torque on head bolts

Discussion in '2-Stroke Engines' started by blompod, Jan 29, 2007.

Tags: Add Tags
  1. blompod

    blompod Guest

    I checked the head bolts on my 50cc in the process of breaking in and the head bolts all took a good half turn without any effort at all. I dont have a torque wrench and was wondering if nipping them up after every other ride is ok. Planning on getting a torque wrench down the track but they are not the cheapest of tools . Thankyou :D
    sorry this should have been in technical :???:

  2. Guest

    Guest Guest

    I wouldn't waste your time on a torque wrench. Get some better nuts or double nut each headbolt. My bolts get loose often.
  3. gone_fishin

    gone_fishin Guest

    blompod: warning! sometimes it's the BOLT and not the nut that has loosened.

    ok, if you don't have the funds or other resources to change out headbolts or nuts, i strongly suggest next time you check the headbolts you make absolutely certain each one is fully screwed into the block before re-torqueing. otherwise, as the bolt loosens and you re-tighten the nut, you will eventually pull the bolt outta the block, stripping the hole in the process.

    ps-any time anyone feels a topic would be better suited in another forum, simply
    PM srdavo with the details and it's a done-deal 8)
  4. bolton75

    bolton75 Guest

    A beam type torque wrench does not cost much money (generally - some of them are dear but I'd just get one of the cheaper ones) and is perfect for use on bicycles. Simple and effective.

    Generally the click type torque wrenches are the ones that will set you back quite a few $$$.

    I've always found Parktool tools to be of good quality and they sell two different types of beam torque wrenches (TW-1 & TW-2). Check it out and decide for yourself.
    Last edited by a moderator: Jan 26, 2008
  5. fetor56

    fetor56 Guest

    Those cheap beam type TR's arn't particularly accurate and since u don't need much pressure in the first place i would be concerned about using one.
    I've found that a MODERATE pressure with a spanner or socket(regularly) is a good check for tightness.When checking only apply enough pressure to see if the head bolts other words don't go tightness crazy. :)
  6. will_start

    will_start Member

    Jan 20, 2008
    Likes Received:
    torque wrench idea for non torque wrench owners

    Hi All,

    Here's my Torque Wrench(TW) idea for those without one.
    { here's a link for those with no idea what a Torque Wrench is }

    If we had people who had a torque wrench they could work out the number
    of turns it takes to get the torque limit reached on their bikes

    Get a few people to do it on Same size engines.
    Then Average the figure.

    Then we would have a torque setting for beg-giners
    with no Torque wrench, but probably with a socket set.

    The starting point would be when you can gently
    turn the nut until it stops you tightening.
    Or maybe until it hits metal would be the starting point?

    Here's my experience:
    I went and spent $45 on a micrometer torch wrench
    that gives 1 inch pound increments.

    here's a pic of one of similar type.

    The setting in a couple of the online manuals said use
    12 foot pound, which I believe is 124 inch pound
    (12 inches in a pound right, I mean foot :cool: )

    I had a socket wrench, that initially, i used to tighten to varying
    amounts. It was a guess.

    If I had a number of turns in mind, at least that would
    have helped determine how many turns was in the range of being right.

    Like the Carbie screw setting of 4 and a half turns.
    It may be 4 on some, may be 5 on others, but at least you have a figure
    to aim for. That setting done by a newbie could be 3 or 7.

    The manual says always tighten the head bolts, a friend told me not to
    tighten too much or I'll blow the head. So I ended up buying the tool
    to stop my fears of snapping the bolt, or it being the reason
    my bike would never start.

    So, with my TW, I am going to re-tighten my head bolts from a starting

    I'll report back how I started and how many turns for each head-bolt.
    Probably later this week.

    Some are bound to shoot down this idea,
    some are bound to consider the idea.
    As Homer says, so easy to criticise, so hard to create.

    I think I just found my sig.


  7. Alaskavan

    Alaskavan Guest

    Will, I think 12' lbs = 144" lbs. Someone else has probably mentioned this, but what the heck. If you have a good fish weighing scale, hook it on a (breaker bar) wrench 12" from the center of the socket. Pull on the scale. When the scale reads 12 lbs, I think that would mean you've applied 12 ft. lbs of torque.
    Last edited by a moderator: Jan 26, 2008
  8. ibdennyak

    ibdennyak Guest

    Interesting concept. Been wrenching on my equipment for quite a few years, and Snap-On learned to love me. :roll:. Not passing judgement, just adding information. What a torque wrench measures is the friction developed to put a given amount of tension on a fastener. So you are already using apples to measure oranges. (Ideally you would measure the straight line tension on the bolt.....not practical when you are laying under a Cat in the mud replacing bearings. :yuck:) Torque wrenches measure friction very accurately, but other factors like lubrication, tensile strength of the fastener determining stretch, etc. enter into it, and can cause discrepancies. Counting turns adds more error possibilities because of different gasket compositions etc. That being said, who knows, it might work. I kind of think you may be over complicating the issue, but it can't hurt. The big thing would probably be using a big enough amount of samples to get a good average. If it works, I have a friend in Wisconsin I would like to introduce you to. He always said he used the bulge of his bicep to determine torque on the head bolts of his diesel farm tractor. Unfortunately, he also spent more time looking at his bicep bulge, than using the tractor. Blew lots of head gaskets. :grin: Anyway, try it and see what shakes out. Oh, by the way...your starting point is called "finger tight". :grin:

