10 Rules
Part compatibilities
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In the course of working on my various bikes, I have discovered sometimes by luck and sometimes by trial and error that certain parts are compatible accross bikes. Here is a simple list of my findings thus far:

1. Both left and right controls from 2005 CBR600s will fit the VFR750 if you replace the wiring pigtail, even the choke lever fits.
2. Autozon sells a simple bayonet fitting that can be used to replace the stock tail light fitting on the CBR1100 in order to accomodate a Luxeon based 1157-RLX5 lamp from superbrightleds.com (a fantastically bright tail & brake lamp)
3. Throttle cables from a 2005 CBR600 are close enough in length to fit the VFR750.
4. Stainless steel brake lines from a 1st gen VFR750 will fit a 3rd gen with a little slack (good with risers!).
5. The ECU from a 2000/2001 VFR800 is NOT compatible with a 1998/1999 bike due to changes like the automatic choke and O2 sensors on the newer bike.
6. GSXR750 bar ends will work on a VFR750 if a single space washer is used.
7. Mirrors from a 5th generation VFR800 will fit a 3rd generation.
8. Gas caps from early Hurricane 600s will fit 1000s.
9. The CBR1000F will run just fine with the fuelpump removed and gravity-feeding fuel.
10. The clutch slave cylinder from a 2007 CBR1000RR fits the VFR800 perfectly.
11. The clutch line from the CBR1000RR fit with a little work too and provides less pipe expansion than the stock VFR line.
12. 1st and 3rd generation VFR750 fairing retaining bolts are the same.
13. ~88 Honda Hurricane CBR600 and CBR1000 gas caps are not interchangeable unless you swap out the main spring retention ring.
14. Non fuel injected CBR1100xx tanks are NOT compatible with fuel injected models because of the fuel pump opening.
15. 98 VTR1000 Hawk risers fit the 98-01 VFR800.
16. CBR1000RR mirrors use a 40mm hole spacing, the VFR800 uses a 50mm hole spacing, so make up a spacer that will both adapt the hole spacing and extend your mirrors outward slightly.
17. Power commander III USBs for all VFR800s share the same hardware, it's just the map that differs.
18. The stitch gear from newer (6th gen) VFR800s can be used on the older (5th gen) VFR800s, the pins in the plug just need to be moved to the correct location in the plug.
19. 98-01 VFR800 pedals and levers are compatible with all CBR1100xx models.
20. The (simpler) exhaust header from a 4th gen VFR750 will fit onto a 3rd gen, but not with a centerstand.
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I will add more as I discover or remember them!