Well, this is no fun.

Decided to head out for a spin this evening. Got a mile from my house, waiting for a light. When I got the green, I got after it and BLAMMO! The Sportster started running like **** on a stick. No power. What sounded like severe decel pops. Pop pop pop!

Dumb luck that I was so close to home. Turned around and limped back to the garage.

While it was still running, I put my hand by the rear cylinder and could feel very strong pulses of air coming at me.

Shut her down. Did a compression check, which was sort of iffy since I don't have a starter.

But what I found was not good. Got compression on the front cylinder. Don't know if the actual amount of compression is good (back to the kicker), but at least I got something.

Got dead nothing on the rear. Not even a wiggle on the dial. Zippo.

Not sure if this is relevant, but yesterday there were a couple of times where I thought she felt a little weak. Nothing as dramatic as the episode today. Just weak.

I was thinking at some point I wanted to re-gasket the top end on this, just to tighten her up a bit. Guess that's happening sooner than I planned.

I can't think of anything else to do but pull the heads and get a look at what's what. I'll start by pulling the rear rocker cover and seeing if I can spot any trouble with that valve. It really felt like the rear cylinder was kicking air back through the carb, which is what makes me think its a stuck valve. I suppose its also possible that I've got a severely blown head gasket.

Anyway, wanted to toss this out and see if anyone has any thoughts.

 

or a Broken Valve Spring.

 

Not sure if this is useful, but all the videos I make finally became useful.

Here is a vid I put together showing what it sounds like, both before (when it was good) and today. You can really hear the air whistling through...something.

 

That doesn't sound like a bade valve.. I think you had it right the first time.. Head gasket.. What brand did you use?

 

Never opened up this motor. As far as I know, it's stock.

I suppose at this moment, it doesn't make much difference either way. Top end is coming apart. We'll see what it is from there.

 

K, not a big job to rip the head off, hell you know that with your Last upgrade on the Glide... Anyways post up some more of those great vids and use Cometic. Might as well get a .030" the little extra comp might even make it fire better....

 

I know someones gonna yry and talk you into getying it all muscled up

 

That's head gasket problems.
When you rebuild use either James or Cometic steel gaskets.

Since you are gonna be in there anyway sounds like it's time to upgrade the cams!!!!

 

Found some video from when I got back to the garage. The motor was still running at this point, but unfortunately, there's no audio. If you look close, you can see the air blowing out of the rear cylinder pushing against my hand.


As tempted as I am to take the opportunity to hot rod this thing up, I need to be a bit careful. I've had conversations with guys who ran that LedSled kicker with high-comp motors and ended up breaking the mainshaft where the ratchet mechanism screws into the end. I should have a conversation with Pat about that. Recall that on that kit, you replace the transmission mainshaft with one (made by Andrews, BTW) that has a large, female threaded end on it that accepts the ratchet thing that engages the kicker itself:



I haven't had mine apart since the build, so I'll be interested to get it open and see if there is any sign of wear or stress on any of it.

Anyway, for now my plan is to get a complete Cometic top end kit and just re-gasket the whole works, with the understanding that that could change depending on what I find once its opened up.

Any ideas on what happened here? The donor bike showed 20k on the clock when I got it, and I've only put 1500 or so on it since the build was finished. 21.5k seems like an awfully young motor for this failure, particularly if its truly all stock (as every indication says it is). I'm trying to think of a reason that something I did caused this, and can't think of one. I did the kicker conversion, the magneto, and the S&S carb. All external to the motor. I don't see how any of that could have had an effect on the head gasket (or valves). Just trying to think this through. Is this going to turn out to be "just one of those things", or is there something more fundamental I need to be thinking about?

 

Could it be something as simple as too much heat?
ausually the rear jug is the hotter
running one. And the gasket maybe?, was nicked and wore trhough?