Project Miatabusa, Part 9: Thank God We Finally Found a Starter!
by Dave Coleman
This seemed like a problem with two easy answers. The Miatabusa would need a starter. Miatas have starters, and Hayabusas have starters, so we should have our pick of starting options for this thing, right?
Except that no…
Here's a Hayabusa engine in its natural environment, freshly yanked from a crashed Hayabusa. You can see the tiny, 2-pound starter right above the big, black clutch cover. Attached to the nose of the starter, though, is a bulky gear reduction box that lets that tiny starter crank an 11:1 engine. That gear reduction box is about 2 inches deep.
As you can see with the gear reduction box removed and the Miata flywheel installed, there is simply no way we could keep the gear reduction box there. Sure, we could make the flywheel shaft longer, pushing the engine forward in the car until there is room, but if we move the engine even 2mm forward of its current position, the Hayabusa engine case runs right into the back of the steering rack. Not gonna happen.
Oh well, say goodbye to the 2 pound Hayabusa starter, say hello to the 10 pound Miata starter.
Miata starters have a bulbous pinion support shroud that sticks into the bellhousing. This is great for supporting both sides of the pinion and making the starter more robust (or cheaper to make, since the shaft and bearings can probably be lower grade), but it means the starter absolutely has to fit into some part of the bellhousing that is made to accommodate this giant proboscis.
The big starter notch in the bellhousing is the only place there's room for a stock Miata starter. Unfortunately, that's almost perfectly in line with the Hayabusa engine's crankshaft, so the starter won't be going there.
Even a starter with an unshrouded pinion will still have to occupy some space between the flywheel's ring gear and the bellhousing, and the only place besides the starter notch where there's sure to be room is that big open space at the top of the bellhousing. That also happens to be the only place on the engine side with any room.
So, the new starter would have to go approximately where the original Hayabusa starter went, but for entirely different reasons.
Somewhere in the great wide world of starters, there's surely something that will fit in the notch between the Hayabusa engine case and transmission case, line up with the Miata flywheel, have the right tooth pitch for a Miata, and have an unshrouded pinion, right? Sure, but where?
Tim, naturally, found one in about 30 seconds, simply by turning around and grabbing the Tilton Super Starter that was sitting on his workbench. The starter was a leftover from an old project, but it just happened to be almost completely right. Everything was right except for the tooth pitch on the pinion (which was something for a Jeep). All we would have to do is order the one with a Miata's tooth pitch. Simple.
No. Longer. Available.