Author Topic: 1972 CB750 Bobber project  (Read 1470 times)

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Offline Prophet302

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1972 CB750 Bobber project
« on: November 14, 2011, 04:59:41 PM »
So a few weeks ago I picked up a 1972 CB750 from a friend. The bike was in pretty poor shape and the engine seems to be froze up. I decided to build a bobber out of the bike and enlisted the help of my friend Matt. We tore the bike down and I sent the engine off to my brother-in-laws shop. (Later he asked me what kind of engine it was so I am picking it back up this Saturday to rebuild myself.) I ordered the weld-on hard tail conversion from TC Brothers. We split the frame and welded the hard tail on. The original tank was beyond repair so I picked up a set of Harley Fat Bobs from a friend. We modified the frame to mount the tanks and I am presently waiting on CycleX to send me my seat, brackets, taillight and headlight I ordered. I am going to run stock forks, without the gator boots, and a nice set of triple trees from CycleX.  We are going to be rebuilding the engine ourselves using a shop manual and this forum. I am sure that between the two it wont be a huge issue. I keep trying to upload photos but for some reason it wont let me... reckon I am better at tinkering with bikes
1972 CB750 Bobber project
1986 Shadow VT500

Offline Prophet302

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Re: 1972 CB750 Bobber project
« Reply #1 on: November 20, 2011, 06:33:54 AM »
Still cant get my photos to upload, connection times out. Oh well.... Since first post I have ordered a new rear fender and strut kit (TC Brothers), bars, headlight and taillight (CycleX). Got the taillight and headlight in. These two were custom pinstriped so I snatched them up and put them up. Seat hasn't arrived yet. Picked up my motor yesterday and started the tear down. Got the shop manual on PDF and printed it out. Used an impact driver and removed all of the screws in the valve cover with no issues. Read and reread the manual before we started to even try to remove the rocker arms and camshaft. Several minor details they neglected to mention, a bolt or ten here and there. Got everything out with ease up top. Number 1 piston was froze to the cylinder wall. That took some time to remove. Valves look ok (at best), lot of carbon build up. Pistons look like crap. Cylinder walls look like crap above the pistons, beautiful below. (Wish I could upload the pics!) Judging from the top end, everything was oiling good. Passages are clear. The bottom end, Crankshaft, connecting rods etc... look great. As soon as we broke the piston free it freed the engine up. Everything rotates freely now. Took off the covers and removed the starter. (Popped one of the starter mounting ears, joy and rapture...) Removed the AC generator bolt, debating on the puller now. (20mm x 1.5 bolt?) Looks like all the screws holding the gear shift were punched by the factory to prevent loosening... Any suggestions? Dont want to round these off and end up trying to drill them out. Also, can I separate the cases with the AC generator attached to the crankshaft? Any suggestions would be appreciated....
1972 CB750 Bobber project
1986 Shadow VT500

Offline Prophet302

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Re: 1972 CB750 Bobber project
« Reply #2 on: November 20, 2011, 10:35:27 AM »
Here are the pics of the engine tear down so far.... seems that I can load up the ones that were taken with my friend's cell phone.
1972 CB750 Bobber project
1986 Shadow VT500