How to change from KM to mi on wintech bike computer

I couldn't find the manual for the 2005, the 2006 says the automatic transmission should be inspected every 24,000 km (15,000 mi) and changed every 60,000 km (37,500 mi).
The manual transmission should be inspected every 48,000 km (30,000 mi) and has no recommended change within 180,000 km (112,500 mi) where the maintenance schedule ends.

Here is the owners manual for the 2006, the maintenance schedule is section 6 almost the very end.
2006 Suzuki Forenza Owner Manual

To change the unit of measurement on your Giant Prime+ e-bike computer from kilometers to miles, you can follow these steps:

1. Turn on the computer by pressing the button on the underside of the unit.
2. Press and hold the "Set" button until the screen changes.
3. Press the "Set" button repeatedly until you see "UNIT" on the screen.
4. Press the "Mode" button to select "UNIT."
5. Press the "Set" button to confirm your selection.
6. Use the "+" and "-" buttons to toggle between "KM" and "MILE."
7. Press the "Set" button to confirm your selection.

Once you have completed these steps, your Giant Prime+ e-bike computer should display speed and distance in miles instead of kilometers.

Oil change intervals for motorcycles depend a great deal on your riding conditions and riding style. For lower-revving street bikes, I often change my oil about every 2000 miles (~3200 km). However, someone with a sport bike who regularly revs their engine closer to the redline, I would suggest a more frequent change interval. Off-road / dirt bikes should have their oil changed sooner because of the dusty conditions. The oil is still full of lubricants, but it is contaminated with dust and dirt that clogs the filter and eventually goes right into the engine, increasing wear. I can't offer much guidance for dirt bike oil change intervals.

15 mi = 24.14016 kilometers

In your manual it will be under SETTING YOUR ODOMETER. the manual does not specifically say, but it should be one of the flashing choices when you are setting values.

Hi,
When the vehicle is started and right after the ignition check, if there are less than 300 km (200 mi) left
to the next Service, the specific icon flashes for 5 seconds. Once the service mileage has been reached,
the icon remains steadily until the Service is reset.
The warning light can be zero set even if the mileage is lower, up to 300 km (200 mi), compared with
the Service mileage. During the 300 km (200 mi) before the service warning light comes on, the light
flashes 5 times each time the key is set to ''ON''.
The light should turn on first at 1000 km (625 mi). Successive times are strictly at 10000 km (6215 mi)
20000 km (12430 mi), etc
RESET
Hold the MODE button down.
Turn the key to ''ON'' and wait 10 seconds.
During this operation the service icon flashes.
Good luck,
Alex
PS-Don't forget to vote me, thanks!

You may want to just go to http://www.mavic.com - I don't see anything but catalogs for download there, but they may be able to provide you with a manual.

Here's where having a good relationship with your local shop comes in REAL handy. Ask 'em if you can look at the instructions in one of their wintechs. If you're lucky, you might even be able to make a copy. Of course, your shop has to carry your model.

Good luck.

if memory serves me right, use the left button to get to the average time function and then hold the right button down for 4 seconds. The km/m field will flash and use the left button to select the miles then push the right button to confirm. Hope this helps!