Stella Weak Spark

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toigo
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Stella Weak Spark

Postby toigo » Sun Feb 10, 2013 11:24 pm

Trying to get a 2 stroke stella running that was sitting for 2 years and I'm not too familiar with them so hopefully someone has some advice.

I cleaned the carb, checked the jetting, installed a GGR Carbon Fiber reed, new gaskets on the carb box, reed block, and below the carb, the idle screw is backed 1.5 turns out.

The bike also has a Pinasco pipe on it.

Compression in the cylinder feels fine. If I take the airbox off and hold my thumb over the opening on top of the carb with the throttle open i can feel the gas being drawn out of the carb. Gas is flowing fine to the carb.

I got as much of the old gas out as I could and topped it off with fresh gas. I also shot a tiny bit of 2 stroke oil in the spark plug hole since I was worried the 2 stroke system wouldn't be primed and didn't want anything to seize. Also put a new B7ES plug in. Stella's seem to have B6ES stock, but this had a B7ES in it.

So initially the bike would almost start occasionally on a kick. Right before the piston stopped moving after a kick it would fire 2 or 3 times, but only as the piston movement slowed down and not while the bike was being kicked with the piston moving faster. Eventually this seemed to stop and I thought I just flooded it, but even with plenty of kicking with closed fuel and open throttle and I'm not getting anything.

So I think I've narrowed it down to ignition or possibly to fuel/air not making it's way through the ports to above the piston. I also disconnected the kill switch to the CDI (green to white/green) wire in the horncast

I get a spark, but it seems very week and intermittent. Some kicks I can see it, other kicks I can't and it seems to have gotten worse as I've been trying more. I snugged up the connections everywhere I could see and still am getting the same behavior. So I'm thinking one of these:

1. Bad Coil
2. Bad CDI
3. Bad Wiring/Connection Somewhere
4. Something bad in the Stator (The bike lights up when kicked)

The Stellas have a separate Coil and CDI, so I can't easily swap my P200 CDI/Coil on there without running a bunch of extra wiring. So for anyone familiar with Stellas are any of the 4 possible causes I listed above common? I can test the resistance in the Coil based on the Stella Service Manual, and both the coil and CDI are pretty cheap from SIP, but I wondered if this just sounded familar to anyone before I ordered either of them. I had also seen some advice to replace the stock HT lead from the coil to the spark plug with an NGK one.

adrienna
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Re: Stella Weak Spark

Postby adrienna » Mon Feb 11, 2013 4:00 pm

I asked Aaron what he thought, and he suggests replacing the spark plug cap with a 90-degree NGK cap and the wire while you're at it.

A few years back, my Stella would just die while I was riding it. Eventually replaced the cap and boom! fixed.

-Adrienna

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toigo
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Re: Stella Weak Spark

Postby toigo » Mon Feb 11, 2013 4:39 pm

Thanks Adrianna. I'll try to swap the HT lead and spark plug boot off of my P200 today to see if that does it. Also, found this pretty german woman to help me troubleshoot.

http://www.youtube.com/watch?v=8VwRCAHT_XY

Also, just curious. Is it a terrible idea to shoot a quick bit of starter fluid in the spark plug hole? I'm pretty sure it's a spark issue, and if I couldn't get anywhere with that then I'd be real sure it was a lack of spark.

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toigo
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Re: Stella Weak Spark

Postby toigo » Mon Feb 11, 2013 8:34 pm

So I turned off the lights in my garage and compared the Stella spark to what I get on my P200 and the Stella definitely has a weak spark compared to the P200. It's intermittent and hard to see even with the lights off, but is there occasionally. The P200 spark is bright and very easy to see.

I swapped the spark plug, NGK spark plug boot, and HT lead off of the P200 and put them on the Stella, but nothing changed.

So I'm getting a spark, but it's just very weak. I'm hoping that this is just the coil and not the CDI or stator so I'm going to try swapping that out first.

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dcunited4life
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Re: Stella Weak Spark

Postby dcunited4life » Wed Feb 13, 2013 2:00 pm

All your raffle bieks r belong to us.

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Zeets
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Re: Stella Weak Spark

Postby Zeets » Wed Feb 13, 2013 2:28 pm

dcunited4life wrote:All your raffle bieks r belong to us.


Did you just have a stroke?
Zayretow

70' Vespa Sprint (2009 LML power)
74' Yamaha RD350 (pinger)
2008 Suzuki DRZ-400SM (thumper)

dirtyhandslopez
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Re: Stella Weak Spark

Postby dirtyhandslopez » Wed Feb 13, 2013 8:38 pm

toigo wrote:I can test the resistance in the Coil based on the Stella Service Manual


Did you ever do this?

