So what did I break? - Honda 450X

[Rusted]

2006 Honda CRF450X

On a trail ride this afternoon west of Strawberry today. The it had rained earlier, so the ground was damp with mud in spots, not bad, but the surface was soft. On one of the little water bars I burped the gas just to give it a little jump and then the engine stopped. It won't start, it does not even try to start of cough. Sometimes a kick start (maybe 1 in 20) will drop easy with little to no resistance. Other than that it feels like it gets good compression.

I purchased this bike used a year ago. It has always felt like it runs well. There has always been a concerning 'cam chain' noise from inside the engine and I have read about others with the same report, so I have not been very concerned about it. The whole way home I have been wondering if I have broken the cam chain, or if there has been a valve failure. I had South Valley Motor sports check/adjust the valves ~10 months ago and they commented that they had to use the thinnest shim to get the valves right, and that next time I would need the head machined. Since it is used that is the only real history I have on the bike.

Where to start? What did I break?

To make my day worse my buddy tried to strap me out with his Honda 250 and burned up his clutch, so I get to replace a clutch on his bike as well..... At least I made it home before midnight

 

[Unimog]

Purely a guess, but I would guess the cam chain got loose and slipped, leaving the cam timing way off.

 

[Rot Box]

Oh man that's not good The easy test is pulling out the spark plug. Kick it over and make sure it is getting spark.

After that I'd look into the valve train. Start with removing the fuel tank then take the valve cover off. You'll be able to see the chain and also check valve lash and cam timing. I hate to say it but thinnest shim and a valve adjustment 10 months ago on a CRF = good chance of valve death but who knows at this point.

 

[Caleb]

That's a tough one. I'd do what Rot Box suggested. It's not that tough to get in to the valve train to inspect (a little tricky to get the cover off and out of the frame, but it's doable). Also, a new clutch is cheap, steels and frictions for probably $40 if you go with the Tusk ones (which work great, that's what I always use on all my bikes if they are available) and they're even easier to replace, takes about 15 mins…maybe less. Also, take it for what it is, but I paid South Valley to adjust my valves once and they were worse after they adjusted them. I made them redo them twice and was never happy with the outcome. So get in there and measure your valves on your own, you may just get lucky. I've got a set of feelers and a shim kit if you want to borrow it. Most of the time on the CRFs, the general rule on valves is adjust once then replace.