Re: 1981 CB750 C custom "DOHC" Engine ISSUE

Posted by Dwrecktum on Sep 12, 2010; 8:22am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/1981-CB750-C-custom-DOHC-Engine-ISSUE-tp1456569p1459946.html

Alright... story continues! reading back I realize my first post sounded like i'm an idiot... It was 3 am.. I was tired and frustrated... But that night i did spray a pile of fluid film into each cylinder...

This evening... First... Pulled the starter and confirmed that it spins like a dream... Tried turning the crank on the genny side... No movement at all what so ever... Pushed it down the road at all our might in 5th dropped the clutch and turns out the clutch slips... lol... likely adjustment... seems like its cranked up pretty tight... Rolled it back in the garage, and put it up on the stand...

Tore the engine out... when removing it was easy to see in the exhaust pipes that #3 had been running lean or hot... and #1 rings had been passing a bit of oil...

Engine on the bench:
Tore the valve cover off and unbolted the cams... "E" is the only damaged one showing excessive wear but cam appears fine with no real pitting and surface is in good condition... All other components are good ish...  cept 1 cap screw that broke when trying to remove it... i haven't figured out how i'm getting it out yet... Removed the cylinder head... Took a bit of mild tapping but it eventually came... Now the issue... RUST #3 and #4 being the worst... used a wood dowel to hammer on the pistons that were near TDC and eventually got them freed up... Some gradual cranking back and forth and eventually full rotations were possible with no real restriction... Removed the cylinder block... Which was a nightmare to get off!! and Voila...

#3 and #4 wrist pins don't move freely... #1 and #2 look like new ish... So ultimately I need pistons rings pins... Everything below looks good except some surface rust on the #4 connecting rod which seems to come off no problem... I've decided to refuse to split the case... There's no reason to do so... I'll need to either hone or bore the head... I'm thinking its gonna get bored a mill or two over...

**!!Now i really need the suggestions... What should i get... and from where and what else should i be looking for just in case... !!**

Sadly this bike needs a little more tlc for an oil change but i'll love it all that much more when its done...