Benelli Dynamo Compact

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Benelli Dynamo Compact

Postby Lotus54 » Sun Apr 10, 2022 4:27 pm

I picked up a Benelli Dynamo Compact mini a few years ago. My original plan was to maybe stick it on the back of the van and use for very short little trips when out camping. I didn’t do anything until after the 3 years for ‘ownership in doubt’ was cleared. And even then I thought they just sent the title. They don’t- after three years you need to go in and apply for a real title.
Anyway, I took the engine out since the kickstart shaft is sheared off. I did ride it- ran and shifted fine.
First bike I ever rode was a Benelli Dynamo Trail - pretty much the same bike but this has lights and road tyres. I still have that one.

I thought I had a flywheel puller- but if so I don’t know where it is. So I decided I’d make one. Seemed like a good time to learn how to cut threads on the lathe. For metric, the half nut is not ‘engaged/disengaged’ like for the inch threads. Instead it is left engaged and machine just put into reverse. Actually worked a lot better than it sounds.
It took me a bit, but I did get it so it fit into the flywheel fine. Then I drilled/cut threads (this one with a tap) inside. Went to use it, dang- I forgot to check the size of the crank. The hole was not big enough to fit over and it was not deep enough to just bore it (should have make it taller I think). Anyway I just drilled/tapped to 12mm and that was fine.
Popped the flywheel right off. I did make it in brass, so if it was very recalcitrant It could have stripped. But I wanted to learn how to do it with brass before doing steel- especially with my little mini machine.

I’m in no big hurry on this bike- I have some other jobs I want to do before this even gets a lot further. I will likely split the cases and see what I need (although I think I have everything) then just finish the engine before even starting on the rest.
1976 OSSA Super Pioneer- 78 Benelli 750 sei,72 250 2C Benelli, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, Lotus Elan S3
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Re: Benelli Dynamo Compact

Postby John H » Sun Apr 10, 2022 7:52 pm

Way to go! Threading can be a challenge sometimes and takes patiences to get it right.
There will be a donated Benelli 65cc auctioned off April 23 at the bike show posted here. Do you need another one?
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Re: Benelli Dynamo Compact

Postby Lotus54 » Sun Apr 10, 2022 8:33 pm

Need one? Ha.
But I would be interested. (Also that other bike you showed me)
1976 OSSA Super Pioneer- 78 Benelli 750 sei,72 250 2C Benelli, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, Lotus Elan S3
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Re: Benelli Dynamo Compact

Postby Lotus54 » Wed Apr 13, 2022 6:45 am

On this bike the countershaft sprocket is a tapered fit (with woodruf key). Since the shift shaft goes through the middle of that shaft (it has an internal engagement dog) you don’t want to press on that to remove.
I have factory service manuals, but the picture of the puller was hard to see how it was made.
I ended up making a spacer that would press on the correct part of the shaft and allow me to use one of my regular two arm pullers. It was on darn tightly, but it came off ok and no damage.
It did take me a little while to make, since the piece of aluminum I used to make it was quite a bit larger in diameter than I needed and I can’t take much off at a time with my little machine. Turns out I could have left most of it- since it really was only the first mm that it needed the puller. Oh well, it was fun anyway.
1976 OSSA Super Pioneer- 78 Benelli 750 sei,72 250 2C Benelli, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, Lotus Elan S3
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Re: Benelli Dynamo Compact

Postby Lotus54 » Thu Apr 14, 2022 5:19 pm

Next I had to remove the ‘pinion gear’ (drive gear of crankshaft). Another taper fit with key.
Not much room and none of my pullers would fit.
I was trying to figure how to make one- hopefully without spending 3 hours. I found a very small tie-rod end puller at the discount parts store. I just had to make the opening a couple mm larger and put a small taper on the end of the bolt, so it would stay centered on the crank and not wreck it.
Worked quite well.

Next will be to separate the crankcase- I have gaskets, seals, rings coming. I already have a new kickstart staft. I’ll see what else it may need once apart. Rod bearing feels good, all the other bearings feel good in place. But certainly I will check all.
1976 OSSA Super Pioneer- 78 Benelli 750 sei,72 250 2C Benelli, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, Lotus Elan S3
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Re: Benelli Dynamo Compact

Postby John H » Thu Apr 14, 2022 11:35 pm

Soon you will have a box full of Benelli Dynamo special tools. Always makes the projects more interesting when you have to make do. Sometimes it gets challenging but that's all part of the hobby.
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Re: Benelli Dynamo Compact

Postby John H » Sat May 07, 2022 11:31 am

How's the little Benelli Dynamo coming along? Is the special tool tray filling up? I'm constantly building special tools, many are just for holding a part that needs repaired, sometimes with another special tool.
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Re: Benelli Dynamo Compact

Postby Lotus54 » Sat May 07, 2022 12:26 pm

It is coming along. I ordered bearings and they just shipped.
I got a new air compressor (Quincy rotary screw) so I can use the vapor honer in a LOT more comfort.

So next I’ll finish vapor honing, install bearings and reassemble cases. I’ll likely make a special tool to pull it together. The bearings are all pretty tight on the shafts.
I made up a crank spacer to make sure it does not move halves, but I’ll make a little better one for reassemble. I did do a quick check on crank and it was well within specs.

But I needed to make an inner spacer for my OSSA hub, so took it off. (Of course I somehow goofed up and instead of making it a little long and trim to fit- I made it too short! Arrrggg. Oh well, making another).

Making an attempt to clean up shop too- since I have too many projects right now.
1976 OSSA Super Pioneer- 78 Benelli 750 sei,72 250 2C Benelli, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, Lotus Elan S3
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Re: Benelli Dynamo Compact

Postby Lotus54 » Thu Jun 30, 2022 6:03 am

I didn’t take pictures yet, but I will try before putting cases together.
I installed all the new bearings, checked crank for runout and the gearbox, crank and kickstarter is in.
The reason I had to split the cases on this one in the beginning was a sheared kickstart shaft. I had a new one- but not until now did I notice it is slightly different. I think it will be fine- but I will be taking another old side case (with no bearings) to test fit and make sure all is good. I will likely need to make up some shims to assure proper fit, but I will see.

Gearbox is interesting in that it has and internal dog and gears to do not move. For a pretty low power engine this works just fine and makes for a very nice shifting compact gearbox. It does require a good positive stop setup for each gear, but that is pretty simple also.

I have not even started on the chassis, one thing at a time for this.
1976 OSSA Super Pioneer- 78 Benelli 750 sei,72 250 2C Benelli, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, Lotus Elan S3
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Re: Benelli Dynamo Compact

Postby Lotus54 » Wed Jul 27, 2022 11:41 am

I got my new Vaporhoner setup. Still a couple little things I want to do- but tried it out and worked really well.
It will easily fit a 21” wheel, I did an 18” Borrani rim and it came out really nicely. Plus the Dynamo engine side cover.

I added more lights. It has one (fairly decent) AC one. But I added three more long LED waterproof strips. They run off 12Vdc and I have a power supply that I turn on with the same switch as the stock light.
The tanks on the left are for the ‘closed loop’ water. The water used to rinse parts (there is a spray nozzle inside to wash off parts after finishing- or to see if done) and the one for rinsing the window. Overflow water goes into those tanks and they keep most of any sediment out with those two.
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1976 OSSA Super Pioneer- 78 Benelli 750 sei,72 250 2C Benelli, 68 Benelli Dynamo trail, 76 OSSA GPII Phantom, Beta XTrainer 300, Lotus Elan S3
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