head acorn nuts coming loose?.

I put roughly 300 miles on my new engine. I was riding the other day and the bike had a lack of power, pulled over and it died. I found the 2 inner head nuts on the right side had come completely off. I got the bike restarted and I was getting compression from the holes.. this doesn't seems normal. the engine has been rephrased with 81mm weisco pistons and LA cylinder sleeves. I think the compression is in the 11 range.

I torqued the head to 30ft lb with a freshly recalibrated digital snap-on torque wrench. I also used ARP moly grease as a lubricant. I was thinking of using blue Loctite and torqueing the head all over again.

here is the bike in question

Loosening of the head nuts and bolts after a rebuild is pretty normal. You need to retorque them several times in the first few hundred to a thousand miles. All your new fresh gaskets are compressing, causing the nuts and bolts to become loose. Eventually, after several retorques, the gasket compression will have reached it's limit and the torque values should hold. Still, even after that, it's a good idea to check those head nuts and bolts like once a season.

do you think the Loctite is necessary? or just stick with the lube.

NO LOCTITE!
You could have blown the head gasket.
Is it running okay now?
If not compression test time.
By 300 miles You should have retorqued engine bolts a few times at least.
on new head gaskets I like to torque the nuts.
Then retorque the next day.
even better if you can wait for a few days before first start, retorque every 24 hours.
then after first start next morning retorque.
When the torque is holding at speck your gtg
Then retorque every year.

No Loctite needed. I anti-seize all my fasteners. Never had any come off like you did but I retorque multiple times. Yes, I do find some loose ones during these retorques, mostly the large acorn nuts on top and the two bolts under the spark plugs. The rest seem to stay tight mostly.

torque is usually dry as any lube will give a false reading, no top motor mount also lets stuff move easier... oh well just keep checking torque and hope it settles in before blowing the head gasket out

Maybe the lack of a head steady, top engine mount, may have something to do with loose nuts.

jayel said:

torque is usually dry as any lube will give a false reading, no top motor mount also lets stuff move easier... oh well just keep checking torque and hope it settles in before blowing the head gasket out

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never torque fasteners dry... As a Mercedes Benz master tech I've performed extensive amounts of engine work. the bolt heads and threads are always lubricated to give a true reading. nowadays everything is torque angle is this is more accurate.

malloym said:

I put roughly 300 miles on my new engine. I was riding the other day and the bike had a lack of power, pulled over and it died. I found the 2 inner head nuts on the right side had come completely off. I got the bike restarted and I was getting compression from the holes.. this doesn't seems normal. the engine has been rephrased with 81mm weisco pistons and LA cylinder sleeves. I think the compression is in the 11 range.

I torqued the head to 30ft lb with a freshly recalibrated digital snap-on torque wrench. I also used ARP moly grease as a lubricant. I was thinking of using blue Loctite and torqueing the head all over again.

here is the bike in question

Click to expand...

The bike looks great!

malloym said:

never torque fasteners dry... As a Mercedes Benz master tech

Click to expand...

As an xs650 amateur master tech, self-proclaimed, I would beg to differ. From the factory manual - "Unless otherwise specified, torque specifications call for clean, dry threads."

xjwmx said:

As an xs650 amateur master tech, self-proclaimed, I would beg to differ. From the factory manual - "Unless otherwise specified, torque specifications call for clean, dry threads."

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yea and the manual tells you to surface the head with sandpaper. I'll stick to how I was trained.

I ain't trained in nothing, but I use antiseize on the head bolts. It's just silly how welded to the studs the original nuts often are and almost no compression force left either.

That doesn't mean dry is bad. It means sandpaper is good.

I've anti-seized the head nuts and bolts on numerous bikes of all different brands and types (singles, twins, triples, 2-strokes, 4-strokes, etc.) for over 40 years and never had a problem. I don't reduce the given torque specs because of it either. Nothing gets assembled dry on any of my bikes.

Never, never, torque dry threads! I use Never-Seez anti-seize compound. I've used this brand for many years. I sure there are other good brands.

xjwmx said:

As an xs650 amateur master tech, self-proclaimed, I would beg to differ. From the factory manual - "Unless otherwise specified, torque specifications call for clean, dry threads."

Click to expand...

Aircraft manuals from 60-70 years ago to current machines say the same. I've read a really good N.A.C.A. study on torque of helical fasteners that is still commonly referenced today, and petroleum based thread dressings DO affect final torque, total tension, thread stretch, and the yield threshold of the fastening system. Not saying it's wrong, but it does have an effect. Regardless of the research, I know that it works for people here in multiple applications, but the vast majority of bike fastening systems are never placed under ultimate bearing loads anyway.
For future reference, or shit-can it, whichever you like, milk of magnesia is a good reliable anti-seize for dissimilar metals and high heat applications. The manganese compounds are PH neutral to all but exotic fastenings and act as a sacrificial layer between the metals, and may react with either one or both of the metals present, but prevents them from reacting with each other. No heavy metals like zinc, copper, or chrome to mess with, and zero petroleum present. The moisture content is almost completely water and evaporates with use. I've been an FAA licensed aircraft mechanic since 1993 and have done nothing else but maintain aircraft for the past 27 years. I have been an inspector in a repair station for the past 7 years. Torque angle is only used as a "field technique" in aircraft applications for non-critical assemblies, and is NOT considered as accurate as a calibrated torque wrench for aviation purposes. I cannot verify an un-measurable torque value for an airworthiness inspection.
Not Mercedes, but you can't pull over on a cloud when shit goes wrong.
$0.02

The old issue of scripture vs the precepts of men...

More fodder: http://www.xs650.com/forum/showthread.php?t=27533

If you just follow the direction of the manufacturer, things do magically work out

Having said that, if the threads are oily I leave them that way. If they're dry I leave them that way. If they're crusty, maybe from milk of magnesia, I hit them with my little steel brush. If there's just something about them, after the brush I might put something on them; might be oil or grease or anti-seize or spit.

There are highly regarded votes for both dry and oiled, plus it's easier this way...

I can't remember any stuck fastener except the little screw on the front brake caliper. I anti-seized it, but that's probably all washed out by now, Got to get shorter-lived pads next time...



I'm still alive. To the dismay of a few. But then it ain't an airplane.

What a load of codswallop. Never has so much been said without any meaning

Wouldn't recommend following the manufacturers diagram for the clutch, and it is now regarded that the torque for the 8 main head bolts be 30ft/lb instead of the manuals 25.

Faith is a wonderful thing