Rotax 125 MAX AdjustableVariableExhaust
Introduction:
This information is in addition to the valid repair manual.Safety requirement has to be taken from the valid repair manual.
This information is only for internal usage.Without commitment to advise modifications.
BRP-Powertrain
2010.04.09
Presentation Rotax exhaust valve – only for internal use 3Without commitment to advise modifications
Installationn 1.
Clean the cylinder with brake cleaner and check impulse bore for cleanliness. (visual)
Presentation Rotax exhaust valve – only for internal use 4Without commitment to advise modifications
Installationn 2.
Clean the Exhaust valve with brake cleaner and scotch brite and check the total length of the exhaust valve. ( 72 +/- 0,3)
ATTENTION: Stud screw has to be locked with LOCTITE 648
Presentation Rotax exhaust valve – only for internal use 5Without commitment to advise modifications
Installationn 3.
Insert the exhaust valve as shown on the picture and assure free movement of the exhaust valve.
Presentation Rotax exhaust valve – only for internal use 6Without commitment to advise modifications
Installationn 4.
not correct – gasket interferes contact between valve and cylinder
Apply the gasket on the cylinder and assure metallic contact between exhaust valve and cylinder.
correct – metallic contact between valve and cylinder
Presentation Rotax exhaust valve – only for internal use 7Without commitment to advise modifications
Installationn 5.
Apply the valve rod housing to the cylinder and check the exhaust valve for free movement.
In case the exhaust valve piston get caught, check the position of the valve rod housing.
Presentation Rotax exhaust valve – only for internal use 8Without commitment to advise modifications
Installationn 6.
Apply the o-ring to the stud screw.
Presentation Rotax exhaust valve – only for internal use 9Without commitment to advise modifications
Installationn 7.
Apply the bellow on the valve housing and check the sealing surface for proper sealing. The small hose spring at the bottom of the bellow has to be installed correctly to the groove of the bellow.
Presentation Rotax exhaust valve – only for internal use 10Without commitment to advise modifications
Installationn 8.
Hand tighten the exhaust valve piston to the stud screw and adjust a total length of 73,5 +/- 0,3 mm
Torque the exhaust valve with 10 Nm to the cylinder.
10 NM
Presentation Rotax exhaust valve – only for internal use 11Without commitment to advise modifications
Installationn 9.
Apply the hose spring with Rotax special tool 276070 to the bellow. Assure free movement of the exhaust valve and make a visual check for the correct installation of the hose spring to the groove.
Presentation Rotax exhaust valve – only for internal use 12Without commitment to advise modifications
Installationn 10.
Apply the compression spring to the Exhaust Valve and mount the Valve Cover by means of the spring clip to the housing.
Presentation Rotax exhaust valve – only for internal use 13Without commitment to advise modifications
TroubleshootingR.A.V.E (ROTAX ADJUSTABLE VARIABLE EXHAUST)
Presentation Rotax exhaust valve – only for internal use 14Without commitment to advise modifications
Engine concept Rotax engine 125 MAX
0
2
4
6
8
10
12
14
16
18
20
2230
00
4000
5000
6000
7000
8000
9000
1000
0
1100
0
1200
0
1300
0
1400
0
1500
0
1600
0
1700
0
1800
0
1900
0
2000
0
engine speed [rpm]
engi
ne p
erfo
rman
ce [k
W]
125 Max 100cc
5-8% oil2% oil
n Rotax 125 MAX versus typical 100cc kart engines
Presentation Rotax exhaust valve – only for internal use 15Without commitment to advise modifications
Engine concept Rotax engine 125 MAX
0
2
4
6
8
10
12
14
16
18
20
2230
00
4000
5000
6000
7000
8000
9000
1000
0
1100
0
1200
0
1300
0
1400
0
engine speed [rpm]
perf
orm
ance
of e
ngin
e [k
w]
Exhaust valve closed till 7.500 rpm
Tuned exhaust pipe in combination with ignition timing
7.500 rpm – 12.500 rpm
Ignition timing
12.500 –14.000
rpm
n Performance characteristic of Rotax engine 125 MAX
Presentation Rotax exhaust valve – only for internal use 16Without commitment to advise modifications
1) Exhaust valve
At 7.500 rpm:
Exhaust valve opens through raising pressure in the exhaust system
Till 7.500 rpm:
Exhaust valve closes by compression spring (adjustable)
Low exhaust port timing = longer use of combustion energy
exhaust valve closed exhaust valve opened
High exhaust port timing = shorter use of combustion energy
Presentation Rotax exhaust valve – only for internal use 17Without commitment to advise modifications
1) Exhaust valve
The raising pressure in the exhaust system causing the exhaust valve to open.
