Ignorant newbie needs help regarding head studs

AuntySpam · Aug 12, 2015

I bought a set of new head studs and nuts from Sick Bikes and have installed them on my 48cc Grubee 2 stroke engine. However, two of the studs are higher than the other two, and when I put the nuts on them and try to torque them, they won't torque to 12 ft lbs like the other two did. I read on this forum (somewhere) that sometimes the Chinese don't tap out their stud holes all the way. I'm wondering if this could be the problem or if it's something else. Can anyone help me? I really want the engine to be as good as possible before I even install it and run it, and the two "longer" studs are scaring me!

crassius · Aug 12, 2015

first thing is to check that both ends have same thread - some have 1.0 thread on one end & 1.25 thread on other end

if that is OK, then make a mark so you can tell how far tall ones are going it vs how far short ones are going in

that should be enough info for you to sort it out

2door · Aug 12, 2015

Welcome and we never consider a newbie as ignorant. If you're asking for advice, that's smart. We're here to help you get on the road. You asking for help is why we're here.

If you're trying to use the kit supplied chrome acorn nuts, that's part of your problem. Inconsistant stud length will cause the acorn nuts to bottom out before they apply pressure to the cylinder head. Throw them away or use them for slingshot ammo and replace them with standard or flanged hex nuts.

You said youi have a 49cc (48cc), engine. The studs for the smaller engine are usually 6mm as opposed to 8mm which are used on the larger 66cc engines. The torque value for a 6mm fastener is more in the 60 to 80 inch pound range. 12 foot pounds is closer to 140/144 inch pounds. That's a little too much torque for a 6mm fastener. You're going to break something if in fact you have 6mm studs.

Tom

AuntySpam · Aug 13, 2015

Thanks for the info. My studs are definitely 8mm. I did ditch the acorn nuts and bought regular hex nuts from Sick Bikes. Also, the threads are the same on each end. I will try measuring the difference. I hate to take them out again, but if I have to I will.

Slogger · Aug 13, 2015

My exhaust stud holes are different, one deeper than the other.
I don't worry about it. If you can torque your head down, you're probably ok.
Don't over-tighten, and after a few heat up/cool down cycles check their torque again.

Avoid messing with them (or the spark plug) while the engine is hot, the cheap alloy of aluminum will strip right out.
good luck to you.

crassius · Aug 13, 2015

should be fairly easy, as cyl can stay on - just mark where top of cyl is when stud is in, then unscrew and mark when stud is just sitting on the hole - compare all marks to see how much thread is in the hole - if enough to hold it, you're OK

AuntySpam · Aug 13, 2015

Thanks again for all the practical help. I'll do the comparison test!

AuntySpam · Aug 22, 2015

I found out what was wrong. Two of the head bolt holes are stripped. I took the head off and could easily see this. I've bought a helicoil kit and will go that route to try to fix the holes. :-( At least I know why those two bolts and nuts wouldn't register on the torque wrench!

crassius · Aug 22, 2015

look at the metal carefully before helicoil - seen some ripped out mounting studs that left the metal too weak to hold the helicoil unless a larger size was used

I've come to assume this chinese metal was mixed scrap before melting & recasting & is pretty inconsistent.

AuntySpam · Aug 30, 2015

I drilled my holes out to 21/64", and yes, I think the metal was too weak on its own. It was like drilling through butter. I taped all around it to make sure nothing fell into the engine proper and used a greased q-tip to remove the tiny pieces of aluminum. Now I realize I'll have to take the piston off in order to have clearance to tap. :-(

crassius · Aug 30, 2015

no biggie as long as you think to put a rag around rod to keep the wrist pin clip from dropping into bottom if you drop it

AuntySpam · Sep 3, 2015

Thanks, Crassius, I did that, and it was a piece of cake to get one clip in. Yeh, the other clip, when I picked it up with my snap ring pliers, went boingggg and flew somewhere in my crowded garage! I heard it hit something and then silence. It took me two days, but I found it. It's in now. While the cylinder head was off, I noticed that the base gasket has a tiny rip right near one of the holes (the interior side), so I think I'm going to either replace it or try to glue it.

crassius · Sep 3, 2015

non-hardening permatex form-a-gasket will probably work on small torn spots

mogollonmonster · Sep 4, 2015

Is your head gasket fiber? If it's the typical metal one a rip is bad news man, it takes a LOT of force to RIP metal, could it be corrosion/oxidation? Is it possible you May have done it when you disassemble? If it was me I would just toss it and replace it.

AuntySpam · Sep 4, 2015

It's the base gasket, and it's fiber. I sprayed it with Permatext copper spray before assembling it. Because I was having trouble with the head bolts, I had to kind of stretch the gasket it to get it on. That's when the small rip happened. I'll probably buy a new one. I just hate to have another delay before I get the bike running!

Davezilla · Sep 4, 2015

It never hurts to have a few extra base, exhaust, and intake gaskets in your stash in case you need to do a quick repair or want to try out that new intake or pipe, these are the most common to rip when trying to save one and there's not a spare to be found... and nothing can be worse than doing a quick job and tearing a gasket beyond help then having to wait a week before being able to ride again...
Personally I use copper gaskets because they can be reused over and over again but I do keep spares on hand just in case any of my customers need a quick repair etc...

AuntySpam · Sep 4, 2015

Where do you get copper gaskets, Davezilla?

mogollonmonster · Sep 8, 2015

AuntySpam said:
Where do you get copper gaskets, Davezilla?

Ditto!

Noticed your from Show Low, Auntie? I live in snowflake now but I still work in Overgaard, needless to say, I'm all over the mountain! If you ever need a hand, or just want someone to ride with, let me know and I'll pm you my number. Its a nice ride over that way.

Jmichaelg21 · Sep 20, 2015

In regards to a stripped stud hole on the crankcase if it geabs some but not all the grip couldnt i just use some industrial strength locktite?

2door · Sep 21, 2015

Jmichaelg21 said:
In regards to a stripped stud hole on the crankcase if it geabs some but not all the grip couldnt i just use some industrial strength locktite?

You could but it won't work. Loctite is a good product and the red, or #262 will make a permanent assembly but it won't restore stripped threads. Neither will any epoxy or glue. You'll have to use a helicoil or drill and re-tap to the next larger size. Or replace the case.

Tom

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