I realize there’s a very similar topic here but I didn’t want to hi-jack that thread. I’ve found it very difficult to find flex length suggestions for KT100 using the SR-Y pipe. I think it’s because WKA adopted it and then moved away from it pretty quickly. Our local group still runs them and I’m new enough to karting that I just purchased a pipe used from someone and mounted it the way they had it.
I’m finally getting past the large scale tuning items with the KT100 and I’m getting down into the details more. In checking today my total flex length (piston face to end of flex) is currently 9.75 which is .25 pas the min. I’m absolutely going to put together a flex section that is the min and test it but was curious if there is any testing info / history here that anyone could share? I’m over weight in my class and getting eaten up at the end of the straights and I’m curious if my longer than min flex is part of that equation (weight is the big factor but every little bit counts).
Also curious if anyone has insight on why when the SR-Y pipe was introduced by the WKA that it’s intended flex length was 8.5 and was later changed to 9.5?
I used to run FYSR back in the day and I do not remember a flex length but I can find out when I see Haddock.
The good news is that I have a header and flex piece that I ran. The flex measures 4 inches.
Being too long on the flex will hurt the engine up top as you described.
Measure your flex piece first and we will go from there.
I’ll get with haddock and get the answer for you- he was the one that wrote the rules and continued to do so for the class in Vintage where they run the Current SR Y exhaust in Yamaha Limited.
I run, and our club still races that pipe. I have three flex sections cut to min, max and middle flex legnth lengths, and sometimes swap if I feel the need.
Can’t speak to flex tuning for a weight disadvantage directly, buy you may want to try the max legnth flex. More bottom end may help you pull off the corners a bit better and minimize that speed difference at the end of the straights, but the legnth of the straight probably influences that more.
I run the longest length flex at my local track, and I seem equal to other karts. Previously on the shortest length I was giving up time coming out of corners. Subtle, but noticable difference.
@Andrace What is the min and max length you are allowed to run? We have only a min specification at 9.5" (from the face of the piston) but no max with our club.
Last week I had several sections cut that I will test back to back in a test section last week, but any data I’ve got going in makes the testing that much more focused.
Hi. Im considering swapping out my RLV-L2 pipe for the SR-Y pipe. Only because the RLV L2 pipe doesn’t fit my vintage Margay kart well. It sticks out the back past the bumper. Just doesn’t look right. But i love the power band. How does the SR-Y pipe compare? Any advice would be appreciated.
I would not swap if I were you. SR-Y is a glorified 4 hole can with a little more mid range, it’s not a proper expansion chamber pipe. There will be a noticeable performance drop if you switch.
My understanding of SR-Y is that it was created just so that Sr. Karts would run the same lap times as Jr with 4 hole can…basically it made up the deficit of the 30 lbs added when drivers went to Sr. That’s exactly why our club ran it. It’s easy on motors like a can but it’s not a big power pipe.