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Rehab on a 1980 CB750 C


realjakebaker

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Hello, All. New to the forum. New to motorcycles. I made it known that I wanted to start riding, and one of my friends gave me a 1980 Honda CB750 C. It had been abandoned for two years when he moved out of the country, so lets just say I have been learning a lot about motorcycle maintenance over the course of the past few months. I have been trying to do a lot of the work on it myself, and I have already changed the tires (I had a friend who knew what he was doing help) and rebuilt the carbs. I don't ahve a manometer or a motion pro tool, so I was wondering if there was someone on the forum who would be willing to let me borrow their tool and/or walk me through the carb sync. I tried to bench sync it to the best of my ability, but I think I would really benefit from a vacuum sync since the entire carbs were completely disassembled a week or two ago.

If there is anyone on the forum who owns or owned a bike like this (I feel like there are a ton of people out there that had Honda CB's at some point) and would be wiling to give her a look-see to make sure there is not something that I should be doing that has not been done yet. I really want a vote of confidence so i can start taking this bike out on the road.

 

Thanks,

 

Jake

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I am in Columbus, Ohio.

 

I have been thinking about it and there are some other things that I should really be doing before I sync the carbs. I need to adjust the cam chain tension (looks to be easy... just idle the bike and loosen then tighten two bolts), check the timing (a bit more complicated, but do-able. will need a timing light), figure out what is going on with the charging system (i ran a multimeter between the battery terminals and a fully charged battery has the 12 V that it is supposed to have but it does not climb up to the 14V it is supposed to have at 5000 RPM. I am going to take the cover off the alternator and check the brushes, rotor and stator tonight). I also need to check for a vacuum leak and replace the air filter because it gets a high idle after it has been riding for a little while (vacuum leak test is apparently spraying starter fluid on the carb boots while the engine is running, air filter change should be cheap and easy). I should probably be checking the valve clearances as well, but I don't understand the factory service manual section about how to do it. I also have 4 into 2 exhaust that I want to put on it, because the 4 into 4 that is currently on it is rusted through in a few places. I may also need to re-seat the choke shafts because it is not actuating properly, but taking the carb bank out of this thing and putting it back in is a major "b-word" that I would like to avoid.

 

Like I said, bike was abandoned. Really needs tuned up, and I am trying to do as much of it as I can. It is my first bike, and I only really had it for a couple of months, but I feel like I am getting to know it backwards and forwards at this point.

taken apart

Put back together

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I wouldn't bother with ignition timing unless you've been messing with it already. Valve clearances are easy enough, need feeler gauges and basic hand tools. If you're not charging I'd check the voltage regulator/rectifier first...not sure if 1980 still used a mechanical regulator or not...unless your idle hangs when you blip the throttle I'd just turn it down a bit after it warms up, my 750 does the same thing...The exhaust should be easy depending on whether your bike has the spigots and pinch clamps or the thrust clamps. Make sure you replace the 4 copper crush gaskets thst go between the head and the pipes....you can't see them but they are there.

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I knew about the copper gaskets. Is there a way to test the voltage regulator and rectifier? I know how to test the rotor, the brushes have plenty on them, and I can theoretically test for continuity in the stator without a lot of effort. I havent seen much as far as a reliable test for the rectifier, and they are kind of pricey and people say you will just burn them up if the rotor is bad and you put a new rectifier in.

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