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why no gear driven cams anymore?

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by davesta, Oct 15, 2006.

  1. Hey, i have been noticing now that no bikes (that i can think of), or cars have gear driven cams anymore.. Seems to me that cam chains on a lot of jap bike engines are the weakest link (no pun intended heh heh), and everybody raves about the gear driven cams on the vfr750. I can certainly see why, fantastic noise, no maintainance, accurate cam timing (no stretch). So why no more? Cost, noise (tho its gorgeous), anyone got ideas??


     
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  2. Are you familiar with the concept of built in obselesence,maybe thats why???The VFR750 was the result of a the VF750 that had cams as strong as swiss cheese,a lemon.Then they poured mucho aplenty cashola into totally over engineering them, so they were a tad more robust,the gear driven cam route.Dukes are the same.Not sure about Guzzi's :?:Mr Scumbag who is online at mo I see, is a tad more qualified to talk on italiano machines than myself :)
     
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  3. cam chains are designed to be a breaking point in the engine.
     
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  4. Ducatis use belt drives for the cams. At least mine does, and I think most modern Ducati engines do now. I don't know if there used to be gear driven versions, not having researched that.
    Cam belts are pretty quiet annd reliable, as long as you change them regularly. That allows you to hear the "cling cling" of the clutch :cool:
     
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  5. The OLD 900s and 750s had gear-driven cams, and again that was because the original engines were originally built for racing so noise didn't matter, only reliability.
    Nowdays with noise requirements so stringent, gear-driven cams are just too niosy, and also very expensive to produce. Ducati's belt-driven cams are in line with majority car practice.... As long as they are routinely replaced at the required intervals, they are just as reliable as gears.
     
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  6. Belts are less hassle and more reliable in most cases than chains but are less suited to very high revs and can carry less power than chains.

    Hence their use on Harley's and Ducati's! :rofl:
     
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  7. Actually with a little research I think you would find that some belts can exceed the strength of chains.

    They also have the added advantages of less or no stretching, and wear on metal parts, such as belt pulleys (vs sprockets), is significantly less. Therefore less metal floating around in you motor. Catastrophic failure in belts is also less common these days, and usually less damaging than a chain failure.

    But hey, whatever turns your cam. :grin:
     
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  8. Gear driven cams are ideal from a reliability and high performance point of view, but add expence and complexity to engines. They are also tend to be too noisy for modern regulations

    I don't think all VFRs were cam drivem. Just the RVF 750s and the vf1000. I could be wrong there.

    Chains don't tend to break, but do wear and as they do, they adjust the valve timing, which is not the best for performance. they are however, relatively cheap and you don't need to worry as much with things like oil seals.

    Belts are quieter and don't stretch over the length of their life. They do, however, stretch under load. In designing with them you need to allow for valve overun, because they can bang valves into pistons under high revs.

    also belts do just snap. They are much better then they used to be, but chains don't tend to do that.

    It's also hard to make them look good.
     
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  9. All the VFRs had gear driven cams -from the 400 thru to the RFVs. I'm pretty sure even the butter cam VFRs were gear driven.

    About all I can think of for not using them would be expense of manufacture & maybe wieght :? Gear driven cams are certainly reliable & are simply the best in terms of timing accuracy. Absolutely brilliant to work on as well when shimming valve clearances. Simply line up the marks & you're done after removing them :) No tensioners or sprockets to fiddle with.

    PS V Tec VFRs went to timing chains.
     
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  10. Ok, I could be thinking of the earlier VF750.
     
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  11. The RC211v still uses gear-driven cams...
     
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  12. Yeah, but next years bike is going to run hydraulic valves.
     
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  13. 1942 Harley 45 engine production to 1978 used gear drive cams and chain drive rear

    Ducati Beval drive sqaure case (gear driven cams) also chain driven rear


    Davesta , yes its a fix it world $$$$
     
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  14. 1942 Harley 45 engine production to 1978 used gear drive cams and chain drive rear

    Ducati Beval drive sqaure case (gear driven cams) also chain driven rear


    Davesta , yes its a fix it world $$$$
     
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  15. Honda SP1 has gear driven cams..........
     
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