Help Help Help! Broken Bolt on top of motor!

[Anonymous]

OK, I've got a '79 GS 750L and right next to the #1 Spark Plug there is a small bolt that goes through the head and into the jug that was leaking oil. So i check the tightness of the one next to the #4 spark plug, and it is really damn tight. So I proceed to start tightening the #1 bolt, only to have it snap off completely on me. Now, my biggest question is: Is this a critical bolt? (Meaning, am I gonna destroy my motor if I ride with it broken, or warp the head, etc.) Or, is it a non-critical piece that seals oil in, and do you think it would be an incredibly bad leak? I don't have the cash right now to take it into the shop to have it professionally fixed, but I am still new enough to motorcycles to know that I'm not really ready to pull the head off and start fiddling with things either, even though if something like this had happened on my car, I'd have it half torn apart by now.

Any help is appreciated.


If anyone needs a picture of what I'm talking about, just ask, and I'll get one up ASAP.

[Anonymous]

OK.. found a pic of it on BikeBandit:

http://houseofmotorcycles.bikebandit.com/partsbandit/showschematic~dept_id~989147.asp

The bolt is #10

[argonsagas]

Driving the bike with a missing head bolt will eventually harm the engine, but one cannot say precisely how much or how fast it will occur. You have identified the most likely problems that might be expected.

Increased oil leakage is the first one, as you already have leakage, and the snapped bolt has relieved whatever pressure there was in that area.

On to repairs...


When you tightened this bolt, did it turn in the threads, even a little bit?

This is important, because it may mean the difference between a repair you can do and a trip to the machine shop, head in hand.

(Even if it did not move, you can still try the following, but be aware that you have a lesser chance of success)

If it turned a bit, then the threads are clear, and you should be able remove the broken bolt at home.

I don't know the size of the bolt, but the following will work for you:

First, find out the size of the bolt....not just its diameter, but its length. You need this info before doing anything else.

Using a Dremel or similar tool, and being careful NOT to touch the head itself, smooth off the top of the broken bolt, making it flat.

Carefully using a SHARP centre punch, mark the exact centre of the bolt.



Drill straight down into the bolt with a freshly-sharpened 1/8 inch drill bit.

Do this slowly, using little downward pressure...let the bit do the work.

Once you have a clean start, place a drill-stop on the bit, so that you can drill to within 1/4 inch of the bolt length, but no more.

This is your pilot hole.

You will have to drill more, using a larger bit, but which size is needed depends on the diameter of the bolt. You need one that will take out most of the bolt body, but do NOT touch the threads.

You do this in increments to ensure the hole is enlarged without danger of snapping the drill bit.


Add some penetrating oil to the bolt top, and let it sit for at least several minutes, then do it again.

Now you use an Easy-out, which is a tool with left-hand twists, and will lock into the remaining bolt material and allow you to remove it as you normally would, if it had a head.

For the E-Z out, use a professional quality tool ONLY.

Some cheapies look like they have reversed threads: they are NOT good quality tools.

Better ones have sharp clefts cut lengthwise.

Ignore the cost; buy only the best.

This is an area where price truly makes a huge difference.

Breakage will occur with any of them if too much torque is used.

The difference is in probability: a cheap tool, and/or a screw-type one might work, but a more reasonable expectation is that it will probably break and while you might be able to remove it, the opposite is more likely, and that pretty well guarantees a trip to the machine shop.

If it does not easily move, do NOT use more torque.

Get a smooth nail of a diameter just slightly smaller than the drilled hole, and which will extend an inch or so above the head when inserted in the hole.

Insert it and shield all the surrounding engine area with a piece of metal.

Using a propane torch, heat the nail until it is red hot. Keep it that way for about 30 seconds, then use a pair of pliers to remove it.

Put your centre punch back on the bolt and tap it sharply, once.

Re-insert your E-Z out and remove the bolt.

You may have to repeat the oil and heat, but the bolt should come out this way.

Patience is key.

