I emailed famed motorcycle crankshaft company, Falicon, to ask them about stroker cranks for the new Triumph tiwns. Here's their prompt reply:
"We do not manufacture a billet crankshaft for this model.
We do modify stock OEM crankshafts to the stroke of your choice."
Woo hoo! No more complaining about "small" engines! One of their mod jobs done to your crank, coupled with the big bore kit of your choice, and you, too, can thump with the best of them. And no further need for those danged engine-killing high rpms. You'll have plenty of power right off idle.
Now, a note about what Falicon said about modifying your crank. There are two ways to increase the stroke of a stock crank. One is to offset grind the existing journal to a smaller rod bearing size and use a custom (or other brand) con rod, which has a smaller rod bearing. This has been done for years with 350 Chevy cranks where the journal is cut down from 2.10" diameter, to the old "small journal" size of 2.00" Just use an early sized Chevy V-8 rod. Also, another make rod can be used, but usually the wrist pin has to either be bored out or sleeved down to the proper wrist pin diameter. The limitation with this method is you can't gain very much stroke increase.
The other way to stroke a stock crank is to weld up the outside of the rod journal and then regrind it to the stock size in an offset manor. The weld is applied to just the bottom of the journal, the area farther away from the centerline of the crank.
Welded stroker cranks have been around "forever" and it is a viable way to increase the stroke. One may not want to use such a crank in a 12,000 rpm racing engine, but for the street or even bracket racing motor, they're just fine. This mod is an offshoot of the standard welding repair job, done on a stock crank, to a burned/trashed/seized journal. It's always done on a forged crank, though a rare cast crank can be saved this way, too.
Many times a repaired journal is first undergound and then chromed back to standard size, making the journal even that much tougher. Hi perf cranks get chromed on all journals, along with oil holes chamfered or even enlarged.
Next consideration is what to do about the piston going farther up the bore with that longer stroke. Usually a custom piston is used, where the pin hole has been moved higher - half the distance of the stroke increase. The distance from the middle of the pin bore to the "deck" of the piston, or main flat part of the piston, is called compression height. If you stroke your Hinckley twin from 68mm to 78mm, then you would need to have a piston with the pin moved upwards 5mm to compensate for the change.
Sometimes this pin movement is not always possible (the stock pin location being as high as it can practically go), so one mod that has been developed for bike engines is a barrel spacer, usually machined out of aluminum plate, and installed under the barrels to raise them. A combination of spacer and wrist pin change could be done, too.
If one were to do a stroker kit in combo with a Wiseco big bore kit, Wiseco could move the pin for you as a custom operation when they made up your kit.
Yet another way to compensate for the longer stroke would be to get a shorter con rod. Since custom rods are commerically available for Triumph twins, you could special order some slightly shorter ones, say from Carillo. Heck, an accomplished machinist could even make his own rods out of aluminum bar stock!
Now all ya need is the money.......
