OP
@popgunandy avatar
UTC

Hooked
61 VBB 76 Rally 200 79 P200 80 Sport 100
Joined: UTC
Posts: 288
Location: Folsom CA
 
Hooked
@popgunandy avatar
61 VBB 76 Rally 200 79 P200 80 Sport 100
Joined: UTC
Posts: 288
Location: Folsom CA
UTC quote
I've never seen this happen before...one of my scooters suddenly started running like crap and when I opened the carb box I discovered one of the bolts had worked its way loose and created a massive air leak. It's weird because I've easily put 100 miles on her since the last time I touched the carb and all of it was trouble free.

Anyway, besides retightening the two bolts does anyone have two cents on this? I did pull the cylinder head and confirmed no damage there.
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@sdjohn avatar
UTC

Johnny Two Tone
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8545
Location: San Diego, CA
 
Johnny Two Tone
@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8545
Location: San Diego, CA
UTC quote
Get all new hardware, I had some like that and even loctite wouldn't hold them
OP
@popgunandy avatar
UTC

Hooked
61 VBB 76 Rally 200 79 P200 80 Sport 100
Joined: UTC
Posts: 288
Location: Folsom CA
 
Hooked
@popgunandy avatar
61 VBB 76 Rally 200 79 P200 80 Sport 100
Joined: UTC
Posts: 288
Location: Folsom CA
UTC quote
sdjohn wrote:
Get all new hardware, I had some like that and even loctite wouldn't hold them
Including the studs?
@socalguy avatar
UTC

bodgemaster
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: UTC
Posts: 7155
Location: So Cal
 
bodgemaster
@socalguy avatar
63 GL, 76 Super (x2), 74 Primavera (x2), 79 P200, 06 Fly 150
Joined: UTC
Posts: 7155
Location: So Cal
UTC quote
There should be a spring washer on each bolt to keep it under tension when tightened down.
@sdjohn avatar
UTC

Johnny Two Tone
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8545
Location: San Diego, CA
 
Johnny Two Tone
@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8545
Location: San Diego, CA
UTC quote
I'd do studs too, you don't know what part is jacked. And yeah SoCal is right make sue you have the spring washer in there too
UTC

Hooked
P200e
Joined: UTC
Posts: 129
Location: Eureka, Ca
 
Hooked
P200e
Joined: UTC
Posts: 129
Location: Eureka, Ca
UTC quote
Just put it on with the correct washer, tighten it down, and ride.

It's nothing.
@ray8 avatar
UTC

Molto Verboso
Joined: UTC
Posts: 1888
Location: Los Angeles
 
Molto Verboso
@ray8 avatar
Joined: UTC
Posts: 1888
Location: Los Angeles
UTC quote
Popgunandy wrote:
I've never seen this happen before...one of my scooters suddenly started running like crap and when I opened the carb box I discovered one of the bolts had worked its way loose and created a massive air leak. It's weird because I've easily put 100 miles on her since the last time I touched the carb and all of it was trouble free.

Anyway, besides retightening the two bolts does anyone have two cents on this? I did pull the cylinder head and confirmed no damage there.
There should be a spring washer under that bolt.

It looks offhand like you torqued the right side bolt, then tightened down that left bolt. What happens with Spaco carbs especially is they will get deflected by that steel bolt. When you go to torque down the left bolt you're fighting that deflection, so it feels like it's tightened down when it isn't. Both bolts have to be torqued in unison, slowly.

I'm betting you're fine if you torque 'em correctly, with maybe a new silicone gasket.
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9951
Location: Nashville

71 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9951
Location: Nashville

71 Days Since Last Explosion
UTC quote
For the carb, I tighten then hand tight, then alternate 1/4 turns with the torque wrench until they both click. Ideally, they will click on the same turn.
@scooterist avatar
UTC

Molto Verboso
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
Joined: UTC
Posts: 1558
Location: Tucson, AZ
 
Molto Verboso
@scooterist avatar
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
Joined: UTC
Posts: 1558
Location: Tucson, AZ
UTC quote
I had a similar problem on my engine. At one point during the engine swap we put the wrong size engine case studs, not only made it run horrible but it also ran very hot and it would take 20-25 kicks just to start.

Another think that I found is that one of the carburetor 11mm hollow nut was cracked and therefore it wasn't tightening on the stud.

Your solution is to put brane new engine cases studs and brand new carburetor 11mm hollow nuts/bolts with the two sets of new washer each.
UTC

Hooked
various, but less than I used to have
Joined: UTC
Posts: 175
Location: San Anselmo
 
Hooked
various, but less than I used to have
Joined: UTC
Posts: 175
Location: San Anselmo
UTC quote
If the other bolt stayed tight, high probability your carb is warped now. Take it off and set it on a true flat metal surface.
@sea avatar
UTC

Hooked
'61 Cushman GS150, '62 GS160, '74 Rally 200
Joined: UTC
Posts: 118
Location: Seattle, WA
 
Hooked
@sea avatar
'61 Cushman GS150, '62 GS160, '74 Rally 200
Joined: UTC
Posts: 118
Location: Seattle, WA
UTC quote
I would only tighten anything related to the carb by hand, and never over tighten. Just tighten the screws until they are snug (and alternate, as suggested). I would not use a torque wrench. These scooters were designed for people to maintain (mostly) on their own, and do roadside repairs. It's really not that scientific.

Regarding your post question, you need to periodically go around your whole scooter and check all the bolts and screws, and tighten as needed (carb, wheels, steering column, etc.). Over time, these will all loosen to a degree.
@sdjohn avatar
UTC

Johnny Two Tone
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8545
Location: San Diego, CA
 
Johnny Two Tone
@sdjohn avatar
'15 GTS300, '86 PX125EFL, '66 VBB, '01 ET4
Joined: UTC
Posts: 8545
Location: San Diego, CA
UTC quote
for the carb bolts I recommend a torque wrench, it is EASY to overdo them
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9951
Location: Nashville

71 Days Since Last Explosion
 
Lucky
@chandlerman avatar
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9951
Location: Nashville

71 Days Since Last Explosion
UTC quote
sdjohn wrote:
for the carb bolts I recommend a torque wrench, it is EASY to overdo them
I 100% agree with this.

The whole point of torque wrenches and torque specs is to ensure the right amount (neither too much nor too little) of tightening.
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