| Also known as | PS103 |
| Listed in parts books | Not catalogued by year yet |
VALVE SPRINGS 500/350 TRIUMPH UNIT - Replaces 99-3754)
Valve spring for the Triumph unit-construction twin, replacing 99-3754 and later superseded by 70-4011.
This is a valve spring for the Triumph unit-construction twin, listed for the smaller-displacement unit engines in our catalog. It's a replacement for the earlier 99-3754 spring, and it was later succeeded by 70-4011, so if you're chasing down parts under an older or newer number, all three refer to the same basic component in this family.
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Valve springs close the valve after the cam and rocker push it open, keeping the valve seated properly against the head so compression and gas flow stay where they should. On a unit twin these live under the rocker box, one per valve, and they take a beating over the years from heat cycling and fatigue - not a part people usually think about until it's making noise or losing tension.
Our record on this one is brief beyond the description and the numbering history above, so if you've got a specific engine in front of you, give us a call and we'll confirm fitment before you order.
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