Runs absolutely perfect then wont start

How do you stop the engine after a ride? I assume a switch of some sort. Perhaps the switch is dirty.
Leo
 
Then I shut it down for five minutes and start it with no charge kicks.
I shut it down with the key switch under my ass. That's the only switch I have.
 
Ok. Im thinking cap. It ran fine with the new cap. I need to decide on an upgrade. For now I'll run a switch or that might do it. Thanks for the input. Much appreciated.
 
If it were me, I would add a switch to the headlight. The seems to be the only recent change you've made to the set-up. Also, I would add in a small 12v power source for additional assurance. Getting stranded sucks but I think it could be easily remedied.
 
I put a switch in today before I left today. Something is interrupting my spark after it gets hot. It started great last night so I figured it was the cap. Guess not. I have a ride on the way.
 
I'd still suspect the cap as part of what's going on with the bike. The more I read about the Sparx caps the less I like the idea of them and want to use a name brand, industrial capacitor. I have seen capacitors in other applications lose capacitance over time.

Have you ohmed the coil when the bike is hot and won't start? I'd be willing to bet you have an intermittent short in one of the windings.
 
NONclow said:
My best guess.....your cap is not rated for the draw and is overheating.

Get a bigger cap, or swap the HL bulb for the weaker one and try it.
Click to expand...
Your comment makes the most sense - ie capacitor rating insufficient for job.

It was working fine before the headlight wattage increase. Now it's handling more current.

Since it stops working after the engine runs for a while, perhaps the capacitor dielectric is breaking down and shorting to ground.
 
I'm no electricity guy by any means. Are you saying my cap is overheating while I'm in motion? The way I see it it has to be the cap, my switch, or my coils because it starts if I eliminate the cap and use a battery.
 
I just a battery to it after checking the resistance on the coil. Started right up. I'm gonna have to do some research on caps or at this point install a battery.
 
no loose wires on the coil or anything silly that could be causing an intermittent ground? Have you tried checking V when it wont start? maybe carry a little voltmeter with you to check things over next time it leaves you stranded...
 
Nope. Everything looks good. Funny thing is it will start off the cap after I use the battery. I'm seriously stumped.
I installed the switch in my bucket today thinking I had it made. No so much.
 
After a ride does the cap feel hot or hotter by touch, gloves first(?:wink2:).....
How about when it fails?
If the (bad) cap is underrated, too much current transfer creates heat It needs to dissipate even if mounted well enough in the air stream.

Not to mention the polarity could also be reversed.

You need more cap!.........................or a battery.........
 
It was definitely hotter than not today. It's not by any means in an airstream. Hasn't been since I built this pile. Neither is my reg/rec. I realize that's not good. But I'm stubborn and my electrical box (a small oxygen bottle with the top cut off and tabs added to hold it together) looks awesome!!
 
Well the cap was pretty warm when I had the issue. Thing is I keep the cap and the reg/rec in a small oxygen bottle that I cut the top off. Not the best idea I guess but this bike has been flawless since my first run out with it but the headlight is the last thing I changed and being a mechanic by trade I should realize that it's part of the issue.
So... as far as caps go the sparxs I have has two hot leads and the ground and everything else I look at just has two. So that's confusing me. What size cap is sufficient?
Another thing that's confusing is why it will not start until I put a battery to it but if I immediately hook the cap back up its fine with the fucked uP cap. That just doesn't make sense to me.
I'm about to run the 35 watt lamp and see what happens.
 
Well the cap was pretty warm when I had the issue. Thing is I keep the cap and the reg/rec in a small oxygen bottle that I cut the top off. Not the best idea I guess but this bike has been flawless since my first run out with it but the headlight is the last thing I changed and being a mechanic by trade I should realize that it's part of the issue.
So... as far as caps go the sparxs I have has two hot leads and the ground and everything else I look at just has two. So that's confusing me. What size cap is sufficient?
Another thing that's confusing is why it will not start until I put a battery to it but if I immediately hook the cap back up its fine with the fucked uP cap. That just doesn't make sense to me.
I'm about to run the 35 watt lamp and see what happens.
 
sickofitall said:
Well the cap was pretty warm when I had the issue. Thing is I keep the cap and the reg/rec in a small oxygen bottle that I cut the top off. Not the best idea I guess but this bike has been flawless since my first run out with it but the headlight is the last thing I changed and being a mechanic by trade I should realize that it's part of the issue.
So... as far as caps go the sparxs I have has two hot leads and the ground and everything else I look at just has two. So that's confusing me. What size cap is sufficient?
Another thing that's confusing is why it will not start until I put a battery to it but if I immediately hook the cap back up its fine with the fucked uP cap. That just doesn't make sense to me.
I'm about to run the 35 watt lamp and see what happens.
Click to expand...

How warm was the cap? Were you not able to touch it for more than a second? Truthfully the fact that it was really much above ambient temperature it would have me a little concerned. It's being over worked.

Truthfully I would just fit the highest farad capacitor that I could fit. I use them in other applications similar to this to smooth out current ripples (inconsistent voltage) in high amperage DC applications. The demand is usually very close if not briefly above the supply and can cause funky things to happen.

To get another type of cap of cap to work check for polarity of the capacitor (it'll be marked or a stripe on the heat shrink around it) and match that on the bike, + to +, - to -. if you have more than one positive wire at your current terminals you'll have to put them all on the single positive post.

I can't explain the cap and battery swap scenario. I initially understood this as you putting jumpers on the bike with both the cap and battery being used.

I have been looking around a bit myself at capacitors and found a few options.

This has 10x the capacitance of the sparx capacitor
http://www.ebay.com/itm/3-x-Western...045216?hash=item2103a4af60:g:2aoAAOSw4HVWFSNi
This one has 20x
http://www.ebay.com/itm/CDE-99000uF...399346?hash=item2101c1ceb2:g:nm4AAOSwMmBV5v3n
And while looking around today I found this, and it seems super intriguing. Significantly higher energy density than the previous two options and obviously much smaller. I will be trying this myself shortly. It will however need some kind of case because of the board.
http://www.ebay.com/itm/16-Farad-16...976694?hash=item3d1804dbf6:g:egkAAOSwG-1WzdPG
 

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