Triumph T150 T160 X75 BSA Rocket3 A75 Primary Drive Conversion “Racing”

CONVERSION OF THE PRIMARY DRIVE "RACING"

This service was developed with the cooperation of a triple owner from USA that uses his triples mainly for racing.

While he was very enthusiastic with the already known conversion, that replaces the original needle roller bearing on the outer primary drive cover with a much stronger roller bearing of the NU series and the original thrust bearing  (NTA2233) with a phosphorous bronze bearing, he had his doubts about the bronze bearing. His concern was, that the bronze bearing will generate a small amount of friction at high turning speeds making a racing engine lose precious Bhps at full speed.

I then investigated the possibility of installing a ball thrust bearing in exchange of the bronze bearing. So, here it is the new conversion which is using in place of the bronze bearing, the ball thrust bearing 51109.  Therefore, this new service is an updated and innovative version of the already known Primary drive conversion. This service applies to road and racing triples.

Analytically here are the benefits of this conversion:   

-Rectifying the problem of the needle thrust bearing of the outer cover by replacing it with the much stronger ball thrust bearing No 51109.

-Replacing the needle roller bearing of the outer cover with a much stronger from the NU series (NU1007M1).

-Eliminating the problem of a reconditioned shock absorber spider. As it is already known, it is extremely critical for the primary chain that the shock      absorber unit is turning true.  However, a reconditioned spider (removing the rivets and replacing the inner part with a new one) is impossible to turn true  again.  So, for this conversion a new spider is made from a one piece surface hardened steel and is heat treaded. This spider will never wear and it will    always turn true.

The work that will be done is the following:

-Machining of the outer cover.

-Checking the alignment of the inner to the outer cover and, if necessary, rectifying it.

-Construction of a new shock absorber nut (original part 57-2480) with 20mm hexagon. The new nut will be supplied with a new seal.

-Construction of a new housing for the bearings of the outer cover (the NU roller and the 51109 ball thrust bearing) made from aluminum alloy 7075 in  order to reduce weight.

-Construction of a new one-piece spider from case hardened steel. The outer end of the spider will have the inner race of the 51109 bearing and the  inner race of the NU bearing attached on it.  These can easily be removed, in need of replacing, using a suitable drift and a universal extractor (please  view the appropriate photos).

Below is a comparison table for the original and new thrust bearings:

Regarding pricing list please refer to the table below:

Total for T150 X75/R3 1010 euros

Total for T160 1030 euros

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