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Thread: Oddball engines and prototypes

  1. #2461
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    You can find just about all there is to know about the two-stroke Aermacchi and AMF-Harley-Davidson racers here:
    http://www.pit-lane.biz/t7437-oldies-les-aermacchi-deux-temps
    I took the 500cc twin apart about 1976 (the perks of a technical editor). The gearbox sprocket-mounted rear brake disc had gone by then, but the four reed valves were still in place. Works rider Walter Villa later confided that they'd done an experiment, converting the intakes from reed valve to piston-ported, using a lot of Devcon.
    It improved rideability in the wet 1000%, he said.
    It's the same story as with the Cagiva 500-4: crankcase suction alone is not very good at fully opening the reeds; exhaust pipe suction is needed as well.
    When you close the throttle, combustion stops and pipe suction stops. So when you open the throttle again, the reeds are reluctant to open. So you open the throttle a bit more, and a bit more still, and after a while the cylinder contents are again pure enough to react to a spark, and combustion and pipe suction recommence.
    But now the throttle is wide open: an effective high-side recipe.
    Click image for larger version. 

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  2. #2462
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    I note in the Pit Lane thread, mention of the very pretty 125 they marketed. I had a customer for whom I'd built several Aermacchi replicas - 4 strokes.
    He looked around this part of the world for several years for a 125 motor with no success. He was quite keen on my building a replica 125 to round off his collection. Wouldn't have been difficult either - forks and brakes were common Italian stuff. Probably should have sourced an engine from the US - I'm pretty sure the HD badged dirt bike 125's were the same engine.

    I've already asked Husa what size is the engine he has, LOL.

  3. #2463
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    Quote Originally Posted by Frits Overmars View Post
    ...........
    I took the 500cc twin apart about 1976 (the perks of a technical editor). The gearbox sprocket-mounted rear brake disc had gone by then, but the four reed valves were still in place. Works rider Walter Villa later confided that they'd done an experiment, converting the intakes from reed valve to piston-ported, using a lot of Devcon.
    It improved rideability in the wet 1000%, he said.
    It's the same story as with the Cagiva 500-4: crankcase suction alone is not very good at fully opening the reeds; exhaust pipe suction is needed as well.
    When you close the throttle, combustion stops and pipe suction stops. So when you open the throttle again, the reeds are reluctant to open. So you open the throttle a bit more, and a bit more still, and after a while the cylinder contents are again pure enough to react to a spark, and combustion and pipe suction recommence.
    But now the throttle is wide open: an effective high-side recipe...........
    Very interesting Frits
    There was obviously a lot of stuff going on with works machinery that we wouldn't have believed if we had been told back then!!

    How can it be that such a simple piece of machinery such as the two stroke engine can become a convoluted mind wrenching piece of machinery?

    That's really what keeps these three threads alive! (this thread + Bucket Foundry and ESE). with the promise of ever increasing power dangling ahead, but always just out of reach! Most of the info on two strokes from the sixties up till the two thousands all now more or less available and being drip fed from the regular Gurus on these threads (too many to mention) - this needs to be kept going to combat (or even work in with) "Farcebook"
    Strokers Galore!

  4. #2464
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    Quote Originally Posted by Grumph View Post
    I note in the Pit Lane thread, mention of the very pretty 125 they marketed. I had a customer for whom I'd built several Aermacchi replicas - 4 strokes.
    He looked around this part of the world for several years for a 125 motor with no success. He was quite keen on my building a replica 125 to round off his collection. Wouldn't have been difficult either - forks and brakes were common Italian stuff. Probably should have sourced an engine from the US - I'm pretty sure the HD badged dirt bike 125's were the same engine.

    I've already asked Husa what size is the engine he has, LOL.
    Click image for larger version. 

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    I think this is the engine version you want
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    i have this version
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    I have seen pics of Early Cagiva MX bikes using this engine bottom end
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  5. #2465
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    Re the 250 i had seen plenty of these type pics of the air Cooled version bottom
    But not this type. Apologies to Frits if its in the pitlane thread i can't see itss pics without logging in.
    Click image for larger version. 

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    Click image for larger version. 

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    lookd like Cagiva carired on with the same design later
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    http://www.motodeimiti.com/cagiva-250-cc-gp/?lang=en
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  6. #2466
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    Q.U.B. 500, if it hasn't been posted already

    http://www.eurospares.com/graphics/e...00ccSingle.pdf

    cheers,
    Michael

  7. #2467
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    looks like there were at least 3 if not more versions of the 125 racers
    Click image for larger version. 

