Assembling the ape 50 engine and differential

Unfortunately, the images to this post were lost in a server crash.  i’m preserving the text in case it is of any help to anyone.

Alright. sorry this has been a few weeks late but here it is; assembling the differential and engine on an Ape 50. It’s been a busy spring here at Hodgespeed.

So, here you have the four engine case bits for an Ape 50 and the differential. First you’ll have to swap the cylinder studs for the longer 125 studs if you’re upgrading displacement as we are.  you’l also need to install the Christmas tree in the flywheel side case and the clutch basket in the other main engine case along with all bearings and seals.

Now, attach the inner differential case to the clutch side case.

Here you’ll see the first mistake i made. You need to insert the three differential cover bolts on the left hand side in this picture into the case, before bolting the two pieces together. otherwise, there’s no way to get them in the holes, similar to those two annoying case bolts on a handlebar bike engine. save yourself the do-over and put them in before you bolt these case bits together. you need to use gasket goo (witch i personally dislike) on this joint. there is no paper gasket.

Now, insert what is the rear axle on the scooter, but is the output shaft to the transmission on the Ape. make sure to line up the shifter with the shifting fork, and get the gears lined up with the christmas tree. some people like to install this shaft and then put the gears on, as it is slightly easier that way.

Next, we’ve got to put the differential together.

Here you see how all the internal bits go together. it’s pretty straightforward. three gears and a shifting fork for the reversing gear. gasket goo again here, no paper gasket.

Now, back to the other side. from here it’s like a regular smallframe except way simpler because there is no kickstart mechanism. i never realized just how much work that added getting that lined up, but this thing just flew together in no time compared to a scooter smallframe case because of this omission. no runner biffers to install, not spring to fiddle with, no quadrant to line up. just set the parts in the engine and bolt together.

First you install the crankshaft, then grease the gasket surface.

Then you put the gasket on.

Then you grease the gasket

Then you install the flyside case.

If you’re using 50cc-style ball bearings, you’ll have to tap into place. if using the needle style bearings used in all other displacements, it’ll just slide right on.

Notice these two case bolts:

Leave those out for now, because you need to use them to install the engine mount.


Now, install the crank gear. to get good speed you need to go way higher than you’d think, as there is a 1.68:1 reduction in the differential. as a result, the gearing i went with was so tall i needed to clearance the case a little to fit it.

now install the clutch.

Then install the clutch push plate and cover, repeating the grease-gasket-grease from earlier.

Install the top end.

And here’s the issue i found. Most scooter carb setups do not work with the Ape because of the T-shaped engine mount. The reed block will not go together here. the solution? Polini makes a reinforced performance engine mount. here they are side-by side.

the mounting points are the same, but it is Y-shaped to clear whatever carb you want to run.

See? the carb manifold now fits. Here’s another shot of it.

And now to resolve one of those weird little things. there’s a hose that goes from the stock carb to the intake tract, and i didn’t bother to look too hard at it to figure out what it did. needless to say, the 25mm carb doesn’t have this bit, and I’m just going to close it off for my build.

I used a bit of stainless rod in some vynil tubing, and then put that over the nipple on the case.

now, install the stator and flywheel. And here we have another issue. the electric start gear interferes with the malossi 136. score the cylinder fin with a cutoff wheel and then grab it with pliers and break it off. use a grinder to clean it up and to clearance it so it doesn’t rub.

install the flywheel cover and cooling shroud and it’s pretty much ready to go in the bike.

next installment we put it in place and possibly wrestle an exaust snaking.

Leave a Reply