Editing User:Eric/sandbox/Progressive Refinements (section)

=== 1951 ===
{| class="wikitable"
|+
!Date Introduced
!Chassis No.
!Unit No.
!Modification
|-
| 4 Jan. 51
| 1-0221 051
| 266 644
| <u>Belt pulley</u>
Now: Small modified shim, outer dia. 4 mm, inside dia. 3 mm

Formerly: outside dia.  5 mm, inside dia. 4 mm
|-
|16 Jan.  51
|1-0244 171
|270 484
|<u>Cylinder head</u>
Now: inner valve spring modified
|-
|18 Jan. 51<br />9 Feb. 51
|1-0224 763<br />20-09 940
|
|<u>Choke control cable</u>
Now: guide sleeve for thrust spring
|-
|19 Jan. 51
|1-0225 376<br />20-09 065
|272 061
|<u>[[Crankcase / Progressive Refinements|Crankcase]]</u>
Now: made of electron

Formerly: remelt alloy
|-
|27 Feb. 51
|1-0235 501
|284 793
|<u>Distributor drive</u>
Now: distance spring fitted again
|-
|21 Mar. 51
|1-0241 734
|287 661
|<u>Camshaft gear</u>
Now: made of "Resitex" plastic (for export only)
|-
|27 Mar. 51
|1-0242 600
|293 200
|<u>[[Muffler / Progressive Refinements|Muffler]]</u>
Now: modified pipe
|-
|28 Mar. 51
|1-0268 333
|from 324 902<br />up to 327 026
|<u>Valve seat ring</u>
Now: material  VCN 25 in a number of cases
|-
|6 Apr. 51
|1-0243 731
|294 845
|<u>Heat control sheet</u>
Now: front sheet relocated into heating box
|-
|18 Apr. 51
|1-0 246 090
|297 815
|<u>Generator</u>
Now: RED 130/6 – 2600 AL 16

Formerly: AL 16
|-
|April 51
|
|296 606
|<u>[[Crankcase / Progressive Refinements|Crankcase]]</u>
Now: openings (oil throwers) provided in both crankcase halves 40 x 11, right hand side
|-
|24 May 51
|1-0 253 943
|307 219
|<u>Cooling system deflectors</u>
Now: modified shape
|-
|28 May 51
|1-0 254 576
|from 307 944<br />up to 308 886
|<u>Cylinders</u>
Now: fins and deflectors inside cover plate
|-
|17 July 51
|1-0 268 548
|352 081
|<u>Valve springs</u>
Now: gradation for valve springs at cylinder head
|-
|1 Aug. 51
|1-0 272 706
|330 345
|<u>Oil breather</u>
Now: filler cap with clamp spring.
|-
|21 Aug. 51
|1-0 278 121
|336 759
|<u>Cylinder head cover</u>
Now: cover plate made of one piece
|-
|26 Nov. 51<br />26 Nov. 51
|1-0&nbsp;305&nbsp;813
20-&nbsp;019&nbsp;034
|369 483
|<u>Valve seat ring</u>
Now: valve seat ring for exhaust valve made of V2A steel (standard)
|-
|26 Nov. 51
|1-0305 813
20-019 195
|from 369 483<br/>up to 372 422
from 381 035<br />up to 382 910
|<u>Valve seat ring</u>
Now: lead-steel material in a number of cases
|-
|27 Nov. 51
|1-0306 417
|from 370 472<br />up to 370 556
|<u>Valves</u>
Now: with caps in a number of cases
|-
|10 Dec. 51
|1-0309 833<br />20-019 589
|
|<u>[[Carburetor / Progressive Refinements|Solex carburetor 26 VPIS]]</u>
Now: throttle hole diameter 1.4/1.5 mm
|-
|17 Dec. 51<br />18 Dec. 51
|1-0311 923<br />20-019 942
|376 900
|<u>Throttle ring</u>
Now: spot-welded
Formerly: screw-mounted
|}