Running rich enough to blow hole in exhaust can

I'm stumped! I bought my first vfr a couple months ago and am about $500 deeper and 100 hrs are so more invested then I want to be. Last week, after a severe loss of power around 5k rpm I pulled the throttle body off to clean the injectors. While that deep into the bike I also cleaned, etched and sealed tank, replaced fuel pump and filter, plugs coils and wires, stator and regulator.
Expecting the bike to run like it was off the showroom floor I jumped on for a spin around town. At first all was promising until the bike started to surge and backfire around 65mph and 7k rpms. I turned around to head back home when a back fire blew a 3 in hole in the exhaust can through both sides! (It was aftermarket) I got off the bike to see what had happened and the cat was glowing red along with the inside of the exhaust can. I ordered a stock exhaust off eBay and put it on today. I tinkered around abit in hopes I could figure out what the heck is happening but it still heats the cat up till its red hot.
Here are the symptoms. It'll start just fine. Warm up to 165-170 within 3-5 minutes. If I keep rpms below 5k and putt around the neighborhood all is well. When I get out on the main road and start revving it up above 5k it's fine for about 30 seconds or so till it gets angry then losses power and backfires at which point the cats glowing red.
I'm assuming it's running extremely rich? Anyone have any ideas why? What am I missing?
Thanks for any thoughts you can throw my way! This is my last effort before the dreaded dealership.

 

Certainly sounds like you are dumping unburned fuel into the exhaust, all right. Had that happen in a car. In that case it was a PCM fault. The spark was sufficient at idle, but above I think 1500 RPM, the power would decline, a misfire developed, and the cat would get so hot that smoke rose up through the console from the underbody heat.

This is not fuel or mechanical parts related, it is ignition, IMO.

There are members of this forum which will know way more about how the system works than I do, and I expect them to chime in quickly.
One thing you can start with is going through the standard checks for electrical issues, like overheated connectors, etc. And, get a reading on the running voltage for your bike.

I advise against spending any more cash before giving the wiring, particularly in the ignition system, a good close inspection.

You did not say what generation you bike is, but since FI, then Gen 5 or later. I do have a shop manual for the '98 - '00 bikes. A quick scan of the ignition section talks about the ECM and how it can be damaged by electrical surge. There are also tests for the pulse generator.

Quick question: Prior to the ride when the issue of lost power first began, had you recently done any electrical work on the bike?

Good luck.

 

The bike was a barn find and had been sitting for, well the guy said 3 years which probably means more like 5. It's a 2000 with only 9,000 miles so hasn't been ridden much. Anyway as soon as I got it I had to replace the starter relay so I have had my hands in the ignition system a bit. I replaced the stator and rectifier because my first thought when the bike started to lose power it was electrical. I put a meter on the batter and the voltage was dropping down to 2-4 when I'd rev the bike but now it's still only around 13-14. I'd suspect it should be more but haven't kicked around yet on that topic. Anyway I've look pretty heavily into wire connections and nothing seems amiss thus far. Btw thanks for your response man!


Sent from my iPhone using Tapatalk

 

Forgot to mention I also did a compression check and all was well there!


Sent from my iPhone using Tapatalk

 

My ST1100 had some ignition related issues, where it would start and idle fine, but fell flat on it's face through the midrange with lots of popping and farting due to weak sparks. I eventually traced this to low voltage getting to the coils due to corrosion in the the big red connector which connects the right bar controls to the loom.

After this was cleaned up the bike ran well but I still got occasional part-warm 3-cylinder action, which I traced to a bad connection between the spark lead and the plug cap.

If you haven't already done so, I'd suggest you pull every connector apart, clean the pins and apply some dielectric grease. Then go hunting for the frame earth connections and do the same.

 

What do the plugs look like? Are they all the same?

 

Did you use new fuel?

 

Can you check for restrictions in the air box & tailpipe. If it was left for that long anything could be blocking. Nests can appear anywhere lol

 

Thanks Terry,
Those are almost the same symptoms. I will check/clean connections today. Do you know what kinda voltage should be pushing to the coils?


Sent from my iPhone using Tapatalk

 

Thanks Pete, it does have new fuel, and a new air filter. When I pulled the plugs the first time they looked like they aged differently. Two where fouledish and black and the others where opposite. What's this a sign of?


Sent from my iPhone using Tapatalk

 

Sounds like two plugs aren't firing correctly. I am not familiar with 5th gens, so do you have stick coils over each plug, or do you have standard coils with wires going to the plugs? If the latter, the two that were fouled are on the same coil, you now know where to start looking for corrosion or testing to see if the coil is shot...

 

The 5G uses individual coils for each cylinder because it has a 180 degree crank. 360 degree crank V4's like the 1st gen or my ST1100 only need a coil per bank of cylinders because they fire 360 degrees apart.

Here's the system diagram from the service manual. There's no obvious connector that would affect just two plugs.





Which two plugs looked sooty? I'd be taking a very close look at all the wiring/connectors for the coils/plugs for those.