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

2 Stroke Kart Engine Forums
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Never knew that Tillotson might have issues with cornering :open_mouth: I have thought that because theres no float flapping around its impossible to have problems. Good you brought up your experiences :+1:

Since you mentioned its happening while cornering to the left - I suspect the fuel gets pulled out of the slot thats on needle side. That slot feeds both high and low jets. By quickly shifting to 4th the rpms drop - the motor doesnt need as much fuel as on lower gears so it is able to run with what ever is left on the slot :man_shrugging:

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Im not sure is it the reason but I would test it by doing something that limits fuel getting out of the slot. I would try by gluing a piece of metal sheet with epoxy - a fence to the wide channel. Tillotson has secured some planking plugs with epoxy so that should work just fine. I drew an example to the channel with a marker. Like a baffle thats used, for example, in oil pickups in race and rallycars

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I would leave a 1-1.5mm gap between fence and the channel so fuel gets in and out but not so quickly. Just to see does it help - does it cure the problem on left hand corners. The gap shouldnt need to be larger as tightest point in fuel delivery is the needle valve hole. And its already supplying fuel to the aux fuel bore via throttle shaft. If the baffle doesnt work just pry the piece off. Having a lambda would tell right away is the engine running lean or what

Yeah the quest for power never ends :rofl: The reed cage insert will become the next tight spot ie restriction if moving to carbs over 36mm or so - it needs to be ported / enlarged /removed. Stock has somewhat oval opening after casting/machining, measuring around 34mm x 36mm. The reed flaps need examination as well - do they open enough at higher hp levels

Good that you will test the 36mm dellorto :+1: It will be immediatelly evident was the tillotson the restriction.

Im pretty much set on lectron carb - if it works on corners that is. I hope I get some email back from the factory. After reading and watching bunch of videos guys having the thing on bikes I think it will do the job just fine. I will go minimum 40mm

Ok thanks for pointing out - 17k would be awesome ! I´ll try to make it happen :+1:

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82

Could you run the Tillotson upside down? That might void any issues with air pockets and fuel slosh. Any air would be naturally push out of the jets being the highest points leaving no place for the fuel to slosh to. Being a pumper, there is no issue with orientation.

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No way in hell at 175 is going to hold together at 17k. Which is good because it’s not going to get near that without some crazy porting, or a nasty timed downshift. That’s a big heavy slug in there to be slapping about at 280 times a second. It would be good for a dyno pull and a YouTube video maybe, but poor on the track.

Speaking to the overall concept, typically the diaphragm pumper carb design works well in karts which is why it’s stuck around. The design holds up well with bigger fuel demands such as 250cc methanol karts which are pulling over double the fuel flow of a 175 as methanol generally requires about 40% more fuel.

But it does have challenges with gear changes. I’d say the next logical step might be a 39mm or 42mm slide.

You could try adding the likes of a Dellorto pulse fuel pump to ensure demand fuel is available on the pump side of the needle.

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Wow, the quest to keep learning never ends! Which I love btw.

Thanks a lot for taking the time to explain as well as the photo. I’m thinking about what you’ve explained and it’s definitely worth trying, just to see what happens, if it works I owe you a beer or two :beers: for sure making the Low richer doesn’t work, I’ve tried a billion times and the engine just has no power on all corners, even a tiny bit richer is noticeable, it wasn’t so sensitive with the X30 engines, I’ve had a few of those, this 175cc is more challenging.

At the moment we’re are experiencing a heatwave down here in the South of Spain, it happens every year during the summer, so I’ve got to wait, it’s way too hot at the circuit, I’m also waiting for our dear Dellorto carb, most likely I will try that one first and see what happens, if everything goes well, that’s it, I’m keeping the Dellorto, especially if I manage to get to 150km/h or more :muscle: (the Dellorto works very well with the DD2, I like it, very reliable - although the Tillotson and Tryton carburetors of the X30 have been very reliable as well.)

Most likely a Lambda sensor will be next, just for curiosity I’ll spend the money - we only live once :man_shrugging: (A much older friend of mine who’s retired, spent his whole life working on classic cars in the UK and he’s been a karting enthusiast since he was a kid, spends his days buying old engines and fixing them, I guess he just can’t let go of the tools and the greasy hands plus the satisfaction of fixing engines, mainly bike engines these days, At this rate, with all the information in this forum, plus my curiosity, I fear I’ll end up like him and like you, he seems very happy :smiley: He races with a rotary engine, an Axiro XR50.)

Lectron has been around for many years, great carburetors, not cheap though, let’s hope they write back and let’s see what happens :+1:

As soon as the heatwave goes away and I get the Dellorto I will comment on the experience, looking forward to it.

@KartingIsLife I’ve never ever seen a diaphragm carburetor on a shifter, that’s new to me, I guess they thought it would be “easier” to play with on the day of a championship, that’s what I’ve heard, as opposed to be changing jets, I don’t know?
I think in most tracks the Tillotson works fine, but sometimes it doesn’t. The track I go to goes uphill and downhill, and that’s when I get that issue, I have to shift very quickly from 2nd to 3rd and on to 4th, as I previously said, once I’m on 4th it’s perfect, and it’s always turning left :man_shrugging: Turning right it’s no problem, I can rev 2nd and 3rd as long as I want to, plenty of power there :man_shrugging: We’ll see what happens with the Dellorto.

I’ve thought about the 17000rpm as well, I don’t know anyone that’s purchased the 175 without a limiter, so I’ve no idea if it comes with a different plug, probably not very reliable but they do sell it like that, or at least some dealers do give you the option to choose :man_shrugging:

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I don’t think you can have a Tillotson upside down, :thinking: well I guess you could but you’ll have to adapt it, you’d have to move the hole…:thinking:

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If you want to go DEEP down the rabbit hole you could try something a speeduino standalone ECU to control ignition in a very finite manner, even controlling it via throttle position. What I like about this is that you may find gains in power without sacrificing entry speed and can even tune it to optimize power delivery out of the turns for chassis stability.

The fuel issue is an interesting one. For sure pump diaphragm carbs seem to struggle with the kind of abrupt start/stop throttle application of a shifter. It’s something Tillotson worked hard on during development of the 175. But it’s usually been more of a fuel curve response thing vs running dry.

I can’t recall the exact setup on the 175, but if it’s similar to the likes of an OK with a pulse hole, you can usually rotate the feed cage and flip it upside down.

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Thanks!
That’s an interesting suggestion (speeduino standalone ECU) :thinking: I’m going to look into it, and also since you’ve mentioned it, I guess maybe in order to test the Tillotson upside down, if all I have to do is rotate the feed cage, then I will try that next time, easy peasy :+1:

Your previous idea, a Dellorto pulse fuel pump, makes sense and I’ve thought of that a few times, that could work. We will see what happens with the Dellorto carburetor, if it works fine and on top of that I gain top speed, that’s a win-win situation. I could use the fuel pump that comes with the Dellorto to try it out on the Tillotson :+1:

A while ago I exchanged a few messages with a guy that I believe is quite familiar with the 175, SRS Engines, I believe he’s in Texas, let me find the message he sent me and I will upload it in a few minutes. Let me know what you think please.

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Yeah that’s John Sefcik I think? Very well known tuner. There’s actually some 175cc (SKUSA Spec) dyno charts from him on the forums here.

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Yeah, that the guy, John! Very helpful, here is the message he sent me

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