Questions after tear down and inspection
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Member
'63 Vespa 150 VBB2
Joined: 17 May 2019
Posts: 5
Location: Seattle
Sat May 18, 2019 10:04 pm quote
Hi all, this is my first post here. Working on my first Vespa project, a '63 150 vbb2. Have done lots of wrenching on other stuff, but this is my first foray into Italian scooters.

Picked up the scooter for a good price. Was "assembled" by seller who had bought it years earlier in boxes after nice paint job. Scoot looks great and seems very original/unmolested, but seller admitted it needed a good going through before hitting the road. Coil was cracked, had no spark and cables all needed adjustment.

As I was turning the engine over to work on spark issue, it started binding up every few rotations. Seemed strange, I rotated forward, backward and it would just stop randomly and I could hear a scratching sound coming from inside the case. Finally decided to split the case to see what was going on. Inside, I found some mangled wire lodged in the crank and piston area. Was able to extract the wire, and everything spins fine now, but the piston and cylinder were gouged pretty good. Piston is a 57.8, it's already on 4th oversize, so I guess they are toast.

The wire had me concerned as I have no idea where it would come from. Too thin to be from clutch or Cush springs it seemed. Pulled the clutch, driveshaft and cush assembly and couldn't find the source of the wire, any idea where it could have come from?

On inspecting the gears, I found that the driveshaft play was a bit too loose and the cross was pretty hammered so will order thicker shim and a new cross. I also found some marks on the smallest cog of the driveshaft and smallest cog of the cush assembly (see pics). I can't tell if these marks are supposed to be there, they are pretty uniform in size/shape and I don't have new gears I can use as reference. Thoughts? Are these trash or good to go? [/img]

2019-05-15 21.55.53_LI.jpg

2019-05-18 17.57.00_LI.jpg

2019-05-18 17.57.20 HDR_LI.jpg

Ossessionato
73 Rally, 74 Rally, 76 ET3, 80 P200, 63 Li125, 65 Li225 Silver Special, 86 Elite 80, 2015 HD Road Glide Special, 2011 Ural Tourist
Joined: 18 Jan 2012
Posts: 3184
Location: Oceanside/ SF
Sat May 18, 2019 11:13 pm quote
Are both wrist pin clips in place? Previous owner may have used wire clips instead of circlips. There’s nothing wrong with using them but most stock motors use actual circlips.

The pics of the gear are fine. Picture two shows the top of the Cush gear and the cutouts the kickstart cog rides on.

Rather than looking at the ramp on the last pic, look at the insides where the shift cross makes contact. Is that square or rounding out?
Member
'63 Vespa 150 VBB2
Joined: 17 May 2019
Posts: 5
Location: Seattle
Sun May 19, 2019 9:17 am quote
Thanks for the response. Both wire clips were in place on the piston when I removed it. The inner parts of the gears look OK.

Trying to decide on whether to replace with stock size cylinder kit (57mm) or oversize 61mm, which requires different head. Not planning to upgrade carb or exhaust, will it make a difference in power? Any experience on re-jetting to suit the larger size? Just the main jet? I think I have a 20/17 carb.
Addicted
GL, PK, PE200
Joined: 24 Apr 2012
Posts: 594
Location: Deep in the heart of Texas
Sun May 19, 2019 11:16 am quote
Replacing the carb and the exhaust will make a difference in power. A new 20/20 carb should have the correct jets for a standard cylinder. With oversize cylinder and bigger exhaust requires increase in main jets 3-5 points maybe a lil more.

Lets see some pics of your project.
Member
'63 Vespa 150 VBB2
Joined: 17 May 2019
Posts: 5
Location: Seattle
Sun Jun 16, 2019 5:22 pm quote
Making progress, got the engine back together and rebuilt the clutch as it was slipping badly when kicked.

Now I'm back to my original issue with this scoot. No spark. The coil that came with it was cracked so replaced the coil, points/condenser, and plug, then gapped the points. Have not dialed in the timing yet but have found TDC using a homemade tdc tool. I've tried hooking just the red and back from the stator to the coil with no luck. I've tried connecting the reds and backs from the harness to the coil as well.

