1965 Benelli / Motobi 200 Sprite

[Canuck750]

One thing I learned from my visit to the Benelli / MotoBi Museum this summer is that for the most part the fasteners on the bikes appear to be chrome with no face stamping



The fasteners on my project were badly corroded and I did clean them up and have them cad platted but the finish is nowhere as nice as the chrome bolts I would like to have, but chrome is very expensive and I have had bad results in the past trying to get bolts re-chromed. So for this bike I bought a bunch of new stainless steel bolts and nuts but the faces are stamped and the stainless is not bright polished



I filed off the face stamping, then I ran a foam pad random orbital sander with 240 grit over the face and slightly domes the top surface followed by a buffing on a coarse wheel with white polish

stores open 24 hrs near me

I replaced all the 6, 8 and 10 mm bolts and nuts, the results are hard to tell that the fasteners are not chrome

[Antietam Classic Cycle]

I've seen more than a few "fresh from the crate" Benellis and none had chrome plated bolts. My guess is whoever restored the bikes for the museum added that touch.

[Canuck750]

I've seen more than a few "fresh from the crate" Benellis and none had chrome plated bolts. My guess is whoever restored the bikes for the museum added that touch.

Good point Charlie. Going through my museum pictures I can see that all of the mini bikes have standard bolts with face markings. Most of the egg motor bikes have polished heads on the bolts but not all. The 1967 125 Sprite has a bit of both. Maybe early Motobi models had chrome or polished stainless or perhaps, like me, the person who restored the bikes on display prefers a little more bling.

[Canuck750]

I bought a pair of cheap chrome shocks, 12" eye to eye for the Benelli, I will eventually strip the shocks down and paint the bodies black to look like the originals, the outside diameter of the springs are a bit larger but its ok for what I am after.



https://www.ebay.com/itm/292976459948

[Canuck750]

Waiting on some engine parts to move forward so in the meantime I made up a fresh set of axle nuts; an odd size, M15 x 1.25, 22mm wrench size. I used 304 Stainless a steel rod, 25 mm (1”) diameter, cut the flats on the milling machine and bored the center to cut the threads with a tap, parted to length on the lathe. A lot of work for three nuts but this is a very hard size to find, could only find them in the UK as Ducati single axle nuts, would cost me about $12 a piece, not that I saved anything with the cost of stainless and cobalt drill bits to bore out the centre’s.





I took a shot at making stainless dome nuts for the shocks, a lot of work, I found the correct thread pitch of M10 x 1.0 stainless on eBay for a reasonable price.



Made up stainless washers as well for the 15 mm diameter axles. Something very satisfying about making something so simple.

Three nuts, three washers, three hours later, good thing I am not doing this for a living!

[cliffrod]

Very cool- I like them, Jim.  That’s the whole point of having the machines in the first place. 

On Sat, I did similar work making a couple of spacers for the slightly long throttle cables on my CX.  Eventually, I’ll shorten the cables but didn’t feel like that much fiddling work at the time. 

[Canuck750]

  the whole point of having the machines in the first place. 

Very true Clint. I wonder though if the need to make something precedes the purchase of a tool or does owning the tool create a need to make something? The more I explore machining the more I think I can make, fix or create and this keeps leading to purchasing more tooling.

[Huzo]

So this a Benelli ?

[2WheelsUp]

Just stumbled across this thread... amazing work on a beautiful bike! In the past I had little to no interest in bikes of this era but since viewing builds like this on the forum over the last year I now appreciate the quality and technology that goes into them. Wish I had the skills and knowledge to offer technical advice, all I can say is to keep doing what you do.

[cliffrod]

Very true Clint. I wonder though if the need to make something precedes the purchase of a tool or does owning the tool create a need to make something? The more I explore machining the more I think I can make, fix or create and this keeps leading to purchasing more tooling.

Not sure how it works at your place, Jim, but the line between “need to buy” and “excuse to buy” often gets blurry around here.

[Canuck750]

So this a Benelli ?

Yep, Benelli retained the MotoBi label after the MotoBi wing of the family where brought back into the fold. The two stoke twin was developed during the DeTomasso reign and was also badged as as a Moto GUZZI.

[Canuck750]

Just stumbled across this thread... amazing work on a beautiful bike! In the past I had little to no interest in bikes of this era but since viewing builds like this on the forum over the last year I now appreciate the quality and technology that goes into them. Wish I had the skills and knowledge to offer technical advice, all I can say is to keep doing what you do.

