1996 jd425 20hpKawasaki liq cooled 825hrs.

I mow 3-4 acres each week and been running fine.

I keep my eye on the gauges generally. Last week while finishing a large yard it suddenly bogged down. Quickly glanced at gauges and temp was totally hot. Limped it to the trailer and let it cool. Came back started right up but missed badly when attempting to add throttle. Seems to run mostly on one cylinder. Oil and water were fine. I havn't ckd plugs or wires yet. My brother thinks it is the cam because of the quick temp rise. Visited JD dealer today and service mgr said most likely cam issue. They want a $1000 for the job or I can get a cam kit for $150 plus gaskets, etc.

My question is: Has anyone here done this job? Special tools required? Anything in the line of surprises to expect?

I'm going along with my brother and dealer on diagnosis and willing to dig into this engine with the dealers prompting that this 1996 engine has plastic/nylon timing gear and anything past 450-600hrs tells him it's due.

Any comments/suggestions/information is welcome.....

thanks