1980 RD 350 LC (4L0) problems / modifications.

During '80, the RD350LC had problems with exhaust studs breaking, exhaust pipes craking, acceleration problems (mid-range misfire) and too rich oil pump. These pipes breaking were the result of engine movments and too fragile pipes.

To resolve these problems, YAMAHA propose during '80 to replace pipes (reinforced) under warranty, new carbs settings and new oil pump setting.

'81 & '82 RD350LC models were sold with the following evolutions: new cylinders, new carbs (stamped 4L0-01 instead of 4L0-00 for the '80 one), new exhaust mounting on cylinder & new pipes (differents from the solution proposed during '80 ), add 2 tie rods fixed to the underside of the crankcases and extending forward to the frame and new red valve . There were 2 types of front brake calipers.

So there was 3 different solutions of exhaust mounting from '80 to '81.

The 4L0 models never had calorstat in the cooling system it's why during winter with cold temperature, they have difficulties to reach the good temperature level. To solve that, Here is a solution commonly used ->

 

Evolutions guide

PART
First '80 model
'80 modification
'81 & '82 model
Carbs

Main Jet 160

Main Jet 140 done by dealers
Oil pump
stroke adjustment done by dealers
Cylinders
-
No
New: Identification #1 & #2
Pipes
-

New replaced by dealers: Identification #1 & #2

New: Identification #1 & #2
Reed Valve
-
New after 4L0 - 004669 in factory
<-
Engine tie rods
No
No
Brake calipers
-
New after 4L0 - 007721: Identification #1 ,#2 and #3
<-
Front fork
Swingarm axle
No grease nipple
No grease nipple

Differents shock absorber (4L0-00 for '80 and 4L0-10 for '81 and '82 ?): #1 & #2

 

Here are documents that YAMAHA communicated to his dealers during '80:

Exhaust system (in English)
Exhaust system (in English)
Exhaust system (in French)
Exhaust system (in French)
Carbs / oil pump setting (in french)

 

For oil pump, YAMAHA recommand for the minimum stroke adjustment a gap of 0.10-0.15mm instead of 0.20-0.25mm.