Thanks Two Wheel, I never used to pay attention to the smaller bikes but now I find I am fascinated by all the small displacement Italian bikes that were so popular in the 50’s and 60’s. The quality of the engineering in the small machines is pretty high. I particularly like the aesthetic of the MotoBi / Benelli ‘egg’ motor bikes.

[Huzo]

Yep, Benelli retained the MotoBi label after the MotoBi wing of the family where brought back into the fold. The two stoke twin was developed during the DeTomasso reign and was also badged as as a Moto GUZZI.

I thought of no one but you when I saw it.
A roadside two bit vendor had it for sale at €500….
He did not start it, but had no qualms about doing so if I’d wished. Was on the way from Venice to Cortina in the Dolomites.

[Canuck750]

I thought of no one but you when I saw it.
A roadside two bit vendor had it for sale at €500….
He did not start it, but had no qualms about doing so if I’d wished. Was on the way from Venice to Cortina in the Dolomites.

That’s looks pretty nice for 500 Euro! I read they were decent bikes but I don’t think they had oil injection. If it were on this side of the Atlantic it would be on its way to my garage for that price.
Thanks for posting!

[Huzo]

That’s looks pretty nice for 500 Euro! I read they were decent bikes but I don’t think they had oil injection. If it were on this side of the Atlantic it would be on its way to my garage for that price.
Thanks for posting!

No worries.
Reply #176 on my trip thread reveals a lot more.

[Antietam Classic Cycle]

That’s looks pretty nice for 500 Euro! I read they were decent bikes but I don’t think they had oil injection. If it were on this side of the Atlantic it would be on its way to my garage for that price.
Thanks for posting!

Sold in the US as the Benelli Phantom. Down on horsepower from their Japanese contemporaries, largely due to smaller ports. Cast in provisions for an oil injection pump and delivery lines, but one was never fitted. Conjecture was that they meant to use a Mikuni oil pump, but since it was imported it would have had a tariff attached. Would have driven the cost of the Phantom even higher.

[Canuck750]

The 'before' picture, a big box of joy arrived via UPS this week, a box only a gear head could love



The engine sat in the ultrasonic cleaner overnight in Evaporust, it was pretty clean this morning but neither the crank pinion gear or the magneto were in the mood to leave the engine behind despite my best coaching with pullers and a big impact.

The magneto did eventually come free with a lot of small taps with a brass hammer on the end of the puller bolt torqued down as much as the impact would deliver, it came free with a thud, shot up a couple inches and gave up.



The crank pinion was another beast, one of the puller leg threaded studs snapped clean off from the pressure but the pinion did not budge.



After replacing the puller leg I took the block to the welding table, crossed my fingers and struck up the oxy/acet, a slightly carbon flame and with the puller cranked to the nines I touched some heat on the gear, bang, almost immediately the puller and gear literally flew off the crank shaft end and fell to the floor. Success!

The crank feels real good, it was the crank I needed most for another engine, stator and magneto and some gears and hopefully I will finally have a complete 200cc motor for my Beneli / Motobi build.

Everything stripped and vapour blasted, lots of parts to now sort through and pick the best between two motors

[cliffrod]

Very cool.  Glad to hear about good progress.

But what about having most/all of a spare egg motor lingering around the shop…? Do you think it may serve as the grease on that slippery slope to a second Benelli?

[Canuck750]

Very cool.  Glad to hear about good progress.

But what about having most/all of a spare egg motor lingering around the shop…? Do you think it may serve as the grease on that slippery slope to a second Benelli?

A confession:

I bought a complete (well mostly complete) 200 Sprint along with the motor, the second box is still on transit, fingers crossed it arrives! UPS has been a nightmare for shipping to Canada, had to fight to get duties and taxes reduced from $492 to $92, on top of shipping.

In any event my plan is to build a 250 racer type for a regional hill climb in British Columbia called the Rocky Mountain Giro. I have accumulated a complete 250 egg motor (early 4 speed) and after seeing the faired Motobi racers in Pesaro I have a new itch to scratch. The long fibreglass race tank, short hump back seat, rear sets, clip ons and 2LS front brake on Borrani rims is calling to me.

I have been secretly thinking of an Aermacchi Ala d’Oro race replica using a Harley Aermacchi race frame (ERS type) I have got a hold of and fitting a dry clutch 350 five speed motor to it, will still pursue collecting parts for that long term build but a Motobi racer is going to be a cool project as well.

It’s a disease, hopefully incurable, and I have ideas for custom rear sets, triple clamps etc I could take a try at fabrication.

