[size=16px]I bought a 1989 flstc a few years back. I was told that the engine was built to 95 ci....if it was built, it should've been 96 ci. But it runs great with lots of torque thru the entire rpm range. Doesn't even leak oil yet so I don't want to tear it apart yet. Tons of torque but doesn't like to go much over 80/85 mph. (Neither do I to be honest). I'm wondering if anyone has ideas on how to tell if it's been built beyond original 80ci at all just by looking at it. Any ideas?[/size]

 

Someones idea of "built" may not compare to any one else.

If it's supposedly 95" it would be fitted with oversize cylinders and have had the crank cases bored out also. If you look at the left side case under the cylinders for the serial number, that would tell you if it's an aftermarket case and just above those numbers, look at the cylinders for casting numbers. If the cylinders are stock, it cannot be a 95 inch engine.

Here's what a factory cylinder looks like on the bottom left where it meets the cases.

 

Unless it was simply Stroked...in which case, it would most Probably be Taller at the Cylinders.

 

Could it be geared low so you get all the uumph down low and run out at the top end ? What RPM's are you talking about at what speed ?

 

Certainly could...That's how we do the Drag Bikes on purpose...

 

Probably just stroke with 3.5 jugs. Could remove a spark plug and measure the swept volume.
With a 4 3/4 set of wheels your at 91cubes. Or they bored your jugs to 3 5/8 with 4 5/8 wheels. I’ve never liked opening the cases for big bore on EVO’s too many times seen cracks and broken cases. They seem to handle more power if you leave the meat with 3.5 jugs. In average state of tune with average hop up compression and cam it’s worth a HP per added cube. So say a hopped stock 82” is 80-85 Hp adding the 10-13 cubes might get it to 85-98 Hp. If it doesn’t run hot and your using pump gas it’s probably mild like 10:1 compression and maybe a EV 13, 27 or SE cam.

Side note.. the 4 3/4 wheel 91 inch will make more torque than the 4 5/8 3 5/8 jug combo and cost half as much to build… so my money is they used 4 3/4 and cleaned up the bore with like 20 over pistons and “called” it 95”

in the world of dedicated drag bikes that opinion changes cause you get into heads that have modified valve sizes and angles and chambers that breath in the upper rpm’s better.. so more power with bigger bores. But with street heads with nothing more than a decent port clean up and good valve job, the stroke is better than the bore because the heads will make better power down low below 6k rpm.

 

There is a number of the left crank case. No other numbers above that or Any where else on the engine that I have spotted.
The numbers on the crank do not match the vin.

 

Some good info in here. Thanks.

 

I really don't know. There's no tac but pretty high by the time I reach highway speeds even in 5th.