Dammit I've done it now.

[Jd Powell]

On the way home from the grocery store today I was suddenly assaulted by a horrendous clattering in my top end. It started out sounding like the cam chain adjuster had backed off. It quickly escalated to a much more horrifying racket. We cruised home (about 5 miles) and I began my investigation. Upon pulling the valve cover I noticed four circular indentations inside. All 4 bolts holding the A cap (left side exhaust cam cap) had pulled out and were banging against the valve cover. The culprit? The rear right bolt had sheared off and the weak link caused all three of the others to strip completely. I've got the head disassembled now. Tomorrow I am planning on getting the necessary time-serts (heli-coil) to fix the stripped bolt holes. Unfortunately I do not know how I am going to get the sheared bolt out as it broke approx 1/4 in below the surface. Since these bolts are specially hardened I imagine trying to drill it so I can grab it with an easy out will be fruitless. Any body have a brilliant suggestion? This bike is my only transport. It MUST run by Monday. Lucily all the important parts survived the trauma. I guess these bikes are about as bullet proof as they get. BTW the bike is an '80 GS1000G.

[posplayr]

Ouch

Sorry to hear that . I would try and drill so what happens use plenty of oil. :?

Posplayr

[Steve]

Unless you have some good machine shop-quality equipment in your garage, you might just have to take it to a machine shop. With a good vise and drill press the chance of slipping off the broken bolt is minimized. They will also likely have the proper bit to remove the hardened bolt.

Unfortunately, you may not find such a shop open on Saturday.


.

[49er]

Drill it, and use an easyout. Try and get a pilot drill (3mm-1/8") centered as accurately as possible in the broken bolt. Next go up to 4.5mm.
Before using the easyout, soak the area in penetrating oil and leave for 24 hrs. Apply a small amount of heat to the aluminium around the bolt before going with the easyout. Be careful not to break the easyout or you really will have a problem. If you find that it wont back out with minimal force, drill the bolt out, and fit a heli-coil.

[robertbarr]

I vote machine shop. If you get busy with power tools in there, trying to get that hardened bolt fragment out, you could very promptly need a whole new cylinder head.

[Suzuki_Don]

Make a metal piece to fit in the hole with an 1/8th inch hole in the centre to position the drill bit in the centre of the broken bolt. Could use a small diameter metal pipe. Either metal brake pipe or small fuel line. It needs to be a close fit on the outside, prob. about 4.5 or 5mm with the 1/8th inch hole down the centre. In my experience these bolts are not that hard. They should drill OK. If all else fails drill the remainder of the 6mm bolt out and use a spare bearing cap bolted into place to make sure the broken bolt hole is drilled in correct position for when it all bolts back together again. Only other option is to replace the other 3 holes with heli-coils and because they are more sturdy and will give extra grip you could get away with only 3 bolts if you are not riding that far to work until you can do a proper job. In this case do not use excessive revs on the bike.

[Dink]

Hardened bolts are hardened after manufacture, the core (inside/centre) is still soft. So go gently, start with the smallest drill size possible and go from there.

Dink

[Sunburn]

I had a 82 GS750T that did somthing like that. I got the bike with 1800 miles on it in 1988 for $900 at 25,000 it lost power and was making noise one day. Got it home pulled the Valve cover and found the intake cam had burned up in the cam journals scaring the head.

Clean bike, but I junked it. Sold it to my borther in law for $300 and got another one for $1100. Looking back I should have just got another running motor. But that was 1989.

[Redman]

JD,

Two comments:

- I had 3 broken (and missing, so someone knew about it, grrrr) cam cap bolts in GS1100GK I bought. And I unknowingly ran it that way for a several hundred miles with no evidence of any problem. When I discovered this, I then found all the other cam cap bolts to be greatly overtorqued, and in fact 4 more broke as soon as I tried to loosen them. Not having drill press and such, I took head off and took to a machine shop. They got all but one out and drilled out the other and installed a helicoil. So I cant give much advise on how to go about removing the broken bolt, other than I removed mine with my checkbook.