[cliffrod]

A confession:

I bought a complete (well mostly complete 200 Sprint along with the motor, the second box is still on transit, fingers crossed it arrives! UPS has been a nightmare for shipping to Canada, had to fight to get duties and taxes reduced from $492 to $92, on top of shipping.

In any event my plan is to build a 250 racer type for a regional hill climb in British Columbia called the Rocky Mountain Giro. I have accumulated a complete 250 egg motor (early 4 speed) and after seeing the faired Motobi racers in Pesaro I have a new itch to scratch. The long fibreglass race tank, short hump back seat, rear sets, clip ons and 2LS front brake on Borrani rims is calling to me.

I have been secretly thinking of an Aermacchi Ala d’Oro race replica using a Harley Aermacchi race frame (ERS type) I have got a hold of and fitting a dry clutch 350 five speed motor to it, will still pursue collecting parts for that long term build but a Motobi racer is going to be a cool project as well.

It’s a disease, hopefully incurable, and I have ideas for custom rear sets, triple clamps etc I could take a try at fabrication.

Misery (ecstasy?) enjoys company,  Jim.  Numerous projects are waiting here, too- Guzzi, Ducati, HD, Aermacchi and more.  Then, when I went next door a couple of hours ago, my mother had set out a few pics she had found of me in the TR3B from when I was 16 & 17.  It’s also waiting in the garage for some r&r love and attention.  Man, I love that old car… 

Maybe we can convince each other along the way that there’s really nothing wrong with doing what we love to do…

[Canuck750]

Maybe we can convince each other along the way that there’s really nothing wrong with doing what we love to do…

Well said Clint!

[Canuck750]

Another stuck part, the rocker pins are secured into the cast body with set screws, these small ( M 5) set screws have a pointed end which mate to a groove in the dowels. The dowels are not moving smoothly, probably rusted and full of gritty oil.

The set screws are stuck, really stuck, I drilled out the staked edges of the screws, tried tapping, tapping ... and more trapping, penetrating fluids and finally heat, no way they would budge. I clamped the casting in my mill vice and drilled out the set screws, I used an 8 mm diameter end mill, it will work with the 6 mm steel inserts I have.



tapped the cast body to take the new steel inserts



screwed the inserts in, then using a 10 mm end mill cut out the section of the insert that fell below the 11 mm dowel pin opening, then used a 11 mm reamer to get the correct finished opening





I made new 6 mm set pins from a 6 mm x 1.0 stainless steel bolt with the end turned down to a point





marked the depth with blue marker, then cut off the bolt and saw cut a flat slot into the stub

red locktight to secure the new set pins, pre-oiled the pins and reassembled the rockers and sprung washers



One more part ready to reassemble.

I am going to try and make up new bronze valve guides, the guides are so badly worn, the motor must have smoked like crazy when it last ran.

[Canuck750]

One last bit of work on the replacement crankcases, Benelli used a couple roller bearings in steel cases for the cam support, earlier versions of the motor I have used caged rollers open on the inner and outer faces. These steel cases seize to the steel bearing supports, not an ideal design but I am sure Benelli never thought these old nails would be brought back to live some 55 years on.

The steel cases would not budge so I poked the rollers out and used my MIG to weld a healthy bead along the circumference of the roller case and across a face to knock it out.



Let it cool and it pokes free with little effort



I found a listing on eBay for a company in the UK that will make any valve guide, I ordered four, they will run me about $40 a pop all in. I can barely buy the stock guide material for that price. I sent them this sketch to make up new guides. I found a 7.5 and 7.48 mm reamer on eBay from China for cheap to finish the guides to my used valves. Based upon factory tolerance I should finish to 7.48 based upon the slight stem wear of the valves.

[Canuck750]

I pressed the con rod small end bush out of the replacement crankshaft I picked up. Glad I did, not only is the fit to the piston pin sloppy but the bush is cracked.

[Canuck750]

I found a big surface plate, new at Busy Bee Tools in Canada for under $90! 3" thick X 12" x 18", a bargain. I had been waiting for over a year for one to come in, all the others were apparently scoped up by a company that makes headstones for pets, I guess a nice big piece of granite is not cheap, no idea how they can sell these for so cheap.



I coated the surface with valve lapping paste and a couple of minutes of vigorous figure eights and back and forth and the surface is smooth, I did all the gasket surfaces and lapped the head top cylinder as well.



