Big Bore Kit - What else is needed

[Folkie]

Originally Posted by Folkie

Can you do a stroker conversion on an Evo?

Apparently you can, but I've never heard of anyone doing it.

[rocketmangb]

I think there is room on a rigid mount
Certainly no readily available cranks for a Rubbermount

[Folkie]

I did a Google search and found someone who makes one (for solidmounts).

Just puzzling over hammer6315's comment:

Originally Posted by hammer6315

I like strokers; very pleasant midrange power.

[rocketmangb]

Yes
Was unusual if not cryptic !

[aswracing]

The most popular stroker kit is the S&S 89" ... 3-5/8 bore x 4-5/16 stroke. Not available for rubber mounts.

The reason you don't see a lot of them is because they make the motor taller. The cylinder height is 5.087", where the stock cylinder is 4.650". So the motor ends up taller, which causes issues with fitting in the frame, as well as requiring a custom exhaust, wide intake manifold, bracketry mods, long pushrods, etc. And they still require case boring like the 88/90 inchers, albeit not as big.

By comparison, an 88 or 90 incher comes out stock height and doesn't introduce all those problems. So they're much more popular.

Bore area and stroke make equal contributions to torque. So it's not like doing an 89 incher at 3.625 x 4.313 makes more torque than a 90 incher done at 3.875 x 3.813. In fact, at equal cylinder pressure the stroker will make a little less torque, since it's a smaller motor. The bigger bore does however create more room for valves, and therefore has the potential for better cylinder fill, particularly at high rpm. It's just an all-around better way to do it.

[Folkie]

As far as I can see, S&S doesn't sell (at least not currently) a stroker crank for solidmount Evos. The only Sportster stroker crank they list is # 32-3055, for 1977-E81 Ironheads.

[aswracing]

Page 337 of the 2018 catalog:



They've been offering that 89incher for about forever. AirBozo here on the forum has one. I made him a manifold for it.

[Folkie]

I stand corrected. They don't list it in their web catalogue.

[lmarshall73]

Originally Posted by rocketmangb

I would do the clutch as well

Added with a note. I'll upgrade mine when I replace the carb & manifold unless I need it before then.

[hammer6315]

Originally Posted by Folkie

Can you do a stroker conversion on an Evo?

Talking Sportsters now, S&S sells stroker kits for evo Sportsters up to 2004. Nothing for rubber mounted Sportsters. I called them a year or two about this situation, and they did not know when or if they would offer them. Wa-Wa!