1965 Benelli / Motobi 200 Sprite

[Antietam Classic Cycle]

Looks great! BTW, 123 Bearing is in France. 

123Bearing
CRT 4 de Lesquin Rue Léo Ferré
59273 FRETIN - FRANCE

[Canuck750]

Looks great! BTW, 123 Bearing is in France. 

123Bearing
CRT 4 de Lesquin Rue Léo Ferré
59273 FRETIN - FRANCE

I guess I wasn’t paying attention to their website, I just assumed they were UK, great service though, I ordered the crank big end needle bearings and cup rollers late last week and less than a week later they arrived. Can’t beat the prices either, I used to have a helpful local supplier but no longer.

[Canuck750]

I got another 200 Sprite parts motor bottom end in trade for some Cardellino parts. The cases are excellent and will be used in my 200 motor. A bunch of other bits will find a home in the 250 and 125 motors.





A night in the ultrasonic tank then an afternoon of vapour blasting.



The bike suffered a broken transmission gear, probably sat for decades after the transmission went bang.



I am hoping I can repair the damaged crankshaft tip with
My MIG and turn it back in the lathe.



The rotor was fused to the crank, someone had tried to get it off before and whatever puller they tried damaged the crank and tore the threads out of the rotor spindle. I cut the rotor brass body off the steel Center (I have a spare) and used serious heat and a big bearing puller to get it off, amazing how stuck it was.

[Canuck750]

It’s taken many months of searching for parts, buying a couple donor engines, and research but I have finally got a rebuilt 200 crankshaft with new rod, pin and main bearing and while I was at it I had a 250 crank rebuilt with new pin and bearing and a 125 with NOS webs and bearing.



So now it’s time to go through all the boxes of parts and build a 200 for the project bike.  I will have a rebuilt 125 and 250 for future projects



Back to work on the Benelli

[Canuck750]

sorting through parts today, I have three sets of transmission pieces and used the best of the gears and dog, getting the snap ring off the output shaft to separate the rotating gear was a heck of a job, there must be a trick or a special tool, this snap ring has no holes in to open with a standard set of snap ring pliers. three small flat blade screwdrivers opened the ring to free the gear, I sure could have used three hands.

A very helpful tool is the Tusk crankshaft puller, not too expensive and it cleanly pulls the crank into the ball bearing without resulting to a soft mallet on the opposite end of the crank and disturbing the freshly trued crank



I pressed in a new small end bush I had made up by a machinist and reamed it to 18mm, drilled the oil passage holes. I also ran a 10mm reamer through the case cam follower bushings, one of the bushing was very tight.

crank set in one case and it spins so smoothly



Once the transmission and gear shift drum were installed I found there was a very stiff / tight fit across one set of meshing gears. I went back through the stash I had and found another gear that fits much better. I tested the shift mechanism with a small vice grip on the shift drum output shaft, it moves easily through the gears and neutral seems to be easy to find without the detent in place,



I should get the cases joined tomorrow and get on with the top end.

[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]

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?

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.