This last weekend I was out in my Z6 and as I was running down a trail, it started to increasingly slow down with no throttle response, and when I came to a stop it died. It would not start back up, so we trailered it back home. To me it seems like a fuel issue. The fuel pump does not appear to prime with the ignition, but we pulled the line off of the pump and when turning it over it does pump fuel. Without much knowledge on these things, my initial thought is a bad injector. Anything else I should look at besides the injector?

[2015 Z Force 800 53/Trail EPS]

I would start with the machanical aspects first..ie check compression,  ease of rotation, valve clearance & timing...ect. Then move on to fuel pump volume and pressure, then voltage tests as in static and cranking battery voltage and coil voltage, then sensor tests like the CPS.

Here's the Z6 service manual. Download it as it has all the specs you will need. Have fun.

https://documentcloud.adobe.com/link/track?uri=urn%3Aaaid%3Ascds%3AUS%3Aaa6a3817-0472-4bca-95d2-c01deecb4baa

Well I brought it home and tore into it yesterday. Replaced the injector and it does spray fuel. still won't fire. pulled the plug and checked for spark, which was good. Next will be a compression test, but I need to find an adapter for my compression gauge, as that plug seems smaller. I suppose it could be a coil also...

Well, compression test came up empty so it looks like a rebuild. Not ideal, but what do you do I guess.

[2015 Z Force 800 53/Trail EPS]

Well, compression test came up empty so it looks like a rebuild. Not ideal, but what do you do I guess.

Could have just jumped time. Might check the valve timing for the heck of it.

I hate to guess. No substitution for good diagnostics.

What do you mean by "empty"? No compression at all? Even jumping a tooth will produce at least some compression all other things being equal.

If no compression at all, then ....

Valve train/chain/gear failure (Not turning cam)? Broken or stuck open valve? Valve spring failure? Hole in piston?

Or ...  the compression tester didn't seal or otherwise failed. Put your thumb over the plug hole to see if any pressure is generated.

Tore the engine apart and the piston is essentially destroyed. I have a rebuild kit coming that has a cylinder, piston, rings, etc. I am a little concerned about timing when I put it back together, but I think I saw a previous post about it so i'll look for that.

Could you post a picture of the piston?

[2015 Z Force 800 53/Trail EPS]

I think I have a Z6 shop manual. if you need one...let me know.

I think I have a Z6 shop manual. if you need one...let me know.

Thanks, I may take you up on that when we get that far.

Could you post a picture of the piston?

[2015 Z Force 800 53/Trail EPS]

Wow...that's F'n ugly..

It's odd. No build up which is good, but looks like oil starvations on one side. I wonder how this could happen.

Is the wrist pin ok? Spark plug look OK?

Wondering about fuel wash affecting the oil film (injector?). Inspect the valves and seats for pitting or uneven wear.

[2015 Z Force 800 53/Trail EPS]

With all the metal wear, I wonder the condition of the bottom end.

With all the metal wear, I wonder the condition of the bottom end.

Agreed. I will pull the oil pan off and see whats in there.