OP
UTC

Hooked
Rat 2003 Stella 2T; 1979 P125x (in pieces, out for paint)
Joined: UTC
Posts: 384
Location: Madtown
 
Hooked
Rat 2003 Stella 2T; 1979 P125x (in pieces, out for paint)
Joined: UTC
Posts: 384
Location: Madtown
UTC quote
I finally got my p200 project back together, two years in, and had it briefly on the road to start break-in and trouble-shooting. I built the scooter over Covid from the ground up, using an old p125 frame and buying the engine part by part. It's been a long and frustrating learning experience!

Anyway, the scoot ran, but I must have screwed up the kickstart install; the lever wasn't springing back and the starter gear was slightly grinding on the gear stack. So after a few trips around the block decided I had to split the cases and re-install.

So that went OK, I got the kickstart working properly, but when re-installing the engine I accidentally let the wires from the stator short each other. The battery was still installed and the CDI was hooked up, and from what I can tell the battery tried to send its voltage backward into the stator, eventually blowing the fuse off the battery.

This is my theory, because I've kicked the crap out of the scoot and can't get any spark. The stator ohms test OK. Is it possible that I burnt out my CDI somehow? What's the consequences of shorting the stator wires with the battery attached?
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9942
Location: Nashville

70 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: 9942
Location: Nashville

70 Days Since Last Explosion
UTC quote
In general, the CDI takes a lot more electrical punishment than a motorcycle battery is going to dish out, but that's not to say it's bulletproof.

Also, if you tripped the fuse, that's a short to ground, which happens fast and even relatively delicate electronics (e.g. CHT's) have survived me doing that before.

I assume you've isolated the ignition from the rest of the bike? Only connected the red/green/white from the stator to the CDI, no kill switch wire, and still no spark?

How are you confirming no spark? By holding a plug against the cases or some other method?

I'm still not entirely certain how you'd have even managed to short the battery back to the stator. The battery should sit downstream of the regulator/rectifier, so if you were able to feed DC back, you might want to consider other wiring issues at play here.

Do you have a wiring diagram of your as-built wiring?
OP
UTC

Hooked
Rat 2003 Stella 2T; 1979 P125x (in pieces, out for paint)
Joined: UTC
Posts: 384
Location: Madtown
 
Hooked
Rat 2003 Stella 2T; 1979 P125x (in pieces, out for paint)
Joined: UTC
Posts: 384
Location: Madtown
UTC quote
It was running perfectly before I yanked the engine, and I haven't buggered with any of the wires (except detaching the CDI from the stator and removing the stator from the bike). I've tried three different spark plugs and the bike won't start. I've disconnected the kill switch wire from the CDI, still no start. I re-attached the spark plug wire to the CDI. I tried to see a spark in a dark garage, holding the plug to the cases, but nothing. Wet spark plug shows that fuel is getting through.

Usually my RPM meter will register briefly when I kick, but it doesn't now.

The only things I noticed were the blown fuse and, before I noticed that, that the connectors to the purple, black, and red wires from the stator had popped out of the slots in the junction box and were touching.

Any more thoughts welcome...I just ordered a new CDI, they seem untestable, so maybe that will cure it.
@chandlerman avatar
UTC

Lucky
76 Sprint V, 63 GL, 62 VBB, 05 Stella, 66 Smallstate, 79 P200E, 66 Lammy S3
Joined: UTC
Posts: 9942
Location: Nashville

70 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: 9942
Location: Nashville

70 Days Since Last Explosion
UTC quote
They are unfortunately untestable, and the fact that they're potted in epoxy doesn't help.

Only other thing to check (and maybe you already tried this) is making sure the plug wire connections are still good. The rubber boots can hide the fact that the wire has pulled loose of the base. I've been fooled by that before.
DoubleGood Design banner

Modern Vespa is the premier site for modern Vespa and Piaggio scooters. Vespa GTS300, GTS250, GTV, GT200, LX150, LXS, ET4, ET2, MP3, Fuoco, Elettrica and more.

Buy Me A Coffee
 

Shop on Amazon with Modern Vespa

Modern Vespa is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to amazon.com


All Content Copyright 2005-2024 by Modern Vespa.
All Rights Reserved.


[ Time: 0.0079s ][ Queries: 3 (0.0017s) ][ live ][ 313 ][ ThingOne ]