I surfaced smaller parts with a sheet of 400 wet and dry paper




I started wiut

[cliffrod]

Not surprised it’s hard to get stone.  My orders for custom granite (raw stock) from the manufacturers are currently requiring min 8-12 months lead time.  Even more pedestrian dimensional stone components are comparable lead times if you aren’t ordering a semi trailer load at a time.   So I would expect properly lapped surface plate stone to be a long schedule as well and not surprised that cheaper priced stones were bought up to be repurposed.  You just can’t get stone right now.  It’s an industry-wide issue.

So, while I impatiently wait, it’s to see more of your bike progress, Jim.

[Canuck750]

Not surprised it’s hard to get stone.  My orders for custom granite (raw stock) from the manufacturers are currently requiring min 8-12 months lead time.  Even more pedestrian dimensional stone components are comparable lead times if you aren’t ordering a semi trailer load at a time.   So I would expect properly lapped surface plate stone to be a long schedule as well and not surprised that cheaper priced stones were bought up to be repurposed.  You just can’t get stone right now.  It’s an industry-wide issue.

So, while I impatiently wait, it’s to see more of your bike progress, Jim.

I shouldn't be surprised that finished stone, like everything else is in short supply these days.

I have been busy getting a bunch of parts ready for bright zinc plating but this time I am taking the extra step to finish the bare steel parts of the visible components to a decent bright finish in the hope that once plated the bright zinc will have that like new bolt look. In the past the plating I get done is very good but it has not been like new in shine. I have three sets of kick start and brake pedal levers and a bunch of axles and shafts with exposed heads. Some pits remain on the pedal components, the depth of the rust was very deep and I have already spent three days getting this small batch of parts prepared.
The kick starter parts should be chrome plated but I am not too happy with the chrome shop I have used for years and until I can find a good shop the bright zinc will have to do,



All of these pieces were rusted and several had very deep pits, I almost considered throwing a brake pedal away but went after these parts with a series of random orbital foam backed sander papers, 100 / 150 / 240 / 400 and then on the polishing wheel with white polish stick



The 'other' parts are mostly inside the motor and not visible, the rest of the exterior fasteners are stainless steel

Most to the engine studs and shaft threaded ends needed attention, everything chased and ready for plating. I pulled the axles and swing arm shaft out of the Aermacchi 250 as well, the bolt hex ends had to be cleaned up on the lathe and mill, just knackered after decades of ham fisted abuse, likely from pipe wrenches and vice grips grabbing the heads.

[Canuck750]

I can finally say with confidence I understand the differences between the Benelli 4 Speed 'egg' motors; 125, 200 and 250 cc.

The rumor I have been told a couple times is that all three share very similar bottom ends, this is only partially true to the extent of the transmission parts, even the cases are slightly different across the range. For example a 125 and 200 4 speed motor share the same frame mounting bolts, the 250 has a different lower frame location point.
125 and 200 cases are very close but there are differences in the type of small diameter needle bearings used between the two, including the depth and bearing covers.
My point, which I have now learned the hard way, is that not much actually interchanges with the bottom ends other than a 125 and 200 share the same con rod but the crank webs are not interchangeable.

When Its all said and done I have accumulated a 125, 200 and 250 motor for a 200 bike! One day the 'other' engines may find a home in a chassis.

Nerding out here but for the recorded here are the measurements and diagrams I did to catalog the bottom end differences in my quest to find ONE good crank.

[Canuck750]

My friend George, retired professional welder TIG welded replacement aluminum fins on my Benelli 200 engine case and rocker cover. This outer long fin was almost completely broken off, I have just a little bit of cleanup to do and the repair will be almost invisible



Four fins were broken off the rocker, again just finishing to do

[Canuck750]

I picked up the reconditioned head today from the machine shop, new guides pressed in and reamed to size and the valves reground.







I dropped the crankshaft off with a NOS crank pin and a new caged needle roller bearing I purchased from 123 Bearing in the UK - 30 mm O.D. x 24 mm I.D, x 15 mm width. I asked the machinist about the suitability of the bearing and he told me he uses similar bearings all the time rebuilding dirt bike cranks so I think I am good to go. Dry fitting the bearing ion the con rod with the pin felt great, almost no play whatsoever.

The 'new to me' pair of crankcases have been cleaned and all new bearings fitted, double row close fit ball bearings, standard ball bearings and cup needle bearings all purchased from 123 Bearing in the U.K.





I have sent the cylinder studs and misc bearing covers out to be bright zinc plated, I will hopefully have the bottom end back together in a couple weeks at the latest.