Loss of power and lots of sparks out of my exhaust. What did I break?
 

9000 rpm sustained on the highway in the fast lane. Plenty of oil. Coolant temperature nominal. Suddenly the bike loses power. I head check the lane on my right, and see a goddamn fireworks display coming out of my muffler. I keep the throttle pinned, but the engine is not firing. I make it over two lanes and then she roars back to life. She's running pretty shitty, but I slow way down, finally make it to the right hand lane, and figure if I pull in the clutch she will never start again... and I'm less than a mile from my exit. So I keep trucking. It has no power down low, so I have to downshift and keep the revs around 6000 in order to continue moving. She sputters again, and I move into the breakdown lane. I'm less than a quarter mile from my exit now. I get off the highway, down the ramp, and rev the bike in neutral to keep it from stalling. My house is just a couple miles from the exit, on 45mph and 25mph roads. By the time I pull into my neighborhood, my bike is running fine again. I pull into my driveway and it idles normally. I hit the kill switch, then try the ignition and it restarts fine.

There are no strange noises, and there is nothing obviously wrong with the bike. It revs freely, and makes no weird noises when I do.

Bike has 2800 miles on it. PO said he had done the 500 mile service and valve adjustment. I bought it with 1500 miles on it, so it wasn't due for 300 more miles.

What happened, and how bad was it?

Charles.

Update: Found the potential source of the sparks. The catalyst is mostly gone. There's a hole ripped right through the center of it. When I bought the bike the catalyst was fine. So, either that burned on its own (unlikely) or bits of hot metal took it out (more likely).

I'm going to do a compression test this weekend, and also rent an inspection probe and see if i can spot damage. My bets are that I lunched a valve.

Charles.

Oh man, I'm sorry to hear that. I never ran the bike that hard. When I adjusted the valves I triple checked everything to make sure it was right.
You say it still starts and runs fine with no weird noises? Will a bike do that if one of the valves is toast?

I've just had a crazy thought- I wonder if those mud daubers or yellow jackets built a nest inside the exhaust and over heated the catalyst?

Last summer I found a couple of good sized yellow jacket nests, one under the rear fender, and one behind one of the radiator shrouds? Both of them were about 3 inches in diameter. That's when I bought the cover.

Yup, just did a compression test. 80psi. I should have more like 180psi. I doubt she'll start cold.

So.... maybe this is the opportunity for me to put in the 300cc big bore kit right from the get-go.

Charles.

Another update: Exhaust valves have zero play. I can't fit my smallest .0015 (.038mm) feeler gauge in there. Also... access to the exhaust valves SUCKS.

How bad is removing the head? Can it be done with the engine in the frame?

Charles.

Did you adjust the vales and rechecked the compression? You may know this already but check the compression with the throttle open.

i would try readjsuting the valve and then testing compression again, before going whole hog on a tear down. if the valve is tight, it will cause a lean burn, which in turn WILL melt the cat... it may just be the tight valve and nothing else wrong....

That's my plan right now, I'm going to adjust the valves this evening. Got so much to do at work that I can't take any more time for farting around in the garage.


Charles.

Wow! They tightened up quick. I had them set tappy and happy at .08mm. Yea, access sucks. I had a hell of a time trying to get my fat fingers + a feeler gauge in there.

Well, so far so good. The exhaust valves had zero clearance but the intake valves were set properly. Warm engine last night, it made 80psi of compression. After adjusting the valves today it made 95psi of compression.

Since the bike has a built-in compression release, I'm hoping that the 95psi is simply where the compression release starts bleeding off pressure. Bike started easily. FAR more easily than it has ever started since the day I took it home, even though the battery was pretty run down from cranking the motor during the compression testing.

I have to take it out on a bunch of rides to see if I somehow avoided catastrophe. If it's reliable again... yay. If not... new head.

Charles.

Spoke too soon. It started earlier but now it won’t restart. No idea why. I’m frustrated and will work on it more tomorrow.

Charles.

Compression is at 100psi now. Plenty of hot fat spark. But I don’t smell fuel. I wonder if this was a fuel issue from the get go. I mean, power loss was like a light switch, and then it came back on just as sudden. If not for the hella sparks from my exhaust and my vaporized catalytic converters, I would honestly not have suspected a burned valve at all. I would have suspected fuel or spark.

Charles.

Can you hear the fuel pump when you turn the key on?

Did you do any electrical work before the the problems started? Maybe there is a bad connection somewhere.

No, no electrical work. I had never removed the tank before this. I always hear the fuel pump cycle.

Latest update:

Bike wouldn't start this morning. I loosened the side panels and slid the tank back, then propped it up vertically to check for kinked lines. No kinks. I pushed on all the connectors, and everything was properly seated. I tapped on the fuel filter. I sat the tank back down, turned the ignition on, and it started immediately.

So, I'm thinking this is a fueling issue. Either the injector or the fuel pump... but I'm leaning towards the fuel pump. I've read that the sock can deteriorate when a bike sits for a long time with the same fuel in it, and then it gets sucked into the pump and clogs it up. And this bike did sit a lot before I bought it from you. I'm betting that sloshing the fuel around and upending the tank is what allowed the bike to start. I'm going to get a siphon pump to drain the fuel out and then remove the tank and inspect the fuel pump to see if the sock is present and accounted for.

I'm not sure how a fueling issue can cause my catalyst to burn out, but if the whole problem is a faulty fuel pump I will be THRILLED. Easy and cheap to fix.

Charles.

Well, it did sit idle for a while but I'd start it once in a while to let it warm up. I noticed if I let it sit up for a few weeks then start it the pump would make a light squawking sound but after warming up it and starting it again it wouldn't make that noise. Sounds like you might have found the problem. As far as the catalyst, maybe a partially blocked fuel filter would create a very lean condition and possibly superheat the catalyst? FI systems are a little bit of my mechanical knowledge range. A clogged injector wouldn't be out of the question, those holes are tiny.