I thought I would start a discussion to give others the heads up on what chassis mods to do and where I have found useful links to get started on the 4SS class
I've setup my 4ss kart with a 2015 Arrow X3 Vegas kart and Briggs and Stratton LO206.
Running the factory 4 stroke engine mount from ikd, I am choosing to run the engine "close" to the main rails of the chassis, this is in hope that it will reduce the stress the chassis feels as I rail kerbs.
I'm running the clutch as an "in-board" setup where the sprocket is closer to the engine cases. This is also in hope of reducing the fatigue on the main bearings.
To do this on the Vegas chassis I had to move the seat over 20-30mm from a standard 2t kart engine setup. This was done with a few wallops to the main seat stays with an 8lb sledge hammer and then re-drilling the front holes of the seat.
I ended up buying a chain breaker/joiner to extend the available chain length to 114 links. Which works for the stock drive sprocket.
Testing will commence next weekend and should be able to update you all with carbi settings and starting gearing for most tracks
After a day at the track the engine is run in and after a lot of trial and error, the carb settings are feeling good.
I had to re-level the float heights in the bowl as they were set too high to the point where the engine was dumping excess fuel into the overflow bottle. 20-21mm from the edge of the carb to top of floats when inverted was the final setting. Needle position in P3 worked best.
Drive sprocket was changed to a 20t. I feel like 20-77 will be very close to the start gearing for higher top speed tracks. This many teeth required a very long chain at 120 links. It will be interesting to see how long the multiple re-joins in the chain last.
Thanks for the info!
I plan to run a Torini TX250 Supermaxx when i replace the KX21in a couple of months. Finally a higher powered 4 stroke class!
Im also on an X3 chassis, Will update once i have something useful to add.