I suspect the stator, but don't want to throw more parts at it if it could be a wiring issue. The wiring harness on the scoter side is a little funky

There are five wires coming out of the stator which seems normal and matches the wiring diagrams I've seen.
Black
Red
Yellow
Blue
Green

The scooter-side harness wires are a little different:
Two yellows (soldered into a single pigtail)
Two green (soldered into a single pigtail)
One thin Green with grey dots
One black from harness
One black zip tied along harness
One Red

There is no match to the blue coming from the stator
There is no match to the thin gauge green with gray dots
I have no idea what the extra black wire is for.

To isolate the spark issue, which wires should i be focused on and what tests can i run?

2019-06-16 17.46.34.jpg

2019-06-16 17.50.15.jpg

2019-06-16 17.49.34.jpg

Member
'63 Vespa 150 VBB2
Joined: 17 May 2019
Posts: 5
Location: Seattle
Mon Jun 17, 2019 5:01 pm quote
bump, any insights on this wiring and lack of spark issue? Should I just start a new thread since it's a little off topic from the original title?
Addicted
GL, PK, PE200
Joined: 24 Apr 2012
Posts: 594
Location: Deep in the heart of Texas
Mon Jun 17, 2019 5:10 pm quote
Sorta difficult to diagnose from just looking at wires from junction box but someone maybe can help you. Do you have a picture of the stator and what diagram are you using?
Veni, Vidi, Posti
74 50s x2 78 P200 84 Cosa 58 AllState 68 Sprint 80 50special + projects
Joined: 22 Nov 2010
Posts: 6886
Location: seattle/athens
Tue Jun 18, 2019 8:06 am quote
I don't know how your stator is wired, but I'd try this. First disconnect all the wires and use a small LED or meter to check for pulses between black #1 and red #2. If you see flashes or meter movement and the coil is good, you should get spark w/ only those two connected to your coil. If not, time to look inside.

wires.jpg

Member
'63 Vespa 150 VBB2
Joined: 17 May 2019
Posts: 5
Location: Seattle
Tue Jun 18, 2019 10:21 am quote
Thanks! Will try that out tonight and report back.
Hooked
Vespa
Joined: 25 May 2016
Posts: 350
Location: US
Tue Jun 18, 2019 11:52 am quote
also check the wire to see if any has crack on the insulation that couldve shorted with the ground. This is between the stator and the case exist hole.
Hooked
1964 GS160, 1966 90ss
Joined: 08 Sep 2011
Posts: 217

Tue Jun 18, 2019 12:35 pm quote
I'm in Seattle too. I have a couple of spare coils you can try if you think yours is bad. PM me if you get stuck.
Veni, Vidi, Posti
74 50s x2 78 P200 84 Cosa 58 AllState 68 Sprint 80 50special + projects
Joined: 22 Nov 2010
Posts: 6886
Location: seattle/athens
Tue Jun 18, 2019 12:45 pm quote
Good catch ph0ngvu! You probably should take off the bakelite terminal box & inspect the wires as far as you can without pulling the flywheel yet. tape off the ends of the others for now. I assume #1 & #2 come from the stator, 1 is the ground, 2 should be ignition and 3 I assume is where the ignition goes forward to the kill switch that does its job by grounding it. If that wire is shorted somewhere inside the frame, no spark, so we're eliminating that possibility.


Also, can we have another look at this if you haven't already sorted it out? From to the left w/ cylinder raised up? I agree w/ MJRally that it looks like a stray wire type wrist pin clip.

wires2.jpg
in the blue circle, how does that look up close and under the terminal box?

Molto Verboso
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 1067
Location: Siam
Thu Jun 20, 2019 5:09 am quote
gmontag wrote:
I'm in Seattle too. I have a couple of spare coils you can try if you think yours is bad. PM me if you get stuck.
I've got four or five of those things and they don't work. Just put in a cheap Taiwan made coil and all is good. Those brown things are notoriously shitty.
Enthusiast
1979 P200E
Joined: 01 Jan 2018
Posts: 90
Location: Houston
Thu Jun 20, 2019 7:16 am quote
Curious about that mangled wire. Wonder how it got there...
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