General Category > Bike Builds, Rebuilds And Restorations Only
1965 Benelli / Motobi 200 Sprite
cliffrod:
Looking great, Jim. How much difference is there between transmissions vs displacement? Have you accumulated that many spares for each combination or are many of the parts interchangeable regardless of displacement?
Canuck750:
--- Quote from: cliffrod on January 12, 2023, 05:08:13 PM ---Looking great, Jim. How much difference is there between transmissions vs displacement? Have you accumulated that many spares for each combination or are many of the parts interchangeable regardless of displacement?
--- End quote ---
Thanks Clint,
As far as I can tell the 4 speed transmission is the same across the 125 - 200 and 250, The 125 and 250 were also available in 5 speed and I think the crank cases are unique for the 5 speeds. There are many small differences between the engines, the 125 and 200 share side covers, the 250 is unique, the heads and cylinders are individual but some head parts are interchangeable. I am learning every day about the differences and I think I now hopefully have all the parts for the 125, 200 and 250.
Today I must have assembled and split the cases a dozen times to shim the transmission shafts, shift drum and kick start shaft. Benelli does not show a case center gasket but on each of the three engines I have put together the cases are just far too tight without a thin center case gasket. I have made my own gasket in each case and I have collected a good stock of thin shims to fit the various shafts.
I previously had a 200 cylinder bored 2nd over and matching NOS piston and rings, fitted a set of new cylinder base gaskets - paper / aluminum / paper, and fitted re-plated studs.
I will pull the 125 motor out of the frame tomorrow and install the 200 motor then fit all the rest of the parts with the engine in place.
I want to get the engine running and sorted before I pull the bike apart for painting. I need to tackle all the electrical next.
Canuck750:
swapped out the 125 motor for the 200, just three bolts and the motor drops straight down, so simple and its pretty light without the clutch and primary gears.
the head gasket is just a thick rubber seal for the push rod tubes and studs, the head is sealed by the cylinder liner fitting tight into the aluminum head recess, I think this is the design in many engines, Ducati does similar on the bevel twins.
installed the drive sprocket and the sheet metal cover that keeps dirt out of the stator area, fitted a new condenser and replaced the lighting coil with a spare I had, new wires
I should have installed the shift drum cap and woodruff key with the motor on the bench, twice the key fell to the floor and I spent a long time finding it each time
Clutch is pretty simple, the five springs are put into tension by hooking the top of the springs over a loose steel ring
stripped and cleaned the oil pump, its slides in from below and the gear engages the center of the cam shaft, a new soft rubber seal was installed
this motor was missing the M9 x 1.25 head nuts, I found flanges examples on Ebay from China but the wrench size is 14mm not the stock 12mm, I machined the flanges off and I can just get an open end wrench over the nuts but torque is by feel, I cant get a socket on
The bike deserves a period correct Magneti Marelli plug, love the pink
made up some 6mm studs for the carb flange, I need to rebuild a carb from my stock of used Dellortos,
Next to go through the wire schematic and make some new wire harness sections, fit a 6V coil and connect the electrical up inside the headlight shell. Hopefully I will get a good spark.
I gave up on building a 125 motor, the NIS crank I bought won’t work, it is for a 5 speed. I decided to build up another 200 cc 4 speed with all the spare parts and a gods pair of 200 crank cases. I guess if I do build a race replica it will have the 200 motor.
Canuck750:
I got some time in on the Sprite this past week, installed a reproduction wire harness I found on Italian EBay, it’s an accurate copy.
I installed a brake, clutch and throttle cable. For the throttle I had to make a solder ball end to fit the throttle, I made a little ‘pot’ from 1/2” diameter pipe, about 1/2 “ tall, melted solder into the pot and then dipped the bare end of the cable, I balled up the strands, and then once cooled I sanded the blob into a ball.
I ordered a NOS light dip switch/horn button and a rear brake pedal switch to finish off the electrical. The CEV speedometer I have had a very small diameter threaded mount for the cable and doesn’t work with he speedo cable I bought, need to come up with something for that.
I used the original type wire terminal connectors used on Italian bikes of this vintage.
I ordered from Detlef Burian what I hope is the last of the parts I need, a new exhaust header pipe, a few little clips and rubber parts. I think I am getting close to completion of the dry build and starting up the motor. Then to strip it down and get on with paint.
Antietam Classic Cycle:
Sweet!
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