SOLVED: Loud noise at start and start fail

[Motorhobo]

I've been putting off dealing with this for almost a year now since this my dog's ride, not mine.

Charged up brand new Odyssey battery, started right up, then cut out and gave me the same noise and start fail I had last year:



Crank up the volume to hear how ugly that sounds when you're standing right next to it.

Here's what I've done:



-New battery
-Replace starter with spare from running bike
-Cleaned under-tank plug with contact cleaner
-Cleaned EFI connector with contact cleaner
-Cleaned starter connection with wire brush and contact cleaner
-Checked coil connections
-Cleaned main ground connection at transmission

The lights come on and the headlight appears strong. When you hit the starter sometimes it fires, sometimes it just clicks and hums a little. I've had that with a weak battery, but this one is brand new, so it's not that.

I didn't do the backspin since I replaced the starter with a known good one, but I will do that tomorrow. I haven't done the ignition switch maintenance thing but will do it tomorrow. In the meantime, I'm wondering if anyone has experience with this noise. If it's related to starter relay, I have a spare but I'd like to get y'all's feedback before I start the troubleshooting thing.

Thanks for any input --

MH








 

[The Mighty Gryphon]

Pull the plugs and make sure they're bone dry.  Crank the engine with the plugs out for a couple seconds with the tank connector unplugged to blow out any fuel that may be in the cylinders.  Reinstall the plugs and try again. 

I have found that my bike's are very easy to flood if the throttle is open any more than what the "choke" opens it.  With the fuel injection system, it seems it is really easy to drench the spark plugs if they don't fire right away.  Pulling the plugs and spinning the engine is a good way to get rid of any extra fuel in the cylinders and see how the engine spins with no compression.

You might also want to do a load test on the battery to see what the starter is actually getting from the battery.  Even new batteries have been known to have problems with supplying cranking current.

[mw074]

  I am a big fan of the Bosch spark plugs. I use my used K bike plugs in my torpedo heaters and the Bosch are the only ones that don't foul out in a short time span.

[Martin]

+1 sounds like it was flooded. Do what Gryph suggests. If it keeps on flooding chief suspect is the temperature sensor or it's connector.
Regards Martin.

[Motorhobo]

I'll do as y'all suggest and report back...but I've been flooded and had wet plugs and it's never sounded like that before. In the past when I've had flooding problems it's been because of low cranking power and hence not enough power to fully ignite on start. Strange thing is, this thing started suddenly while I was parked downtown. I was able to get it to run and rode it home where it's been sitting since. I put a new battery in and it ran, so I thought that was the problem -- but it happened again and I pushed it home. The sidecar rig is too wide to fit on my trailer :-(

The point is that it sounds like something electrical is the cause and the funky noise is the symptom. I've heard a lot of noises in my 18 years of bricking, but that snapping/whacking/hacking one is a new one on me.

Anyway, I'll try some stuff out tomorrow and get back to you...

[Chaos]

That thwacking noise caught my ear.  No idea, but it sounds like something mechanical.  Duh, big help, I know.

[rbm]

Could it be the alternator drive cup broken, parts thwacking between the drive dog and the vanes on the drive cup?

[Motorhobo]

Could it be the scrotator drive cup broken, parts thwacking between the drive dog and the vanes on the drive cup?

That's a distinct possibility, Robert, I'll get my stethoscope and check that out first.

[stokester]

Pull the plugs and make sure they're bone dry.  Crank the engine with the plugs out for a couple seconds with the tank connector unplugged to blow out any fuel that may be in the cylinders.  Reinstall the plugs and try again. 

I have found that my bike's are very easy to flood if the throttle is open any more than what the "choke" opens it.  With the fuel injection system, it seems it is really easy to drench the spark plugs if they don't fire right away.  Pulling the plugs and spinning the engine is a good way to get rid of any extra fuel in the cylinders and see how the engine spins with no compression.

You might also want to do a load test on the battery to see what the starter is actually getting from the battery.  Even new batteries have been known to have problems with supplying cranking current.

I'm with you on checking the load capacity of the battery even with a new Odyssey, which is what I use, especially as it appeared before with a weak battery and you just put in a new one.

Be sure your connections and ground is clean and tight.

[bocutter Ed]

The scrotator drive may be pooched but that shouldn't affect starting. It will start without an scrotator ...

Alternator drive aka monkey nut cup ...

[Motorhobo]

I replaced the starter relay and that hellacious sound went away but now I don't appear to be getting any spark. Fuel pressure at the rail is good. Cranks strong but no ignition...not even a sputter.

[Motorhobo]

This appears to be fixed -- I had a double whammy with the starter relay and the ignition switch. The relay had a cracked housing which someone had covered with duct tape. I'm pretty sure it was the cause of that thwacking noise. After replacing it I didn't have enough power to start, so I removed the ignition switch to find duct tape where the retaining tangs were supposed to be and a cracked plastic housing in the interior. But I did get the switch working and the bike starts and runs great now.

So, for the sake of search engines -- if you hit the start button and hear a loud noise (see top of thread for audio) and your bike won't start then you may need to replace your starter relay!