Does anyone know if hd if still using platic parts on the chain cam ? 

Anyone had a engine fail with this problem ? 

Has anyone done this and whats the cost ?

They work well, crank runout has to be within spec of .003 off the top of my head to run one. 

They are also expensive when compared to chain driven. 

also if the motors left bone stock, like stock cam's stock valve springs. I think the adjusters will last longer. as heaver spring pressure would put more load on cam chain and adjusters. the first twin cams came with old style valve springs, but new ones have beehive springs so less valve seat pressure they also use 7mm valve stems so valve train lighter. i had a tuned up 88 TC & every 20k had to change tentioners, then soon after a tentioner change the new tentioner fell apart, was the outside tentioner, got lucy got it with all parts still in cam chest not mown in crank case. so i bit bullit went gear drive kept same cam grind ( just s&s gear drive ) at the time there was some wild claims that going gear drive gave an extra 6HP. i had andrews 55 cams chain drive, picked up near new used gear drive andrews 55 cams from friend in USA. you need to change cams when you go to gear drive as with chain cams rotate opposite way as gear drive but thats only difference if you keep same grind cams. I found there was not even one HP in it, was the same. but the gears & the cams still in the bike 100,000k ? (mate owns bike now ) just the crank pin slipped and crank went out of Coppoling took the crank end oil pump with it but gear drive was ok, was just lucky as did not ride it far when crank pin slipped or would have taken the gear drive out too. got a used near new crank had pin spot welded so gears spot welled stock 88" stroke made a strong motor!! just more trouble than most would go to.

you hear people knock twin cam's & say EVO the best. well i have seen three EVO crank pin's break in half.

I only heard about this not to long ago , and was wondering what the go was .