HT Engine Specifications

Discussion in '2-Stroke Engines' started by AussieSteve, Dec 15, 2009.

  1. AussieSteve

    AussieSteve Active Member

    Yep. (And thanks for the port timing info.)

    Here's a clickable link to the Pipe Calc Applet
    Last edited: Sep 4, 2010

  2. HeadSmess

    HeadSmess Well-Known Member

    right, today has been a success :)

    1mm stainless and some swearing, and would you laugh if i said a star stake and at one point, a tractor implement? well, how else do i bend the **** stuff?

    just got back from testing my 8000rpm tuned pipe i made, or 60km/h approx.(from the applet, using 750K exhaust btw)

    had to resolder and drill the jet back to 0.6, and did it hit 60?

    you bet your *** it did :)

    awesome band from about 25km all the way to 60, 55 up hill. sounding sweet.

    also very loud, until i do the final bend... yes, thats no muffler right under my ear... :lol:

    im also about to learn how to post pics here so forgive me if they dont work at first...

    Attached Files:

    Last edited: Sep 5, 2010
  3. AussieSteve

    AussieSteve Active Member

    That's pretty good. My (66cc) tops out at 7400rpm, (expansion chamber not yet fitted), let alone tuning for those revs as usable. I have an SBP pipe to fit, just need to get motivated.

    0.6mm is surprising for a main jet. Mine tuned well with an 0.72mm, from an 0.79mm stock.

    The pipe's looking good.
  4. HeadSmess

    HeadSmess Well-Known Member

    mines the Z48, and i had the jet at just didnt wind up when i piped it. so 60 it is :)

    um....with the standard exhaust, with a 13mm outlet over the stock 10... i got 66km :) no tacho, so i guess 8500...

    but, THIS holds the speed, unlike the stock, which as we know, dont like much over 40 on the flat...

    the next experiments with pipes? hydroforming, using just seam welded sheet, profile cut to shape... make em thin...light! ring..ting...ting..ting...ting

    that pipes just a very temporary setup like that...though it is sorta cool... :D

  5. AussieSteve

    AussieSteve Active Member

    My bike got 52kph on the flat standard, after some basic tuning and drilling some holes in the exhaust. With the shift kit, I can get about 70kph max on the flat and about 80kph on a gradual downhill. I only weigh 50kg, though.

    If you accurately calibrate your speedo by sitting on the bike and rolling forward one turn, then entering that value / pi as the diameter, you can calculate rpm from your speed using JPilots Gear Ratio Calculator.

    The primary ratio is 20:82, (4.1:1) and the secondary ratio is 10:44, (4.4:1), for a 44 tooth rear sprocket. (Adjust to suit your rear sprocket.) Leave the third field at 1:1.

    You'd find that any further refinements of the pipe would result in minimal gain. You'd get a much better improvement with some balancing and a high-compression head at this stage, along with a decent carby. Not CNS etc, but Mikuni or similar quality.
    I have a Rock Solid Engines billet head, but at 16:1 CR compared to the stock 6:1 it makes the engine very hard to turn over.
  6. HeadSmess

    HeadSmess Well-Known Member

    yeah, i could be anywhere between 35 to 55 on the flat before i did any tweaking, but most of the time in the lower regions.... only another 16 kg here :)

    temperemental? yes. right time of day when the humidity is just right, she would scream, then a few hours later? hmmph. the sort of times you wish you had spent some time setting up the derailleur properly... cant do much in granny gear.

    interesting that with the now much leaner settings, its less grumpy, and in fact, sorta prefers the heat... i shall see as the days get longer i suppose, if it stays that way...

