scotto-...right, it's true stuff breaks - but I think this may be about whether or not the engine itself is primarily responsible, if the lower end bikes are truly suitable, and if there's any frames in particular that should be avoided because of that.
lol - ya go jumpin' everything in sight and ofc yer gonna break stuff engine or not, I too "fondly" remember breaking the Dtube/head weld on various bikes jumping stuff, mostly unsuspended bikes not made for that sorta shenanigans - and not motorized.
If you track down the source of that "stress", practice a lil postmortem forensics - there's much to be learned. For instance - cracked/broken welds on the Dtube (unmotorized) are usually a sign of landing front wheel first, but may be just poor welding skills, undercut in particular. A jumping bike should have additional gussets in that location, as you've noticed. Bottom bracket breakage is primarily the fault of insufficient quality components - it is after all where ALL your weight is when you land... if yer still on the bike heh, handle bar breakage is usually a sign of bars that are too long (excessive leverage) and/or don't have the crossbrace - all of this is obvious after the fact, but would still be a problem if people didn't think about the cause and take steps to prevent it.
Ignoring and dismissing the causality of component failure only dooms ya to making the same mistakes again
Originally Posted by happyvalley
Some of each probably but I've seen an uncanny number of frames cracked directly right at the mounts....almost like a sawzall was attached there rather than a motor. Noted, these were all using china girl engines with stock kit mounts.
Really? I've not seen or heard of this... My first thought was the U bolt style oversized tubing mount or the drilled Dtube method... but you say stock mounts? Do you have any pictures?