175SSE vs Modena vs TM KZ10c for “open” racing

[Peter (Peter Hake)]

I have a lot of respect for those that want and have the guts to experiment, please let me know how all that goes, most of the experiments that I’ve done haven’t been successful, trying to get more power from these engines is not easy, most of the time you either get disappointed or end up causing damage, but it is definitely worth trying.

When it comes to the Super Shifter, I’m not sure you need more power it has plenty of it, it really is a rocket , well… sure why not, we all want more power don’t we!!! So go for it!!

I know the app you were using, and yes that app is only good for the Super 175, with the HB-10A (I sent an email to the guys that created that app asking them if they could renew that app and include the carburetor HB-15A but they never replied to me, and read a number of comments of people that had used that app and they were complaining about the app not being of much use So even if they eventually add the Tillotson HB-15A to the app, I’m not sure if it will work

Let’s see, settings for the HB-15A would be very similar to what they wrote inside your box, so Air 1:15 that for sure, Low 1:30 although depending on the circuit you can go to 1:25 to 1:40 so if you have very tight corners go for 1:25-1:30 and if you have wide fast corners go for 1:35-1:40 and High 1:40 (for sure not 2:15, that’s way too rich) but once again if you have very long straightaways go for 1:40-1:45 and if the straights are not too long go for 1:35-1:40 (keep an eye on the EGT.)

Now, here are a couple of things to really pay attention to:
My HB-15A carburetor came with a pressure spring of 42 grams, and that stupid spring drove me crazy for many months, the engine in a couple of very tight corners would die, it didn’t have the response that it’s supposed to have, I was closing the Low to 1:05 in order for it to work properly, until one day I made a couple of phone calls to some people that have a lot of experience with this engine and they said “well, you didn’t replace the pressure spring? You must use a 46 grams spring or it will not work properly as you come out of those tight corners”
So, I replaced the pressure spring from a 42 grams to a 46 grams and Bingo, that engine is flying out of every corner, what a difference
So check your HB-15A and see what pressure spring it came with, a 46 grams spring will cost you less than 1€ only a few cents.
I wish someone would have told me way earlier, it would have saved me tons of frustration, I even thought about selling the engine, even if I bought it brand new at the beginning of 2020

And then also the following… a friend from the Netherlands that runs a Super Shifter team said to me “what ignition do you have, is it the Selettra ignition or the PVL ignition?” So I checked and mine came with the PVL ignition, which is the ignition that comes with the latest engines, the older engines came with the Selettra ignition, so my friend told to replace the PVL ignition for the Selettra ignition, which is something they had done to all their new engines.
So I bought the Selettra ignition, got rid of the PVL and once again Wow! What a difference it made, the spark, the power, the sound, it just made the engine run as it really is supposed to.

So a 46 gram pressure spring and a new Selettra ignition have restored a smile on my face I now LOVE IT

Given that your engine is second hand, it is possible that yours is older than mine and it came with the Selettra ignition, in that case, just check the pressure spring and that’s it, you’re good to go, no need to spend 300€ on a brand new Selettra ignition.

Hope that helps, let me know how it goes in the lab, be careful with the squish

By the way, if I’m not mistaken the KZ world champion will take place in Sweden this year, so that’s close to Finland If you feel like watching proper racing

[Mikkometalli (Mikko Härkönen)]

Great tips Peter - thanks a lot ! I will try your carb settings next time on the track

My needle valve opens at 0.62 bar - do you remember at what pressure the 46 gr spring opens ?

Didnt know the differences between ignition components. I have the pvl stuff on - will try the selettra - another great tip

Supershifter moves around all right. I´ll try if I can make it a bit snappier. Propably impossible or quite hard as you have experienced - it is a race engine after all - developed by people who have designed more engine parts than I have eaten potatoes.

