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Project A festering thought of building an 8 cylinder 500

Discussion in 'Other Projects - Other Bikes (non 250's)' started by Gen, May 6, 2021.

  1. Gen

    Gen Well-Known Member

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    April 2020, I decided the only way to get the idea out of my mind, was to "have a go".
    A "true" V8 was not in my budget, although I had played with CAD , costs were prohibitive.
    It started with some left over MC19 bits, one set of crankcases with a crook cylinder liner, & my race (salt) co-rider, Rob Wilson (our team is called "TwoBob Engineering") donated one of his spare MC19 donks.
    I discovered the early MC19's cylinder liners won't press out, as the crankcases were poured around them, so I needed another engine, & bought a roughy from a wreckers in Adelaide, which turned out to be a bad choice, all the head bolt threads were either stripped, or helicoiled, badly, more on that job later,,,
     

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  2. Gen

    Gen Well-Known Member

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    After attacking the crankcases with a hacksaw, & 4" cutoff wheel, it was time to work out driving the camshafts, after the clutch gear became redundant, 3rd gear was the right diameter , but due to the difficulty in accurately locating its grade 8 Cat bolt axle, an elliptic version was designed
     

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  3. Gen

    Gen Well-Known Member

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    Then the crankcases were jigged, then tacked.
    I fossicked around in the creation station and found Holda XL125 clutch spur gears would do the crankshaft coupling duties, once adapters were machined up to mate then to either end of the cranks.
    One engine, in relation to the other, was turned around, so although they each rotated in the direction Mr Honda planned, they now turn opposite each other on the geared side (end)
    I'm using one oem oil pump to feed both boxless engines, driving out the back of the pump, via an extended shaft, chain driven from the "other" engine to which it lives
     

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  4. jmw76

    jmw76 Well-Known Member Premium Member

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    Great project. Really keen to see how it turns out. One thought that I have. Are you sure a single oil pump is going to be up to the task? I would be inclined to consider a higher capacity unit to make sure that you do not get bearing starvation at high revs/load. Maybe look at another model pump, assuming you have enough space. I have used larger capacity oil pumps in my GSXR motor that I use in my race car. I made a spacer for the housing and then used the rotor assembly from another model.

    SAM_0393.JPG

    Cheers

    Peter.
     
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  5. Gen

    Gen Well-Known Member

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    Pissing off the gearbox / clutch supply should be enough, but a pre start pump spin will give me an idea on pressures
     
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  6. Gen

    Gen Well-Known Member

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    Moving on, after the two crankcases were welded together, it was time to fit the gears


    Then make a new sump plate & front engine plate, the sump involved turning up longer O ring sleeves to compensate for the 4mm plate
     

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  7. Zippy

    Zippy Active Member Premium Member

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    :Drool:


    Please succeed with this!
     
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  8. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Very interested to see this take shape

    Although it was a very different project in every way, the Tularis 800 comes to mind with the belt drive between the crank and clutch as a means to attach a transmission - his engine and transmission were essentially two different modules assembled with the belt
     
  9. Gen

    Gen Well-Known Member

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    I'm stuck on the inline configuration idea, combined with chain drive, although using a Guzzi 'box (& frame) is an option, the wheelbase would be pushed past "right"
    There is also another problem to consider , 18,000 rpm, there isn't a clutch made, that I'm aware of , that'll not disintegrate before that kinda revs, belts might also not enjoy them, combined with 70 HP, although the blown MC19 used a 20mm hdt belt to spin the supercharger, and survived

    The V50 Guzzi 'box has it's primary reduction after the clutch,,,,
     

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  10. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK, for some reason I though this was going like in a Guzzi, inline is obviously easier as you don't need to transition from rotation in one direction through 90 degrees to the other

    Always wondered if there were significant frictional losses with bevel gears, I suspect not as otherwise they wouldn't have used them

    I recall doing some reading, chain drive is the better of all other alternatives with frictional losses, when I mistakenly thought it would be belt drive due to less inertia

    One other thought, you may be able to use a YZF750 alternator for power if you have an available, accessible and patching gear to couple it with
     
  11. Gen

    Gen Well-Known Member

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  12. gregt

    gregt Well-Known Member Premium Member

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    To bring the engine output on center, and slower, you could mount a small gear on one crank outboard the couplers - driving a larger gear which is the output shaft.... Should be possible to drop the output speed at least 40%.
    It'd just be a short gearcase so shouldn't affect overall length too badly.
     
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  13. Gen

    Gen Well-Known Member

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    While I wait for some warm painting weather, I'll share a few more pics

    butt.jpg coupled_n.jpg heads on.jpg heads.jpg mandrels.jpg sump 001.JPG
     
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  14. Gen

    Gen Well-Known Member

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    It was a long 3 weeks sorting the coupling gear case, oil pump drive chain, & intake manifolds out


    closer 003.JPG closer 004.JPG closer 006.JPG closer 007.JPG closer 008.JPG closer 009.JPG
     
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  15. jmw76

    jmw76 Well-Known Member Premium Member

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    looking good.
    Can not wait to hear it running.
    With those straight cut gears, linking the cranks, it should make some interesting music at 18k rpm.
     
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  16. Gen

    Gen Well-Known Member

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    I have a horrible feeling those gears won't stay together at 18.000 :minigun:
     
  17. jmw76

    jmw76 Well-Known Member Premium Member

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    Well time will tell.
     
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  18. gregt

    gregt Well-Known Member Premium Member

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    Tip velocity will be high. Lubrication could be fun. The more likely scenario is a destructive harmonic.
    How are you arranging the cranks ? What firing order ? Exact mirror image ?
     
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  19. Gen

    Gen Well-Known Member

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    Yep.yep &
    Oil bath & splash from oil pump drive sprocket
    #8 fires 60 degrees after #1, working 'round the engine, 1 to 8
     
  20. Gen

    Gen Well-Known Member

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    I've been chasing the reason one crankshaft seems awfully tight to get turning, the way I went about it was to oil up the engine while spinning the oil pump with a drill,,80 psi pressure @ about 100 oil pump rpm is good, & good enough to pressurize all bearing shells, the more I turned, the easier it got, to a point,,,,,now I can hear a bearing arguing with it's journal softly, but that should have left some marks for me to find,,,,
    Off with its ass,,again, out with all 4 cams, again, off with crankcase lower, again,,,that should keep my busy 'til the weather warms up a bit, 'cos it's been bloody freezing in the creation station for the last 4 weeks :headbang:
     
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