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+--- Thread: Setting up my H1 (/showthread.php?tid=4669)
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RE: Setting up my H1 - Ian McGowan - 15-07-2020
Your 160grm piston is very light without a spring, standard H1 pistons + needle without spring usually weigh in at 215 gm ( no spring ever fitted.) the OM piston + needle (no oil damper, solid centre rod) usually weigh in at 245 gm again no spring ever fitted. A HS2 piston + needle (usually fitted with a red spring which is quoted as a 41/2 oz spring = to 126gm.) weigh in at 108 gm. 108 + 126 = a total piston load of 234 gm.
I personally think that turning down the weight on your piston to give an all up weight of 160grm was a mistake but, this can be more or less rectified by using a blue (21/2oz = 70 gm) spring to give an all up piston load of 160+70= 230 gm - more or less the design weight of the original un-sprung piston assembly. ( As you probably know, light piston = weaker mixture; heavier piston = richer mixture.) OR, you could add a lead washer to reinstate the piston to its original 215 gm. With a standard weight piston the AN needle should be about correct with the jet adjusting nut turned down 2 complete turns (12 flats) from its fully up position. That should always be your starting point.