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  1. #41
    CB750 Enthusiast KIRBY's Avatar
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    OK, thanks.

  2. #42
    CB750 Guru amc49's Avatar
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    That weeds out DOHC engine, no kickstarter on them at all.

    You will tear out the kickstarter gear there, it is geared backwards for leverage and will tear up quickly. As well, it is not positively driven both ways, one way it slips 100% and that engine will not be hooked up to the other.

    When you join any engines you join at the crank pretty much only, if you use primary drive you will tear it out too (as someone else pointed out and he is an expert on SOHC) as it breaks too with only one engine on it not two.
    Last edited by amc49; 10-12-2019 at 01:20 AM.

  3. #43
    CB750 Enthusiast KIRBY's Avatar
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    I just icked sohc because I thought they would be cheaper.

  4. #44
    CB750 Guru amc49's Avatar
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    Not so, the DOHC never hit the classic status the SOHC continues to hold even now.

  5. #45
    CB750 Enthusiast KIRBY's Avatar
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    Is the DOHC hardier? More able to handle added power? They advertise this heavy duty chain to hold up under 90 HP. http://cyclexchange.net/index%20pics/kit%20bike.pdf
    Last edited by KIRBY; 10-12-2019 at 10:51 AM.

  6. #46
    CB750 Guru amc49's Avatar
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    The article there is somewhat misleading. The Hyvo chain type is not as rpm limited as they have you think, it gets used in the DOHC and at higher rpm, they redline at 9500 rpm and the OEM 1100 there makes 108 hp.

    The problem of chain morphs into another one. Look at the SOHC split crankcase in pic #5 of that article. The crank has a main bearing then the chain then a rod assembly THEN another main bearing. Meaning that once you stress the crank enough to begin to yank it out of true with the chain load you also yank that first unsupported rod (#3) out of true as it does not have a main bearing on both sides of it. The result is that that particular rod can spin the bearing much easier than the other three and exactly what the DOHC begins to do with bigger motors and more power. Even a stock 750 DOHC will show more rod wear on one side of the rod bearing if the engine is run hard.

    With the assumed power of the 1100 Honda made changes but they made things worse instead. The chain got widened to carry more power but the added weight then made the crank flex even more and more rod problems. Why most guys who race then use a 900 crank instead, it has the smaller chain but still lasts about the same and harder to chew up rod bearings on it.

    So, 12 of one thing and a dozen of another.

  7. #47
    CB750 Enthusiast KIRBY's Avatar
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    I'm learning a lot.Thanks!

  8. #48
    CB750 Enthusiast KIRBY's Avatar
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    This guy has installed a supercharger on the right side of his crank case. How do you do that? Seems that would be where I want my transfer gears.Click image for larger version. 

Name:	CB 750 Supercharged.JPG 
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  9. #49
    CB750 Addict Medyo Bastos's Avatar
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    What does the other side look like?im guessing itís off the other side like a drouin


    Sent from my iPhone using Tapatalk

  10. #50
    CB750 Enthusiast KIRBY's Avatar
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    And this guy has his supercharger pulley mounted on the left side of his crank case. If I could have one shaft on the right, and the other on the left, I could bolt them together!Click image for larger version. 

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  11. #51
    CB750 Enthusiast KIRBY's Avatar
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    Quote Originally Posted by Medyo Bastos View Post
    What does the other side look like?im guessing it’s off the other side like a drouin
    Here's both videos:

    https://www.youtube.com/watch?v=f929aVvlnGw

    https://www.youtube.com/watch?v=A2y0WRvQnuY

  12. #52
    CB750 Enthusiast KIRBY's Avatar
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    IF I could get the power of both engines to the transmission mainshaft without using the primary chain, would one transmission handle the power from both cranks?
    Last edited by KIRBY; 10-23-2019 at 10:57 AM.

  13. #53
    Moderator dirtdigger's Avatar
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    For a while. I dont really think you truely understand the forces you are dealing with trying to run two engines together and with little to no benefit. You would be better of building a solid single engine with a bigger bore and a good cylinder head, ignition, carbs and exhaust. A lot of drag racers back in the day tried many things tying multiple engines together. The successful ones used blower belts and stand alone transmissions. Couple used the stock transmission but drag racers tear down weekly and replace what is worn and broken. Do some research on muli engine 750 drag motors you will see what I mean.

  14. #54
    CB750 Guru amc49's Avatar
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    X2.

    The more you overdo it the more frictional losses you incur by simply too much of everything. It's like the jokes we used to crack about 500 hp. 440 cubic inch Chrysler motors, they were built so heavy duty we joked it took another 100 hp. just to keep all those huge parts moving, and then the 500-100 hp. =400 hp. motor got passed by other 400 hp. motors that were smaller and lighter.

  15. #55
    CB750 Enthusiast KIRBY's Avatar
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    So, if a chain will pull the bike, why not the primary chain. Is it something about linear speed of the chains?

  16. #56
    Moderator dirtdigger's Avatar
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    Well the drive chain is considerably larger the the primary chains. The primary chains were never designed to do what you want them to do. They work fine in a stock engine but you want to double the working load by adding another engine along with added shock and engine harmonics. Its not just as simple as added horsepower, you also have to look at the added shock of trying to get two engines to run perfectly the same as well as the added harmonics of two engines trying to run together.

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