Head Stud Question

Discussion in '2-Stroke Engines' started by pucksterpete, Jul 25, 2010.

  1. pucksterpete

    pucksterpete Member

    :confused:Newbie question. I have 66cc Grubee Skyhawk and I am in the process of switching the acorn nuts on the head studs. Could someone tell me what type of thread I have on these studs. (See Pics) The thread is different from any remaining studs on this engine. My basic problem, I live in France and our local home depot doesn't have the correct thread on their lock nuts. If anybody could share some light on this I would appreciate it.:bowdown:

    Thanx,

    Pete
     

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  2. Pablo

    Pablo Motored Bikes Sponsor

    They are either M8X1.0 or M8X1.25. They sorta look like 1.25, but I would be amazed if you didn't have those in Fronce, because M8X1.0 is a bit more rare. I say look elsewhere than HD.
     
  3. Al.Fisherman

    Al.Fisherman Active Member

    Pete, I'll agree with Paul in the fact that the MOST common 8mm thread is going to be 1.25. To add to that the only thread a 6mm comes in is a 1.0 Take a 6mm stud (a screw from the clutch cover will do) and overlap it on the 8mm stud (thread on top of thread). If the threads fit perfect then it tells me they are both a 1.0 thread. If not then the 8mm stud is a 1.25 Having said that I'd recommend that you change out both studs and nuts, not just the nuts.
     
    Last edited: Jul 25, 2010
  4. AussieSteve

    AussieSteve Active Member

    My guess is that they're 8mm x 1mm. I think that the threaded section is 20mm long and I count 20 threads. (Actually looks like 21.)
     
  5. pucksterpete

    pucksterpete Member

    Well here is what I got

    I guess I have 8 X 1.0mm studs (see Pic for overlapping stud threads). I went to this large home depot like store (Castorama) here in France the other day and bought 2 types of nylon locking nuts (2 diff sizes). 1 type for the front & rear mounts, exhaust & intake studs, all fit fine. The 2nd type for just the head studs. The only ones that do not fit are the head studs. The nylon locking nuts are the same drive for the ratchet 13mm as with the acorn nuts, but the threads are different. So, I assume that the nylon locking nuts I bought for the head studs are 1.25mm, would this be correct? They did not have any other type of nylon lock nuts. Thank you :bowdown:, to the three of you for your help in this matter. Now, I must find a store that will have what I need. To Pablo, can't wait to install the shift kit, it should be arriving here any day.

    Thanx,

    Pete
     

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  6. Pablo

    Pablo Motored Bikes Sponsor

    Looking at the new picture and agreeing with Steve's count = M8x1.0
     
  7. pucksterpete

    pucksterpete Member

    Correct 1.0mm

    You guys are correct the studs are 1.0mm I had to go to a bolt & nut distributer 15km away in another town to get the correct Nylon nut (see pic). No one around here in Corbeil or Evry, France had it. What a pain in the a s s. So, I plan on using blue 242 loctite, washers (where needed) and nylon lock nuts on the front & rear studs, head studs, exhaust and intake studs.

    What about using blue 242 loctite to the clutch cover bolts and clutch arm cover and anything else that might need it?

    Thank you again for all your help. :bowdown: I just want make sure I have this engine prepped before I mount with shift kit.

    Thanx,

    Pete

    Also, from what I can tell every stud sticking out of this engine and even the bolts for the clutch cover etc are all 1.0mm thread. France's 2 large hardware stores that I went to carried the 6mm X 1.0mm nylon locking nuts, but for the 8mm it was 1.25mm thread. Why wouldn't they carry the 8mm in 1.0 thread? Just doesn't make sense.:rolleyes7:
     

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  8. Al.Fisherman

    Al.Fisherman Active Member

    Out of the box, I replace the OEM hardware, with a grade 8.8. The OEM junk is around a 3 and the problem can be that they will stretch. They can't seem to take the torque that the cast aluminum can. The problem with the proper torque, in this case, is dependent on the cast not the stud when up grade is made. The 8.8 will take more torque then the case will. Hardware I replace...Cylinder studs, engine mount studs, exhaust studs, and although not needed the intake...that is all. The clutch cover, drive gear cover, and the magneto cover have screws that I just tighten by hand. I use (in my case) red lock tite on all replaced studs..none on the others seem to be needed. But if you do, yes blue. 6mm torques between 50 and 60 INCH POUNDS..I use 50 and just for the record 150 to 200 INCH POUNDS on 8mm and I use 150. NEVER had a stud strip, stretch, or loosen up. All my studs have either double locking nuts and or nylon locking nuts.

    Might want to look at these pictures... http://www.motoredbikes.com/album.php?albumid=1018
     
    Last edited: Jul 26, 2010
  9. Al.Fisherman

    Al.Fisherman Active Member

    I'm having a hard time trying to keep up with this thread.. In the first post you say that the cylinder studs threads are different .. that means the 6mm studs are 1.0 (as that is the only standard thread they come in, not considering a specialty cut) and that would make the 8mm a 1.25. Why would you be looking for a 8mmX1.0mm nut?? Are the threads on the 6mm stud and the 8mm stud the same or not???
     
    Last edited: Jul 26, 2010
  10. pucksterpete

    pucksterpete Member

    Thank you very much for the insight on this. I don't want to ruin this engine because of too much torque or loose nuts & bolts. The pics have helped out tremendously for proper mounting.

