ATV engine rebuild question(s)

Anyone ever rebuild an ATV engine? Just wondering the difficulty level and special tools needed.

 

Top end is not bad. Bottom end makes it quite a bit more involved. Just finished my 400ex’s motor

 

Helping a friend out but they said the crank is bent. So I assume it hit/broke a valve. Ive messed with vehicle engines but not ATV. Im sure timing is critical but is there any special disassembly tools needed?

 

Not on my Honda. Was water ingested? Just make sure you have torque wrenches for assembly. A bent crank means a total overhaul and likely a lot of expensive parts and machine work. May be better off money wise if you buy a running replacement motor off eBay.

Have the valve seats milled and the valves/valve seals installed by the machine shop to avoid buying special tools. (Cheap)

The biggest challenge with mine was keeping track of what bolts went where (nbd). They all look the same but are different lengths. YouTube helped a lot more than the OEM repair manual

 

Im not sure of the extent of damage. Im getting information from a friend who isnt really mechanically inclined and he is getting the info from a co-worker. But basically they said it was running then it just quit. they took it in to a shop and they said bent crank. That is about all I know. Im going to try and get with my friend and go look at it. See if anything outside is cracked or how they came up to that determination and maybe get some info from the owners.

 

not engine related but changed the pads on my ATV and it was easy task. I finally found out why intermittently hitting a bump i would hear a click/pop sound. went away for a while then back to intermittent. Turns out my lower ball joint nut and steering nut were loose!! only on my right side? Dunno why, re tightened the nuts and no more clicking!