HT Engine Specifications

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

  1. AussieSteve

    AussieSteve Active Member

    One of the things needed on this site is a quick reference for engineering and tuning specifications, rather than having to search and sort through heaps of posts for lesser details.

    I started a thread in the 'Forum Help and Suggestion Box' on this subject, A 'Specifications' section would be helpful. , and Tom suggested starting the specs thread here. If there's enough interest, he might make this sticky.

    To benefit everyone, it would be good to keep this on-topic as much as possible and to avoid wild or off-the-wall recommendations.
    What we need are 'factory' recommendations, specs, clearances etc.
    Also clear illustrative pics of spark plug colours and procedures such as float level measurement and clutch adjustment would be good.

    Copied from the above thread:-

    A couple to start the ball rolling.:-

    2009 HappyTime 2-Stroke Engine:-

    Recommended spark plug (48cc and 66cc): NGKB6HS, (colder), or NGKB5HS, (hotter).

    Spark Plug Gap (48cc and 66cc): 0.6mm, (0.024")

    Recommended Fuel/Oil Mixture (48cc and 66cc):
    Run-in: 16:1
    Thereafter: 20:1

    Compression Ratio (48cc and 66cc): 6:1

    Compression, (measured):
    48cc: ???psi - Anyone? (I'll edit)
    66cc: 115psi

    Max Power:
    (These figures from ZBox Australia )
    48cc: 1.2kW, (1.6hp), @ 5500rpm
    66cc: 1.7kW, (2.3hp), @ 5500rpm

    Bore x Stroke:
    48cc: 40mm x 38mm
    66cc: 47mm x 38mm
    N.B. Capacity = pi * (Bore/2)² * Stroke. e.g. pi * (4.7/2)² * 3.8 = 65.9cc.
    (Calculate in cm.)

    Overall Weight:
    48cc: 9kg
    66cc: 9.5kg

    NT Carburettor:
    Bore: 14mm
    Float level (48cc and 66cc): 21mm (Measured with carb upside-down and gasket removed, from gasket seating surface to highest point on float when float is held level)
    Main Jet:
    48cc: ??? - Anyone? (Again, I'll edit)
    66cc: 0.7mm or 0.79mm
    Some carb tuning pointers might be good, too.
    Plug black, (mid-throttle settings) - lower the needle
    " " , (3/4 to full throttle) - smaller main jet

    Some sources of jets and so on:-
    Range of main jets: Rock Solid Engines, (Australia)
    Replacement (stock) Slide: thatsdax, (USA)
    Replacement (stock) Slide Needle w/ 'C' clip: thatsdax, (USA) , Rock Solid Engines, (Australia)

    ... Steve
    Last edited by a moderator: Dec 17, 2015
    ChoppaStile likes this.

  2. I already tried doing a thread like this, the engines from diffrent websites and diffrent models all have diffrent horse power and some with diffrent stud sizes. everyone will reccomend diffrent oil-to-gas ratios. there are some things that will be the same , but the carb/carb slide/sparkplug will have to be adjusted depending on where you live.

    Im all for a 'Specifications' section,even if it answers just the basic questions of sizes of stuff for new people. Could include what size chain and sparkplugs to buy, stuff like that.
    Last edited: Dec 16, 2009
  3. AussieSteve

    AussieSteve Active Member

    Hi cabinfever1977, I see you added a bit. That's exactly what I mean. The exact power output is irrelevant and hopefully everyone will tune their engine individually, but some basic specs gives people a good starting point.
    Things like stud size aren't that important initially. (Later, they can be, for those that want to replace the stock studs with decent or longer ones.)

    Some tuning tips could easily be included, including a pictorial or two on plug reading/carb tuning etc. Possibly even a bit on performance modding, but more important is the standard stuff, inluding primary gear lubrication etc.
    On spark plugs, my first post gives the two most recommended plugs. Again, not a bad starting point. Same goes for the 0.6mm plug gap.

    Chain size and alternatives is a good idea, too.

    ... Steve
  4. AussieSteve

    AussieSteve Active Member

  5. olkoot

    olkoot New Member

    spec thread

    Steve, I think it's a good idea for newbees to have a good basic assembly and maintenance guide( did someone actually put the carb on upside down?) For people that are more mechanically inclined, something like this sounds impossible, but after building two Grubee 66cc with my teenage sons in the last two weeks i've found that these guys need some basic assembly help. Let me know if I can help. ...Ken the olkoot
  6. olkoot

    olkoot New Member

  7. AussieSteve

    AussieSteve Active Member

    Yeah, Ken, some things that many of us are used to from owning motorcycles are totally alien to others.
    Also, even for those with motorbike experience, clutch adjustments etc. are specific to each motor.
    A workshop manual would help everyone, especially MB newbies.

