it could be bad reed valves or might need a carb rebuild. im haveing the same problems wiht my ski and i took the carb apart to check the diaphrams and jets then i took out the reed valves and 3 out of 8 were lifted so i orderd new ones. you might wanna start with all your fule line hoses and make sure there not clooged and also check your fule filter for dirt aswell. if all that's good then start with your reed valves take them out and check them out"they should all be flat on housing and not bent up or cracked/chiped ect. if those are good then check the next thing your carb.... good luck and let me know....
it could be the plug but is most likely the carb. it either needs too be rejetted or you have a float that is sticking
It could keep the engine from running, but not the valves from moving.
Valves will clatter if the engine is overheating.Valves will clatter if the engine is overheating.
It all depends on if you have an interference engine or not, if you do valves could hit pistons if running at the time
The belt breaking would be the problem. Investigate why it broke.
could be the regulator
Could be that your valves are out of adjustment or if you have the nonadjustable valves then it could be a build up of carbon on the valves.
The fan or water pump,
it could break a valve, but will probably just bend a few.
Any number of things could cause a Yamaha Raptor 660 not to start including a blockage in the fuel hose. There could also be a problem with the carburetor.
Your problem could be in two locations F. Garay == ==
Sounds like it is burning oil either due to excessive engine wear (RINGS OR VALVES) or if just on start up from a stop light etc. could be valve guides or seals