I have a 05 1200xlc that the engine decided to redline while I was on the highway without changing the throttle position. I pulled in the clutch and tried to kill the engine quickly, but not before damage was done. It had been making some unusual noises before that It seems to be "knocking" in the rear cylinder and it sounds terrible. Will only stay running for a few seconds. I assume I will need to rebuild the engine but don't know where to start to determine how bad it is.

Here is the video I took of the engine running after it decided to screw up.
https://photos.app.goo.gl/1ZCgRaBmqWC8Wkh47


I would like to do this myself with the help of a service manual and any help I can find on the internet. Does anyone know where I should start determining the failed parts? I plan to document the whole tear down and rebuild process with pictures and videos so I can remember how it all came apart.

Thanks in advance.

 

Backfire may be caused by a bad ignition unit or Crank Position Sensor. The rattling sounds like a collapsed lifter or 2. The biggest concern is how did it go redline by it's self. It might not really be all that bad but the only way to know for sure is dissect and inspect. Replace parts as needed.

 

I would start with a compression test.
That can help determine if there is a problem with a head gasket, rings or valves.

 

I Know it took me awhile to get around to it, but I did a compression test. Rear cylinder isn't really low compared to front. 180psi on the front like you expect, but around 30 on the rear. What does that tell you? Also the rear plug looks like it actually broke. Don't shame me for the plugs condition as this is a friend's bike.

 

30 PSI and a broken plug
Equals mechanical damage
Take it apart
Guessing is pointless

 

When you say pointless, you mean pointless to try to rebuild/repair? I have a week off this week and was hoping to get to working on it.

 

No, "pointless" as in "hoping it's nothing" is a waste of time. There is definitely some engine damage, you just need to see how far it went. Hopefully just some top end issues, and nothing involving the case components. Pull the head off the cylinder with the broken plug, and go from there.

Good luck!

John

 

Before pulling head off..... That plug doesn't look damaged from impact. Put a new set of plugs in and try to run it again. Your statements about compression are contradictory. First you say the rear isn't really low compared to front. Then you say front is 180 psi and rear is 30 psi. That's a 150 psi difference. So which is it? If it's only 30 PSI in the rear, yes you have a serious problem. If there is just a 30 PSI difference, you still have an issue but maybe not as bad. 30 PSI is within the "user error" range of possibility. So slow down and verify before you getting deeper than you may need to.


If that fouled plug is from the rear cylinder that is probably a good bit of the running problem. If there is internal damage to the motor running it a little more isn't going to make that big of a difference yer gonna have to tear into it anyway.

 

Also for future reference don't pull in the clutch on an engine that's "running away" That will just let it run as hard as it wants. Hit the kill switch with the, if the doesn't work hit the rear brake hard to stall it out.

The situation you describe is kind of odd. If I'm not mistaken that is an EFI model, which means the rev limiter should have cut in at red line or before. It shouldn't have even been able to hit red line under load without throttle input anyway. If it happened the way you describe it, you have more than engine problems, you got some freaky **** going on with your throttle or the ECU. Bottom line is what you describe shouldn't be possible.

Maybe sit and replay that moment in your head and see if you are remembering it either incorrectly or incompletely.

 

Best advice so far…