    Next chance I get, I'll search for a few useful threads (with pics) for assembly, adjustment, repair etc. and post links here.

    The 'Crash Course for MotoredBike NOOBS' thread has a number of useful links, for starters.

    (Originally, I was going to keep editing and adding to my first post as I got more info, but it seems that there's only a short time window before the 'Edit' option is removed.)

    ... Steve
  8. bigdan

    bigdan Member

  9. AussieSteve

    AussieSteve Active Member

    Hi Dan, you're right on the mark. What I picture is an online workshop manual, much like the workshop manuals that are available for motorbikes. (Produced by 'Clymer')
    It would begin with engine specifications, follow with tuning specifications and then, chapter by chapter, provide detailed info with pics on most tuning and repair procedures, with a 'Troubleshooting' chapter towards the end.
    A good index at the beginning.....
    It would probably work best in either html or pdf format, but then a 'Submissions' thread or similar would probably be needed, to allow people to suggest inclusions.
    There was a wiki manual started, but it never really got off the ground.

    ... Steve
  10. AussieSteve

    AussieSteve Active Member

    This is all still happening. I'm in the process of putting together a post on carburettor tuning / plug reading / plug chops, with pics. (In 'Word', for now. I'll transfer it when done.)
    Might be a little while, though. Xmas calls.
    Anyone with any other useful stuff, please post it here. Lubrication, clutch adjustment, chain adjustment etc etc.
    When this thread has run it's course, it might be possible to collate all the info into a single manual.
    Just thinking, a 'Common Problems' section of the manual would be a good idea, covering tensioner setup, carb inlet sealing, frozen clutch and some of the other regularly recurring hassles, especially during setup.
    A lot of this is already in 'stickys'. It's just a matter of getting it all in one place and organised.
    ... Steve
    Last edited: Dec 22, 2009
  11. AussieSteve

    AussieSteve Active Member

    Got the thread on NT Carb Tuning Basics started.

    I hope that all of this isn't a waste of time.

    ... Steve
  12. arkives1

    arkives1 Member

    ht engine specs

    Great idea and wonderful work so far Steve. I'm relatively new to all this information so your posts are extremely helpful to me. The video on 4 stroking was excellent as I would have noticed the difference in sound but would have no idea what was happening or why. Thanks a lot for you efforts.

  13. AussieSteve

    AussieSteve Active Member

    Thanks, Woody.

    ... Steve
  14. CaptJ

    CaptJ Member

    I found this today, the most informantion I've seen.
    Awesome post.
  15. AussieSteve

    AussieSteve Active Member

  16. CaptJ

    CaptJ Member

    Extremely useful Steve, your doing a excellent job on HT information.
    When I recived my new engine I had to disassemble the carb for inspection and it passed. Haha! :detective: After re-assembly it worked.
  17. AussieSteve

    AussieSteve Active Member

    From what I've read, pulling the carby apart is a very good idea. Some guys have found the main jet and/or needle jet loose in the bottom of the float bowl fresh from the factory.

    ... Steve
  18. adb140275

    adb140275 Member

    The higher the number, the hotter the plug. just thought i'd throw that out there.
  19. AussieSteve

    AussieSteve Active Member

    No, with NGK, the higher the number, the cooler the plug. ie. A B5HS is hotter than a B6HS.
    (Just thought I'd throw that out there.)
  20. HeadSmess

    HeadSmess Well-Known Member

    bloody hotter...colder.... i still get confused :(

    if its black but not cause its rich, the plug is too cold, right? and hotter plug has less ceramic so it heats up more, burning off excess oil/carbon..which is the black....

    keeping in mind the engines tuned...

    yes? actual addition here was


    Ex : 140 degrees. open

    In : 106 degrees. open

    piston induction : 120 degrees? not very important anyway.

    EX port area : approx 260mm2

    and a good program for tuned pipes that ive used a few times on other engines...

    measurements are as close as i could measure, and are really only a guide... it will only effect the pipes performance by a few hundred rpm either way...