn’t enough for a 27, ball park is one and a half turns high and one turn low. If you’ve it set at 19/16 that’s the problem 100%

Oh ok so its baisicly 19 by 1 devided by 16 and thats 1.87

In sweden it is 6 celcius now and the app said it so idk

1-8/16 is one and a half turns. So 1-9/16 is just a smidge more.

Show me 20 char

This is my app set to 6 deg.

I use jetting iame x30 and its something like this

Are you sure it’s set up for HW-27 not Triton carb? Those settings look to be for the Triton

Triton ball park is 1:1 on both high and low.

HW-27 1.5:1 high vs low. At 6 deg your high should be 1 full turn plus 40 minutes

Thats not mine wait 1min imma show what my says now

There you go. That’s not 19/16 it’s 1-9/16 and 1-1/16

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And thats for the temp outside and the air thickness that it downloads atomaticly

How does that work how do i put it like so

You have it in hours/minutes underneath. Turn both screws to closed then imagine your looking at a clock face. 1 hour is one full turn, minutes is minutes on the clock.

There is a tool you can buy to do it precisely, but unless you’re chasing hundredths of a second there’s really no need

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Oh ok thanks i really apriciate it. I think i would ruin it if i wasent here


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