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    this one Water cooled 74
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    it looks like the 125s may have only used the rounded crankcase with similar clutch side shape to the 4ts
    The 125 engines all seem to have brackets to mount to the frame either front or rear or just put on backwards
    The 1969 1970 1971
    Seem to be what you are after later 125's have diffferent right side cases and clutch gear and kickstart. pic below. the bulges is a autolube pump
    I am not sure if the later top ends bolt on to early cases but the later ones appear all alloy.
    The 125's are all 3 port though the 175 and 250s seem to be 5 port.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  8. #2468
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    Quote Originally Posted by Michael Moore View Post
    Q.U.B. 500, if it hasn't been posted already

    http://www.eurospares.com/graphics/e...00ccSingle.pdf

    cheers,
    Michael
    QUB 250cc data:

    http://yorkshireferret.blogspot.com/...-cylinder.html

  9. #2469
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    i think the 500 did alright in the ulster GP and the few local event races it ran in.
    QUB later helped out a 500 GP team with i think Jerry Mcwilliams. running a Harris YZR later Honda and Aprilia in the 250 class
    the other part of optima which was a software and tech company that did automotive stuff inc fuel injection that had some tie in with QUB
    Colin Seeley handled the running gear. For the early bikes.

    oh here they are
    http://www.optimum-power.com/Virtual%202-Stroke.htm
    http://www.optimum-power.com/default.htm
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  10. #2470
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    Quote Originally Posted by Frits Overmars View Post
    You can find just about all there is to know about the two-stroke Aermacchi and AMF-Harley-Davidson racers here:
    http://www.pit-lane.biz/t7437-oldies-les-aermacchi-deux-temps
    I took the 500cc twin apart about 1976 (the perks of a technical editor). The gearbox sprocket-mounted rear brake disc had gone by then, but the four reed valves were still in place. Works rider Walter Villa later confided that they'd done an experiment, converting the intakes from reed valve to piston-ported, using a lot of Devcon.
    It improved rideability in the wet 1000%, he said.
    It's the same story as with the Cagiva 500-4: crankcase suction alone is not very good at fully opening the reeds; exhaust pipe suction is needed as well.
    When you close the throttle, combustion stops and pipe suction stops. So when you open the throttle again, the reeds are reluctant to open. So you open the throttle a bit more, and a bit more still, and after a while the cylinder contents are again pure enough to react to a spark, and combustion and pipe suction recommence.
    But now the throttle is wide open: an effective high-side recipe.
    Click image for larger version. 

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    Copied off the net necessity is the mother of invention. they just could get big enough Reed valves. although TZ750 was probably ample for the HP.
    “We’d made a 350 cc version of the 250 twin, which by now was liquid-cooled,” Fabris says. “We also built a 385 cc version of that, and in the final round of the 1973 500 cc Italian Championship at Misano, Bonera gave Phil Read on the four-cylinder MV Agusta a lot of trouble throughout the race, and only narrowly finished second to him, ahead of all the other true 500s, after setting the fastest lap. Well, that set us all thinking about what might be possible with a purpose-built full 500, and since Walter Villa, who had by then also started to ride for us, didn’t like the 385 and wanted to race a full 500 cc bike, we decided to ask our management to let us build one.”

    The answer from Harley’s Italian subsidiary’s management was a positive one – but with certain conditions. Though its Italian spinoff was doing okay, the U.S. parent company, then controlled by AMF, was suffering a slide in sales owing to quality issues and increased Japanese competition, so there was a strictly limited budget to develop the bike, and it would have to be offset by making a customer version available. A minimum of 25 examples of this had to be built in order to homologate it for AMA competition. Otherwise, go ahead, guys – see what you can do!

    As always in Italy, passion overcame whatever restrictions might have been thought to be imposed, and during the spring of 1974, engine designer Egisto Cataldi – already the creator of the 250/350 cc parallel-twins that would shortly gather up a total of four World titles – worked after hours at home to design the RR500 engine from a clean sheet, with only the gearbox casing and some minor details carried over from the smaller engines.

    Overcoming Limitations

    Riding The Harley Davidson RR500Like the smaller powerplants, the new Harley RR500 was also a liquid-cooled parallel-twin with a 180-degree crank, and its six transfer/dual intake/single exhaust port cylinders that were canted forward 15 degrees from vertical measured 72 x 60 mm for a capacity of 488 cc.

