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New Indians still using pushrods ?

Discussion in 'General Motorcycling Discussion' at netrider.net.au started by basejumper, Aug 31, 2013.

  1. So the new Indian makers have just designed a brand new motor. Why in the world would they design it with pushrods and 2 valve dinosaur technology? Why not twin cams and multi valves? Beats me. Anyone got any ideas ?

  2. #2 Vertical C, Aug 31, 2013
    Last edited: Aug 31, 2013
    Pushrods take less maintenance, no valve adjustments.

    Why are overhead cams better on a cuiser where power isnt really a priority? If you want to go fast get a sportsbike, plenty of them.
  3. Because, on a big displacement, high torque, low power motor with a redline south of 6500 rpm, pushrods and two valves per cylinder are all you need. The advantages of a lighter, more rigid valve train and, to a lesser extent, the better breathing of multiple valves only really make a worthwhile difference at higher engine speeds than any Indian will ever see.

    Also bear in mind that the general push towards OHC technology was driven more by a desire on the part of manufacturers to reduce parts count and manufacturing steps, thus reducing their own costs than it was by a desire for higher performance. For all but a handful of sports models that was a secondary benefit which meant the punter would ask fewer questions about paying more for an engine that actually cost less to produce.

    Besides, apart from a few out and out competition specials and badge engineered Royal Enfields, real Indians never even graduated to overhead valves so a low tech engine is entirely in keeping with the latest zombie bikes.
    • Agree Agree x 6
  4. ^^^^^^That
  5. Because it's an Indian.
  6. Their market research shows that these are features that their customers want.
  7. Yamaha MT-01 has push rods---whats the problem.
  8. I never knew that. I assumed it was at least as high-tech as the old Virago lumps with their SOHC layout.
  9. Nup.OHV,via pushrods.
  10. Probably the most stupid comment Ive ever read.
    Whether a motor has OHC cam with direct actuation or rocker arms,or is OHV with push rods,there is still wear in the system.
    With modern metallurgy,there is very little wear in the rods,arms etc. of either system.
    The constant in all set ups is valve seat recession.
    Although vastly improved with modern metals,all valve seats will experience recession due to a valve hammering them at high revs and at a high temp for long periods.
    Perhaps some people dont realise why thats why valve clearances need adjusting-its not wear on the valve train.

    Shall I start on OHC Vs OHV ?
  11. Actually with my experience it's about 50:50 as to whether you add or subtract come adjustment time, depending on the model.

    Pat's general philosophy is correct, however. If you are designing an engine that only revs to 6500, then OHV, 2-valve is all you need.
  12. OHC is all about reducing valve bounce at high revs.
    Taking it to the next level will require stronger or double valve springs.
    That in turn wears valves and seats at an increased rate.
    Or go for desmodronically closed valves-perhaps the perfect system in theory.
    • Like Like x 1
  13. Or get a two stroke, no valves, cams, push rods etc, at all.
    The old 1970's Kwaka 750 triple will still give most modern 750's a damn good run.
  14. No they wont,you are a dreamer.
  15. And there endeth the lesson.
  16. ~75 bhp on a good day in standard trim? I think not.
  17. Two valve engines generally have lower valve surface area than "multi-valve" engines. This results in higher gas velocities, and improved low-end torque characteristics compared to "multi-valve" engines. This is because the gas volume effectively has to move faster through a smaller opening to achieve the same result.

    A similar concept to using long inlet trumpets versus short. Long inlet trumpets offer improved low-end characteristics compared to short, but short offer greater "responsiveness" to rev changes. Partly to do with the intertia of the air mass.

    It's only when you get above 6 or 7 grand (or thereabouts) that 3, 4 and 5 valve engines really start to get real advantages over 2 valve jobbies.
  18. christ, the wrongness of that hurst me head. I don't even know where to start.

    Wish my day wasn't so busy.

    I'll start with what you got right, inlet velocity does affect the ability of a cylinder to fill and thus torque.

    What you almost got right. Valve surface area. Surface are doesn't come into it. It's only proportional, because of geometry and in itself not a factor.

    What matters is valve circumference. It is this, multiplied by the area under the angle, lift curve that determines the total inlet profile of an engine.

    As to what gives an engine more torque, it's the amount of explosive mixture in the cylinder and the volume of the cylinder.

    It is mythology that 2-valve engines have better torque characteristics. Show me two engines that are designed for the same revs and are the same capacity and it will be the 4-valve engine that gives the fatter torque curve, simply because it gets more mixture into the cylinder and thus gives more cylinder pressure after ignition.
    • Agree Agree x 1
  19. Why did Honda bother with V-tec if 4 valves produces just as much torque as 2?
  20. The Honda engines were 4-valve long before they added V-Tec to the mix....
    And let's nor forget that up until very recently, the Holden V6 was a pushrod derivation of the ancient Buick V6,