Suspicious X30 tryton carb behaviour/settings


So I have X30, fully rebuilt engine and tryton carb. Last sunday I was breaking in the engine with L jet settings of 1:10 and H 1:30. I started to push a little too early and it seized, this was that I thought was the root cause. So new honing, new piston next size in and to the track again yesterday. This time I opened the H more 1:45 to be sure I have enough cooling and lubrication. This time everything went well, I’m new to tryton and X30 so I’m a bit worried as it seems like I can open the H to over 2 TO and still it will not “4-stroke” on straigths and exhasut temp will anyway be in the 600C range. I get really bad drive in the range 8-11K rpm with the H 2TO but at higher rpms it pulls well to 14 (didnt try more yesterday because of my suspicion).

So my question to you that are used to x30 and tryton carb.

  1. should I even be able to run the engine on straights with the H jet 2 TO?
  2. in what rpm ranges shoud I see most effect from L vs. H screw
  3. should the x30 engine “4-stroke” heavily on a long straight with H 2 TO?
  4. seems like I could have some odd restrictoin on the fuel side as opening of the L and H jet only have effect under say 11K, over that it anyways runs fine (leans out) anyway. (lack fuel althoug 2TO H jet)

All gaskets are new, reeds, carb membranes etc. popoff is 0,85bars (12psi?).

Maybe I’m just afraid to seize it again :slight_smile:

Thanks in advance.


My advise, get the jetting for IAME app.

You set you atmospheric data direct from local weather station automatically, tell it which carb and type of track, it tells you exactly where to set your H/L

1:30 seems very high and rich for Tryton. Ballpark they should both be around 1. I set my app for Tryton carb just to show you the difference - previous post it’s set to Tillotsen


yes, thats why I’m suspiciuos of that something isnt right. because it runs fine on high RPMs even with 2 TO on high RPM but starts to 4-stroke and missfire in the 8-11K range.

Should maybe try that app.

what will tryton look like if you put 11-12psi popof?


You can’t change the pop off, it gives you what the minimum should be. So long as you’re above it it’s good.

I’d try with App settings. Just out of curiosity what’s your run in method?

The first time (when it broke) I was pushing more after 5min, up to 14k.

This was how i did it the second time.
5min 4 -10k part throttle
5min 4 -10k 3/4 throttle
5min 4-12k 3/4
5min 4-14k full throttle but not full on long straight

so next time I need to be sure I have enought fuel on top.

But the concern is as said → should it even rev to 12 with H jet 2 TO.


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Yeah def you pushed too early. Programme sounds fair, just make sure you’re not driving those 5min at constant rpm. Let it rise and fall gently up to the limit for that part of break in.

It’ll run yea but you’ll foul the plug quickly. I’d say you’re good to set normal jetting and go have some fun.

Yes I was going up and down all the time. If not in a turn then I was coasting and sligthly braking it down and then on throttle again.

After the last 5min a continued to run it like the last 5min for 30min, and was testing the H settings and what’s when i became suspicious of the effect of H jet in this case as the EGT still came up to and over 600C with the H open 2 turns.

ok so it will run clean (without 4-stroking) but kill the plug more easily?


Pretty much, run in sounds good.

The one from Jet lab or ISEnet ?

ISE net

20 charcactersssssssss


Anyone else having some thoughts regarding my fear of fule delivery problem at high RPM. Or was the problem just between steering wheel and seat the first time and that there is no problem with the fuel delivery at high RPM.


General info based on my experience with these carbs…

My casual observation is that the pop off might be a tad high at 12PSI? The screenshot above shows screw settings based on 9psi. It’s crucial that the pop off matches when comparing screw settings.

Higher pop off will reduce the fuel flow, leaning the jetting when demand for fuel is greatest, around peak torque and above. Sometimes to the point that it’s difficult to compensate with the screws.

A fouled plug can be cleaned with a blow torch to go again. Do not use a wire brush :joy:. You can also use Ether (starting fluid) to clean the plug.

Set pop off at 9psi and send it. Worst case scenario it’ll be on the rich side, but plugs are cheaper than pistons.

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I had no idea you could change the pop off :grin:

Every day’s a school day :nerd_face:

Oh it’s critical. Pop off in a pump carb is somewhat equivalent to float level.

Here’s a guide on how to set it on the OG KP site :laughing:

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:skull_and_crossbones: :joy: :skull_and_crossbones:

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yes, I did some research before I posted and also measured the popof and it seems high. Should I just compress the spring between fingers to try to lower the spring rate?

ok so this was interesting, that I may not be able to correct with H if the pop off is too high. I thought that you could compensate.

I have to measure the pop of several times again to be sure it really is that high, but I saw many youtube clips and read that guide also before so it shoul be measured right.

You can compensate to an extent, but there’s a point where the fuel flow coming into the jet chamber, (past the inlet needle which is controlled by the popoff pressure) becomes the choke point. Basically, there’s not enough fuel being supplied to the jet for the demand being applied to it.

It’s possible that the needle and/or seat (separated when pop off pressure is reached) are sticking, causing the higher reading. So start with a cleaning and let us know what you find.

Hey now don’t be starting something :smiley:

That terminology is from the man himself E.C. Birt. A legend when it came to kart carburation, especially pump diaphragm carbs. If the terminology works for him and 1000’s of racers, it’s good enough for me.

@KartingIsLife what about good practises on how to lower if it really is too high. New spring? or can I get the spring rate change by pressing it togehter? Thats not usually how springs work but these are really small…