VBC1M (190 Super) engine build
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Wed Jun 13, 2018 12:15 pm quote
Ok, so it's time, at long last, to rebuild my VBC engine. This belongs in my 1976 150 Super, which has had two or three different engines over the past four years. The objective of this build is to reunite the scooter with it's factory engine, and to make some modifications for power and robustness reasons. I thought it would be useful to document an old (pre P) rebuild, particularly as this will get some interesting new parts. To summarise, it will comprise:

- VBC1M cases, ported to match a Pinasco Magny Cours base gasket
- Rotary pad opened up and inlet enlarged to suit a 24/24e carb
- DRT oil seal adapters for crankshaft (easier to change Viton seals)
- SIP/Mazz conversion crank (PX taper, 60mm stroke and mild duration increase)
- BGM 177 or Pinasco Magny Cours (187cc due to stroke)
- PX125 gearbox from a 2013 PX (68T primary)
- SIP 'Sport' banded Cosa clutch with 22T gear
- Ignition from 2013 PX125
- Box exhaust eg. BGM BB or Polini, or Scorpion expansion
- 10" wheels (cause I prefer the look and they will suit the gearing)

The 1976 cases are almost early P series, with three ports and the plastic oil slinger, but using the old crankshaft design with the narrow taper and the big 25x62x12 ball bearings either side.
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Wed Jun 13, 2018 9:52 pm quote
Case porting
I had only molested PX engines before, and had always needed JB Weld (or other brands) to build out the material prior to porting. This older motor had loads of meat, so no filling was required. Ok, the porting was not as aggressive, but still enough to go through a PX casing !!

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Before porting, the black marking out the area to be removed

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After porting. Just the finishing and cleaning to do.

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Wed Jun 13, 2018 10:11 pm quote
DRT crankshaft seal adapters
Probably the only reason I wanted to document this build was due to the use of DRT's new seal adapters and the SIP/Mazz conversion crank. Also, with a typical PX and LML build, you have the straightforward bearing and seal arrangement, which has been documented here loads of times. The build of an older motor is different in the crank region, as the method of installation is very different.

These shots of the DRT adapter are prior to me fitting the oil seal. I'm not yet sure if it's best to fit the seal before or after the crankshaft installation.

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Flywheel side crankcase with DRT adapter inserted.

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Close-up of DRT adapter inserted. Outside of case.

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Inside of flywheel side casing with DRT adapter inserted.

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Close-up of DRT adapter, inside of casing.

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Thu Jun 14, 2018 12:45 am quote
Clutch side adapter and seal
Not quite sure how to approach this. The adapter is slightly more than 7mm thick, according to the digital verniers. An old style clutch side oil seal is supposedly 6.5mm thick, although I measured a brand new one at 6mm. Something tells me I'm not going to need the spacer that came with the DRT adapter. Even then I'm concerned there won't be quite enough depth for the 12mm thick bearing, which on these engines is installed onto the crankshaft first, before the whole assembly is installed into the crankcase.

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Traditional clutch side seal for the older engines (new) next to the DRT adapter. The adapter is supplied with the seal already installed.

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Thu Jun 14, 2018 1:18 am quote
Hybrid/conversion crank + bearings
The SIP/Mazz crank has the traditional clutch side web for an older motor, but the flywheel side has the PX taper, allowing you to use a modern electronic ignition from a PX. The one I bought is a longstroke (60mm) and it has been cut to open the inlet earlier. I wouldn't call it a 'race' crank, but hopefully the resulting inlet duration will be a big improvement over the stock VBC.

I have lengthened/opened up the rotary pad to further advance the inlet opening, and to give a slightly later close. It also needs to be bigger to be fed by a 24/24 or 26/26 SI. The 150 Super had a piddly 20/15 from the factory!

crank fly side.jpg
Crankshaft - flywheel side

crank clutch side.jpg
Crankshaft - clutch side

crank + bearings.jpg
Crankshaft with SIP performance bearings installed

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6499
Location: Victoria, Australia
Thu Jun 14, 2018 7:07 pm quote
Great project! I have two Super cases, a 1974 and a 1975. The '75 has a P type needle flywheel bearing.

I wonder if the extra 1mm actually might help stop any lateral movement (although it's probably not the problem it can be with the roller bearings)? It may be worth contacting DRT to see what they say about it.

And since you haven't bought a cylinder yet, check out this one - New 177 contender
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Thu Jun 14, 2018 11:00 pm quote
Ginch, all I can think is that Douglas, which assembled Vespas in the UK, were using older spec. engines/cases as late as 1976, despite other markets getting the P style. I am surprised, as Douglas was not manufacturing anything, which they had done in previous years. Parts bin roulette I guess.