    80 on a pushie.... nah, ill wait til i get my license back to do 80+ again :)

    one last thing while i think of it.

    indexing spark plugs. ideally, the open side of the gap should face the exhaust port. i have no idea why, but its one of those things that can make a marginal difference, and is far more noticeable as the cylinder size increases. i noticed my head was on 180 degrees out.

    shame i always have to make three or four tweaks at a time so i can never really point at one thing alone.
    Last edited: Sep 7, 2010
    FurryOnTheInside likes this.
  7. steinway

    steinway New Member

    a little bird told me that the generator on the 66cc engine can output electrical power to lights which upto 5-9V 4.8-18A (AC).

    Is there anyone had use this source to your lights?
  8. AussieSteve

    AussieSteve Active Member

    The little bird should have also told you to post in the appropriate place.
  9. HeadSmess

    HeadSmess Well-Known Member

    and that lil bird shoulda mentioned search too :p try the electrical section, perhaps....

    (ps...i severely doubt it can give 18 amps!)
  10. Ivan H

    Ivan H New Member

    Hi Steve, heres some info for anyone who ever wants to split the cases or replace the main or countershaft bearings. Case bolt torque setting 75inch/pound, crank end float 0.003" to 0.008". Recomended to change all the case fasteners for automotive grade or high tensile socket head. Cheers
  11. Ivan H

    Ivan H New Member

    Oh yeah, I forgot to say,,, torque the cases in 3 goes, starting at 25inch/pounds, then 50, then 75, & use the "always opposite" pattern when torqueing & u cant go wrong. Cheers
  12. sp454e

    sp454e Member

    specs what is the air gap between the mag loop and magnet
  13. sp454e

    sp454e Member

    thanks ivan i need to know the gap on the magneto loop to the magnet
  14. Cali-Rider

    Cali-Rider Member

    I think the 66cc had a 40mm stroke with an 89mm conrod, as where the 48cc has a 38mm stroke with a 85mm conrod. The piston diameters seem correct, but you might want to add these:
    They should all have a 38mm stroke/85mm conrod other than the 66cc.
    Last edited by a moderator: Dec 17, 2015
  15. hopkinsbiker

    hopkinsbiker New Member

    According to strava, my max Wheel power, after drive train and friction losses is 1253 watts while climbing a hill. My max power occurs around 30 m.p.h. My top speed is 33 m.p.h.

    Specs: All stock, ebay 66cc motor, 44t , 700c single speed road bike.

  16. Fabian

    Fabian Well-Known Member

    That's an easy question to answer: cut a half inch wide strip from the top of a cereal box, approximately 3 inches long. With the magnet is in the horizontal position, slide the cardboard strip around the magnet and along the upper and lower arms of the magneto coil.

    Now with the magneto coil screws loosened, turn the crankshaft so that the magnet is in the vertical postion. Tighten the screws and remove the cardboard strip.

    Your air gap is perfectly set!
    FurryOnTheInside likes this.
  17. jaguar

    jaguar Well-Known Member

    this is from my site:

    Here are the measured distances from the top of the stock cylinder:
    engine exhaust transfers intake* piston skirt**
    48cc 28mm 32mm 55.5mm 44.8mm
    60cc 28.7mm 33.1mm 56.3mm 45mm
    66cc 29.3mm 33.1mm 57mm 44.7mm

    * measured to bottom of intake port
    ** measured from top edge of piston
    (66cc is the cylinder the factory calls 80cc. It is 66cc when measured the most common way.)

    Assuming a .7mm deck height (distance from top edge of piston to top of cylinder at TDC) here are the port durations in degrees:
    engine exhaust transfers intake blowdown*
    48cc 140.7 110.3 113 15.2
    60cc 135.7 100.6 116.8 17.6
    66cc 141.6 114.7 117.6 13.5
    * blowdown is the number of degrees that the exhaust gas has to exit the exhaust port before the transfers open. For this engine 20 degrees is perfect if ported per my recommendations.

    To have perfect 157/117/120 degree port durations and 20 degree blowdown change the distances to these:
    exhaust transfers intake or piston
    25.6mm 31.2mm 56.8mm 44.5mm (48cc, 60cc)
    26.9mm 32.8mm 57.1mm 44.6mm (66cc)