Yes, this front guide appears to be the 650 motor's "Achilles heel". I think pretty much every long time 650 owner is going to have to deal with it. Hopefully only once though, lol. The originals have lasted all these years (30+) and are just now starting to fail regularly. Hopefully the replacements will do the same. That means most of us won't have to worry about another failure in our lifetimes. The replacement should outlast us, lol.
But, it's not a bad thing having to go into one of these topends. Usually other things need addressing, not to mention just cleaning all the carbon out. Valve guide seals are often all hardened up now, cam chains stretched, valve seats leaking, ring end gaps too big (rings worn) or bores worn. They also benefit from some minor porting (basic clean-up of the "lumps and bumps") and the elephant foot valve adjuster screw mod.
But, it's not a bad thing having to go into one of these topends. Usually other things need addressing, not to mention just cleaning all the carbon out. Valve guide seals are often all hardened up now, cam chains stretched, valve seats leaking, ring end gaps too big (rings worn) or bores worn. They also benefit from some minor porting (basic clean-up of the "lumps and bumps") and the elephant foot valve adjuster screw mod.
Last edited: