IAME Super Shifter 175 Cutting out

Hi, since you seem to know a little bit about the Super Shifter, here is a question for you.
I have a Super Shifter, but I live in Spain, so my S.Shifter is the European version, I bought it in January of 2020 but with the covid restrictions that we’ve had over here, I haven’t been able to drive the S.Shifter more than a couple of times since I bought it, so yesterday I took it for a ride and here is my main problem.

I was told to set the Tillotson carburetor L 1:30 H 1:45 (I think in the good old USA you describe it as L 1:50 H 1:75) so with those settings the engine runs very well, but there is one curve where the engine dies, it feels as if it’s too rich, so I set the low at 1:15 (1:25 in the US) and it improved but still not 100% on that same curve, so I made it even leaner, L 1:05 and that solved the problem.

Now, a couple of things, as to why the engine dies on that curve every single time with the Low set at L 1:30, I don’t know, it’s a slow curve going downhill turning left, there are other slow curves at my local track, but it’s only on that curve where the engine dies, not on the others; and as to why making it leaner solves the problem on that curve, I also don’t know. But here is my fear, I don’t dare to go full throttle on the straights of the track as I fear that having set the Low so lean (L 1:05) will end up seizing the engine, even if I set the High richer I’m still scared to be honest.

I contacted Tillotson here in Europe and they told me not to set the low leaner than L 1:15 (L 1:25 USA) They said that in the US the Low can be set leaner, at around L 1:05 but given that the European version is different, I was told not to set the low so lean, so I’m confused and unsure of what to do… My question is, if the EGT doesn’t go higher than 650-675 degrees Celsius, can I still seize the engine when having the Low so lean?

Here in Europe we usually have an EGT sensor and we normally try not to have the temperature higher than 650-675 degrees Celsius, so anyway, if you have some thought I would appreciate, I’m a bit lost.
I used to have an X30 with the traditional Tillotson carburetor and I’ve never had a problem with that curve, or any other curve of the track, so as to why the 175cc dies in that one curve all the time when I have the low set the way I was initially told, I just don’t know :woozy_face:

Right now I left it at L 1:05 and H 1:50 but I didn’t drive full throttle on the straights, I’m scared to seize the engine which is basically brand new, so…
Thanks in advance, I hope I explained myself clearly.


First of all, its wise to follow the tillotson advice. Going too lean on the low can definitely hurt the engine, especially in the lubrication of the bottom end of the conrod, regardless of the egt temperature. Because you are saying that this only happens in one particular corner, going downhill etc, is there something else going on? Is it an issue with the fuel pickup from the tank, maybe, or something electrical?
Please do not rely on the settings from the Usa, the engine is different, the fuel is very different, so I would ask locally in Europe. The iame dealer from Spain is your best bet. Please contact him for further assistance.

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Also, in the Usa we had a problem with the tillotson needles being reversed (hi in place of low, and vice versa ). Check and make sure they are correctly placed, it is very easy to make the same mistake, they are very difficult to tell apart. Are your needles marked H and L? If not, make sure they are appropriately placed!
Anyway, it s difficult to diagnose issues from thousands of miles away. Your best bet is to contact somebody experienced and local to your track that can troubleshoot the issue methodically. I would certainly contact the Iame importer for Spain and ask for help.

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If you lean the low but keep the high where it needs to be in order to hit your target EGT, then seizure should not be an issue.

If this issue you’re experiencing is specific to one corner, then you may want to look at throttle application, as we’ve experienced issues where applying maintenance throttle while approaching an apex can cause the engine to starve for fuel.

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If not ,why not?

In the old days the high speed screw was a T bar. The low speed had a round head with a screwdriver slot into which a washer could be brazed. The carb body had H&L markings cast in.

No chance of confusion

Thank you!
I’m not sure what to do, I do fear damaging the lower conrod bearing if I make it too lean, I’ve tried with a full tank so it’s not lack of fuel, I don’t see how, if anything, it’s too much fuel, it takes about 10-15 meters for the engine to take off after having gone through that corner, it’s always in that one corner, always and nowhere else, doesn’t make any sense but it’s driving me crazy, I can’t push on the straights, even if I set the high very high it’s too risky, I’m way off the settings I was given here in Europe (L 1:30 H 1:40) I have the Low at 1:05 so that’s almost half a turn less, that very lean for the Low, it’s very weird, in all the other corners the engine functions perfectly with the settings I was given (L 1:30 H 1:40)
IAME here in Europe has no answer, I either try the Dellorto Carburetor or I sell the engine, which would be a shame.
But thanks! :pray:

Do you have an aerial photo of the track, and could you highlight the corner where you’re experiencing the issue?

Could it be that a fuel line is getting pinched at some point? I’ve had it where my knee has pressed against the fuel supply line causing intermittent cut-out issues.