    Thanx

    Pete
     
  11. Molotov256

    Molotov256 Member

    Minor Complications

    I received my Pirate Cycles package the other day (quick shipping from them this time around!), and I'm having a **** of a time getting the piston to slide back into the cylinder now with new rings on it. I ended up breaking one of them, so I'll have to order a new set anyhow, so I've got some time on my hands again :annoyed:

    I tried the hose clamp and soup can method, and that didn't work well at all because the soup can was too big to slide into the cylinder enough to be of any use. I got the top ring in by hand, but then I noticed the bottom one was broken, so I just left the engine apart and grabbed a beer instead of throwing the @#!$ thing across the garage.

    So... how do I get the piston back into the cylinder with new rings on it?

    As for the head bolt discussion, my engine happens to have 8mm 1.00 thread studs as well. The new bolts from Pirate Cycles are for 1.25 thread pitch, just in case anybody was planning on ordering engine studs through them. Double check your existing thread pitch first!
     
  12. AussieSteve

    AussieSteve Active Member

    I've done it with my fingers all my life and never broken a ring. You could try again, a little more gently, or you could buy a ring compressor, if you can find one to fit. (Should only need your hands on a single-cylinder engine.)

    8mm x 1.0mm is hard to get in many areas. I needed longer studs when I fitted my billet head, but couldn't get 1mm pitch threaded rod locally.
     
  13. GearNut

    GearNut Active Member

    The soup can (or proper ring compressor tool) should not enter the cylinder in any way, shape or form! It abuts against the bottom of the cylinder but the only parts that go inside the cylinder are the piston and rings.
    If you try to fit all 3 inside the cylinder you are going to have a heck of a time cussing and cursing until something breaks.
     
  14. pucksterpete

    pucksterpete Member

    My apologies, the head studs are 8mm X 1.0mm (thread), the rest of the studs (exhaust, intake, both front and back mounts are 6mm X 1.25mm (thread) ) The 1.0mm thread is the odd one, I can only find that at a Nuts & Bolts distribution company, everything else I can find at the hardware store. Why wouldn't the head studs be the same thread size has the rest of the engines thread sizes? Thanks again for the help.

    Pete
     
  15. GearNut

    GearNut Active Member

    You have an odd engine then.
    The side cover screws (except magneto cover), case screws, exhaust studs, intake studs, and engine mount studs are all M6x1 on every HT engine I have worked on.
     
  16. pucksterpete

    pucksterpete Member

    Its my first 66cc Grubee Skyhawk. Got it from Spookytooth. Maybe, I am wrong about the sizes. I know that the head studs are larger than the other studs on the engine. The hardware store here in France only had the right thread size (1.25mm) for the other studs, not the head studs (1.0mm). What size studs and thread sizes are normal for these engines to come with?

    Thanks,

    Pete
     
  17. Al.Fisherman

    Al.Fisherman Active Member

    Is this a FACTORY, out of the box bought engine or did you buy it from someone that had put it together before you got it?

    I haven't seen any cylinder studs that was anything but a 8 x 1.25, although they do in fact make a 8 x 1.0. With that said I've heard that some of these engines came with 6 x 1.0 mm cylinder studs.

    In 50 years, I have never seen a 6 x 1.25 mm stud or bolt. I could be wrong (send a link if you can dispute) but 6mm comes in a 1.0 only and a 8mm comes in either a 1.0 and 1.25...Your intake, exhaust, and mount studs being 6mm have to be a 1.0 thread and NOT a 1.25 thread.

    With this, if the threads on the cylinder studs, and those on the exhaust/intake are the same you have a 8 x 1.0mm stud, if not the cylinder stud is a 8 x 1.25.

    Take two studs that you KNOW are the same...like two cylinder studs. Overlap the threads and look closely, the threads will be a PERFECT match. Now do the same with a 8mm and a 6mm stud. If they are not the (not just close) EXACT same then the 8mm is a 1.25. (since 6mm comes in a 1.0 only)

    If there is something you don't understand in this post please let us know, as of this moment I can't think of anything that has not been explained to you (from various members), about the stud sizes on these "STOCK" engines. It seems cut and dry to me. There are NO magical thread sizes made for these engines.

    If the online postage price is correct, I can send you (4) 8 x 1.0mm and (4) 8 x 1.25mm nylon self locking nuts for $6.00US (4.7 Euro), if need be. I also keep them in 6mm.
     
    Last edited: Aug 11, 2010
  18. pucksterpete

    pucksterpete Member

    I purchased the 66cc grubee skyhawk from Spookytooth cycles. Here is a picture of the head stud and clutch cover. To me the threads look the same, which I believe they are 1.0mm thread. The nylon lock nuts that I got for the intake, exhaust, front and back mounts here in France say M6, nothing about thread size. So, I assumed they are 1.25mm thread, I guess I am wrong, so with that, then all the studs coming out of this engine are 1.0mm. I couldn't find the nylon locking nuts for the head studs at the hardware store here, but did find the nylon locking nuts for the other studs on the engine at the store. That is what I didn't understand, why have those and not the others for the head studs. Thanks for explaining.

    Pete
     

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  19. Al.Fisherman

    Al.Fisherman Active Member

    OK....try this...... Remove a nut from the chain tensioner (either one of the three). They are 8 x 1.25mm, and see if it will fit the cylinder stud. Yes it fits they (the studs) are a 1.25 thread, no it won't they (the stud) are a 1.0 thread.
     
    Last edited: Aug 11, 2010
  20. pucksterpete

    pucksterpete Member

    I am running a SBP Jackshaft, so I don't have the chain tensioner your referring to. So, your head studs are 1.0mm?

    Pete
     
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