Setting Of The Exhaust Valve Timing (Only Fr 125 Max) - Bombardier-Rotax FR 125 MAX FR 125 Junior MAX Installation And Operator's Manual

Operating Instructions FR 125 MAX, FR 125 Junior MAX and FR 125 Mini MAX

9. Setting of the exhaust valve timing (only FR 125 MAX)

Engine performance graph will differ with a closed (performance graph 1) or open (performance
graph 2) exhaust valve. The best performance characteristic of the engine will be achieved when
the opening time of the exhaust valve is at the intersection of the two performance graphs.
If the exhaust valve opens too soon, the engine acts as per performance curve 2 (for open exhaust
valve) which gives less performance at this r.p.m. range, and you loose
acceleration potential.
If the exhaust valve opens too late, the engine acts as per performance curve 1 (for closed exhaust
valve) which at this r.p.m. range gives less performance, and you loose acceleration potential.
The engine reaches maximum performance even with the exhaust valve wrongly adjusted, but you
loose performance and acceleration potential.
Motorleistung [kW],
performance of engine [kW]
26
24
22
20
18
16
14
12
Leistungskurve 1
10
performance curve 1
8
6
4
2
0
Diagram 2
Note: The opening of the exhaust valve is clearly audible. The bigger exhaust timing
results in a higher sound pattern.
Note: The exhaust valve should open for kart operation at the engine speed of 7500 r.p.m.
Note: The correct setting of the opening time of the exhaust valve has to be determined at
kart operation.
Seite/page 98/108
Leistungsverlust bei falschem Schieberöffnungspunkt
Performance loss at wrong exhaust valve timing
optimaler Schieberöffnungs-
zeitpunkt / optimum valve
opening point
Schieber öffnet zu
früht / valve opens
too early
Schieber öffnet zu
spät / valve opens
too late
Motordrehzahl [1/min.], engine revolutions [rpm]
performance and
Leistungskurve 2
performance curve 2
Ausgabe/edition 09.2003