Tech Tip: Hobbit Ramp Plate Mod

There are a ton of PA50I’s out there.  They are somewhat undesireable, being the “slow” model of the Honda Hobbit.  What few people know is that they can be cheaply de-restricted and transformed into a “II”.  There is a whole list of modifications that can be made, but one in particular does not appear to have been attempted thus far.  Most people will scavenge a variator ramp plate from a II and grind it to fit on the I.  The primary difference is a steeper ramp for more variation which gives you higher top speed but also stays in the low end longer.  Nick Jobbitt, helping a new moped rider with the derestriction of his I, came up with an interesting modification to a I ramp plate.

CAM00361

First, cut into the sides of each ramp.  an angle grinder or Dremel tool works well for this task.

CAM00362

Next, apply heat to the base of each ramp and carefully bend it down as seen in the photo.  During this mod, we noticed stress cracks opening up that may have occurred during the original stamping.  More on those later but just watch for them.

CAM00364

Tac-weld each corner to hold it in place.  This is an important step to make certain the ramps will stay put.  TIG welding works well for this, careful welding with MIG can also work.  Ideally you want to add as little material to the plate as possible.

CAM00365

Complete the welds on each ramp.  Work your way around the plate to prevent heat warp.  I used about 55-60 amps of heat with TIG and it took a little time to blend in the weld but I felt it made it easier to ensure a complete weld.

(Optional) If any stress cracks occurred while you were bending the ramps, weld these up as well.

CAM00366

Voila!  a “II” plate for almost no cost.  We have yet to field test this plate but once we do, I will provide an update with how well it works and hopefully it lasts a long time.

This entry was posted in Mopeds.

2 thoughts on “Tech Tip: Hobbit Ramp Plate Mod

  1. This looks like it needs to be very very precisely done to me, if the ramp plates are not all at the exact same angle all the way down you will cause the sliding outer pulley to run out of true which will wear out the bronze bush, rollers and slide bushes.

    Stock cranks are prone to snapping anyway so adding imbalance is the last thing you want to do.

  2. Honestly, I cannot wait to get this plate on a II conversion and see how it handles the stress. It very well may break! I really doubt it will cause problems on the thicker 1 crank though.

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