I'm going to be very careful with the clutch side measurements, which is what shipscat advised in the other thread. Once that crank is in, I don't want to have to pull it out again.

Thanks for the 'steer' towards the VMC, but my current thinking is to re-use an existing cylinder. More on that as it comes together.
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Mon Jun 18, 2018 1:30 am quote
Clutch side DRT adapter installed
This was not easy as it's an incredibly tight fit. Into the oven at 100 degrees centigrade for 15 minutes, then the adapter was tapped in from the clutch side, rather than the crankcase side. I didn't want to damage the brass ring on the way in. The installation took a few bigger taps with the hammer and socket, but was eventually fully home. I then used the circlip that was supplied with the adapter. The ends come much further round, presumably to provide a greater surface area for the adapter to sit on.

A few hammer/socket marks on this side, but shouldn't be an issue.

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Looking into the clutch side crankcase.

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Clutch side view of the adapter, seal and circlip.

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Mon Jun 18, 2018 1:45 am quote
Crankshaft installation
First time I've done this on a pre-P engine, and not a particularly enjoyable experience. Shout out to a good Youtube clip courtesy of Robot at Scooterwest.

Using the oven again to 100 degrees C, and with a layer of 2T around the bearing, I got the insertion angle wrong on the first attempt. Having tapped the crank back out, I went in again with more success. A few taps with a deep socket and the crank web 'wedge' in place and in it went.

I was confident the bearing would go in far enough to seal the rotary pad, despite the adapter being 0.3mm thicker than a traditional oil seal. I had reduced it's thickness from 7mm on a piece of sandpaper on glass, as the DRT adapter is almost 1mm thicker than it needed to be.

Once all the way in, the crank shoulder is only just protruding beyond the lip of the oil seal, and I am expecting some fun and games with clutch spacers.

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Tape in place to soften the step that the oils seal will need to ride.

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Crank inserted........phew!!

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Clutch side view of the inserted crankshaft

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Mon Jun 18, 2018 2:02 am quote
Christmas tree and gearbox installation
As said above, I bought a complete gearbox from a 2013 PX125. This gives me the stronger EFL axle, better cruciform, chunkier gear cogs, and the ability to space the main gears better, using spacers and circlips on both sides.

The VBC input shaft works well with the PX christmas tree, albeit narrower at both ends, and requiring the old style M9 input shaft nut and captive washer. I hope that the weedy input shaft is not going to be an achilles heal in this motor.

With the christmas tree and gearbox installed, there was a grinding sound as I spun the primary. Turns out the cush drive rivet heads were catching on the DRT circlip that is used to retain the oil seal adapter. Having taken the gearbox out again, I removed the DRT circlip and replaced it with the stock Piaggio item. This fixed the issue and back together it went.

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Looking lovely, but the primary doesn't spin cleanly.

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The Piaggio bearing and seal retaining circlip fixed the problem.

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Mon Jun 18, 2018 7:50 am quote
Flywheel side ready for final assembly
Flywheel side case half is now ready, with a new driveshaft/gear selector roller bearing and new rubber kickstart buffers. I decided to install the flywheel side crankshaft oil seal before, rather than after the two case halves come together. Good decision? We'll see very soon.

flyside.jpg

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Tue Jun 26, 2018 8:39 am quote
Case halves back together
This was easier than I had anticipated, having never built an old style motor with the big bearing pre-mounted on the flywheel side of the crankshaft. The fly side casing went into the oven at 100 degrees C for 20 minutes, and then with a little use of the kickstart, the case half just dropped on. I must have got everything lined up perfectly first time! Beginners luck no doubt.

With all of the crankcase bolts in place and nuts torqued down to spec., the crank turned beautifully, with just the usual resistance from the two oil seals.

case1.jpg

crank2.jpg

case3.jpg

Addicted
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Wed Aug 01, 2018 12:45 pm quote
I got home from holiday and decided to finish this build, even though time is tight. I had decided to use my BGM 177 kit (later one with graphite coated piston), but had never used one with a 60mm stroke crankshaft. In the end, I went with the 0.4mm base gasket and the 0.5mm head gasket, as I'd done previously with the 57mm crank, only this time I added a 1.5mm head spacer to take up the extra piston travel. I'm hoping for low end grunt, rather than a high revving setup.

The clutch I'm using is a SIP Sport, which is based on the Cosa clutch, but reinforced in many areas, and it has a 22T gear installed. In conjunction with a SIP 2.50 rim and 100/90 Schwalbe Raceman, this provides a useful upgear to the PX125 box.

