High compression head............

Discussion in 'Performance Mods' started by geebt48cc, Nov 17, 2011.

  1. geebt48cc

    geebt48cc Member


    Does anyone know anything about the new Manic Mechanic high compression head for 2/stroke 66cc? I've milled stock head all the way, and its got twice the power, but wonder if theirs is better?


  2. jaguar

    jaguar Well-Known Member

    I think it has a squish band but I have tested both types of heads and it makes no difference. That is because a small bore engine does not have much distance from the spark plug to the outer edge of the cylinder. The flame does not have far to travel and so does not need the help of extra turbulence caused by a squish band.
    The only advantage to be had by the optional head (for you) is the extra cooling because of extra surface area.
    For more info on the head you could look at this thread: http://www.motoredbikes.com/showthread.php?t=25506
  3. haddenboy

    haddenboy New Member

    I personally have never used a manic mechanic head because much of the reviews I read also said they did not notice any increase in power. However, I have used a puch moped high compression head and I can tell you that it has definetly made a difference in performance. Depending on which engine you have, this is an exact size bolt on. I have two of these heads. First is on an old 66cc grubee starfire motor and the head needed no modifications the fit. Second is on a grubee super rat motor and I had to expand the mounting holes on the head. Nothing a little bit of time and a dremel couldn't handle though. Definite increase in low end torque, however the one downside is it makes the engine much more difficult to start.

    Hope this helps
  4. richirich1113

    richirich1113 Member

    hi, Geebt48cc , its been awhile since we exchanged posts, since then ive changed motors and did alot of upgrading, on the other site under the "mountain and road bikes" the thread "genisis 29r almost done?" is my bike. i have the MM head. i did notice alot of improvement over the stock angle fire head. there is alot more compression. Now when i start peddling and pop the clutch the back tire actually skids then fires right up on the compression stroke. There is definatly more torque to the motor. it also changed the sound to a more throaty healthy sound. The motor also does run alot cooler ,even after riding it hard it seems like just minutes after shutting it down its back to cool to the touch. If you are thinking about getting one , id say go for it
    But alas after all that work, my bike now sits in the garage thanks to a local rookie cop trying to save the world from MBs. WA laws suck!!!!
  5. geebt48cc

    geebt48cc Member

    Hey, Rich, I'm hearing that story more and more about police. I've not had any problems, but I've just been not so much the right place YET? What is going on there in WA?

    So, I milled head down flush, and even pulled head gasket off.(only with slant) I've put about total 400 miles on this 66cc and the last 170 have been when milled. Yes, major compression here as well. Bike and I weigh about 340lbs and will run 98% hills here in SW Va at decent pace without the pedal thing.

    Rich, do you know if size 700X47C would work on this 2009 Schwinn gateway? I'm really wanting to get the widest tire for pavement that will work? Uno stability is what I'm after, and can still run upper twenties ok.

  6. richirich1113

    richirich1113 Member

    Well the 47c would be like a 1.85 inch tire, on my genisis the tires are 29x 1.65. The 700 is the same as 29" . For me the 1.65 are stable and handle good , but im only weighing 170. I think being a larger diameter tire helps with the stability. So i would think a 700x 47would probably work out ok.
    And about the cops , here in Wa the law tecnically make all ICE bicycles illegal no matter what the cc. To be legal it would have to be state patrol inspected and meet all the equipment requirments like a motorcycle and have to be titled and licenced and DL required. Alot of areas people have been getting away with it but really its just a matter of time and a bored cop. The cop was hoping for a dui arrest, before he even ran my name he told me if i have a suspended or dui I was going to jail. since i just dont have one he let me go but made it clear if i was seen again id go to jail and bike impounded. in this small town you would be seen.but he did say if i had an electric bike i wouldnt be hassled.
    So you can check out my electric in the electric section under HI-POWER CYCLES 104 Ebike. Its not exactly legal but its electric hehe.
  7. geebt48cc

    geebt48cc Member

    Da"", trying to show you who's wearing the badge huh?! Uno, that's just so uncalled for!! I get the biggest kick out of taking the time for any of the" boys in blue" using it to pull over such a petty offence? That does nothing but make the police department overall look very weak. Just think of all of the stuff that's taking place in comparison!!!!!!!!!!!~

    .............SAD, very sad............ PS-Looks like he would of used his stun-gun on you? It really does sound like you were out of control.
    Last edited: Dec 9, 2011
  8. richirich1113

    richirich1113 Member

    yep , just a rookie hoping for a suspended/dui arrest. you know i was not speeding ,i was wearing my helmet. I told him "com on ,there are only two other MBs in the whole town. he tells me " i know ive already stopped them and told them the same thing" what a jerk. And the funny thing is i was contacted by another member that lives in the next town 20mi away and he told me the police srgt. there is allowing them to ride with no problems. Unbelievable.. At least he let me peddle it home , which i just went around the corner fired it and hauled *** home. me peddle- i dont htink so. Well unless the laws change somehow my gas bike is now a dead issue :(
  9. lazylightning@mail.r

    lazylightning@mail.r Active Member

    Hi Glen,

    Can I ask you why you didnt try the milled down stock head without the head gasket? Why only the slant? I milled my stock head down to the fin level surface and polished the inside of the hemi. With the spark plug in, the end of the spark plug is still down in the threaded hole and nowhere near the level of the hemispherical combustion chamber area. The piston at top dead center is still far from reaching the top of the block, 3 or 4 mm to go. I don't see any chance of the piston even coming close to the head or plug. The bikes got alot more pep since I modified the stock head. I'm using a 35 tooth rear sprocket and my jet is bored out to .8mm and needle is all the way down for more leaness at low speed. I haven't tried it at richer with the higher compression yet.