Anyway - I will post the results about squish experiments - good or bad

[Peter (Peter Hake)]

I do not remember at what pressure the 46 gr opens, I’m so sorry, but I can check next time I go to the track (I don’t keep my karts at home, I keep them at the track)

I was at the track this morning, trust me, that 46 gr really works!!
Today I was reaching 670ºC-680ºC EGT, a bit too much I think, so next time I’ll open the High a bit more, but the Low at 1:30 is perfect, as long as you can keep the Rpm up there around the tight corners, but the engine is a rocket I really love it

Good luck experimenting, just be aware of detonation, you could add an “octane booster” to the fuel just to be a bit safer, at the very least an octane booster will improve your engine’s stability under compression by increasing the octane rating of the fuel you are getting at the pump, you really want to prevent engine knocking *the Selettra ignition will for sure make it snappier

[Mikkometalli (Mikko Härkönen)]

Well the first test is done - drove 78 laps in total in several stints. The squish was set at 0.8mm - the engine made more power than with 1.3mm squish - thats for sure. Everywhere. It felt and sounded sharp. I liked it. Pulled the plug many times - had a look with a camera - there were no signs on piston top of detonation

Then in the end did a stupid mistake - forgot to lower the radiator curtain…It was only 5-7´C on saturday and it took some time to get the motor up to temp. Now with the curtain all the way up - coolant temp went well over 100´C and quite a bit of water steamed out. In the last few corners the exhaust note became noticeably sharp - ill sounding. As a racer with little sympathy/brain that didnt make me lift - motor detonated/seized after the start/finish straight, locked rear wheels and I spun out off the track. After getting to the pits - camera showed eroded piston edges and aluminum on cylinder walls

Well - After all this carnage - The bore is still within 0.01mm in roundness. Very scarred but perfectly round

Time to try the tight squish. Im thinking about 0.4 - 0.5 squish - I have to search a bit what has been the limit on other engines and make a guestimate what would work with this motor. If anyone has experience - about any engine - give a shout how tight you have managed to go without touching the head. I dont have experience how much parts flex at high revs

Propably old news for fellow karters but with the 175 supershifter - going as tight as the rules allow produces the best power/sharpest motor, or if its an open engine - a 0.8mm squish worked (for me) - it didnt detonate. I was running on 98 octane pump gas

Peter - I ordered the 46gr spring Tillotson also sells 47 gr spring so will try that too. With the spring installed by the factory - I dont know the stiffness - I didnt get the adjustments quite perfect - had to lean out low screw close to 1h 15 min and it still felt need for improvement. I kept making adjustments the whole time I was on track. I tried few ways to measure the spring stiffness but kept getting mixed results

[KartingIsLife (James McMahon)]

I think you might have reached the mechanical limit for squish. That ring on the piston is very very concentric. I think you have both detonation and slight head contact there.

If you haven’t checked the crank bearing for radial play and the rod bearing for signs of play or overheating is recommend you do so.

For sure replace the small end bearing with the piston.

[WheelSpin (Spencer Uzri)]

That cylinder will need to be honed, or re-sleeved if that’d put it out if spec; top end parts are (aluminum) toast. Also 2nd the recommended check for play in the rod.

[Peter (Peter Hake)]

Thanks for sharing all the results of your experiment, I admire you, you have a lot of guts.
I think the Squish on the Super Shifter comes from the factory in such a way that the engine will last for a greater number of hours without having to replace the piston too frequently, such as it is with a KZ-TM engines.
Going for 0.4-0.5 squish sounds like a massive risk to take, but…best of luck, please let us know how it goes

The spring that came with my Tillotson carburetor was a 42 gr, as soon as you try the 46gr you’ll notice the difference and you’ll be able to set the Low at 1:30 more or less (with the 42gr spring I had to have the Low at 1:05, so very, very lean.)
If you do test the 47gr spring, please let us know how it goes, I’m curious, you may have to go richer than 1:30
Looks as if you have a CRG Chassis, great choice!

[Mikkometalli (Mikko Härkönen)]

Thanks for all comments and tips

I measured - the rod hadnt developed play

Local machine shop honed the cylinder - it came out perfect - didnt have to go up in size. Iame sells piston with 0.02 intervals

Found out after googling a bit that in 50cc engines 0.5 has worked and on snowmobiles 0.6 has been the racers choice on squish. So machined the head to 0.6mm squish with 1 degree opening towards the plug. I was advised by local 2 stroke guru that the engine most likely now falls flat on high revs. It might need squish width reduction.

I also bought brand new cylinder head - I need to make comparison between combustion chamber volume after all machining. Have no idea what comp ratio is at the moment.

