Open KT Piston


New member
I'm putting together an open kt and I'm wondering what piston to use for a 54mm cylinder and if there are any spacers needed to correct port timing. Also what carb would be a good choice for this. Thanks
You can use either a Sudam piston, the new Burris piston or if your lucky, an NOS Wiseco piston. Both the Burris and the Wiseco pistons do not require a spacer but, the Sudam piston does. That is, if you use the stock rod. If you change out the stock length rod with one or Kermit Bullers rods, I think you can run the Sudam piston with no spacer. Might be some minor machining needed to be done. On the carb, I hear a Tillotson HL360a converted to Alky does wonders. I know of some that run duel carbs on open KT's.

Brian #89
KT rods are 100c.m. and so too are lots of other 100c.c. engines, the others are usually better material and made better, I would recommend finding one and making it work.
What is the recommended piston to cylinder clearance on a kt? Also for the Burris piston do you have a base gasket and head gasket thickness that would be correct? I imagine the base gasket thickness may also depend on the porting of the cylinder.
Base gaskets can be doubled and head gaskets are available in lots of sizes, but use will always be determined by port timing. also if you are building a true open engine and are not limited by a stock stroke rule, a 54 m.m. crank along with the big piston can get around 131 c.c.'s.
no expert , heres what I believe if you have a stock an put a big bore piston in you won't change much port wise.
piston should met standard specifications.
that said piston skirt length may need adjustment via measuring the skirt to piston pin depth , replicate this and little should change.
now it may not be the best for an open ,. but should run as well as it had previously . Of course base gasket will affect port timing and subsequintly piston skirt length as well as piston to head clearance so if you change anything here, everything changes. Keep everything the same all should be good . There is no one size fits all base gasket or head gasket , pretty engine specific. of course you want to be sure everything clears. ring locating pin location is critical it needs to be on intake side. clearance.003 jmho
What I have is an engine I got from someone. It is just the bottom end, cylinder and head disassembled. I figured I have most of the pieces so I might as well put it together. It has the yamaha rod in it and after cleaning up the cylinder it measures 54.02mm. I don't have the previous piston that was in it and there's no spacer that came with it. I think I may just bore it out to use one of the burris pistons.
gonna stick my neck out a little farther. adjust gasket thickness so piston is just at top of cylinder. then set squish with head gasket thickness. could also do per old ikf tech procedure with light check of port, no tech tool needed.or have a pro do it roughly 125.00
I want thinking about having an engine builder do it but was wanting to take on the challenge. Worst thing that could happen is a screw up and it sits on a different shelf in the shop. Lol
not really that hard. the hone or bore is problem, 1 you need a ridged hone so the stones do not catch the ports.
if its all stock and you are not concerned with tech it should be fine.
use solder in spark plug hole roll engine over remove and measure that's your squish clearance. .035-.020 for a pipe
book called racing the kt100 would give you all the info you need.