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  1. #1
    CB750 Member wesgreen305's Avatar
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    NEED VALVES FOR 1972 CB750k2

    Hey guys, Im 16 years old and am working on building a 1972 Cb750 and eventually making it a cafe bike. this is mostly a learning experience for me and i have already learned so much.

    I have no valves or valve set up at all. I am hoping somebody has a set somewhere and maybe is willing to sell. If not maybe if somebody has some info as to where i could get that kind of stuff all in a package. I could get it in a bunch of different places for the different little pieces but would be much easier to get it all at once.
    Also any information regarding which valves from other years or anything would fit my bike.
    Anything helps,
    Thanks.

  2. #2
    Moderator dirtdigger's Avatar
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    Are you starting with a complete motor or parts of a motor? cyclexchange.net and dynoman.net I my go too places for 750 motor parts. cb750 supply also has cheap aftermarket stock type valves but I prefer the aftermarket type valves. the k style heads all use the same valve and valve springs. the f2 uses bigger valves and different valve train parts. It may be easier for you to go on ebay and buy a complete head and have it rebuilt. I would send the head to cycle x or to APE for a rebuild...probably APE beings they are rosamond ca and would be close. Would help to know how you are going to build the motor as far as stock or a performance build so I can direct you to what parts to use.

  3. #3
    CB750 Member wesgreen305's Avatar
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    Quote Originally Posted by dirtdigger View Post
    Are you starting with a complete motor or parts of a motor? cyclexchange.net and dynoman.net I my go too places for 750 motor parts. cb750 supply also has cheap aftermarket stock type valves but I prefer the aftermarket type valves. the k style heads all use the same valve and valve springs. the f2 uses bigger valves and different valve train parts. It may be easier for you to go on ebay and buy a complete head and have it rebuilt. I would send the head to cycle x or to APE for a rebuild...probably APE beings they are rosamond ca and would be close. Would help to know how you are going to build the motor as far as stock or a performance build so I can direct you to what parts to use.
    Thanks dirtdigger,
    I bought the bike in pieces and have been searching stacks of boxes for each part. I am almost certain I was not given anything to do with the valves other than the rocker arms and such. What do you mean by buying a complete head? Would the valves and things be in there? And what would need to be rebuilt?

  4. #4
    Moderator dirtdigger's Avatar
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    If you are trying to put a motor together from boxes of parts I think you are in for a long road of headaches. The 750 motor is not one to really learn on especially if it is pieces. I think you would be better off buying a complete motor. If you have never been into a 750 before there are a lot of parts and small parts that are critical to its survival. Its sounds as though you dont have much of any motor experience so i would suggest a complete running motor. Lots of things go into a rebuild. as far as what goes into rebuilding the head...you have the valve guides that wear out, then the seats need to be cut along with needing new valves and springs, then the head needs to be checked for warping. None of this can be done by someone that has not done engine work before. Any machine work that needs to be done in the bottom end needs to be sent out to a machine shop. I think you are in for more then you realize as far as putting a motor back together from a box of parts.

  5. #5
    CB750 Guru amc49's Avatar
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    A big part of the problem will be if the original parts were not matched to each other, if just tossed in boxes then you have lost all of the matching that occurs when an engine runs. After that the parts need to stay with each other and if not done then it adds tremendous trouble to getting one back together to STAY together. Mismatched engine parts in a worst case scenario can blow up an engine easily in less than five minutes. Seen it plenty of times.

  6. #6
    CB750 Addict madmtnmotors's Avatar
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    You will need to be prepared to spend anywhere from $2000 to $4000 just to get the engine assembled properly. 2K will get you something close to stock, while 4K would net you a go-fast motor. And that's if you do most of the labor.

    >New valves, guides, and seals will set you back $500 alone (plus round trip shipping):
    http://cbrzone.com/sohc.html (scroll down)

    This is not a job for anyone without the proper machining tools to match the new valves to their seats. Valve lapping compound won't do the job here.


    And that's if you have the rest of the valve train, including camshaft, cam cradles (or "towers") with matching caps (they're stamped), rocker arms (with tappet adjusters) and the oil control orifices that are no longer available (Honda part# 12238-300-300). If you have to source these parts too, you could be looking at anywhere from $150 (used, unknown condition) up to $500 (or more).


    >You can get a set of four pistons with rings for anywhere from $150 to $1000. Boring/honing the cylinders to fit the new pistons will be anywhere from $150 to $400 (yep, I've been quoted up to $100 per hole)

    >You should have the crank balanced and checked for straightness (if the cases are separated and the crank is loose)

    >New cam chain, or at least new cam chain tensioner components

    >You should seek experienced guidance if the lower cases are separated. The transmission assembly is not very intuitive, even with all of the manuals that are available.

    >New gaskets and seals

    >Total tune up components including points/condensers, air filter, oil/oil filter, spark plugs, spark plug boots, etc

    >New crank bearings?

    >New rod bearings?

    >New clutch (new friction disks at the very least)



    Then you can start on the frame, suspension, brakes, wiring, and all the other miscellaneous pieces to complete a functioning motorcycle.


    Pictures would help us understand what you have to work with.
    I know, I know, "everybody else is doing that way"...

    High price to pay for being "stylish"...

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