I will make a test and see if theres any head contact.

With 0.8mm there was no contact - my machining marks on the squish band were in pristine condition and there were no marks on the piston

Also pic of spring part numbers

[Peter (Peter Hake)]

Seems like the experiment is coming along nicely

It would be cool to test the engine on a Dyno and see the results of that tight squish.

Let’s see how it goes with the 47 spring

I was having fun this past weekend with the Super Shifter and that thing is a monster, the acceleration is out of this world, it keeps going, and going, I wonder what the top speed would be on a vey long straightaway, I’m doing around 140km/h on my local track, EGT around 650ºC

Definitely Low 1:30 High 1:45 Works perfectly with the 46 spring,

Best of luck with all the testing

[Peter (Peter Hake)]

Yesterday I tested the 48 gr spring (sorry, I had to do it ) and…
I LOVE IT !!!

[Muskabeatz (Evan Batt)]

Did the 48g spring require any tweaks to your jetting? What EGT were you seeing with setup?

What were the notable differences with the 48g vs. the 46g spring?

[Mikkometalli (Mikko Härkönen)]

Ok - good to hear - I will test the 48gr spring too

Squish test has moved on and piston to head contact started at 0.48mm. Just barely kissing the head

I have now set the squish to 0.65. Machined the squish angle 0.5` open towards the spark plug.

Had a talk with a local dynoshop owner - we´ll try to mount the kart to his dyno and see what results we get with stock squish/stock head vs 0.65 squish high compression head. He hasnt run any karts on his rollers so fingers crossed

I had a dnf last time, the clutch hub lost its splines → no drive. My fault - had noticed some play but didnt check on time what was wrong. Renewed pretty much everything inside right engine cover + clutch parts. So keep an eye on your clutch hub that it is seated tight. The material on the hub was softer than the drive axle so there was 0 wear on axle splines The new part had cast iron splines mated to the alu hub, cant tell from the old part was it all aluminum

The starter was full of crap - after cleaning the starter now engages every time

Fitted the selettra inginition but havent had time to drive/test

Noticed that iame kz screamer has the same clutch (?) or at least some of the parts. Kart shops offer ergal clutch plates for the screamer. Third the weight of steel. So ordered those - They should arrive in a week or two. I dont do standing starts so they should last just fine

[Peter (Peter Hake)]

No need to change anything, EGT is fine with the 48gr, and my local track has a very long straightaway, Top speed 142km/h and I’m only doing 13100-13200 Rpm on 6th gear, so I’ll Change sprocket and will try to get close to 14000Rpm on 6th gear, for sure will get to 145km/h, EGT around 650 at the moment, if it goes above 680, open the high a couple of minutes, although I’ve done 690 EGT in the past and nothing happened, only noticed it when I went home and downloaded the telemetry from the Alfano 6, just make sure the water temp is between 55 and 60, especially if the outside temperature is below 20.

Difference between the 42gr, 46gr, 48gr is the response of the engine coming out of the corners, 42gr is kind of sluggish, 48gr is awesome, it takes off right away!

[Peter (Peter Hake)]

Thanks for the info, let us know how the Dyno test goes, fingers crossed ( I’ll be surprised if you get anything above 50hp or above 28Nm)

[Mikkometalli (Mikko Härkönen)]

Ok had the kart on dyno today and got some results. We made some 25 dyno pulls and consumed about one tank of fuel

Dynoshop owner recommended to fit a lambda sensor so day before welded an insert to the exhaust. Glad I did because the motor was very lean on top. I wouldnt have noticed it out on the track. After few runs trying to correct the condition with mixture screw, changed the carburetor gaskets and the lean condition went away

We tested :

*0.65 squish high comp = best low down hp/torque. Falls hard after 12.5k
*0.65 squish standard head = a bit less hp/torque than the above, not the best numbers after 12k

*0.8 squish high comp = at the moment the best compromise. Still falls a bit on its face above 12k
*0.8 squish standard head = just makes less just about everywhere than the above

*1.3 squish high comp = best hp above 12k but doesnt have the low rpm torq/hp numbers of the 0.65 squish high comp
*1.3 squish standard head = all the power is near the rev limit. Doesnt match the above. Lowest power and tq at low rpm but sure loves to scream

