Tillotson HB-10A for Iamex30 super. Questions

Good evening,

it’s my first time working on diaphragms carb and I can’t find much info for the hb-A10 type. It’s the Standart for iame x30 175cc single speed. Is the rule of the thumb that if I’m around 10 psi at pop off and after that holds steady around 8 psi aply also in this carb??

For the x30 and the shifter 175 that works with the Hb-15 I have found some baseline documents but for the 10A seems difficult to find a lot except from the basic guide from iame that tells me only the baseline from the high and low needle screws.

One more question I have is. Which is the easy way to drain the fuel from the carb after use?? because I read it’s not good for the membranes to stay with fuel inside.

Last question is when I check the pop off pressure the carb should be drained of fuel and should I close the needle screws high and low before measurement?

Thanks in advance.
Cheers from greece!

You could apply basically the same setting as for the HW-27 carb.

As for pop off 9-10 psi seems right and steady at 8psi

The easiest way to drain the fuel is to remove airbox and then hookup pressure tester and apply pressure so that the valve opens and fuel comes out :ok_hand:t2:

When pressure test you could test directly at the valve with an adapter, you should drip some fluid into the valve before pressurizing and watch you eyes for squirting fuel! When fully assembled you should empty all the fuel first to check pressure, you don’t need to tighten needles since there is o-rings that seal them👍🏻 I never tighten them when I drove X30 when I tested pressure.

Pay attention to the cap as it could leak at the screw. Check with a bit saliva on the screw if you see bubbles when pressurizing


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Thanks a lot for your help Lukas!

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No problem, don’t mix the needles😁

I’d recommend removing one at the time and then remove the o-ring carefully. Screw back the needle fully until it bottoms out and mark the position, don’t force it!

Then you could adjust outwards to baseline setup more accurate

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Yes Iv learn about the difference at the tip between the two of them!! Here is the photo

I’m sure I’m gonna be extra careful with those…

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I would mark them with a H and L :ok_hand:t2:

Also check if they are bent or worn in any way and replace if that is the case

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I would mark them with an H and L if I were Tillotson!


Yeah, with all that facility they could at least mark them​:poop::flushed:


Yes John !

James at 2019 had a post that show they did a notice and a. Free of charge upgrade for that matter… Coz a lot of us made the same mistake with the needle screws…

Here it is.