https://ia800204.us.archive.org/14/...ice-manual/yamahavmaxvmx12-service-manual.pdf
Print a copy and use a 3 ring binder, the first 64 pp. are annual updates, 'supplements.'
https://www.vmaxforum.net/threads/new-vmax-owner-faqs-new-members-please-read.21240/
Major differences are the 1985-'89 have two pick-up coils for ignition pulses, while the 1990-'07 have just one. The 1990-'07 is generally considered to be the better of the two. There is some anecdotal evidence that if you want to use COP's (coil-over plug ignition coils) that the 1990-'07 are less-likely to be detrimentally-affected by the ohm resistance of what COP's you use, because of the change in the ignition module which was changed in 1990. Apparently the analog 1985-'89 ignition module is more sensitive to differences in ohms resistance in using COP's which do not exactly match the resistance/impedance designed into the OEM ignition module. While there are reports of ignition module failures in the 1990-'07 systems, they seem to be fewer reported.
A company called Ignitech sells ignition modules for the 1990-'07 bikes, and DYNA also sells one. The main difference I can suggest for using an aftermarket ignition module, is to gain the function of a rev-limiter which is adjustable for RPM cut-off and ignition curves for tuning when you use power-adders (NOS, turbos, superchargers, big-bore kits, higher compression, re-ground camshafts, bigger valves). The rev-limiter I consider to be an essential addition if you like to visit VBoost often. These bikes can and will run above factory redline, but if you value engine longevity, you will not do that.
The Ignitech can also serve to control other functions like the VBoost replacing its electronics, and for control of power-adders like regulation of the NOS, if you go that route.
Early bikes 1985-'92 have smaller front ends 40 mm downtubes, sliders, and triple trees/fork & fender braces, also single pair of opposed brake caliper pistons, 2 calipers on the front, w/282 mm vented brake rotors; 1993-'07 are four pistons/two pair of opposed pistons in front, 298 mm vented brake rotors; and 43 mm downtubes, sliders, triple trees, and front fender mount/fork brace.
Wheels are swappable among all years, though the rear wheels are different for 1985-'86 (solid aluminum wheels with rectangular slots) compared to the 1988-'07 rear wheels. There is no official 1987 USA market VMax. The 1985-'86 front wheels were solid spoke wheels, in '88 and to '07 they were solid wheels with circumferential concentric slots.
The #1 best change you can make to a VMax is to use wheels designed to run radials, in my opinion. You can run radials on modified stock f & r rims, or you can purchase aftermarket wheels designed to bolt-on in-place of the OEM wheels. Dymag, Kosman, and other vendors sold them, though they may not be currently available in their inventory, meaning you need to look for used ones, or for the handful of people who modify the OEM wheels to different diameters and widths.
Stock wheels are 15" X 3.5" rear and 18" X 2.5" front. Commonly-used aftermarket or altered OEM wheels are 17" X 5.5" rear, 18" X 5.5" rear, 17" X 3.5" front, and 18" X 3.5" front.
Going with radial tires also reduces your tire aspect ratio, from the 90 series rear 15" OEM wheel/tire combo to something like a 55 series, or 50 series 17" or 18" rear wheel/tire combo. This significantly lowers your bike, which could result in dragging some parts you might-not usually have come into-contact with the pavement, like the exhaust(s), the centerstand, or the sidestand, or the exhaust header pipes while cornering on a bumpy road. These are all things to consider.
The difference in handling of bias-ply OEM size tires/wheels compared to radial tires and appropriately-sized wheels as mentioned above, is that (in my opinion) when you approach/exceed 'take my license away' speeds like triple digits, and especially on poor pavement and/or in the rain, the radials provide much-more of a secure feeling than bias-ply tires, and the feel becomes more-pronounced as you get miles on the tires. If you rode two bikes back-to-back, one with OEM wheels/tire sizes, and the other with radial-specific tires/wheels (see above for common sizing for the radials) and you ran through a tank or two of gas, at the end of the time in the saddle on the radial wheels/tires, when you got-off the bike, you would start saving your $ to make the switch.
I offer some caveats about using radials. DO NOT mix & match radial tires! Use the same manufacturer for both tires, and the same use design. That last one would mean, 'supersport' vs. 'sport-touring.' Use one or the other. Mixing them could make your bike handle worse than stock, given the difference in use for which the tires are designed. You want your bike to handle the same at both ends.
Also, different manufacturers of radials use different designs for the carcasses. Think of the capital letter,
'V' and then, the capital letter
'L'. That is the difference in the way the wrapping of the plies cross inside the body of the tire. Some tires have plies which cross in the
'V' pattern. Others have plies which cross at 90 degrees (that would be the capital letter
'L'). The type of plies construction makes for very-different handling characteristics! In a worst-case scenario, the tires will cause you to experience such a poor-handling bike, that you will curse your foolhardy experiment in radial tire fitment.
Someone may inform you that "my buddy rides a H-D, and
his bike has a bias-ply on one-end, and a radial tire on the other!" That's very true, but they also have teams of engineers who design their bikes to perform with very-specific tires, designed for that bike's geometry and not just what is on close-out sale at One-Eye Bob's V-Twin Parts and Service Emporium/Tattoo Parlor.
One of the things that seems to come-up frequently is some type of oscillation in the handling of the bike. Tire types and sizes can affect this. Of course there are other things which can also affect the bike's handling. If you were stepping-off a GSXR1000 and onto a 35 year old VMax, certainly you're going to feel the handling of the older bike has all-sorts of differences compared to your alloy-framed rigid-beamed, designed-flex, adjustable jounce and rebound, wide wheels/radial tires sportbike. Worn suspension components, loose and or worn-out bearings, old designs using mild steel frames instead of aircraft-aluminum alloy with heat treatment, conservative frame geometry versus 'change your line mid-corner' precision, and who knows what type of tweaks an older bike has experienced after being crashed, maybe multiple times? It would be great to expect that a current model year liter-displacement sportbike and a venerable designed over 40 years-ago 'quickest, fastest bike of its day' are on common ground, but apart from jacking that 'Yamaha' tank badge up and slipping a new bike underneath, that is really about all they have in common.
Pay attention to what your bike is trying to tell you, ride within the bike's and your limitations, respect its capabilities, dress for the possibility of a premature end of your time on the road, due to 'road rage,' inattentive drivers, and road and atmospheric conditions, and you will stand a better chance of surviving each time you climb aboard for another trip wherever your bike takes you. Brush-up on your skills, either at a track day, a MSF course, or just getting used to a new bike's capabilities in handling and braking someplace apart from crowds of traffic. Keep your bike in good repair, carry a cellphone in-case you need 911 (or someone-else does) and enjoy the ride.
