Knock, knock!

Journeyman28778 said:

UPDATE - With the octane boost the thumping is now gone!

It was raining on the way to work, so unless it's humidity related I'd say that the higher octane has temporarily solved the problem. I added about 1/3 bottle of and brought the tank up to about 1/3 full to keep it concentrated.

So, is this a timing issue or a fuel issue I can tune out?

Timing- I was super careful during the rebuild to set it correctly (triple checked). Plus, other than this it pulls like a freight train- super impressive. I asked for drop in cams, so not as precise as dial-in, but should be close if not spot on.

Fuel- I just got the PC5. I plan to install it this weekend and load the tune my tuner did for me. It was converted to TuneECU, which is what's in there now. I also have Auto Tune coming in the next few days. My hope is that for what I paid for those used, I can fine tune it further for less cost and time than revisiting the tuner. I brought it in with a borrowed PC3 that gave him some trouble. Also, I remember him saying that the PC5 would allow fuel adjustments to individual gears, which could be good for solving this situation. Finally, someone here earlier suggested I get the POD-300 and I found it on sale new, so $hiite, why not. Now to learn how to use it all. Very glad it is not the Flux Capacitor or Torsional Bearing.

Thanks to everyone for their ideas and help. I think we have it diagnosed, at least.

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Journeyman28778 said:

Update 12-13-20

Octane did help, but the bike started running worse and despite all that I have going on I had to set aside Saturday to try to figure it out.

Well, "stupid is as stupid does..."


All five caps looked like this. I changed them (the silicone hoses are still good), went ahead and cleaned and re-crimped all the coil wires, cleaned the crank position sensor, balanced the throttle bodies, and threw some Techron in the tank, but I know this was the culprit.

Went riding today and, once again, she's scary fast and runs like I remembered, starts faster, and purrs at idle like a kitten.

I still plan to install the PC5 and autotune in the next few days, but wanted to leave well enough alone for a while to make sure I was back to normal.

If it's been 36K miles (or a lot less!) since you changed your vacuum plugs I might suggest you do so now. It's a $3.00 fix for your E.D. (engine dysfunction).

Anyway, problem solved- thanks for everyone's help.

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TURBO200R4 said:

Just saying
A back fire through the throttle will blow off the plugs and vacuum hoses especlally if the secondarys r not open very much.

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Joesmoe said:

So the stepper motor has no smarts. It simply responds to commands from the ECU. In my case, there was pathological condition where whatever the stepper motor was/wasn't doing, was causing the ECU to command greater inputs, which would drive up the RPM. Then the ECU would recognize the RPM were higher than called for, and reduce. In my case, it would just cycle like that. Others here assisted me with that, and changing out the stepper motor, I have been fine since then.

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