Milled head - WOW!

Discussion in 'Whizzer Motorized Bicycles' started by KilroyCD, Feb 14, 2009.

  1. KilroyCD

    KilroyCD Active Member

    RdKryton came over today and did a little work on my Whizzer. Namely, he exchanged the original head for one that was milled 70-thousandths, and installed the new copper head gasket. Now, I hadn't been in too much of a hurry to exchange the heads as my engine was running quite strongly.
    The change in performance was subtle on flat ground, but for going up hill I can only describe it in three words: "Oh my God!"
    It turned my engine into a torque monster. :grin5::grin5::grin5: If it had the traction, it could climb a tree.
    If you have a Whizzer and plan to mill the head, just do it! You'll be very pleased.:grin5::grin5::grin5:
    Last edited: Feb 14, 2009

  2. RdKryton

    RdKryton Active Member

    It was very interesting to see the difference between the two heads in the way they performed. First off they are the same combustion chamber design just one has .070 milled off the mating surface. Their was a modest performance difference on the flat land. This engine was already very strong. The big difference was in how it pulled on the steeper hills. I cruised up a hill at 20mph with very little throttle applied. Maybe 1/4 to 1/3rd throttle. It pulled great. Chris also almost went through his garage door because the engine didn't stall at the top of his driveway like it used to. One thing I forgot to do is turn the idle down a little for now it idles faster too. His engine already ran good and is basically stock except for the mushroom lifters but this has made quite a difference. This is definitely a good bang for the buck modification. Their is no down side to this modification.


    PS His dog was so pleased too that peed on my feet.
  3. KilroyCD

    KilroyCD Active Member

    This thing has so much torque I'm afraid it might see more air time than a skateboard at the X-Games! :jester:

    Just kidding, you know...
  4. KilroyCD

    KilroyCD Active Member

    You aren't kidding...

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  5. machiasmort

    machiasmort Active Member

    I've been tellin these guys, I took the base gasket (between block and jug) out of my HT. Made sure that the piston wouldn't wrap the head and wow!!!

    Basically the same idea Kilroy. Keep an eye on your brakes now! That motor has more torque and won't like when you pull back on the reigns!

    How do I know when my rims are wore out from brakes?
  6. Hal the Elder

    Hal the Elder Member

    Would this stress the lower end too much?


    I'm interested in any mod that enhances low-end torque, too...except I'm wondering how the higher compression and greater torque will act on the rod & main bearings...will this shorten their lives to any degree?

  7. jbcruisin

    jbcruisin Member

    If I remember right Quenton told me that the bottom end is pretty bullet proof. I'm sure we'll hear the expert opinions soon. Mine runs great over long distances at full throttle. That's pretty much the only way I ride.
  8. Hal the Elder

    Hal the Elder Member

    Ok, Jay...

    I'll wait for word from the Oval Office on the lower end reliability!

  9. RdKryton

    RdKryton Active Member

    If you have the needle bearing in your side plate and the mushroom lifters, you are good to go. Keep good oil in it and you will not have any problems.

  10. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Milling the head.............

    There are several advantages to milling the head on the new edition Whizzers, but most importantly it increases the head surface mating area. Most [if not all] have a very small area between the 10 MM bolts and the combustion chamber. The combustion chamber walls are tapered, and the area between the 10 MM bolts and the combustion chamber increases as the head is milled. Almost always [approx. 95%] the head gasket leaks in this area, and most often on the exhaust side.
    While it is true, increased compression does add extra power, it is most noticable at lower speeds, and the biggest increase is torque, not HP.

    The most common comment I hear about Whizzers is the major difference between the original motor and the new edition version. Everyone that owns or rides an original Whizzer notices the low end "grunt" [torque] and how much easier it is to put the bike in motion. There are three reasons this is so, first the compression ratio, and secondly the combustion chamber design, and lastly the "flywheel" action. It would be next to impossible to duplicate the original flywheel, but the head is another matter.

    The original head was different is several ways, but with a little effort the new generation version can be made to closer match the "torque" of the vintage motor. In order to explain the needed changes it is important to identify the various versions. The WC-1 heads were very similar to the "H" & "J" motors of yesteryear, and in fact the very rare early NE head was a close copy of the WC-1 head but had the "island" machined out for better flow. I guess it would be a good time to mention the early NE head was really strong [did I mention very rare?], but when the "island" was removed the area next to the 10 MM head bolt was reduced too much, and often resulted in a leaky head gasket. I won't spend a lot of time discussing the early head because they are so rare, but milling this version increased the metal surface between the combustion chamber and the 10 MM bolts and reduced the need to replace the head gasket as often.

