Snowmobile
Measure Report
NOTE: This information is only for Yamaha distributor’s use.
MR No.: MRS07005
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Sep 13th 2007
H. Echizen
MODEL PZ50 (8GC1/2, 8GK1/2, 8GN1/2, 8GP1/2, 8GJ1/2, 8GR1/2)
SUBJECT Poor engine starting in cold temperature
PROBLEM:
The engine is difficult to start at below –20 degrees [C].
CAUSE:



When trying to start the engine at –20 degrees [C] or below, the decompressor is kept
activated even after sufficient cranking speed has been achieved, resulting in
insufficient compression due to leaking air-fuel mixture.
Air-fuel mixture becomes lean in the temperature range between +5 and -25degrees
[C].
Around –30degrees, the ECU becomes turned off instantaneously due to the battery
voltage reduced below the minimum working voltage of the ECU.
FACTORY REMEDY:
YMC has incorporated the following countermeasures from the beginning of all 2008 year
PZ50 models.
 Modify the decompression spring in order to achieve enough compression for starting
the engine.
 Reprogram the ECU to optimize fuel injection volume in the temperature range between
+5 and -25 degrees [C].
 Reprogram the ignition control program to keep proper ignition timing.
APPLICABLE RANGE:
Above countermeasure has been incorporated from 2008 production units.
FIELD REMEDY:
If your dealer encounters a similar problem, please instruct them to install countermeasure
kit.
YAMAHA MOTOR CO., LTD.
MR No.: MRS07005
AFFECTED RANGE:
All 2007 year PZ50 models are affected:
Model name
PZ50W
PZ50GTW
PZ50FXW
PZ50MW
PZ50VTW
PZ50MPW
Code
8GC1
8GC2
8GK1
8GK2
8GN1
8GN2
8GP1
8GP2
8GJ1
8GJ2
8GR1
8GR2
Spec
US/CAN
JPN
US/CAN
EUR
US/CAN
EUR
US/CAN
EUR/JPN
US/CAN
EUR
US/CAN
EUR/JPN
Affected range
8GC-000232 to -001916
8GC-001917 to -001951
8GK-000259 to -004437
8GN-000541 to -005863
8GP-000125 to -005964
8GJ-000051 to -003498
8GR-000328 to -003255
PART INFORMATION:
YMC will provide the following countermeasure kits for field remedy:
For Mountain models (PZ50MTW 8GP1/8GP2):
90891-50145 PZ50MTN Description
ECU kit
ECU
Spring de-compressor
Gasket, cylinder head cover
Part number
8GP-8591A-10
N/A
8GC-11193-00
Qty
1
2
1
For other models:
90891-50146 PZ50 ECU Description
Part number
Qty
kit
ECU
8GC-8591A-10
1
Spring de-compressor
N/A
2
Gasket, cylinder head
8GC-11193-00
1
Notes:
1. The ECU differs between Mountain and non-Mountain models. The
decompression spring and cylinder head cover are common for all models.
2. The modified ECUs are available also individually as spare part for ’08 models.
The decompressor spring is Not, being preassembled in the camshaft assy.
Part identification:
ECU:
ID mark:
For mountain models (90891-50145):
Old: 8GP-00 / New: 8GP-10
For other models (90891-50146):
Old: 8GC-00 / New: 8GC-10
YAMAHA MOTOR CO., LTD.
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MR No.: MRS07005
Interchangeability:
It is interchangeable as a set.
Part supersession:
ECU:
2007 ECU has been superseded by 2008 ECU at each parts center.
Decompressor spring:
The decompressor spring preassembled in the camshaft assy has been
superseded at each parts center (as 2008-spec cam assy).
Availability:
The countermeasure kits will become available from YMC parts centers from
September 2007.
SERVICE PROCEDURE:
Decompression spring replacement
1) Remove the cylinder head cover according to the service manual.
2) Remove the decompression spring as shown photo 1~2.
Step1)
Remove
Step2)
Pull
Photo 1
Photo 2
3) Install the new decompression spring as shown in photo.
Insert to hole
Photo 3
Photo 4
YAMAHA MOTOR CO., LTD.
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MR No.: MRS07005
Check these hook points
Check the decomp operation
Photo 5
Photo 6
4) Check the decomp operation as photo 6. If works correctly, the weight return to initial
position like a photo 6.
5) Re-install the cylinder head cover and other exterior parts according to the service
manual.
WARRANTY:
YMC will extend the warranty period regarding the failure herein until the end of December
2009, whether the affected unit is within or out of its warranty period. To qualify for the
warranty, please submit your warranty request with the following conditions:
Warranty period:
Effective until the end of December 2009
MOD No.:
S203
Primary failure part No.: Any of the following part numbers will be accepted as the
primary failure part number:
90891-50145, 90891-50146
8GC-8591A-00, 8GC-8591A-10
8GP-8591A-00, 8GP-8591A-10
8GC-12287-02
Problem Code:
B3
Job code:
S197 (Replace Decomp spring and ECU.), 1.1 h
YAMAHA MOTOR CO., LTD.
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