Iame x30 carb membrane


After only 2-3 hours , my iame x30 starts to run like shit and won´t rev at all. And when I tear down the tillotson carburetor, the membran is deform like on my pictures. Is this just normal behaviour after only 2-3 hours, or could something else in the motor, be the cause of it ??
When the problem appears, i´m noticed that its a little wet from gasoline around the screws at the top(carburetor), same goes for all the gaskets in the “sandwich” construction(carburetor), they are all a little wet from gasoline, but all the screws are tight.
I´m just a club driver, so no high levels at all. The motor revs. perfect 16k rpms, untill this happens to the carburetor, then I do a rebuild and the motor runs fine again, 2-3 hours.


They do distort a little over time, but that seems like a lot for only three hours. What fuel are you running. Pump gas with ethanol could have that affect on the metering diaphragm.

Re-reading your post, it shouldn’t leak at the screws at any point in its life normally. Might be worth putting the tiniest dab of blue locktite on the bolts and maybe recheck the screws periodically.

Hallo James, and thanks for your reply.

Yes i´m running pump gas, octane100, with 5% ethanol… its the best gasoline I can get on gas station.

Yeah i´m finding it a little od, that a 2-3 hour re-build, make it distort like that, with a tiny leak around the top of the screws. All the screws are tight tough, even after 3 hours. Speaking of the screws, anyone who knows what Nm the screws need.

Def not normal. I run mine a whole race season without rebuilding it.

You gotta look to what you’re running through it - fuel and oil. They’re not designed to run ethanol so as James mentions that could well be the culprit, maybe try running with some ethanol stabilizer additive if there’s nothing else available sans ethanol

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This oil at 5% : ELF HTX-909 - GREAT PRICE!! synthetic motor oil on Offer - Buy Now on
And octane 100, with 5 % ethanol. The best pump gas I can get in my country.

Oil type looks fine. I’d say it’s the ethanol. I run 98, no ethanol.

In Denmark, we have ethanol in all our pump gas. I would hate to buy special gas, when i´m only a club driver. I would think, that many other than me run x30 with ethanol in the gasolin.

“ Because it is an alcohol, ethanol dries out the rubber components in a fuel system. This leads to cracking and brittle fuel lines, floats, seals and diaphragms.”

Thank you… maybe this is the coolprint

We have 95 octane with 5% ethanol (10% since August) in Sweden. And the membrane does not look that bad after 3h.

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Is that an OEM Tillotson kit or an aftermarket kit? My track sells an aftermarket rebuild kit that is about 1/3 the price, but they don’t last as long as the Tillotson branded rebuild kit. If you want to make your rebuild last I would either run the carb dry (not always recommended) or take the carb apart so there is no gas in it. At the very least I use the pop off gauge to blow excess fuel out of the top cap. There are some that will change the diaphram every weekend.

Its the tillotson rebuild kit that mondokart Sells.
I use the Pop-off gauge on the inlet after end race day every time.
I just want to make sure, its not something else in the motor, that could be the cause of the problem.

If rebuilding the carb takes care of the issue I don’t think there is a further issue. I suspect that when the diaphram is that distorted the fuel supply isn’t being metereed at all and is flooding the carburator.

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It happened on the track, and I could barely drive the kart back in the pit, It would only like idle, and wont take any revs. The spark plug was very wet. At first I thought it was a ignition problem , so I changed to a new sparkplug. The kart then runs fine 1 round, then starts to go like shit again, and wont take any revs. With lot of White smoke from the exhaust. Took it in pit again , the spark plug was wet again. Next session, it runs fine 2 rounds, then shit again, Lots of White smoke from exhaust . Then took the carb. A part. All The time, the kart starts perfect every time, and idle nicely. I Hope that a new re-build kit for the carb Solves my problem

Do you run the carburetor dry at the end of each race day? You should, the diaphragms don’t like sitting in a bath of gasoline.

I was thinking the same thing. 2-3 hours of run time with the carb sitting for 2-3 weeks full of fuel between use could lead to this

That said I’m lazy and don’t drain the fuel but I put in a new diaphragm every 2 hours and don’t use fuel with ethanol

Everything you are stating sounds like it is flooded / rich although the white smoke is a little concerning as that usually indicates water. As I said above, my guess is the carb is’t metering the fuel and it has to much fuel in the carb which may have also flooded the engine. Also make sure your H/L needles are set correctly.

What readings did you get when you did the pressure test? It should pop around 11psi and hold above 8.

No… How to do this the easy way ? Do I really need to take the carb. a part every time?
I only use the pop-gauge on the inlet, to take the pressure. Someone told me to do that.

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My observation has been that fuel + air (ie, you’ve run the carb “dry”, or pushed the fuel out) might in fact be worse than having the chamber full of fuel… at least between races depending how long it’s sitting… Consider that the pump\metering diaphragm carb principle predates karting with it roots being in chainsaw applications… unlikely to be frequent draining done.

But I have also only used leaded racing gas without ethanol. For ethanol based fuels, it could be better to have the fuel expelled… I don’t really know nor do I think it’s worth the time to find out.

Like a lot of things, it’s easy to go down a rabbit hole there’s lot of variable… an opinions…

So, where does that leave you?
Do a popoff and pressure test, troubleshoot based on those results if needed.

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