    The next generation NE head not only needed to be milled but a lot of time needed to be invested in trying to "smooth" out the maze of crazy angles and sharp edges. Sadly this is the most common head used on the NE motor. As a rule I end up removing a lot of metal from the combustion chamber to blend the walls for better flow, and normally I mill these heads at least .065" ~ .070" to make up some of the compression lost via re-shaping the chamber.

    A few, not many, of the NE motors sported a special head. I call it special because it is "almost" identical to heads I designed & tested in 2006 [except for the oval shaped valve pockets], however I consider it the best head Whizzer offered for the NE motor [did I mention they only made a few?].

    For the few that express concerns about the bottom ends ability to survive milling the head. Of the 4 known crankshaft problems, 2 were "twisted" [caused by using an "impact" wrench], and 2 were snapped off because of early tests with CVT drive systems [I think the flywheel was doing at least 40 MPH traveling down the road without the rest of the motor]. I have one motor with over 165 pounds of compression, and the crankshaft is not something I worry about.

    The cost to have the head milled by the average machine shop is almost always over $75.00. Over the past few years I re-worked the combustion chamber, milled the head, and shortened the head bolts for less than half that amount. Because of the many hours, Dremel stones, sanding drums, and sanding disks needed to make the modifications my rate will increase on March 1st.

    This information isn't intended to "bash" anyone, company, or vendor.

    Have fun,

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  11. Hello Q, I was on the phone with you while you were making this post & there is one thing I forgot to ask you. On one of my other NE bikes I have all the usual upgrades, but the mushroom lifters were not modified. Do you think it would be worth my while to remove lifters & have them modified or wait until I decide to do some intake port work down the road & do it while the jug is removed? I guess my question is will it make big enough of a differance to modify them alone? I'll get those other items boxed up & sent to you this week. Thanks, Dan
  12. srdavo

    srdavo Active Member

    Lest you add in home repair costs, for the garage door. :tt2: :jester:
  13. KilroyCD

    KilroyCD Active Member

    I took the "torque monster" out for a ride today. The weather was in the mid 40s, so I decided to take the Whizzer when I went to the Post Office to mail a letter. I discovered that I can now pull out from a standing start without pedalling (and I'm no lightweight). I really like this extra torque! :grin5:
  14. Hal the Elder

    Hal the Elder Member


    Does your "TORK-MONSTER" also have the auto clutch?

    I weigh you think that Oscar's higher compression will "scoot" me a little better from a stop too?

  15. KilroyCD

    KilroyCD Active Member

    That would be a "no" to the auto-clutch, and I probably have 75 lbs on you...

    ...and yeah, Oscar will definitely like the higher compression.
  16. jbcruisin

    jbcruisin Member

    I was out today too in this unseasonably warm Put my new 50 mph speedo on yesterday. Barely hit 50 mph. Problem I think is in my 26 mm carb jetting. Wish I lived closer to Quenton so I could pest him with these details. Have any good deals on houses for sale near you Quenton?
  17. RdKryton

    RdKryton Active Member

    Hi Jay
    What size jet are you using in your 26mm carb. I ask because my 26mm carb does not like the cold temps either. Hard to start and such. Right now I have the 22mm carb on and it runs great in this cold weather. When it warms up I'll put the 26mm carb back on.

  18. jbcruisin

    jbcruisin Member

    26mm jet size

    Hi Jim,
    Remember at the Rally last year you gave me a jet & a drill bit. When I bought the 26 mm on Ebay after I got home I drilled out the jet that came with it with the bit you gave me. You said the bit would make the jet a 110 (is that correct?). The bike ran too rich so I put in the jet you gave me. It ran okay with that when it was warmer. I don't have many miles on the carb since it turned cold soon after I got it. You told me what size jet you gave me but I forgot what it is. I should write this stuff down. Do you remember what size it is?
    P.S. My bike starts great in the winter because I have a great wife that insists that I always keep my bikes in the house.
    Last edited: Feb 26, 2009
  19. RdKryton

    RdKryton Active Member

    Hi Jay
    Nope I don't remember. I guess I should write this stuff down too. The senior moments are coming more frequently any more. It's all blurring together.

  20. Hal the Elder

    Hal the Elder Member

    Hey Quenton:

    Received my Milled Head, a Copper Head Gasket, the 7 Shortened Head Bolts, and a #82 Main Jet today!

    You must have a really accurate milling machine! I ran a check on the milled surface using my Perkin-Elmer Mark VII Laser Interferometer, and the printed result showed a mean deviation of only 4.65 Microns from absolute flatness! That's 0.00465 millimeters, or 0.00018307 inches!

    This is EXTREMELY flat...good work!

    Would it be hazardous to re-attach the head without a torque wrench, provided I followed your recommended tightening sequence, with a follow-up tightening at a later time?

    I wouldn't mind removing the gas tank, as I've done it before, but I wouldn't want to have to shift the engine in the frame to do the job.

    Last edited: Mar 9, 2009