Triumph 650-750cc Twin, 76-Degree Offset, Stroker Billet Crankshaft

Features:

• 4340 American-sourced steel which is one of the most popular alloys used in performance crankshaft manufacturing


• Rated 140,000-145,000 psi tensile strength


• Triple heat treated


• "Ion Nitrite" treatment for longest life (similar to British Tuftriding)


• Ionized nitrogen is vacuum deposited onto the crank surface in an oven, penetrating .010 to .012 inch into the metal surface and changing the micro-structure of the steel, surface hardness is doubled from 30 to 60 on the Rockwell scale, while fatigue life is increased by 25 percent.


• Shot peened to reduce internal stresses


• Generous Crank "Fillets" for maximum strength and rigidity


• Out-bounded Counterweight to lessen crank flex

Note:

• May be used in conjunction with any stock type Triumph connecting rod utilizing B2026M big-end shells (bearings)


• Use of some rods and piston combinations may require re-balancing based on precise bob-weight specifications (which is out of our control). Some very heavy rod and pistons combinations could require the use of mallory metal where precise balancing is required


• Direct replacement for 1971 and later T120 (650cc) and T140 (750cc) models


• The 76-degree crankshaft can be retrofitted to pre-1971 models by using a specially modified bearing with a metric ID and an Imperial (inch) OD. We stock these bearings for this purpose. For a ball bearing request part number 70-3835/MI.  For a located roller bearing request part number 60-7362/MI. The timing side journal can be re-ground to fit imperial (inch) sized stock OEM bearing (70-1591) if desired


• Cranks are dynamically balanced at 50-percent using a bob weight of 585 grams per journal 


• This must be used in conjunction with a 76 degree electronic ignition (we recommend and stock Tri-Spark) and 76 degree offset specific camshafts


• A high-quality additional oil filter such as our MAP6500 or MAP6510 is highly recommended

About crankshaft bob weight:

• Bob weight is the amount of weight added to each journal before it is spun also known as dynamically balanced. It is calculated in the following manner:

Bob weight = (complete piston assembly +small end weight) X (balance factor) + (big-end rod weight + bearing shells)