I’ve recently acquired an older microsprint that has a Rotax 257 on it. I know that this engine is used in superkarts, so I figured I chance a tech question here, since I may be putting it on a kart anyhow…
1) Engine is set up for alky, or so I’m told. Other than liberally soaking it in Marvel Mystery Oil and replacing all the rubber bits, anything I should look for before firing it up? Piston doesn’t seem scuffed when viewed through exhaust port and has compression.
22) Intake book is knackered…. is there a good source for replacements?
3) The clutch cover and cable assembly seems to be missing, with a flat plate mounted. The shift mechanism is connected to a lever with a push-pull cable and seems to shift fine through the gears, but I’d prefer a clutch actuator be there for safety reasons… I know you’ll want pics, but is this as simple as replacing the missing cover and lever and cable? Why would it be removed to begin with?
4) There’s a pulse fitting in front of the clutch cover / below water pump outlet. That was routed to a Tee system that I assume acted like a pumparound….how do you superkart guys typically plumb a tank? This micro has a right-side tank that’s floor level.
5) I’d like to switch to water-wetter vs. antifreeze — any issues?
Guess that’s it for now. Appreciate any pointers. Regards, ~Ted
The fitting you are talking about is the pulse line for the fuel pump. I run a Dellorto and go straight off the Mikuni round pump to the inlet. Other carbs may vary.
Water wetter is fine.
For the intake boot and clutch part here’s the secret. Search ebay for ATK 250 as this engine was used on ATK dirtbikes here in the states. I know there is a boot and clutch cover there right now. As they have been listed for some time you might want to deal with the them for a better price. It worked for me on the couple items I needed for a spare motor.
These are strong little motors and last well when kept a little rich. Shift gently and take care of the gearbox as gears are expensive and at times hard to find.
Thanks, Dennis…. I’m going to look through my spares to see if the clutch cover assembly is in there…. It’s going to be tough for me to tell what the spares for the 2 “free” 125’s I got are and what’s for the 257. I will try to post pics here.