It's sport tunnel all mods inside the engine OS OEM parts.Stock on the outside.The brass lining is a OS OEM part.IMPBA SCREWED THiS CLASS.iT WAS STOCK CLASS BACK IN THE DAYS AND SOMEONE HAD IT CHANGE IT.NO name here.
Dave
Back in the day the Sport .21 tunnel class was "never" was or intended to be a "stock" class in IMPBA.....Tommy Lee and myself , at the request of Dick Tyndall wrote the current Sport .21 rules in 1995[I think}.....We wrote the Sport .21 rules "intentionally" to remove the motor teardowns used in NAMBA 3.5 OPC Tunnel racing....
That is what precipitated the Go - No Go gage for only the carb and exhaust for inspections.....If you can't get the fuel in and the exhaust out motor mods are pretty much a waste of time....
Over the years that has been proven....The 70 MPH pass that Tommy and David was made with a "NAMBA LEGAL" O.S. .21 outboard.... There are no tool marks inside that engine....period....David has just learned how to put a motor together...
The 70 MPH pass was the whole package ......boat , motor , prop , set -up , weather and driving it through the lights.....the stars all lined up that day and shazaam 70 was the result.....The motor was probably less than 50% of that result....
The inspection gage size numbers were chosen to be inclusive of all [3] 3.5 outboards produced at that time [1995] K&B , O.S. , and Thunder Tiger ......
At that time we wrote the rules there were probably only 8 people in the world of RC boat racing that really knew exactly what a "stock" K&B 3.5 outboard was....K&B made no less than 10 different rods , 10 P&S's , 2 lower units , 3 flywheels , 2 carbs ,2 prop bearings , 2 crankshafts , 2 head buttons , paper gaskets...aluminum gaskets.....etc etc etc ....you see the problem here????...NAMBA teardowns and inspections were a nightmare....
As far as I know there are only 2 of us still alive that know what K&B parts went into a "Stock" K&B motor....
Question.....Why would anybody want to screw with the Sport .21 rules???? The Sport .21 class has proven itself to be probably one of the most successful classes in IMPBA....Even with $550.00 motors it is still thriving....
Don't try to legislate your inability to compete because you cannot learn to make a boat go fast....that is not a rule problem.....get off the damned keyboard and go testing....
To answer Kris's question....Put in a RG sleeve.....if the motor is not coming apart it is a moot point.....