One word of warning to anyone using the DRT oil seal adapters for older motors. The flywheel side adapter stands proud, and prevented my stator plate from seating correctly. I'm using the latest PX 2011+ ignition, but I suspect most stators will have the same problem. I've had to mill the back of the stator with my Dremel to get it good.
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Sat Aug 04, 2018 5:13 am quote
Ridiculous compression
This motor was fine before the top end went on, with the crankshaft turning beautifully. However, it's a pig to kick over, and I'm ready to:

1. buy a Rally 200 kickstart (longer, but the same old style curviness)
2. reduce compression by packing the head out by another 0.2mm or so. With squish at 1.0mm, I'm surprised at how much compression there is.

The motor started very easily. Although I had estimated the timing at 18 degrees BTDC. there is every chance that it's not correct. The old motors don't have the mark on the casting like a PX case. I'll get the timing light and Whale thingy out in due course, but I wanted to ensure that it starts up.

Meanwhile, the PX150 donor (of the BGM kit) now has a DR177 + standard exhaust + 24/24e, down jetted to 45/140 and 160/BE3/120. I have to say it's a lovely ride, and very reminiscent of a stock PX200. So refreshing to ride a Vespa which is [more or less] as the factory intended. The DR is really just a higher capacity PX150 top end, but it provides a really nice spread of power. Does what it says on the tin as they say
Hooked
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Sat Aug 04, 2018 10:21 am quote
looks great how about some scoot pics
Addicted
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Sun Aug 05, 2018 4:44 am quote
Here she is........work in progress!!
1976 150 Super in all her factory glory, obvious visual exceptions being the PX flywheel and CDI, Big Box Touring exhaust, and the SIP 10 x 2.50 rims. On the inside, the engine has a late PX125 gearbox, hybrid long stroke crank, BGM 177/187 top end, PX electronic ignition, and a P2 carb.

The original flywheel cover and carb box top have been left alone ie. not repainted (or even cleaned).

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Hooked
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Sun Aug 05, 2018 9:43 am quote
wow that is awesome really like the color!
Addicted
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Sun Aug 05, 2018 1:32 pm quote
Back in 1986, We were riding around the neighbourhood and saw what looked like a scooter wheel in a garage with the roller door up by about 12 inches. We knocked at the house and they let us take a look. It was a 1979 Primavera 125 in the exact same colour as my 150 Super, and it was very nearly in mint condition. They sold it to us for 50 ($75). What I would give to come across such a scooter today !!
Hooked
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Sun Aug 05, 2018 5:35 pm quote
swa45 wrote:
Back in 1986, We were riding around the neighbourhood and saw what looked like a scooter wheel in a garage with the roller door up by about 12 inches. We knocked at the house and they let us take a look. It was a 1979 Primavera 125 in the exact same colour as my 150 Super, and it was very nearly in mint condition. They sold it to us for 50 ($75). What I would give to come across such a scooter today !!
reminds me of my first true love only 1985 and a 1974 primavera. She wasn't as pretty as your super so my dad helped me paint her Jaguar red.
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50 N
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Mon Aug 06, 2018 12:13 pm quote
Is that the Super that was up for sale on Ebay a couple of months back?
Addicted
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Tue Aug 07, 2018 6:42 am quote
Juan, no it isn't. I bought it 15 years ago. The one I think you mean is the same colour and it's still on eBay. Paintwork is very messy mind.
Hooked
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Tue Aug 07, 2018 9:04 am quote
Beautiful Bike!

I'm also jonzeing to see that Px in the background.
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Fri Aug 31, 2018 8:00 am quote
As per a thread in NSM, I have now swapped out the EFL gear selector box for the original, which I thought would be a problem. However, it looks like the later 'old' style box has the 'pawl' set in line with the gasket face, as per a PX/EFL. The result is a very nice, smooth gear change in both directions.

The engine is hard to start, so my next job is to time it correctly with the Whale tool and a strobe. The carb jetting is there or there abouts for this spec engine, so I'm not going to focus on that for now. Jetting in an '80s 24/24e Dellorto is as follows:

Idle stack: 55/160
Main stack: 160/BE3/132
Filter: new SIP P2 with holes pre-drilled

I have also had to order the longer, but similar looking Rally 200/GS160/SS180 kickstarter, because the high compression makes for a very challenging kick. This BGM 177 kit was easy to kick with a 57mm crank, but with the 60mm, it's tough. The combustion chamber volume shouldn't have changed, because I compensated with 1.5mm extra spacing at the head end.
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