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Weak spark

Joined May 2007
96 Posts | 0+
Cambridgeshire, UK:2002 FS650e
Put bike back together after stripping and cleaning carb. Now it won't fire up. The spark seems weak when I check it with the sparkplug earthed against the cylinder head. Have replaced HT lead and cap and sparkplug. Have also removed s/plug and cap and held HT lead about 10mm away from cyl head. It doesn't seem to spark everytime when kicked and when it does spark it doeasn't seem that strong.

Have checked stator at the connectors with the coil, red-black is 2.8K, green to black is 168 Ohms (whilst disconnected from coil). All connections from stator to coil have been checked. I've also disconnected the orange kill switch lead from the coil whilst doing the checks. I now think it may be the coil that's causing the problem. Any thoughts?
 
can't recall at the moment but it was running fine before you stripped the carb?
obviously checked everything else such as fuel blockages, vent tube blockages, etc prior to turning to the electrics?
 
Re: RE: Weak spark

Hi Loonyburg,

From the readings you have got from the stator I would expect it to do something strange how it was running before you did the carb.
But just because you get reasonable readings from the stator don't be to hasty to point the finger at the coil, these very rarely pack in and when they do the out put is zero

Regards

Sparks.
 
RE: Re: RE: Weak spark

The bike now works really well. 3 kicks required from cold without choke but still need to do e-start lobe mod as it won't quite fire using the button.

So what did we (my son and I) have to do to get it going........
- fit rewound stator by Sparks
- remarked flywheel using TDC method. The factory marks were several degrees out
- regapped valves at revised TDC point
- drained fuel tank and carb and refilled with fresh fuel (BP Ultimate, 102RON)
- put in new plug (IXU24)

The engine is now much more even and seems to be running quieter and cooler with a lot of torque.Power is much more even and manageable. Even though it has a straight through exhaust, it seems quieter than it was before.

Oh and I did replace the CDI unit. Sparks checked the original and it was okay. So I'll be putting a CDI unit on ebay for a 2002 fs650e....any interest?

When I look back on the start of the problems I would say it was fundamentally a gradual stator failure compounded with valve gaps that could never have been set up well due to the TDC mark being in error. The rest is carb set up.

I'll have to take the valve cover off next to replace the e-start lobe thingy and check the cam follower bearings whilst I'm in there.
 
RE: Re: RE: Weak spark

How do you mean? Valve gap can never been set up correctly whit the TDC a couple of degrees out? I didn't know it had to be this precise?

Just don't wanne make the same mistake as you :D
 

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