OP
@msprygada avatar
UTC

Addicted
1979 P125x
Joined: UTC
Posts: 629
Location: Midland, MI
 
Addicted
@msprygada avatar
1979 P125x
Joined: UTC
Posts: 629
Location: Midland, MI
UTC quote
I have a '79 P125x where I am having problems with getting it running because of lack of spark.

If you attach the spark plug wire to the spark plug and touch the spark plug to any metal part of the engine (block, cylinder, and head) and you kick over the motor, you get a solid spark on the plug as well as a good solid illumination in the timing light. You do not have to spin the motor very fast to get a good spark or light the timing light. Then when I put the spark plug in the motor, the timing light will not light and the scooter acts like it is not getting any spark.

I have taken my timing light and attached it to my '65 Allstate and with the plug installed, and slowly kicking that over, the timing light will illuminate no problem (as well as start and run).

The plug is clean and it does not appear that it is fouled out. I have tried several plugs without any success. I have changed out the entire coil, spark plug wire, and plug end for the spark plug. I bought the scooter last fall with a burned piston which I have replaced it with a Malossi P177 kit and in the process of gathering parts and putting it back together, I have had the stator rewired with new leads as the original ones were crispy. A new condenser and points were put in the stator. The magnets of the flywheel appear very strong.

So from my testing that once the plug is installed in the motor, it will not spark. I have attached a ground wire to the spark plug body and touched various part of the motor with no change in behavior. This is a very puzzling problem.

Anyone have any ideas as to what to try or to look for?

Thanks in advance.
@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
It is harder for a plug to fire under compression than in the open. My thought would be a weak ignition coil on the stator or maybe the CDI. Can you get your hands one one to swap out and try ?
I had the same issue with a 64 V90 where it would not fire the timing light with the plug installed ( nor would it run) . I pulled my hair out for a while but ended up fitting a BGM 12V .
OP
@msprygada avatar
UTC

Addicted
1979 P125x
Joined: UTC
Posts: 629
Location: Midland, MI
 
Addicted
@msprygada avatar
1979 P125x
Joined: UTC
Posts: 629
Location: Midland, MI
UTC quote
I have tried two different coils. One original and a brand new one. Both had separate plug wires and plug for connecting to the spark plug
@v_oodoo avatar
UTC

Style Maven
'74 50s x3 '87 PK125XL '92 PK50XLS Plurimatic - & - '58 AllState '68 Sprint '66(?) Super125 and '72 DanMotor Super150
Joined: UTC
Posts: 9618
Location: seattle/athens
 
Style Maven
@v_oodoo avatar
'74 50s x3 '87 PK125XL '92 PK50XLS Plurimatic - & - '58 AllState '68 Sprint '66(?) Super125 and '72 DanMotor Super150
Joined: UTC
Posts: 9618
Location: seattle/athens
UTC quote
Is the plug wet or dry when it won't start? Good solid spark w/ plug out of the motor? Try this: https://modernvespa.com/forum/post1548781#1548781

External inline image provided by member with no explanatory text
OP
@msprygada avatar
UTC

Addicted
1979 P125x
Joined: UTC
Posts: 629
Location: Midland, MI
 
Addicted
@msprygada avatar
1979 P125x
Joined: UTC
Posts: 629
Location: Midland, MI
UTC quote
Well I still cannot get spark when the plug is in the cylinder.

So far I have had stator rebuilt and the condenser and points were replaced, new spark plug coil, spark plug wire, cap, and spark plug. I have had the flywheel remagnetized and still nothing.

Some have said that you need a stronger spark when the spark plug in in the cylinder and under pressure than when outside the motor. Some have said that the condenser could be bad and that will cause a weak spark. I am about the point to convert to the P factory electronic ignition as the next step. Points are not that difficult but this is pretty frustrating. I bought this scooter not running and I rebuilt the engine over the winter so everything else is in new shape and have no clue.

I had Scooter West send a new condenser when they sent the flywheel back and I will put that in this weekend and see if that makes any difference. If the condenser does not work I might send the stator back to have it looked over again.

Anyone have any other things to look for?
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