Sunday, October 16, 2011

When Too Much is Not a Good Thing

Yes, too much may not be a good thing.

Now with enough room in my garage and with it clean enough to not be considered complete chaos, I broke out my project bike. $110 at Nevada Suzuki for a new battery and diagnostics were ready to commence.

Crank, crank, crank, pop, crank, crank, pop. She would barely hit, enough to show that at least she was operable enough to mix some fuel, compress and cause it to ignite, but not enough to be self sustaining.

A few little squirts of starter fluid and she kicks off for twenty seconds and stops. OK. That reduces the possibility the problem is with the ignition system. Even though I drained the fuel from each carb, there is still gunk in the fuel system, so I keep squirting and running until she finally pops and starts running a little.

20 seconds... 30 seconds... 40... 50... a minute. She is alive and breathing fuel, but just barely.

I shut her down and feel the exhaust pipes. Rear cylinder pipe is nice and warm. Good. Front cylinder pipe is cool. Damn! That is the one I had problems with before.

So, while the battery gets a little charge I pull the plugs. With its compact powerplant, just pulling the plugs is a challenge in itself. But, they do come out and the above picture is what I find. Carbon fouling.

Here is where I made a previous diagnostic failure. Memories of my Dad teaching me to read plugs are coming back and I see the error. Before I would pull and read and since they were wet and black, I thought 'oil leak.' But no black smoke. Diagnostic fail.

It wasn't oil, it was fuel. How do I know? This time I leave the plugs out for a few minutes. If it were oil making them appear wet, they would still appear wet after a few minutes in the air. If it were fuel, it would float away in the air and the plugs would look dry.


There was something to chew on now; hard diagnostic analysis. Possible causes: rich fuel mixture; weak ignition; poor compression.

Poor compression is possible, but simple 'finger-over-the-plug-hole' indicate there is compression. It may not be up to spec, but there is. And, if there is indeed a compression problem, it is likely in the valves. There is no cross contamination between engine fluids to indicate any gasket or piston ring failure. So, compression is at the bottom of the possible issues list.

Weak ignition is possible and with my spare parts pile, I can easily replace the coils, plug wires and CDI. Actually, the last time I worked on her, I did swap out the coils and plug wires, so that likely isn't it. But, maybe the CDI. This is high on my list of possible culprits and with a little swap, is easy to confirm or dismiss.

Rich fuel mixture is another strong possibility and very likely the culprit. Getting in there to make fine adjustments is a challenge but not too tough.

So, #1 - Rummage through the garage and find the spare CDI and swap that out.
#2 - If that doesn't work, get out the tiny screw drivers and tweek with the carbs.

Looks like a good wrenchin' Sunday.

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