Modern Vespa

ok I just picked up a 79 p200e from oklahoma last weekend. barn find.
so I put a new battery, new ingnition with keys, spark plug, rebuilt the carb and gas lines. ive had it running a couple times with and without the battery. the previous owner also had it running without a battery he said. now I have like 25% spark, very low spark. do you think the regulator has gone bad. why does it have low spark?

heres a pic of the barn find

I think I read on here that running the battery model P without a battery for a while can damage the regulator. Or maybe it was the stator itself now that I think about it

Don't quote me on that

Nice looking find by the way!

ive been talking to friends that say it might be the regulator also. i wanted to make sure before i buy a 90 dollar part

P series bikes dont use the power of the battery to power the ignition. The battery just runs the batter side of the lighting system - and the horn. The stator is what runs the headlight, charging system (one component of it anyway) and the ignition spark.

Highly unlikely - but take the rubber cover off the coil that is covering the 4 wires (2 green, 1 red, 1 white) Remove the green one that is the outermost - this is your kill switch wire. if it fires up and you have no problems then you have a kill switch wire that is grounding itself out enought to give you a week spark.

Did you change the plug wire? Plug wire cap?
Other possibilities - weak stator, weak magnets on the flywheel, weak coil.

The regulator/rectifier on your bike has nothing to do with the sparkplug.
Weak spark, check, in order-

-the sparkplug, get new
-HT cable and plug cap
-CDI wiring, remove outer green wire (to kill switch) from from CDI and check for spark
-CDI wiring, check condition of red, white and green wires
-CDI itself, best method is to swap it with a known working one.
If you still have no spark you have to pull the flywheel and check the wiring, trigger and ignition coil.

If the battery is not charging, then its time to check the regulator/rectifier.
good luck!

I do think I read a post on here that running a battery system without a battery puts extra strain on some more integral components - I believe it might have been the stator, but it might have been something else. So although the battery has nothing to do with the spark, running sans battery for a long time could still adversely affect the ignition system and shouldn't be done for extended periods without a batteryless conversion. That was my understanding

thanks for all the help.
I putlled the green wire and still low spark.

im going to order a regulator first then coil and wire

I'm going through the same issues with my p200 - very weak spark.

The regulator has nothing to do with spark. The spark comes from a separate coil on the stator, and doesn't pass through the regulator at all.

The new CDI I bought came with a spark plug wire. You might want to buy a new spark plug cap and try that, too. It's cheap. In my case, a new CDI did not change things. It's either the stator or flywheel.

In my case, I believe my flywheel is defective, since the stator checks out when tested with an ohm meter. Two of the 6 magnets on the flywheel are noticeably weaker than the others. I just got a PX flywheel, but I may need to modify it for the p200. I should know in a few days, when I get a chance to work on it.

Good luck, and keep us posted!
Mike

why are you buying a regulator?

ive heard from people that if you run the bike (like the previous owner did) the regulator will burn up.
so should i replace the coil wire and cap? or cdi?

two sides of the brain at work here

xantu is refering to running a bike without battery

it does put a strain on the reg/rec

the battery helps soak up that extra juice put out by the stator



the other side of the brain here is your spark

the two(battery and spark) have nothing to do with the other

as mentioned, the spark is a product of stator to cdi to plug

so, go backwards, plug-plug cap-plug wire(ht)-cdi-stator

DO NOT REPLACE REG/REC TO DEAL WITH SPARK

OKEE DOKEE

I just replaced the wire and cap. it ran for a minute then died. it acts like it running out of gas but ive done all the gas stuff already. I guess next it the cdi?

Thanks for the clarification Jimmy I was looking through some old posts and shaking my head with how confusing some of the back and forth can get.

Kyle - the running for a minute and dying thing could be a non-electrical issue. I know you said you "did the gas thing" but what procedures did you cover in that? What makes you think that the dying after running for a bit is the same issue as your weak spark?

ive cleaned tank, new fuel lines, rebuilt the carb.

when i compare the spark from my running vlb with the p. i looks allot less spark than of the vlb. barely any spark.

Remove the fuel line from the carb - turn the gas on and see if you have a constant flow of gas. your issue sounds more fuel related than spark. However, if your fuel is flowing fine and you do have weak spark then the fuel is loading up in the cylinder rather than burning and causing the bike to die.

When your bike dies - pull the plug - is it wet or dry? If its dry you are looking at a fuel problem - if its wet you are looking at a spark problem.

Jimmy - thanks for the third party clarification - xantu was definately right regarding the lighting side of the electrical system - and those arguing that the regulator had nothing to do with spark were also correct.

i wouldn't replace the CDI just yet. I've had those go out, and they just... boom... go out. seems like they either work or don't.

the coil is part of the CDI.

i'd recheck the plug wire/cap/plug/carb/fuel line/tap again before getting a CDI (suppose a spare doesn't hurt, but those things are expensive!)

def. not the voltage regulator...

i thought the ducati electronic ignition was bulletproof.

could it possibly be the stator or flywheel? seems less likely than easier things...

well i rebuilt the petcock, then pulled the flywheel and stator. found the black wire was squished but i repaired it and still have the low spark problem.
im going to go with coil and flywheel replacement. tha nks for the help. i will keep you informed.

so i replaced the cdi and still not fixed. next is internal coil and flywheel