n Pressure in the exhaust system (schematic diagram)
1 2 3 4 5 6 7 8 9 10 11 12
engine speed (rpm)
pres
sure
exhaust valve closed exhaust valve open
Presentation Rotax exhaust valve – only for internal use 18Without commitment to advise modifications
Leistungskurven mit geschlossenem und offenem Auslaßschieber performance graphs with closed and open exhaust valve
0
2
4
6
8
10
12
14
16
18
20
223.
000
4.00
0
5.00
0
6.00
0
7.00
0
8.00
0
9.00
0
10.0
00
11.0
00
12.0
00
13.0
00
14.0
00
15.0
00
Motordrehzahl [1/min.], speed [rpm]
Motorleistung [kW], performance of engine [kW]
Leistungskurve 2, performance graph 2
Leistungskurve 1, performance graph 1
1) Exhaust valve
Optimal opening timing 7.500 rpm Opening timing
too lateOpening timing too early
n Correct opening timing of the exhaust valve
Presentation Rotax exhaust valve – only for internal use 19Without commitment to advise modifications
1) Exhaust valve n Standard setting of the exhaust valve
5 mm = approx. 2 inch
n Adjustment of the exhaust valveè at the race trackè engine must have operation temperatureè accelerate from 5.000 rpm at full throttle
as soon as exhaust valve opens, noise is changing significantly.
è exhaust valve has to be adjusted to open at 7.500 rpm
n Adjustable rpm range for exhaust valve openingApproximately +/- 300 rpm
Presentation Rotax exhaust valve – only for internal use 20Without commitment to advise modifications
1) Exhaust valve Re-adjustment of the exhaust valve
… is just necessary if the è cylinder or the height of the cylinder (base gasket) has been
changedè condition of the isolating mat in exhaust muffler has changed
(worn).
Presentation Rotax exhaust valve – only for internal use 21Without commitment to advise modifications
1) Exhaust valve –Troubleshooting
n Problem: Missing performance till 7.500 rpm (“bottom end performance”)
n Possible reason: Exhaust valve does not completely close.
n Solution: Check assembly of exhaust valve. Exhaust valve has to touch the cylinder surface in closed position. Metallic noise at closing has to be noticeable.
Exhaust valve does not close completely
wrong
Short use of combustion energy = high exhaust port timing
correctExhaust valve completely closed
Long use of combustion energy = low exhaust port timing
Presentation Rotax exhaust valve – only for internal use 22Without commitment to advise modifications
1) Exhaust valve - Troubleshooting
n Problem: Delayed throttle response out of the curve.
n � To the curve: Engine revs 12.500 rpm, exhaust valve is open.
n � Middle of the curve: Engine revs drop to 9.000 rpm, carburettor slide is closed, exhaust pressure drops àexhaust valve closes.
n � Out of the curve: Engine revs 9.000 rpm, carburettor slide open – delayed response of the engine…
Track sector:
1
2 3
Presentation Rotax exhaust valve – only for internal use 23Without commitment to advise modifications
Ski-Doo®
Lynx™
Sea-Doo®
Evinrude®
Johnson®
Rotax®
Can-Am™
© 2006 Bombardier Recreational Products Inc. All rights reserved.® ™Trademark of Bombardier Recreational Products Inc. or its affiliates.