Might sound silly, but are you in the correct gear for this corner?

Are you running an EGT sensor? That will give you the ability to tune for the straightaways as well, and give you some peace of mind.

If only ONE corner is causing the issue then it’s got to be something easily fixable…

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Thank you… I’ll do a bit more testing but for now I don’t see a solution to the problem, I bought the engine last year and I’ve only tested it a few times as I can’t find a solution to the problem, actually I’ve been racing with my other kart, a DD2, that one never fails, but the Super Shifter was my new toy (4500€) and a month ago I bought a brand new Birel Chassis so… If I can’t make it work I’ll have to sell it unfortunately, I guess I’ll buy a TM R1 engine, there are a lot of those around here and they have no problem, I’m not sure if it’s worth it buying the Dellorto carburetor plus the fuel pump :cry: just to give it a try.
Unfortunately no one else around my area has a Super Shifter, I do have a friend up in the north of Spain that has a S. Shifter and he has zero problems, but his engine is from 2018 or 2019 and it came with the Dellorto carburetor, and his local track is completely flat, my local track goes up and down, and when I go down hill is when it happens, always in that same corner.
My grandpa used to say, “anything worthwhile doesn’t come easy” but this is getting frustrating.
Thanks anyway, if I find a solution I’ll share it here just in case anyone else runs into a similar problem.
If by any chance someone with experience driving a S.Shifter comes to the south of Spain for holidays, let me know, you’ll be more than welcome to test the engine at my local track (Campillos International Karting Track)

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I have tried coming out of that corner in 2nd and in 3rd gear, doesn’t make a difference, I don’t know maybe I could try in 1st gear but that would be extremely slow, you know how short that 1st and 2nd gears are, the problem is more with the engine not responding, If I have to guess, there is too much fuel getting into the engine, I think, and as I said, the leaner I set Low the better it gets.
Yes of course I do have an EGT, but the IAME manual tells you not to set the Low too Low as you can damage “the lower conrod bearing” even if the high is set really high, right now I can’t push on the straightaways, it’s too risky and even with the high set at almost 2 turns I still have a high EGT as soon as get to 5th gear, so imagine if I push the way you should on 6th gear, I’m sure I’d damage the engine. Tillotson here in Europe told me not to set the Low below 1:15 turns and for the engine to run well on that corner I have to have the Low at 1:05 so that’s very lean, very!
Let me see how to upload an areal picture of the track, thanks :pray:

Yes my needle are marked H and L so I don’t think that’s the problem, I hope not.

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Here’s the track…
Google Maps “3D”

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Yeap, that’s the track, thanks a lot!
You can see the starting/finish straightaway, so the problem I have is on the straightaway that is parallel to that starting/finish line, as I come downhill and turn left on the straightaway that’s parallel to the finish line, that’s where the engine dies, I don’t know why but something happens right there, it’s mind boggling.
Thanks again! :pray:

Does that engine have an idle screw or jet? Going downhill slowing down says idle to me. That combined with the low speed setting may be too rich.

So it’s the corner sequence leading onto that straight parallel to the start/finish straight? Is so, are you on partial throttle going through the fast right?

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Yes, the Tillotson carburetor has an idle screw and a low and high jet, I have the idle screw at 1:15 and the Low at 1:30 and the high at 1:40
The manual tells you not to touch the idle screw but “maybe” that’s what it takes… I’ll go this week to the track and try again.
Thanks a lot :pray:

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Yes exactly, is that straight parallel to the finish line.
As I come downhill and turn left to enter that straight parallel to finish line that’s where it always dies, as for the throttle, I pretty much do the same thing that I do on all the other corners, as I enter that straight I gradually apply the throttle.
A total of 4 other drivers have tested the engine and we all have the same problem in that same corner as we enter that straight parallel to the finish line.
It really is very strange, maybe I can record it with my GoPro and post the video over here, I’ll get on it.
Thanks a lot :pray:

Problem solved!
Today I was able to solve the problem, I replaced the pressure spring inside the carburetor, it came with a spring with 42grams and I replaced it with a spring with 46grams, now it’s fine, on every corner.


Problem solved!
Today I was able to solve the problem, I replaced the pressure spring inside the carburetor, it came with a spring with 42grams and I replaced it with a spring with 46grams, now it’s fine, on every corner

Ah, sounds like the pop off pressure might have been too low. Glad it’s running good, thanks for coming back to update us on the fix.

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If anyone else runs into a similar problem, now we know what to do.
A friend that runs a Super Shifter team up in Belgium couldn’t understand what was going on, and suddenly he said to me “what pressure spring do you have inside the carburetor?” So I checked and it was a 42 grams, and then he said “that’s the problem, you need a spring with 46 grams, so go ahead and replace it right away “ so I did and bingo! That engine takes off like a rocket on every corner :muscle:
Thanks so much for all the comments and suggestions.