Performance Boost From Mushroom Valve Lifters!

Discussion in 'Whizzer Motorized Bicycles' started by Hal the Elder, Jan 14, 2009.

  1. Hal the Elder

    Hal the Elder Member


    After installing Quenton's Mushroom Valve Lifters 2 days ago, I finally had the chance to give Oscar a 7-mile test run today.

    The difference in performance was more than I expected!

    Realizing that since the whole purpose of the Mushroom Lifters was to increase the longevity of these components, I was also delighted that there was a noticeable increase in performance as a bonus!

    I now notice that I can use less throttle to maintain my favorite cruising speed of 25 mph.

    And for the first time, I have attained the speedometer's "red-line" speed of 36 MPH, which I have never reached before, with some throttle even left in reserve! (I really don't like cruising on a Bicycle at over 30 MPH!)

    Finally, my "performance yardstick" was cresting Wadena Hill at 27 MPH!

    When I first tested Oscar, before any modifications, my speed at the summit of Wadena Hill was 21-22 MPH. With every modifiication I have made, the summit speed has increased a little each time.

    I would say that the biggest increase in performance was due to my opening of the carburetor restriction.

    The Hi-Flow muffler insert helped, as did the Mushroom Lifters. (The cam advance was already done by the factory) Anyway...I'm really pleased with the performance of my NE-5, and I'm glad I made the mods!

    Last edited: Jan 14, 2009

  2. go-rebels

    go-rebels Member

    This is interesting. The only difference must be the tightening of the gap between the lifters and the valve stem, resulting in a slightly longer duration that the intake and exhaust valves open.

    Or maybe the retuning of the carb's fuel/air mixture after installing the new lifters?
  3. KilroyCD

    KilroyCD Active Member

    Actually, the slightly longer duration that the valves remain open is due to the larger contact area of the mushroom lifters. The lifter remains in contact with the cam lobe for a slightly longer time due to the larger diameter of the base of the mushroom lifter.
  4. go-rebels

    go-rebels Member

    Yes, that's true too.

    Isn't the 0.006-0.008" clearance a little tighter than how they were set at the factory? I didn't bother to measure mine before disassembly.
  5. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Ok Here is the big secret to wider base lifters. The valve is held at WIDE OPEN longer, which means more air/fuel flow.

    Have fun,
  6. Hal the Elder

    Hal the Elder Member

    Wide-Base Lifters vs Hot Cam Duration

    Performance camshaft manufacturers, such as Iskenderian and others, use increased duration or dwell time in their cam lobe profiles for high-performance engines. This is accomplished through modifications in cam profile alone, with no change in lifter base configuration.

    However, increasing the base area of the lifter (Mushroom lifter) has the same (although lesser) effect as a long-duration cam profile, without modifying either duration or lift.

    Of course, some really radical full-race cams have considerable "overlap", where both intake and exhaust valves are open for several degrees of crankshaft rotation, to take advantage of inertial dynamics of gas flow at high RPM's.

    Last edited: Jan 14, 2009
  7. RdKryton

    RdKryton Active Member

    Hey Hal you should feel the difference when you also have a higher lift cam and a 26mm carb. hehehe
    I'm very glad the lifters are installed and you are pleased with the results. You have taken a big step in making your engine bullet proof. The small pieces of lifter that could break off and float around in your crankcase can only do bad things. You have eliminated that possibility and improved your performance as well. A win win situation. I love my Whizzer too and will do everything I can to make it last as long as possible. It would be nice to have someone want to collect these Whizzers 40 or 50 years from now. Keeping them running is one way to make that happen.