Cam End Plugs + Stripped Valve Cover Threads

Hey Everyone, 

It's been a minute since I posted here. I finally got around to re-cleaning and re-sealing my fuel tank, and am trying to check off the rest of my to-do list with the '85 ZN1100. I have so far hit two snags:

1. The valve cover end caps I ordered from Z1 don't seem to be an exact replacement. On their website they listed the ZN1100 as a fitment option, but the parts that arrived were all Rubber, while what I took off my bike is a metal + rubber combination. See pictures linked below. The actual info sheet with the new plugs only list older KZs as fitment options - so I am guessing that Z1 had the plugs mis-listed. Is going all-rubber an improvement? I haven't unwrapped the plugs I ordered in hopes of eventually returning them if they don't fit. 

drive.google.com/file/d/1NtGH-iQfgeySEuJ.../view?usp=drive_link
drive.google.com/file/d/1tYRd-10FfMNwfp1.../view?usp=drive_link


2. One of my valve cover threads is stripped out. I took the best picture I could (below), but it will most likely need at least re-tapping. Is this a relatively common occurrence? Any specific fixes or tricks? I am currently planning on picking up a Harbor Freight tap set- first trying to chase the original threads, and if they aren't worth saving, re-tapping with a slightly larger thread size. I am inexperienced here, so will definitely be doing more research before doing anything- but any and all advice/pointers is welcomed. 

drive.google.com/file/d/15F9JGCi72wo_g9f.../view?usp=drive_link

Thanks for any and all help!
 
 

I would use a Helicoil on that repair. It's plenty strong for a valve cover 6mm bolt.

Just ordered a kit, will arrive this Wednesday. I also e-mailed Z1 to see if they could offer any clarification on my end caps. 

tobeerortobike wrote:

Just ordered a kit, will arrive this Wednesday. I also e-mailed Z1 to see if they could offer any clarification on my end caps. 

The plugs look correct, the OE ones are still available but it looks like you may be able to swop the metal cover onto the new rubber you have

?

 

Valve cover bolts are often over-torqued in an attempt to 'solve' an oil weep / leak.

Most 6mm coarse thread bolts are spec'd at 60 ~ 77 in. lbs. in the Z1 White Manual unless otherwise stated. The 6mm bolts on your ZN1100 are very likely spec'd the same.  There's also a ft. lb. spec. of 5 ~ 6+ ft. lbs., , but that's so low that a ft. lb. wrench won't be very accurate even if it's on the scale.

We initially, torque 6mm Z1 valve cover bolts to 60 in. lbs. (cold), then re-torque (cold) after the first heat/cool cycle.

We'd suggest investing in a torque wrench that sets to in. lb. values.

Good Ridin'
slmjim & Z1BEBE

An additional note. Not to derail Slim Jims remarks but using a torque wrench and relying on one with these M6 size bolts often leads to issues of stripping. And if using a helicoil your available measure of in/lbs will be different. Factory fancy manuals just reference the bible of auto engineers and hardware manufactures graphs and findings. After decades of personal tooling i've never even owned an inch/pound torque wrench. You should "feel" the torque applied, maybe just me though ha. Also WATCH out for other threaded holes that "may" seem ok but have been compromised too, just haven't gotten to that point of complete aluminum thread material destruction.
   

asphalt900 wrote:

An additional note. Not to derail Slim Jims remarks but using a torque wrench and relying on one with these M6 size bolts often leads to issues of stripping. And if using a helicoil your available measure of in/lbs will be different. Factory fancy manuals just reference the bible of auto engineers and hardware manufactures graphs and findings. After decades of personal tooling i've never even owned an inch/pound torque wrench. You should "feel" the torque applied, maybe just me though ha. Also WATCH out for other threaded holes that "may" seem ok but have been compromised too, just haven't gotten to that point of complete aluminum thread material destruction.
   

Totally agree Clay, I am a great believer in "feeling" bolts in (especially small ones) following the correct sequence to ensure the cover pulls down "flat" is key to preventing leaks later. Also don't forget to back the cam chain tensioner off before re-fitting the cover

At one time I worked for a steam turbine manufacturer.  I was assigned to find why customers' techs were breaking  or stripping the overspeed trip bolts on the turbine shaft.  It had gotten to the point where they shipped 2 extra trip bolts with each trip rebuilding kit.  My solution was to make a smaller hex on the trip bolt (the bolt was custom machined anyway - original needed a 1/2" hex socket, we changed the hex size to use a 1/4" hex socket)   Knowing the techs didn't use a torque wrench, my intent was to steer them to use a 1/4" drive ratchet, not a 3/8" ratchet. It worked!  Complaints almost disappeared.  From my own experience I knew the mechanics would not turn a 1/4" drive ratchet anywhere near as hard as the 3/8" ratchet.  The "calibrated" wrist of a mechanic rarely strips or breaks bolts.

I use the torque wrench a lot, never have stripped out a bolt thread yet unless it already has been compromised. Just make sure you use a good quality inch pound and ft pound wrench . And they need calibration once in a while especially the ft pound. I also do the torque in steps then I can feel the thread. Just don't go to the full torque value on thaw first pull. Only other thing I would do is put a Timesert repair in that thread. Invest in the 6mm kit and you will be happy.

Good advice.
I also use a torque wrench (religiously whenever aluminum threads are involved, don't bother to ask why!)  In the situation described, I knew the techs would be in a dark, cramped area trying to finish quick.  The single stage steam turbines we manufactured usually were used to drive oil or water pumps in the bowels of a refinery or plant.

I'm certainly not advising against using a torque wrench which I always use for the likes of head bolts, crank and rod bearing bolts, sprocket bolts etc, when it comes to smaller not load bearing fixings after 40 plus years in the automotive industry you do develop a "feel" for when fixings are "happy"

Good catch on the cam chain tensioner. I followed the manual exactly last time I did this - backing off the cap and spring before and after removing the cover. I forgot to back it off before removal this time - is there anything critical I should do to reset the tensioner before reinstalling everything? 

As far as fastening order - I'm thinking a star sort of formation akin to the lug nuts on a car - i.e. back left corner, front right, front left, back right - finger tight then going back around and firming up. Of course there are a lot of extra fasteners on the valve cover - my plan was to finger tighten the four corners, fill in the middle finger tight, and the go back around and re-snug. Anything I should do differently when it goes back together? I am hoping to get everything sealed up correctly this time.