rebuilding the lower end

[bodfper]

My quad was running great and all of a sudden my 400ex wont run. It will pop and try to run but when its turning over there is an unfamiliar sound that I think is coming from the lower end. Does anybody have any idea on what this might be? Im wanting to do a rebuild anyway on the top end so now that this is happening I would just assume go through the lower end as well but I have no idea where to start when it comes to rebuilding the whole lower end. Any help is appreciated

[CJM]

The one thing I can always say about these 400s is the bottom ends do not break too much. About all thats gets worn is the shift forks-you will know this when you go to shift and it wont hold the gear. The only other thing really that wears out sometimes is the starter-but you will know it just spins and spins usually.

Your could be as simple as a jetting issue or possibly valvetrain related (valves, chain, cam, etc) or it might needs rings (smokes usually tho). Start off by checking the compression if you can and cleaning the carb and see what happens.

[bodfper]

Alright well thanks for the input...the only thing is is that i just rebuilt the top end last year and i could get it to fire just not run...it ran like a champ just before this happened.

[CJM]

Be more specific, what noises does it make and where exactly on the bottom end are they coming from? What exactly does it do when it trys to fire, etc.

[bodfper]

it will crank over and get that pop once in a while and fire but wont stay running. The noise sounds like its coming from the right side of the case and its just a clunking or chattering noise.