Surely this is the quickest way to find out where the problem may lie. Whole lot quicker than swapping parts out.
That's not going anywhere

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dcunited4life
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Re: Stella Weak Spark

Postby dcunited4life » Thu Feb 14, 2013 11:44 am

Zeets wrote:
dcunited4life wrote:All your raffle bieks r belong to us.


Did you just have a stroke?


It's an internet joke.

http://en.wikipedia.org/wiki/All_your_b ... long_to_us

Modified to represent how 7 Hills SC has won every turnbulls raffle bike EVAR! I intend to continue this trend yet again this year.

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toigo
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Re: Stella Weak Spark

Postby toigo » Thu Feb 14, 2013 11:54 am

So here's where I'm at. Someone had a spare coil so I swapped that on with a known working spark plug, NGK spark plug connector, and HT lead and I'm still seeing the same thing. I also ran a fresh wire over the bike from the coil to the CDI on the left side of the bike and still the same thing. I can keep working down the chain (CDI -> Wiring -> Stator -> Flywheel), but if anyone has any other suggestions let me know.

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Zeets
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Re: Stella Weak Spark

Postby Zeets » Thu Feb 14, 2013 4:16 pm

Oh... I'm not so good at the internets.
Zayretow

70' Vespa Sprint (2009 LML power)
74' Yamaha RD350 (pinger)
2008 Suzuki DRZ-400SM (thumper)

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Mikeh
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Re: Stella Weak Spark

Postby Mikeh » Thu Feb 14, 2013 5:00 pm

I'm not a stella expect but, this should be a general guideline;

Disconnect the harness going to the scooter to make sure you don't have a grounding issue on the kill wire.

If it still has issues replace the spark plug with a known good one. Perhaps use your P200 plug so that you compare better between your P200 and this beast.

If it still does not work then Check all the wires are connectors to make sure they are good.

If they are good and it still has problems.

Then remove the flywheel and check to see if the magnet feels as strong as the one on your P200. Perhaps it got demagnitized by someone feeding electricity from a battery into the coils. This is rare but worth checking.

Then replace the CDI components with known good ones.

If it still has problems then replace the pickup on the stator plate.

It's really best if you can find someone that can loan you good parts so you can try things to see if your parts are bad or not. I think there was recently something on Modern Vespa or Stella Speed that explained how to swap P200 ducati parts onto the stella motors with the older components. Perhaps look that up and try your p200 parts on there.

And on a serious note Matt.. you need to ride with me to florida next week. Shall I pick you up on tuesday night on my way past DC ? I am taking the mini van to Raleigh on tuesday night and riding south from there on Wednesday morning. 250 to 300 miles each day.. should be easy peasy. Come on, call in sick to work!

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toigo
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Re: Stella Weak Spark

Postby toigo » Thu Feb 14, 2013 6:00 pm

Thanks Mike. Swapping parts off of the P200 has mostly been my strategy and I haven't had to buy anything yet cause I managed to borrow a coil. With the coil and CDI it gets to be a pain in the ass because they are two separate units on the Stella on different sides of the bike and a bunch of the terminals are lumped together in plastic. I'll try to spot the forum post you were mentioning and just run a bunch of extra wiring to make it work. The Stella CDI has the same Red, Green, and White (and a kill wire) coming into it the same as my P200 so hopefully I can get it rigged up.

This gave me some more background on how a bad CDI could still occasionally cause a spark, but it would be weak.

http://vespamaintenance.com/elec/cdiwork/index.html

500 miles is all my mom allows me to drive to a scooter rally :)
http://movie-sounds.org/quotes/fmj/$5-is-all-my-mom-allows-me-to-spend.mp3


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toigo
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Re: Stella Weak Spark

Postby toigo » Sat Feb 16, 2013 12:43 am

Ran a bunch of extra wires over the bike to get my P200 Coil/CDI on there and the bike started right up so this definitely was an issue of a weak spark.

So it's looking like bad CDI is the answer, bad kill wire (I only ran 3 of the 4 wires to the CDI, in the stella wiring harness all 4 have to be connected at once since they are surrounded by a single piece of plastic), or somehow I had 2 separate bad coils.

Modern Classics has a CDI that I can snag tomorrow and hopefully get the whole bike back together and start to get the jetting right.

Folks were saying that the Vespa CDIs are designed to take a different current than the Stella ones so long term it's not a good idea to run one, but other people are reporting running them for 10k miles without any issues so who knows.

Glad to be able to add identifying a good spark vs a weak one to my diagnostic knowledge.


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