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Old May 9th, 2016, 04:03 PM   #1
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Name: Roger
Location: Mitchell, South Dakota
Join Date: Apr 2014

Motorcycle(s): 1978 Z1R, 1999 EX250

Posts: A lot.
MOTY - 2018, MOTM - Oct '16
17" wheels on pregen, how to

Did 4 conversions this spring, 3 using newgen wheels and 1 using EX 500 wheels. I didn't have much to do with the 500 conversion, but I'm sure rubbersidedown would answer questions on that conversion. This how-to is using the newgen wheels.

The front wheel is pretty straight forward, used all newgen spacers and speedo drive. Axles are the same. Had to make spacer washers on both sides next to the forks, about 4.5 mm each. I ground them to fit without putting any force on the forks and to center the wheel between the forks.
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Made a bracket to weld to the existing caliper mount so it would work with the stock newgen disc, newgen disc is 30 mm bigger in dia.
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I drilled and tapped the bracket to bolt to the stock position on the fork. While bolted in place, I positioned the pregen caliper on the disc and held it in place with a little pressure on the brake lever and rotated the caliper against the new bracket and tack welded it in place. Then took the caliper apart and welded it solid, painted it and put it back together.
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Rear wheel was a little more involved, used the pregen sprocket hub and cush drive rubber and spacers. If you use the newgen rubber you'll need to cut off the little rubber bridges that hold the cush rubber together to make clearance.(sorry no pics)

The spacer inside the hub, between the hub and wheel, needs to have 3 mm removed to center the wheel.
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Take the 3 mm off the wheel side of the spacer, this must be a square cut or it will put uneven pressure on the bearings.
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The nose on the wheel that holds the O-ring between hub and wheel needs to be cut down so that it will just hold the O-ring in place (about 3 mm)
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Just below the O-ring in this pic, is factory machined, and just below the factory machining needs to be machined or ground with a die grinder (above the cush drive spokes) to make room for the hub to slide on the extra 3 mm

The newgen wheel is still 11 mm to wide at the axle, so I took 11 mm off the outside of the rear brake caliper mounting bracket, this also must be a square cut or the caliper won't fit the disc squarely and will bind and twist when the brake is applied.
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The newgen disc will now be positioned properly though it is 10 mm smaller in dia. than the pregen disc (no they won't interchange) which is only 5 mm different where the caliper mounts, hasn't been a problem yet but haven't been to the track yet. I don't foresee a problem, but if someone is worried the EX 500 rear disc is the same dia. as the pregen with the newgen bolt pattern. Clean it all up and mount it on the bike, you'll need to remake the rear brake anchor or tweek it over a bit (that's what I did) and run a drill bit through so the bolt won't need to be hammered in and out.
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