- Athough not related to my experince stated above: I understand that the stripped out cam cap bolts holes more likley happens from there being oil in the hole during reassembly when the bolt is being turned in then the bolt is trying to compress the oil and what happens is the bolt strips out the threads in the hole before the bolt seats all the way down.

Your expereince is that one broke and 3 stripped out all on one cap, and all while the engine running.

[madjack57754]

I have a comment or two on this situation. Pull the offending cam . Stuff a rag down the cam chain tower and get it to a welding shop. A good welder can weld a nut over the broken bolt and the heat from this will expand the aluminum to allow a wrench to turn out the offending stud. I have people bring all kinds of things into my shop to have this done and I've NEVER failed to get the stud out. Last week a guy brought in a WWII Rolls Royce Merlin airplane block and My guys and I took out 6 broken studs that had been twisted off this way, on a nearly irreplaceable block.
That said Heli-coils on 3 of the 4 clamp points will work for the short term. I've run with them in my dragbikes like this after stripping out threads in the cam clamps. I really doubt that you will have any trouble with this providing the coils are installed properly. Steel/Aluminum sandwich is approximately 2X stronger than aluminum when threaded

[rphillips]

Juas my 2 cents worth. Use a left hand drill to drill out broken bolts & studs. The heat & vibration, will sometimes, grab & loosen the broken part. If it doesn't work, you still have a hole, just like you would with a right hand drill. I'm thinking this is the only reason for left hand drills. The hole is no different if drilled right or left hand. Looks like it would make more sense to make 99% left hand drills & 1% right instead of the other way around as it is now. Good luck.

[49er]

Juas my 2 cents worth. Use a left hand drill to drill out broken bolts & studs. The heat & vibration, will sometimes, grab & loosen the broken part. If it doesn't work, you still have a hole, just like you would with a right hand drill. I'm thinking this is the only reason for left hand drills. The hole is no different if drilled right or left hand. Looks like it would make more sense to make 99% left hand drills & 1% right instead of the other way around as it is now. Good luck.

A very sensible solution. It should be sent to the "Tips & Tricks" forum.
Madjack's solution is good too provided there is still some bolt clear of the head bearing surface. I don't believe that is the case here!

[Jd Powell]

Thanks for all the responses. A lot of solid info and a couple of handy tricks. I managed to get the offending bolt unstuck by drilling and using an easy out. I completely stripped the head so all the shavings would be easier to clean out. Upon closer inspection I found a total of nine stripped cam cap bolts. 6 on the exhaust 3 on the intake. I bored all stripped holes on the drill press. Tapped them for steel thread inserts. I prefer these rather than the spring-like helicoils. They have a coarse thread on the outside that grabs the alum better. They can also be set to a desired depth (necessary where the dowel pins will be supported by the thread insert) Also they can be removed again at a later date without drilling.

Since I had the head off and stripped I took the opportunity to catalog the current shim sizes, as well as measured all the valve/spring clearances. Tomorrow I will install the inserts and begin reassembly. Will do a valve adjustment upon reassembly.

[49er]

Thanks for all the responses. A lot of solid info and a couple of handy tricks. I managed to get the offending bolt unstuck by drilling and using an easy out. I completely stripped the head so all the shavings would be easier to clean out. Upon closer inspection I found a total of nine stripped cam cap bolts. 6 on the exhaust 3 on the intake. I bored all stripped holes on the drill press. Tapped them for steel thread inserts. I prefer these rather than the spring-like helicoils. They have a coarse thread on the outside that grabs the alum better. They can also be set to a desired depth (necessary where the dowel pins will be supported by the thread insert) Also they can be removed again at a later date without drilling.

Since I had the head off and stripped I took the opportunity to catalog the current shim sizes, as well as measured all the valve/spring clearances. Tomorrow I will install the inserts and begin reassembly. Will do a valve adjustment upon reassembly.

Well done. Sounds like you've got the project well under control.