Head Stud Question

[Molotov256]

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

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!

 

[AussieSteve]

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.

 

[GearNut]

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.

 

[pucksterpete]

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???

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

 

[GearNut]

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.

 

[pucksterpete]

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.

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

 

[Al.Fisherman]

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

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.

 

[pucksterpete]

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

 

[Al.Fisherman]

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 (Why when 6mm only comes in a 1.0 thread) 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. (They are in fact made, both the 1.0 and 1.25 thread in a 8mm.... weather a particular store carries them is another story.)

Pete

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.

 

[pucksterpete]

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