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@l4nff avatar
UTC

Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
Or something else.

So did a trip a few weeks back. Scoot was running lovely until the trip home when I developed a miss fire and stalling at lights etc. I made a small loop in the HT lead near the coil and all ran well all the way home. Ordered a coil and fit it. Scoot stalls at lights etc, will not tic over very well and is lumpy. Go for a ride and keep the revs up and all seems well, let the revs drop and stall. So I'm thinking blocked pilot jet! Took carb out and the jets blew it out ( with my lungs) and put back together, all good for 5 mins and same issue. Re torqued the head bolts. I did this because I took the plug out and it was white. Went for a small run, and plug is now black and oily. Thought I may have a air leak. Think I might have an air leak, but would that cause it to stall abruptly?

Ok my thoughts are, there is a blockage in the pilot jet circuit, even the I gave it my lungs.

There is/was an air leak and sucking enough air in causes an abrupt stall.

The condenser is shot, although it has only done about 1500 miles.

The coil is defunct, although it gives a cracking spark.

The HT coil on the stator is starting to fail as it's nearly 50 years old.

It's a vespa gtr with a 150 cylinder and head on it. Jetted with a 48/160 pilot, BE5 and a 110 main, sip road 2 and a 20/20 carb. It ran lovely for 350 miles.

Any other thought please before I start spending and chasing and replacing things that are good?
@killo avatar
UTC

Ossessionato
I have a few scooters....
Joined: UTC
Posts: 2225
Location: San Antonio, TX
 
Ossessionato
@killo avatar
I have a few scooters....
Joined: UTC
Posts: 2225
Location: San Antonio, TX
UTC quote
If you've got an air leak, pulling out the choke should keep it running. Try that and see if it makes a difference.

Go through and clean the carb completely. All jets and pathways. It may be one of the pathways that go some junk in it.

The bad coil that I had presented like this for me: at a cold start, it would run fine. At some point as the engine and coil heat up, the engine would die as if you'd hit the kill button. It wouldn't restart until the coil cooled off. Others may have experienced different symptoms but this was my experience.
@moto64 avatar
UTC

Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
 
Molto Verboso
@moto64 avatar
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
UTC quote
" Took carb out and the jets blew it out ( with my lungs) and put back together, all good for 5 mins and same issue." Do that again with compressed air and see if it lasts longer than 5 minutes.
⬆️    About 1 month elapsed    ⬇️
OP
@l4nff avatar
UTC

Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
Ok so I'm back here and scratching my head. I bought two coils and have tried them both and still has the same problem. Bought a new pilot jet and still has the same problem. Thoroughly cleaned the carb to no avail.
So pulled the fly wheel and checked the wiring, all looks good, e.g no splits and continuity. so put it back together and now have no spark. Bought a new condenser and fit it and still have no spark. I have disturbed something but dont know what.

Can anyone explain to me how to isolate the ignition side so I can try that on its own? What wires do I disconnect from the Junction box?

Also what resistance should I be getting across the three coils?

Also when testing the points which dont look bad there was continuity across the contact either open or closed.
Forum member supplied image with no explanatory text
UTC

Addicted
Old douglas ..smallie with polini 115..super with nasco 177
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Posts: 683
Location: New Zealand
 
Addicted
Old douglas ..smallie with polini 115..super with nasco 177
Joined: UTC
Posts: 683
Location: New Zealand
UTC quote
1 unscrew the green wire as test to see if the kill switch wire is frayed in the frame ( it never is)
2 In the pic its not clear but is it possible the brown wire from coil is askew and touching.also look at red it may be just touching green and red may also be loose with that excess copper showing
3 adjust the points gap as close as possible with eye-ometer .
4 did you set stator plate in correct position when you put it back (timing)

long shot.I once mixed up points screw and condensor screw which is longer and the wire connection to the points touched the stator plate due to extra length of screw ,it messed with my head for weeks

Long shot 2 One of my scoots has an erratic habit of the kill switch copper bit inside getting caught on the metal housing and needs a flick of the finger nail for it to pop out again....number 1 might shed light

Good luck
UTC

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PK50XL, PK100S, ET3, Matchless G80S, Honda CBR400RR, Ducati ST4S
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Posts: 614
Location: UK
 
Addicted
PK50XL, PK100S, ET3, Matchless G80S, Honda CBR400RR, Ducati ST4S
Joined: UTC
Posts: 614
Location: UK
UTC quote
Have you tried a new sparkplug? I've been having a similar issue on an ET3 and hopefully the new plug has fixed it. - it seemed ok on its last trip out after fitting the new plug.

Edit - this is for the bogging/stalling, not the lack of spark.
⚠️ Last edited by Matchlessman on UTC; edited 1 time
@moto64 avatar
UTC

Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
 
Molto Verboso
@moto64 avatar
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
UTC quote
If I read the VLB schematic correctly,
Disconnect : yellow ( lights), blue ( brake light), green ( horn).
Red is power to ignition and goes to kill on handle bar switch ( you can try disconnecting it at the box just to check that) , brown ( should be red) to coil. I add an additional black to ground on the frame.
@moto64 avatar
UTC

Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
 
Molto Verboso
@moto64 avatar
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
UTC quote
If I read the VLB schematic correctly,
Disconnect at the box : yellow ( lights), blue ( brake light), green ( horn).
Red is power to ignition and goes to kill on handle bar switch ( you can try disconnecting it at the box just to check that) , brown ( should be red) to coil. I add an additional black to ground on the frame.
Forum member supplied image with no explanatory text
@subetherbass avatar
UTC

Ossessionato
1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
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Posts: 4814
Location: Australa, Mate
 
Ossessionato
@subetherbass avatar
1997 Italjet Formula 125, 2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: UTC
Posts: 4814
Location: Australa, Mate
UTC quote
Why is the green wire bolt not "shiny/reflecting the light" like the others?
Plus, it looks kinda dodgy
Forum member supplied image with no explanatory text
@moto64 avatar
UTC

Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
 
Molto Verboso
@moto64 avatar
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
UTC quote
Looks like it is cocked at an angle reflecting the light differently.
OP
@l4nff avatar
UTC

Hooked
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
 
Hooked
@l4nff avatar
1972 Vespa GTR, 1963 Lambretta LI 125, Royal Alloy GP125
Joined: UTC
Posts: 225
Location: Halifax, England
UTC quote
Sorry people I mislead you with the picture as I had been messing with the junction box, the picture was just to show you the wires and colours.

Thank for your suggestions but I think I have found the problem and feel a little foolish. After testing coil resistance and stator wires and checking behind the headlamp and switch I took the points off.
I had visually checked these in situ and looked ok. But on closer inspection one contact was hollow, I filed them and put back together and kicked right up.

Those points have done less that 2000k.
Anyway new ones on order and hopefully that was the culprit and I can look forward to many event free miles.
@moto64 avatar
UTC

Molto Verboso
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
 
Molto Verboso
@moto64 avatar
'64 Motovespa 150S (177) , '65 VBB, '66 Allstate SF, '66 180SS
Joined: UTC
Posts: 1881
Location: S.Salem, NY
UTC quote
Good for you ! It's the condenser that minimizes the arcing and destruction of the points.
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