[Anonymous]

Wow.. thanks for the info... Also, my big question still not really answered is, is this bolt a critical one? On pretty much every car there are bolts that thread into heads and engine blocks that aren't critical to the operation of the engine. (I.E. a missing head bolt, or cam bolt, etc.) This one that I broke does not look to be a critical one to me, it is very thin, and about 2 to 2 1/2" long or so. As I was turning the bolt, it felt like it was beginning to get tighter, but whether it actually was turning in the threads or not, I can't say...

Needless to say when this happened last night, I was mad as hell, and I'm still not very happy about it today...

[IanFrancisco]

Looking at the Bike Bandit fiche, this bolt #10 doesn't look like one of the main head bolts that seal the combustion chamber but an "auxiliary" that is used to either aid sealing or help prevent warping of the head. If you are a sedate rider (hopefully not sedated ) you may be able to get away with riding it like that but if you like to go fast, that broken bolt is going to be a weak link if it isn't fixed. I agree that you are risking a leak or head warpage if you don't fix it. I have a little Honda single that has a similar auxiliary bolt. The hole goes clear through. If that's the case you may be able to grab the bolt from underneath with pliers and twist it out without going the EZ Out route. Drilling bolts is tedious and great care must be taken to avoid damaging the threads. Machinist work or experienced home mechanic skills needed here.

[vstan905]

My GFs 81 GS650GL has had one of those broken for a long time. I have no idea how it got that way. It was broken when she got the bike and I know for a fact that the heads have never been off this bike. It doesn't seem to be causing any problems and she rides the bike "sedately" so to speak.

[Anonymous]

I AM going to fix it, it's just a matter of when, and how much it's gonna cost me. I don't really ride super fast, a lot of around town, and some highway driving.

vstan, did the bike leak any oil or anything, or was it just broken off? I 'm not a crazy rider by any means, and honestly, I don't see how that thin of a bolt would be relied on to provide any kind of support for much of anything at all... On the other hand, I found a parts bike with a good motor near my house on fleabay, so I may just rebuild that motor and then change them out..

[IanFrancisco]

Rebuilding a spare motor is a lot of work but fun if you're enjoy that sort of thing. The bottom end is the hard part, harder than a car motor. There's a lot of thrust washers and end clearances to get right to make the tranny shift nice. I forgot to mention to check the torque spec for that bolt. Chances are it's only 10-15 ft/lbs which means that the other one on the other side is too tight. When dealing with bolts that have been there for an unknown amount of time a good practice is to not tighten them but try and loosen them off first then re-torque to specs. A factory service manual is the thing to have, the Haynes/Clymer books are good but not as good as the real deal, especially if you want to rebuild a motor. Maybe one of the forum readers has one they can copy for you.

[Anonymous]

I'd love to get my hands on a factory repair manual. I've seen the clymer manuals, and haven't ever used one, and Haynes is OK for most things, but really detailed stuff they gloss over and refer you to a mechanic for, and I think that's just BS. I like building engines, it's relaxing for me even when things don't go quite rught.

[volks28]

I broke that bolt too. I was trying to fix a oil leak, but I guess I made a mess.

The cyl #4 on the bike, right where the bolt is is weak. I think air might be going in / oil may be going out. I think I'll need to fix this soon

Do I need to take the head out, or can I just drill & retap with the engine on the bike? I have drilled and tapped before, it's not too bad.

[jgordon]

I would pull it down...
Remove the broken bolt....
Do a good vavle job...
Throw in a set of rings....
Put it back together and go riding :-)

Do a real good inspection and make sure everyrhing is whithin the specs.
You can usually find a good repair manual on Ebay.

[volks28]

Is it something that a novice (like me) can tackle?

I would pull it down...
Remove the broken bolt....
Do a good vavle job...
Throw in a set of rings....
Put it back together and go riding :-)

Do a real good inspection and make sure everyrhing is whithin the specs.
You can usually find a good repair manual on Ebay.

[jgordon]

If you don't feel at ease thinking about this it is probably best to let someone who knows what they are doing make the repairs and freshen up the motor. If you are mechanically savy and can follow directions the book tells you what to do.

(-:

[Anonymous]

I wish had a place to work on my bike.. I'd do it in a heartbeat.