PX 150 ignition
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Member
Desperately Seeking a PX 150
Joined: 15 Aug 2008
Posts: 12
Location: Colorado
Thu Aug 21, 2008 5:51 pm quote
Hey folks, I thought I might bring my troubles over here from the Stella site desperately seeking help. I have a 2005 PX 150. Unmodified, electric start.

My problem is this: No spark. I've tried everything but a new stator -- can anyone tell from the readings here if the stator is good and maybe the new CDI is bad? or if it is the stator?

Yes, I've tested for spark at the plug. (and fuel and air and combustion) No spark.
New spark plug.
Unplugging the kill-switch wire doesn't help (No ground short there).
New CDI complete with new plug wire
Stator reads within the manual-specified range for resistance

Voltage output while kicking is as follows.

green to white: ~70 VAC
red to white ~0.5 VAC
red to ground 0.5 VAC
red to green ~70 VAC

I'm going to pull the stator tonight to be sure what color connects where. Any ideas? I don't want to replace a perfectly good stator, but I don't know what else it could be.
Hooked
Lambretta SX, Stella, Honda
Joined: 31 Dec 2007
Posts: 300
Location: USA
Thu Aug 21, 2008 6:04 pm quote
Try a new NGK Boot on the end of your plug wire first before getting into the Stator, etc. Those fail frequently on a lot of different Scooters. Available at ant MC shop and a lot of auto parts stores.
Member
Desperately Seeking a PX 150
Joined: 15 Aug 2008
Posts: 12
Location: Colorado
Thu Aug 21, 2008 7:01 pm quote
The new CDI came with a new plug wire and plug wire end. It's not a cap, it's a brass clip that is clearly connected with the copper wire in the plug wire. All shiny and new. Like this http://www.scooterworks.com/Spark_Plug_Clip_P206C94.cfm
with a rubber boot that fits into the cooling shroud.
Sponsor
DL200, TV2, Vega, Lui, GTS
Joined: 11 Nov 2005
Posts: 750
Location: Orange, NJ
Thu Aug 21, 2008 7:14 pm quote
http://www.scooterhelp.com/manuals/VNX1T.VSX1T.service.manual/21.jpg

you need to measure those coils in ohms, not volts.

use that page at scooterhelp to give you the readings needed

if the readings are not in that range, chances are it might just be the pick up that is bad and thats an easy replacement

Gene (typing over Andreas shoulder)
Edit - Because I am shite with electrics - Andrea
Member
Desperately Seeking a PX 150
Joined: 15 Aug 2008
Posts: 12
Location: Colorado
Fri Aug 22, 2008 5:35 am quote
Gene/ Andrea,

Thanks for the input. I measured the resistivity in Ohms per the PX150 Workshop manual. The pickup-to-ground is supposed to read 800 +- 100, it read 600... but given meter sensitivity, user error, etc, that difference isn't really enough to indicate BROKEN is it? Also, I have seen in some industrial applications that a circuit can measure the correct resistance, and still not transmit voltage as intended. For instance, if the Hall sensor isn't responding to the change in magnetic polarity, the associated circuit could still read proper resistance and not be transmitting voltage when it is powered. So after I measured resistance in Ohms, I measured voltage AC. The pickup is only transmitting 0.5 volts and resistance is fine. So I'm double-checking. Is that voltage enough for the CDI to trigger and fire the spark plug?

Do you know how much voltage the pick up is supposed to send out to the CDI? OR do you have ideas about what I might have missed?

From what I can tell, my problem has to be the Stator or the new CDI that I just bought is also bad, but I can't point at what is broken. It's just an idea.

I think I started from simple and moved to complex options. Spark plug (I tried a couple), plug wire, checked for ground-outs in the ignition system and kill switch. It's a simple system, so there aren't a lot of places for that circuit to ground out. Replaced the CDI. Measured resistance as directed by the workshop manual.

The two 'black boxes' in the system are the pick-up and the CDI, and I don't really know how to tell if they're broken. The pickup when reads good resistance. The CDI doesn't seem to have any tests. Perhaps you have some readings on voltage output from the various components on the stator, a test for the CDI, or some other suggestions.
Banned
Pha que
Joined: 30 Jan 2008
Posts: 745

Fri Aug 22, 2008 9:42 am quote
I did not ride my PX today .....But if you tell me what readings you require.
(I am to lazy to read the whole post)

I can get a reading from a completely functioning bike.



And it is always a good idea to just switch the CDI for a known working unit.
Rather than try & diagnose the CDI.

I have only had one new bad one before but it happens.
Member
Desperately Seeking a PX 150
Joined: 15 Aug 2008
Posts: 12
Location: Colorado
Fri Aug 22, 2008 10:34 am quote
Thom,

Bless you bless you for being so kind. What I need are Voltage AC readings from the wires coming off the stator. You probably need to unplug the stator from the CDI.

green to white
red to white
red to ground on the engine case

This way I can know if it's a bad pickup or -by elimination- decide it's another bad CDI.