  10. gothicguy64

    gothicguy64 Member

    if i may

    my rse 48cc motor has a rse billet head an is far superieror to a stock motor

    many a time i have seen another pushie an out dragged it .

    mind my motor is ported an has a ceramic topped piston ummm billet head billet inlet ummm billet cover ,billet clutch lever all rse aussie made

    bloody pity the donor motor is a import ohhhh well
    3500 km later an im yet to get a oil leak or petrol leak ,flat (lol)...i run mr tuffy tyre liners .but i digress

  11. HeadSmess

    HeadSmess Well-Known Member

    should see if you can make it out hornsby way and well see who out drags who ;)

    100% stock but piped... :jester:

    tis a chrusty pipe so it makes all the difference though...


    yeah yeah, im gunna do a mission up the old pacific tomoro... might turn the camera on this time :rolleyes7:
  12. lazylightning@mail.r

    lazylightning@mail.r Active Member

    Wow! Nice pipe! I suppose that it's specially designed for the engine?) I like that small gear in the back, higher top end! I have a 35 toother. Dreaming of making a pipe now though. Planning to make one of those Jaguar's new pipe designs with the wide rpm range.
  13. HeadSmess

    HeadSmess Well-Known Member

    remember i only have 20" rims... so i need the small one.

    could get away with a 36 on the 26" rims. didnt have a smaller one then, never tried.

    honestly notice no difference on this with a 33 or 28... it actually maybe goes a bit faster with the 33... less load, lets it spin faster... iunno :)



    yes, i designed the pipe for the stock engine. though that was a different engine and i have noticed over 10 degree differences in port times across several engines.... mainly on the transfer times. 104 to 114 degrees...hmmm....

    cant get too precise anyways. its hard working sheet metal at .1mm increments. cant be done. theres a lot of "rounding off" of figures, just to make the tapers. (ie 272 mm doesnt divide neatly into 25 mm lengths with 1mm rise on the diameter but 275mm does... limits of software and reality, dammit!)

    3 days on the PC, using fancy plugins for google sketchup to check on final dimensions and shape, and 2 hours in the workshop...
  14. lazylightning@mail.r

    lazylightning@mail.r Active Member

    Wow! 20 inchers) I'm thinking of the day when I'll use 29ers on a fatbike frame for the summer weather. Yes, I use a 35 toother on a 26 inch rim. With a 26 inch rim, each tooth is supposed to represent about 1 mph. So I should be able to do 9 mph faster than the 44 tooth setup. I would like to set it up with the new CVT thingy and use a 25 tooth rear sprocket on my 26's.

    So that pipe is really cool. I like the design, but I'm afraid it's impossible to bend it more tightly, the way I would like to and not ruin the inner aerodynamics. I see you have it going up where the gas tank usually is. Is it good at low rpm's? That's what I need more of)))
  15. HeadSmess

    HeadSmess Well-Known Member

    a pipe doesnt care how tight a bend you have. the pressure waves take no notice of how sharp the turns are (my first pipe had 1 bend, almost a right angle, that was just a plain mitre, not a smooth curve).

    the exhaust gas does like some "aerodynamics" though. just so it can flow without turbulence.

    think of plumbing. smack the end of a pipe with your hand, and the pulse is felt at the other end, regardless of the number of bends and twists.

    whereas water (a fluid) wants the straightest run possible to flow as fast as possible with minimal turbulence.

    what does affect a pipe is changes of section. if you flatten it at all, you need to recalculate length and angle of taper... the reason why i went up and over instead of down and between the cranks. theres only 30mm clearance down below when i needed 70mm at least...

    just made it easier.

    as it is though, i can make exactly the same pipe as a straight one, or (if i tried) all curled up like a tuba... the basic dimensions stay the same.

    low end? huh? never use it. but yes, it will putt along without needing to be pedalled, with almost no throttle. like when passing policeymens... :D its the long 4km uphills that wear it down... :( little ones, no problem, it has a run up, but id go lower gearing if i had to deal with more hills

    when i get the license back and these can become nothing but a hobby ill do a monster pipe for the stingray... about 6ft long. wont rev but should make some low down grunt :)
    Last edited: Jan 5, 2012
  16. jaguar

    jaguar Well-Known Member

    If you'll look at the test results on my web site you will see that there is an ideal length for the pipe for best low end power. Longer than that results in less low end power. On my engine the best extension was 6 inches.
  17. geebt48cc

    geebt48cc Member

    So, Jag, are you saying with the stock SBP expansion chamber set up, all I would need to do is add enother 6" of extension? That would be all the total parts SBP sends with kit, then 6" extension with expansion on end, right?
  18. lazylightning@mail.r

    lazylightning@mail.r Active Member

    Maybe he means the length of the belly of the expansion pipe, the widest part...

    By the way, wouldn't a pipe for a 66cc need to be a bit bigger than the pipe for the 55cc?
  19. jaguar

    jaguar Well-Known Member

    I am sorry I thought you were talking about regular pipe/muffler combo like the long one in the photo.
    For an expansion chamber you need to use my Excel file, enter the exhaust and transfer port timings and target peak rpm and mid-header internal temperature (in Celsius) to find the perfect header length for whatever expansion chamber you are using. That is the detailed way.
    The poboy method is just experiment with different temporary header lengths till you find the right length that gives you the best top speed, preferrably going slightly uphill.
  20. geebt48cc

    geebt48cc Member

    That's fine Jag,

    I do appreciate your knowlegde. So, from judd on, what length would you start with on total system of SBP Expantion Chamber? 6", 16", etc?