Troubleshooting Help? 2000 M750 Won't Start

[bond0087]

To start off with, my bike is a 2000 M750 w/ 24k.

I'll try to give as many details as possible, even though most of them are probably unnecessary.  After being out of town last Fri-Wed, I went to ride to work Thursday morning.  It had rained almost every day that I had been gone, and it was cold and still pretty wet outside Thursday morning (I don't have a garage, so it was outside).  It really did't want to start.  After lots of trying to start it, it finally fired (it was turning over consistently, but not starting). It ran normally for the very short ride to work (~4 mins), until I pulled into the parking lot and it died.  I tried to restart it then, but had no luck.  I figured that maybe the pod filters had just gotten wet and weren't flowing correctly, and that after a bit of drying out it would start.  It didn't. I ended up having to go get my car and leave the bike at work.  That evening, after a while of trying to start, it drained the battery, so I called it a day. After charging the battery overnight, on Friday I tried again to get it started and had no luck.  Today, I put a bit more fuel in for good measure (no working fuel light or trip odometer, so it's always a bit of a guess how much fuel is in there). I tried taking the pod filters off and spraying some carb cleaner in there to start it (didn't have any starting fluid on hand). I made sure that fuel was getting to the carbs, and it was.  Despite all of this, it wouldn't ever fire. I recently added a tachometer and gauge cluster from an 01 900ie, so I tried unhooking that just to see if that was changing anything.  I checked all of the fuses in the fuse box, and all of them were good.  I took the plugs out and cleaned them.  Any suggestions of things to try now?

[Monster750ie]

Does the carbed monster have a petcock? If so is it open? If it is open turn the petcock off so fuel doesnt flow. Then check if you are getting spark at the plugs. Pull a plug leave it connected to the plug wire and crank the motor. See if your getting spark.

[Howie]

Were the plugs wet?  Oily?  Carbon fouled?  Did you check for spark?

[bond0087]

Thanks for the comments.  The carbed monster does have a petcock, and it is open but mine is stuck in the permanently open position right now.  I bought a manual petcock that I'll install soon, but haven't gotten around to it (found one for <$5 for a lawnmower at Advance Auto Parts, and it looks like it will work nicely).

After attempting to start the plugs were wet.

Using a spark tester (One like this), at a gap of about 5-6mm, the spark was thin, inconsistent, and occasionally yellow/orange, so I'm fairly sure that it's ignition related.  I tried to take the battery out of the equation at one point by connecting with jumper leads to my car's battery (with the bike's battery taken out), with no different results. 

With a freshly charged battery, the voltage at the ignition circuit fuse was 12.2V with the key on, kill switch off, then dropped to 11.7V with the kill switch on.  When the starter was engaged, it dropped to 10.9V.

I checked the pick up coil resistance and ignition coil resistances, and all of those checked out.

Any ideas on what connectors could get corroded and cause similar issues? Thanks!

[ducpainter]

You battery doesn't sound too healthy, but that could be from trying to start it.

A very talented Duc tech friend always says when a bike was running fine and you mess with something and it doesn't run fine anymore you should re-trace your steps to see what you screwed up.

I'd look where you connected the tach.

[bond0087]

Thanks for the advice, that's a great rule of thumb.  I generally assume that I screwed things up when it fails shortly after a change as well.  It did run fine for at least a week after the tach upgrade, though, so I wasn't too concerned about it.  I went ahead and disconnected the instrument cluster anyways to take the new tach out of the equation, and couldn't tell any difference.  Interestingly, someone suggested that the wild fluctuations on my tach could be caused by a bad connection somewhere in the ignition, so that's consistent with other symptoms.

As far as the battery goes, I checked the voltage across the battery directly during starting. I don't recall the exact voltage, but I believe it was in the high 11's during starting, while the voltage at the ignition circuit fuse was 10.9.  When the kill switch is turned on and the voltage at the ignition fuse is 11.7, the voltage at the battery is mid-high 12's.  All of that makes me think that there's something causing excessive resistance in between the battery and ignition circuit.  I need to buy some quality contact cleaner and get to work cleaning out connections, but any pointers to common problems would be great in the mean time.

Thanks!

[Buckethead]

Corroded ground cable connection?

[ducpainter]

Corroded ground cable connection?

Not a bad call.

Bad grounds can do very bad things to the ignitor boxes.

[bond0087]

Thanks for the advice; I'll check the ground connection first thing when I get a chance to get back to it tomorrow.  To do that, do you think that I should just check the voltage difference between the ground at the ignition module(s) and the negative battery terminal, or do something else?

[ducpainter]

Thanks for the advice; I'll check the ground connection first thing when I get a chance to get back to it tomorrow.  To do that, do you think that I should just check the voltage difference between the ground at the ignition module(s) and the negative battery terminal, or do something else?

There are several ground connections on carbed monsters that I know of.

One is under the battery, one by the RR, and one to the engine cases behind the right rearset at a mount bolt.

Voltage draw from the boxes is negligible I think

[bond0087]

Gotcha, thanks.  Does the RR ground to the frame via one of the bolts that attach it to the tab off of the frame?  I've noticed (before this problem showed up) that one of the bolts holding the RR to the frame is missing; I wonder if fixing that might make a difference.

[ducpainter]

It does on my bike with a ring terminal on one of the RR mount bolts.

Hard to say if that's it.

Have you checked for spark?

[bond0087]

Yep, I've checked for spark. Using a spark checking tool, I tried an open air gap of 5-6mm and saw an inconsistent, thin spark that was occasionally yellow/orange.  I'll post an update this evening once I've checked the grounds out. 

I've got a ton of work to get done in the next few days, but seeing a forecast of sunny and high's in the mid 70's all week while my bike won't start is killing me! Going to be hard to concentrate...

[greenmonster]

Have you tried a fresh pair of plugs?

[tbyte]

If I leave my 750 out in the rain uncovered I always get water in the gas.  I would charge up battery and spritz some fresh gas down carbs then try to start.  If it fires at all replace gas.