*removing the 5mm thick spacer from exhaust flange improved hp curve above 12k rpm

*airbox lid + filter completely removed = minuscule power advantage - like 1hp
*empty airbox without the filter = the same as above. The airbox isnt the restriction in this motor - running without the box just makes an ear piercing induction noise - thats pretty much to it

The egt was a little bit over 500´C with 0.65 squish+high comp, egt went up as squish gap got bigger - highest egt was with 1.3 squish + standard head at 650´C

Couldnt test 1mm or 1.1 squish as had wrong gaskets with me

The picture included is comparison between 0.65 squish high comp (thin line ) vs 0.65 squish standard head.

I would like to have the power and torq of tight squish and top end of a loose squish

Future test : even higher compression ratio, see results with 1-1.1mm squish. The power gain most likely is not very much but the curve propably goes up everywhere. Should be pretty strong motor. Theres propably some hp in ignition advance

I will fit an lambda sensor kit. It showed to be a good tool for diagnosing whats wrong

All in all these squish/compression ratio mods didnt bring huge amount of power. Few hp or so. To get high rpm horsepower gains I would like to test a bigger carb or modify the throat to a bigger diameter. And make tests with shorter expansion chamber lenght

[Mikkometalli (Mikko Härkönen)]

Here are few comparisons

Thin line high comp 0.65 squish, thick line stock head 1.3 squish

Thin line high comp 1.3 squish, thick line high comp 0.65 squish

Thin line stock head 0.65 squish, thick line stock head 1.3 squish

[KartingIsLife (James McMahon)]

@Mikkometalli

Thin line stock head 0.65 squish, thick line stock head 1.3 squish

With the exception of this one (2hp difference) the peak values don’t vary too much, however the area under the curve sees a large gain with the tighter squish and or higher compression it seems like?

[hallkbrdz (Bryan Hall)]

Less seems to be more.

[Mikkometalli (Mikko Härkönen)]

Yes the tighest squish + high comp head made the most bottom end power. How ever after 12k this combo drops fast. I feel it would have been quite good set up IF we could have managed to keep the curve to the rev limit. We tried by shortening the expansion chamber to improve after 12k but it only improved a little.

I like screamer type engines so it might feel to me like it hits a wall with my driving style. Need to test it on track

I presume as the motor became more efficient air pump with tight squish + high comp - the carb throat became the limit after 12k - flow got too high and choked

Havent checked is boring out the throat possible with the carb - does bigger diameter move aux fuel supply hole to a place where it doesnt work. Might be possible to keep same location by pressing in a small dia pipe

Havent checked does Tillotson make same type but bigger carb. That would be nice - easier solution

[Peter (Peter Hake)]

Thanks a lot for sharing, quite admirable all that testing.

From my humble experience, trying to get more power, on the Low and high at the same time, is an extremely difficult thing to do, I spent some money trying to improve a DD2 engine a few years ago, to make a long story short, you will end up having to change too many parts in order to accomplish a significant increase in power, almost to the point where it is no longer the same engine, once you go for a bigger carburetor you’ll most likely end up having to replace a number of things, even the exhaust pipe.
It is and will always be a compromise between the Low and the high, maximizing both of them is almost impossible, you’ll always compromise either one and from the tests you’ve done, which resembles the tests I did with the DD2 engine, you may get a few extra hp here and there, but nothing too crazy.

Also, having too much power, especially on the Low, ends up being wasted (I tested a Mega R01 engine with 65hp at 6700rpm and a massive 73Nm of torque at only 5800rpm) but with so much of everything, your rear wheels spin like crazy, it is not easy controlling so much torque.
And of course, once you change too many things and hopefully get a significant improvement on Power, you may find that the reliability of the engine has gone down the drain.

I do love the fact that you used a Lambda, I’ve been thinking about that just to fine tune the carburetor (EGT doesn’t seem to be too precise)
If I may ask, what Lambda did you use? And what lambda reading were you aiming at 0.9-1.0 ?
Ive seen that Mychron and Alfano sell Lambda sensors plus the respective modules to connect to, although not that cheap.

Once again, thanks for sharing the results, love seeing them!