    Unlike its piston-port predecessors, the new Biancone (as in “Big White,” referring to the fact that the factory bike raced in a plain white fairing for a couple of its early races) had a reed-valve engine, in an attempt to soften the power delivery and make the bike more tractable on tighter tracks. However, the problem was that there wasn’t yet a reed valve pack big enough for the bike’s requirements – nobody made them at all in Italy, so they couldn’t even persuade someone local to make them a special design.

    The only solution was to use a pair of Yamaha reed valves on each cylinder sourced from the newly launched four-cylinder TZ750, so that meant doubling up on carburetors, too, with two 34 mm Dell’Ortos mounted to each cylinder with the reed blocks splayed apart at an angle for clearance. These were later replaced on the single factory racebike by 34 mm Mikunis, while the total of 18 RR500 engines built (not 25, whatever they told the AMA!) resulted in 16 complete motorcycles being sold to customers that winter for 3,500,000 lire, all of which retained the Dell’Ortos.


    Ignition was provided by a self-generating Dansi CDI mounted on the left end of the crank with just 21 degrees of advance, and the 89 hp delivered to the rear wheel at 10,000 rpm (with maximum torque of 50 ft-lb at just 6,800 rpm – quite a two-stroke tractor!) was transmitted via an extractable cassette-type six-speed gearbox with different standard ratios from the 250/350, matched to a 16-plate Surflex dry clutch positioned on the left behind the generator.
    https://www.motorcyclemojo.com/2018/...icas-gp-racer/
    Cycle or one of the other US mags had pictures of the internals of The RR250 its was the most beautiful things i had seen when i saw it likely 20 years after it was made.
    With its knife beveled gears and Dry clutch and replaceable head inserts and other Italian details.
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  11. #2471
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    There's a lot of stuff I hadn't realized went on in the Harley Davidson world and a lot for me to take in!
    HD managed to exist with all types of machinery without actually mixing the two (the "Hog" boys and the "racing" boys) probably all doing their own things, each blissfully unaware of what the other was doing! Masters at marketing I reckon!
    Or was it just me being blissfully unaware?
    Strokers Galore!

  12. #2472
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    Surprised Harley had issues sourcing reed blocks, they had been using them in the Topper years before this :P

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  13. #2473
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    Quote Originally Posted by WilDun View Post
    There's a lot of stuff I hadn't realized went on in the Harley Davidson world and a lot for me to take in!
    HD managed to exist with all types of machinery without actually mixing the two (the "Hog" boys and the "racing" boys) probably all doing their own things, each blissfully unaware of what the other was doing! Masters at marketing I reckon!
    Or was it just me being blissfully unaware?
    The HD macchis were based in Italy.
    The HD racing Shop in America was tiny and under resourced KR/XR series was there only interest.after the machi 4ts ERS etc finished.
    But they were mainly on their own when for instance Cal Rayborn raced in European match races he did so without HD permission or back up.
    they did however have a wind tunnel as the XR750TT series was a slippery as all hell, plus access to Jerry Branch etc and a whole raft of tuners giving feedback Obrain it seems was a methodical tuner who put in a lot of efffort.
    The XR series had probably one of the best 2 valve heads ever made.
    I am, sure AMF US marketing department interfered with the styling and chassis of the Italian wing as some of the last 350's 4T were Harley ugly.
    Quote Originally Posted by Katman View Post
    I reminder distinctly .




    Kinky is using a feather. Perverted is using the whole chicken

  14. #2474
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    Quote Originally Posted by husaberg View Post
    The HD macchis were based in Italy.
    The HD racing Shop in America was tiny and under resourced KR/XR series was there only interest.after the machi 4ts ERS etc finished.
    But they were mainly on their own when for instance Cal Rayborn raced in European match races he did so without HD permission or back up.
    they did however have a wind tunnel as the XR750TT series was a slippery as all hell, plus access to Jerry Branch etc and a whole raft of tuners giving feedback Obrain it seems was a methodical tuner who put in a lot of efffort.
    The XR series had probably one of the best 2 valve heads ever made.
    I am, sure AMF US marketing department interfered with the styling and chassis of the Italian wing as some of the last 350's 4T were Harley ugly.
    The XR heads were supposed to be based on the 350 Aermacchi ones.

    I've stripped a couple of the late 5 speed 350's - and always marvel at how they could turn a light, nimble single into something approaching a HD Road King
    for weight and lack of performance....

  15. #2475
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    Quote Originally Posted by husaberg View Post
    they did however have a wind tunnel as the XR750TT series was a slippery as all hell
    AFAIK the H-D fairings were developed in the CalTech wind tunnel by the Wixom Bros (who made touring fairings). Guzzi had their own wind tunnel.

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