Thanks
Banned
Pha que
Joined: 30 Jan 2008
Posts: 745

Fri Aug 22, 2008 10:51 am quote
allright I am a bit ignorant when it comes to electrical.....And usually force others to handle those kinds of shenanigans..........
Please excuse my prehistoric methods as I am usually dumfounded by any reading other than Volts or using a test probe.

Example:
so you want the bike off....key on. (mine is battery as is yours)

Pull the wires listed & measure the Ohms from (example) Red probe on red connection & black probe on case.


I have shit to do in the garage at some point & can check it for you.
Member
Desperately Seeking a PX 150
Joined: 15 Aug 2008
Posts: 12
Location: Colorado
Sat Aug 23, 2008 6:48 am quote
I'm sorry. I didn't explain very well.

To measure volts you will need to kick the scooter over while the probes are on the appropriate wires. Some multimeters will require you to move the probe to a different input on the meter to measure volts. Some just require you to turn a switch or dial to AC or VAC (not DC). or something like that. Or both. Make sure you have your probe in the right input ANd your dial on the VAC setting so you don't blow your meter.

Pull the wires off the CDI.

Put your red probe on the red wire and your black on the white or the ground. Then kick it over or push on the kick start sharply with your hand. If your meter is digital, you should get a very brief reading less than 100 Volts AC If the meter is analog, the needle will bounce up to the reading and right back down. The charge is very short when the bike isn't running.

Does that make sense?
Banned
Pha que
Joined: 30 Jan 2008
Posts: 745

Sat Aug 23, 2008 9:06 pm quote
I will try & get you a reading tomorrow when I takam working on another bike.
Greasy mentioned your readings were very high.
Member
Desperately Seeking a PX 150
Joined: 15 Aug 2008
Posts: 12
Location: Colorado
Sun Aug 24, 2008 7:47 am quote
Quote:
Greasy mentioned your readings were very high
.

Hmm. Could be. Does that mean too high? The bike is only 2 years old with 4000 miles on it . I haven't found any ranges for voltage output on any Vespa to compare with. I'm pretty sure the charge coil works, I'm curious if .05 VAC is enough to trigger the CDI.

thanks Thom. It's good to have a little encouragement through this process.
Banned
Pha que
Joined: 30 Jan 2008
Posts: 745

Sun Aug 24, 2008 7:12 pm quote
I have not had a chance to get to this as my wife has been on the bike this weekend...& I am just leaving my shop after working on my lammy for the afternoon.

Sorry about that.
Member
Desperately Seeking a PX 150
Joined: 15 Aug 2008
Posts: 12
Location: Colorado
Thu Aug 28, 2008 3:32 pm quote
Any luck?
Molto Verboso
Midnight Blue GTS 250 i.e.
Joined: 02 Jul 2008
Posts: 1301
Location: Leeds, Yorkshire, England
Thu Aug 28, 2008 3:41 pm quote
One quick tip and this happened to me when I had my PX it turned out that the HT lead was connected to the plug ok but the other end into the coil had worked its way loose, just make sure it's pushed all the way home, may work!!
Member
Desperately Seeking a PX 150
Joined: 15 Aug 2008
Posts: 12
Location: Colorado
Tue Sep 02, 2008 11:52 am quote
Finally, it's running again!!! It was the pickup. The flywheel had been rubbing on the pickup for 4000 miles. I guess the heat finally did it in.


A quick switcharoo, $33, and a little soldering and off she went. Thanks to everyone for your input.


Here's what I learned: A Hall sensor is supposed to be a touch-free element and that's why they last forever. They don't last forever in a touchy-feely environment.

Ride safe.
Addicted
2005 PX150 Spelunking the nether worlds of Vespa Hell since 2009!
Joined: 01 Sep 2007
Posts: 770

Fri May 13, 2011 7:41 pm quote
I recently had the exactly the same problem with my 05 PX 150. All last year I had weird issues from intermittent starting, intermittent plug fouling, running great one day and not the next.

Eventually, it just plain wouldn't start and I discovered there was no spark. While checking out the stator I noticed that the flywheel had discoloration tracks marks on the inside from the black plastic edges of the pickup grinding down on it which I'm sure overheated it, at the least.

After confirming that the flywheel had no visible runout, then cleaning everything up and soldering in a new pickup, I was then disturbed to find the new one was rubbing so hard it dragged the flywheel. So I called the Vespa dealer that sold me the pickup and they said to lightly file down the trailing edge until it didn't rub anymore.

Seems all fixed now, though I'm going to keep an eye on it. Seems strange to me it would be so out of alignment when the flywheel turns true.
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