Ahu dropped a valve. What should I be expecting to have to do?

Just trying to get an idea of the process I need to begin.

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New or rebuild head, frank06 is great but his lead time might be a bit longer than normal. Pull the connecting arm and blueprint the crank for this cylinder, blueprint the connecting rod too. Return with result.

1. Drain oil.
2. Drop pan.
3. Remove damaged piston and connecting rod.
4. Inspect cylinder bore for damage and measure for diameter and taper.
5. Cross hatch hone cylinder block if bore is not damaged and within dimensional limits.
6. Inspect connecting rod for being bent.

Should get you started without spending money yet.

I strongly doubt the lower end would suffer any damage from one little valve. That being said I would source a good used or new head and send it.

^^??

dude rods need to be checked after dropped valve(s). 2:that piston may be gone. if you drop one valve you usually lose at least one more.

garciapiano said:

I strongly doubt the lower end would suffer any damage from one little valve. That being said I would source a good used or new head and send it.

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Other than a BENT CONNECTING ROD the lower end should be fine.

^not a given mr.rattler, seems if you part a rod and such, its recommended a new bearing. that motor seems to have a good amount of use. you can decide how much you want to do,,etc. but head is off.

half the time i pull a piston and rod from a valve hit like OP's, i find that the wrist pin has a scuff and or dent mark like wear . Not all the time, more so on small engines like dirt bikes because of the higher rpm maybe.
Still, you want to blue print that engine if your planning on fixing it. like Ol'Rattler said in #3, do those things first as they are the best and cheapest way to find out if its worth saving. then start blueprinting the entire engine. nothings worse than rebuilding only to have something go wrong because you didnt catch a issue that is invisible to the eye!

Oh, the carnage. I'd be looking for another motor to drop in personally. That hole is probably gouged to hell. Easiest to just swap in a runner.

IIRC the rods and maybe pistons are weighed and you'll need to find a matched set to replace the damaged ones. Carefully check the cylinder bore, the smallest fragment can do extensive damage. I think Frank has a supply of pistons / rods of various weights.

Sorry this happened to you, it's not all that common but you do run across cases of dropped valves from time to time.

Steve