We race in the Mini class with both the IAME Swift and the Vortex Mini ROK engines. Recently, ROK changed the rules and are making us change from the Delortto carb to the Tillotson carb. Our engine runs great on the delortto and poorly on the Tillotson! It floods easily which makes it hard to start, then tuning the needles has been anything but normal. We started with the same basic settings as the Swift, half turn out on high and one and a half on the low, but realized that’s not gonna work. It’s slow to respond to the throttle and bogs out of the corners. With more high, like 1-1/14, it’s much better. We feel like it now needs more fuel on the bottom end but that makes the flooding worse. ( I had heard the vortex made this move to improve starting!)
So, has anyone made this carb change and what ballpark needle settings are you working with?
Here’s some numbers, everything else is the same, tires, fuel, gearing….
Max Rpm 14,080. W Tillotson, 15,100 Delortto
EGT 1142 Tillotson 1190 Del
Needle pops off at 16, holds forever at 10 psi
It was a brand new carb out of the box and over the past few weekends we’ve had it taken apart, cleaned reset and all new gaskets and diaphragm replaced by three different and well experienced Kart team owners!!
It’s very discouraging and expensive! Today I was told by one of the team owners that it’s probably a defective carb right out of the box……what do you all think?
Maybe this will help.
It was more for the Tag Senior engine, but the tuning explanation is spot on.
Thanks for sending that article along Greg!
As we are testing for Rok Vegas in mini I would say you need to take 5 to 8 minutes out of the high and give it way more on the bottom. Do not try and apply baseline Swift settings this motor. It won’t work.
There is no standard 1 1/4 and 1/2 aka 30 minutes for any Swift motor. They all are a little different. We race one nationally that likes 148 on the low even when it is summer in New Castle and our teammates motor likes it at 136. You should be tuning more with your data, high and low EGTs and low corner speeds and if you can run a lamda sensor to see if you are actually rich or lean it will help you immesly. It also helps make sure it is not the squishy bit in the sear.
Carbs are generally not defective especially if you have put a new kit in it. You can always run it on you swift and see hiw it performs.
Thanks for the reply even though I’ve not seen it until tonight! So, the story moved on with my dealer warranting the carb we bought. After that things absolutely fell into place. Tuning the ROK settled down but we still are learning. It is definitely different than the Swift….you’re right none of the settings cross over!
We have been able to get much better performance with this carb and the ROK now and we’re getting better.
I do have a question based on your reply, what egt temps are you shooting for on high end and low end? Also, what are you using for your data, Alfano or Mychron…I’ve heard there is a 50 degree difference between the two!
Lastly, are you Troy’s dad? If so we’ve met in orlando at the Benik tent.
Either way, thanks for your help!