Topic: Striped Rocker Cover Bolt, Now What?

[RickB]

Hi guy,

So after what feels like a year away from the bike, I'm back home visiting and have been getting the bike prepped for a trip with the mates this weekend.

Part of what I needed to do was re-torque down the head as I was getting a lot of oil leaks and it was a freshly rebuilt engine so needed a re-torque now that everything had bedded in.

Anyway, on reassembly I ran into trouble. The middle upper left rocker cover bolt started giving me that dreaded 'no resistance' feeling. I immediately stopped, pulled the bolt out and my worst nightmare had come true.





I have no idea how I stripped it, those bolts are only about 8 ft-lb of torque and I hadn't even gotten to that yet when it gave way. I've never had a bolt pull out a neat spiral like this either. Is this what they call a helicoil? A gift from the previous owner perhaps.

So what should my next course of action be? Do I need that bolt? Would the other three be enough? Obviously I have to fish out whatever mess is left in the hole, but will it damage the engine? Do I need to rebuild it again?!

I'm devastated.

Rick.

[madmtnmotors]

The coil of threads that pulled out are the threads that used to be in the aluminum head. A heli-coil is the coil of threads that is used to repair the threads that pulled out. A tear down is not necessary, but you would have to remove the rocker cover, drill an oversize hole and tap it to accept the heli-coil repair. The correct bit and tap are included in the helicoil repair kit. A 6" square or round piece of rubber, with a small hole cutout in the center, placed around the area of the repair while the repair is made (drilling and tapping) helps corral and control the shavings for cleanup. Patience is key, don't rush it and seek advice/help from someone that has done it before if you're not sure. If you need a machinist to do the work then you might have to pull the head and take it to him. They are not too difficult to do, I've done several. Like I said, just bring your patience.

Good luck. 

[jessezm]

Just responded in your build thread, Rick.   I did the EXACT same thing this weekend...  I'll repair the thread next time I rebuild.  For now there were enough threads to get a bit of grip after securing all the other bolts and all is back together and running fine.  If you can find a very slightly longer bolt that may get you by just fine until you can make the repair.  I know how much of a pain it is to pull your head back off after a recent rebuild, and I don't think you'll need to--you can fix it as detailed in the post above with the skills you've got.   Hopefully, your retorque will also take care of your dreaded oil leaks.  Mine was gone after retorquing.  Good luck!

[madmtnmotors]

You could use a shop vac next to the bit while you drill to also keep the shavings under control.

[MCRider]

SOMETIMES, a 1/4-28 SAE bolt will thread into a stripped 6mm hole. It is slightly larger than a 6mm, but will usually fit in the hole provided, and cut its own threads. If in fact it fits your application, it will draw down very tightly and without concern. Beats disassembly and heli-coil...SOMETIMES. Yes I have done it on CB750 cylinder heads.

If it were disassembled where you could clean it, I'd tap it first. In fact that may work for you as is. Carefully tap a few turns withdraw, clean tap and vacuum hole, repeat.

If you do this I do not know, and would doubt that it could be later fixed with a helicoil as too much material may have been removed. Then a keen-sert type repair could be used. In the meantime, you'd be running. Possibly forever.

[dave500]

i never torque those small 6mm bolts,,just by hand.

[steam-powered man]

can you stick a wire down there and check the amount of available threads?  maybe the hole was drilled longer than needed, and a touch longer bolt will work.   

[RickB]

Thanks for all the great advice guys.

Jesse, saw your reply in my build thread, thanks for that. I'll respond here too just in case someone reads this later.

I took your advice and cleaned out the thread as best I could (most of the big stuff came out with the bolt as you can see) and tightened it down as much as I dared. It is more than finger tight but has some play with a spanner on it.

As it's quite easy to get to (just take the breather cover off), I think I'll go looking for a slightly longer screw tomorrow. Might stick a long one in, measure how much is sticking out and work out just how deep the thread goes and find a bolt that is as long as possible. I'm a little concerned as those four bolts essentially hold the cam shaft in place and I certainly don't know enough about engines to even want to take a chance with that!

A helicoil is obviously the long term solution, but where it's located (right under the coils/frame) I think it would require taking the head off just to get to it, even if someone could drill a helicoil in straight enough.

Once I got the rocker covers all back together I then moved onto the next step in the manual... Setting the tappets (valve clearances?). That was a time consuming, fidgety, frustrating chore. There has to be a better way of doing that? Two cumbersome spanners and a flimsy feeler gauge is torture! Any advice for me?

Thanks again for the help guys, couldn't do this without you lot.

Rick.

[ekpent]

+1 with MC on the 1/4 " conversion. Been there done that.

[lewiszman]

Old thread but new post... I'm embarrassed to say three of the rocker cover bolts on my cb650 got stripped. This is with me already being extra careful after I had to helicoil the adjustment covers. #$%* it's frustrating to work these old engines. The threads were already pretty softened up when I opened her up...

Now I gotta helicoil it... And risk stripping more of these old mashed up #$%*ers since I have to open it up again. Just ranting.

[my79650]

Just did 3 on my cb650. A tip: remove the camshaft out of the way. Shove rags in every spot you can, keep vacuum handy and once the hole is started do it by hand. Took me a few hours but i didn't plug anything with chips. Cam moved makes it easier to do the job, over 300km since and no problems.