  9. will_start

    will_start Member

    Jan 20, 2008
    Likes Received:
    Hey All,
    Alaskavan, thanks for correcting me.

    I can't believe I got the torque setting wrong.
    12 foot pound = 144 inch pound.
    1 foot = 12 inches.
    12 x 12 = 144 not 124. DUH!!

    That said, I had an ex aeronautical engineer set it for me,
    now thats a worry !!

    Oh well, this is why I include as much detail in my posts as possible.
    I left the start point open ended, as I may come up with a better way when
    I do actually get the tools out.

    I never know what I'm going to come up with each time I go out to play.

    Denny, tell your Wisconsin friend to buy a TW, tractors don't come cheap.

  10. kerf

    kerf Guest

    Well heck, might as well dump my opinion in here too. Torque wrenches are inexpensive, aluminum strips easy, cylinders can be warped with incorrect torque procedures. The torque pattern on a 4 bolt head would be pretty hard to screw up. I always tighten to 1/3 torque all the way around then 2/3 etc.
    Does anybody know the specified torque on these head bolts? Wrong torque can be bad. A 60 in. lbs. wrench would be about all I would trust at low settings in aluminum.
  11. will_start

    will_start Member

    Jan 20, 2008
    Likes Received:
    Hey Kerf,

    Whats inexpensive to you living on a $50-100K income may be expensive
    to a kid on a $500 a year income. Believe me I know, been there done that...

    So my idea is centred around helping those with standard tools and no funds
    to buy more. I have easily spent the cost of the motor on tools and spares
    and ...

    To answer your question for the chinese motor 12 ft/lb is the torque given by the online manual I used.

    See below link.

    6. Head Bolts

    Tighten all fasteners after each five hours of operation. It's most important to check cylinder head bolts: tighten in a X pattern to 12 ft/lb. using a torque wrench. A two piece cylinder and head design engine requires head bolts be kept tight. Important: Check head bolts before each and every ride, vibration can cause them to loosen and blow a head gasket. Caution: Do not over torque or head bolts may break off.

  12. azbill

    azbill Active Member

    Dec 15, 2006
    Likes Received:
    personally, I hold my ratchet by the head (not the handle), and tighten
    very little torque that way
    it was a tip here a while ago, I can't remember who gave it
  13. kerf

    kerf Guest

  14. kerf

    kerf Guest

  15. ibdennyak

    ibdennyak Guest

    Very true. One thing I did discover after checking free hand tightening vs torque wrench tightening is that from about 3/8 and down, the gut reaction is to over tighten, and from 3/4 on up the tendency is to undertighten. If I remember right, the torque for a 1/4 inch grade 5 bolt is like 12 ft lbs. That is about two fingers on a box wrench. I also remember replacing a head gasket in a fiat allis crawler...425 ft lbs. That is both arms with a foot propped against the block and using a 3/4 wrench. (expensive sucker). Even a cheap one at least makes one aware of about what is needed. Now as for our metric friends.....they're on their own. :lol:

  16. Alaskavan

    Alaskavan Guest

    Hi Kerf. Those inexpensive TW's you linked to only go to 60 - 65 inch lbs. That's not enough.
  17. kerf

    kerf Guest

    I see that now. The point is there are reasonably priced inch pound wrenched available. I would advise against using a foot pound wrench at this low torque, something in 150 - 240 inch pounds would be about right. I use those other wrenches mostly for setting bedding screws on target rifles.
  18. Alaskavan

    Alaskavan Guest

    I agree about not using a foot pound wrench. I wouldn't trust one much at such a low level of torque.
  19. kerf

    kerf Guest

  20. will_start

    will_start Member

    Jan 20, 2008
    Likes Received:

    I did a tighten of my head-bolts from a light finger tight position.
    It was only 3/4 of a turn that got the torque wrench to stop turning.
    I had to do it in 1/4 turns, but basically that was it.

    Can anyone else do this test on their motor who has a torque wrench ?

    I'd like to know that I'm doing the right thing here too.
    As I don't know that I trust my torqueing skills.