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Honda chop cb75o dohc

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  • 900c motor exploded. Main bearings don’t look that great, we will see what they gauge out at. Things come apart pretty quick after a bit of...”practice”!
    Last edited by Kgi4x4; 01-10-2018, 02:01 AM.

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    • Got the burnt 750 crank next to the 900. Beef cake! The 900 has much more mass especially on #2. The primary is larger also. 27 tooth for the 900. 23 tooth for the 750. The main journals are both 36mm and snouts are identical.
      Still “looks” doable!

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      • Got some more done on this project between appts today. Pulled the 750 motor out SOLO! Wasn’t bad with something to rest my chest on so atms did all work(not back). So far it down to bottom end. Spent quite some time conquering a busted stud. I couldn’t get it to budge last time and wouldn’t mess with it if not for taller deck height, long studs. Welded a 1/2 nut to broken stud. Took 2 attempts and a sledgehammer to “sledge” it all the way out! Long winded little sucker!
        The 900 cylinder/jug drops right in place on the 750 cases. There appears to be day of clearance in the cases to fit the bigger 900 crank! Starting to look like a easy swap!!! Think I have all the gaskets I need in hand too!!!
        found that the inner exhaust tube(uses a piece of 1” inside of 1 1/2” outside header tube, to choke it up) is broken about 1 inch in. So guess a set of tall organ 4into4 pipes are in order. I’ll have to wait till I make some more $ before ordering the bends n tube for that.
        The dual Mikuni carb idea is looking like the way to go. I’ll probly build a pair of manifolds cuz I’m cheap/broke. Carbs only cost $100 each and a 1” throttle with split cable runs right around 50$!

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        • The 900 crank FITS!!!!
          The 750primary chain tensioner and guide must be changed to fit the larger primary sprockets and chain.
          The 750 primary stuff:

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          • The 900 primary tensioner and guide.

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            • Going on a stripper run...have something in mind for the cases!

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              • Im beat!!! Got the hair brained idea to strip paint off cases n give them a quick pass over the polisher. Definitely not going for a miror finish, want a patinaed look. It will do. Cases would take forever to totally polish!

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                • After I inhaled all the little strings I could handle for 1 day, I fit the crank. One of the 750 main bearings was a bit tight. Off the scale on green plasti gauge. I swaped the pair in from the 900 and re checked it. We’re a go! It’s a touch tighter than others but still in range.
                  So now it’s all down to assemble and claying valve clearance!
                  I went to local muffler shop n picked up 20ft of 1 1/2” exhaust tube. I’ll have to cap the ends and fill with sand to keep bender from smashing/squishing light wall tube but gunna try bending up some organ pipe exhausts!!!

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                  • Bottom end went together smooth as can be! Put EVERYTHING in top half case(upside down). And the shift forks slid right in. Scraped away almost all the orange rtv. All back together with grey high torque rtv. So far so good!!!

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                    • Man I’m excited about this motor coming together. Looking forward to seeing what you come up with for pipes as well.

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                      • Kgi4x4
                        Kgi4x4 commented
                        Editing a comment
                        Thx. I’m chomping at the bit to get top end on! I tried to do it solo twice now. Both times It didn’t feel or sound right so holding off till my buddy can come by n give me extra hands n eyes! Hopefully today!
                        I got 20’ of exhaust tube so I guess I’ll start with that(like 5’ each, center pair longer to make it outside the frame). Think they will eventually terminate at about the height of liscense plate bracket on sissybar.

                    • Fun, fun. Fun! We gonna test ride it this weekend?!
                      Biscuits and gravy.

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                      • Kgi4x4
                        Kgi4x4 commented
                        Editing a comment
                        No not near that point. Just tryn to button it up so I can get back to throwing metal dust!!!

                      • PIG
                        PIG commented
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                        Kgi4x4 Come on! Hahahahaha

                      • Kgi4x4
                        Kgi4x4 commented
                        Editing a comment
                        PIG well hell...guess we could run it with the 750 carbs(depending on plug read). And patch that header... hummmmm...

                    • Got to spend a few hours buttoning up the motor. I finally pulled the wrist pins and sunk the pistons on the branch. They fought me even then. To get pins back through rods, I had to pull each piston out to the point of oil rings coming back out, just to clear the sleeves. Anyhow they are all in and rolling smooth! The 900 jug has broken fins so I didn’t clean its exterior nor the head.
                      I used the 750 exhaust cam and the 900intake. Playing with cam timing so it may have to come back out to make adjustments. Hooked up a batterie to prime the oil system. I left the head oil feed line cracked till it made it there.
                      Its all buttoned up so I can finaly get back to deep frying the soft taco. May just try to fire it with 750 carbs and exhaust(inner header welded up of course)! But much work to do before then!

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                        • Ok ok I’m done with it for now I promise...

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