Honda Rebel 250 & 450 Forum banner
  • Hey everyone! Enter your ride HERE to be a part of November's Ride of the Month Challenge!
1 - 9 of 9 Posts

·
Registered
Joined
·
31 Posts
Discussion Starter · #1 · (Edited by Moderator)
Can anyone out there possibly enlighten me as to why I keep snapping cylinder studs despite keeping them below the max torque value? Any input of value appreciated, I give thanks and praise in advance.

Pre-season I had to replace a faulty base gasket, everything went breezy fine, that was until it was time to torque the cyl stud nuts. Snapped a few on me torquing very gingerly to 14ft lbs or so. Got replacements, they torqued down no problem at all.
Unfortunately, one of the non cylinder stud bolts cut loose on me causing the top end to shake loose, causing need for yet another top end rebuild.

Rebuilt yet again, snap another BRAND NEW cyl stud! For some reason, it will only torque down so far, it looks like its tightening, goes so far and then SNAPS! Tried my torque wrench on a 12mm foot peg bolt for reassurance, wrench clicks no problem.

I just got done rebuilding once more, I still had some spare unsnapped studs thankfully. I torqued them ever so gently & gingerly, wouldnt go to spec but they are tight to the point that any further will snap the stud. They currently wont easily loosen with a crescent wrench.

Everything seems hunky dory so far after a test ride, I figured for now just keep a 10 & 12mm ratchet close by and a close eye under the valve cover daily. Tighten if/when needed, until I get in a new set of studs.
 

·
Super Moderator
1987 CMX250C AC
Joined
·
3,222 Posts
Have you considered testing your torque wrench for accuracy?
Most can be adjusted if needed..

I'm assuming you are using an inch pound wrench as a foot pound wrench wouldn't be all that accurate set to 14ft lbs if yours goes that low..

The Cylinder head bolt torque is listed as 7-10 ft lb in 1st gen shop manual and 9 ft lb in 2nd gen manual..
Cylinder head/Camshaft holder nut is listed 15-18 ft lb in 1st gen manual and 17 ft lb in 2nd gen shop manual..
thus the two manuals agree except 1st generation manual gives a spread of value.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #3 ·
It is in fact a Harbor Freight special, but my clicker will read both units of measurment, 10 being the lowest for ft lbs further reinforcing what you just told me. I must also mention some of the studs were visibly stretched which concerned me with the torque being so low already. The ones in there now are all fairly equal in length (little to no stretching).

So my late personal bike guru (god rest his wonderful soul) had once told me when I see 7-10 ft lbs in a shop manual that it means hand tight, do not try precision torquing when its that low, hand tight will do it every time.

My Clymer manual calls for 12-15 ft lbs on the cylinder stud nuts & 7-10 ft lbs on the other 3 bolts. Now if it is a huge no-no, then my next question will be embarrassing. Is it ok to use threadlocker on the cylinder stud nuts? I didnt use it this time around.
 

·
Premium Member
1985, 86 CMX250C, 81 CM200T, 74 CL360, Invisible to cages, treat them accordingly. Avoids Road RAGE!
Joined
·
2,875 Posts
Most here will use a Clymer to level the table that we're working on rather than EVER trusting its torque tables. The Honda Service manuals are the best, followed by anything before the aforementioned brand.
 

·
Super Moderator
1987 CMX250C AC
Joined
·
3,222 Posts
While there is no mention of thread locker in repair manual, I don't see any reason you couldn't use it..
 

·
Super Moderator
Joined
·
31,959 Posts
If you can find a long enough tap, I would freshen the threads and blow out the hole with high pressure compressed air, in case there is some crud in the holes. The late Duckster said using any liquid (oil, thread locker) will change the torque value unless it is specified to do so in the manual. 7-9 foot pounds isn't much, but that's why I invested in a inch/pounds torque wrench. I can't tell the difference between those values doing it by hand.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #7 ·
If you can find a long enough tap, I would freshen the threads and blow out the hole with high pressure compressed air, in case there is some crud in the holes. The late Duckster said using any liquid (oil, thread locker) will change the torque value unless it is specified to do so in the manual. 7-9 foot pounds isn't much, but that's why I invested in a inch/pounds torque wrench. I can't tell the difference between those values doing it by hand.
Thanks, rebuilding the top end 3 times over the past month has been a bit frustrating to put it lightly! Ive come across some stuff called "screw glue" im gonna try on the cam tower nuts until I get new studs in. Fortunately I just got approved on a new Trident 660, soon enough I wont need to rely on my CB250 daily and can calmly tend to it/customize it at my leisure : D
 

·
Super Moderator
1987 CMX250C AC
Joined
·
3,222 Posts
I find no indication screw glue is formulated for use on engines internally where it will be exposed to heat and oil..
I find no specifications for the product on their web site unlike the Thread Lockers they sell.
Product Font Screenshot Parallel Web page



Permatex brand Screw Glue isn't listed as one of their many thread lockers
Product Font Technology Display device Electronic device


Be careful of what you use, it may not result in effect you expect.
Was surprised to find Locktite Red Chinese knock off I've used while looking up screw glue.
 

·
Registered
Joined
·
31 Posts
Discussion Starter · #9 ·
Ok, wow thanks for looking into that for me there! I opted using the screw glue on just the 3 bolts not part of the cam holders. Stuff works! Checked a few times now after some miles put on and they are not budging! Stuff may actually hold a little too well, I hope to not need to touch that top end for a good while now either way. For the cam holder nuts, I did a light savory drizzle of blue thread-locker over them, it appeared that 2 nuts needed minimal tightening after three full 60 mile commutes. I found that reassuring : ) Valve clearances held up as well, at the bare bottom of the spec nets me what I find to be the most normal sounding!
Since the BBK install, it was very hard to get a new baseline on how the motor should now sound overall, I assume the higher compression ratio in turn results a louder valve chatter in general and some new/different noise is par for the course.
 
1 - 9 of 9 Posts
Top