Camshaft journal caps HELP please

[angusgst]

Prepare yourself... I could not make this up.

Yesterday I decided to check the valve clearances on my GS500, because they'd never been checked and the bike's done 42,000 km. The exhaust valves were fine and the intake valves were marginal at 0.03mm, so I decided to replace them. That was fine, no problems.

I didn't have the Suzuki valve tool so I removed the shims by taking out the camshaft. To replace it I bought a new torque wrench, one of these babies: http://www.justtools.com.au/prod4534.htm .

So first time using the torque wrench today on the journal cap bolts... everything's going fine. Tightening gradually in a criss-cross pattern at the specified 10Nm limit I hear a 'click' for each bolt. Perfect! Until I go to check the valve clearances again, and realise that the journal caps are sitting up a little. That's strange... I then undid the bolts, which were already loose. hmm... To find that all four had snapped off inside the head. 

So I've obviously applied way too much torque. The question now are "why?" and what to do about it. If anyone could help me out on those two points I'd be very appreciative. I presume the best bet for the bolts is to drill a very small hole into each from above, then to insert something pointy and grippy (small screwdriver?) and try to reverse them out. Pics are attached below for clarity.

[adidasguy]

There's a difference between:

inch pounds

foot pounds

newton meters


Most likely you had the torque wrench on a difference scale that what you read in the book.

I am not sure what to do now.


manual says:
Camshaft journal: 8 - 12 N'm

Looks like you went all the way to 25nmn. Over twice the max torque.

[crzydood17]

1st count yourself lucky the bolts went and not your head threads.

2nd. take off the head. take it to a machine shop... then very carefully rebuild it with the correct torque settings...

3rd pray you didn't really break something...

[weedahoe]

Another thing is a wrench that isn't calibrated correctly. Another thing is trying to torque bolts that had already been torqued before and we're stretched

[sledge]

Look closely at the bolts, the threads have stretched and they have all snapped in the same place ,2 or 3 threads down from the shank which is the weakest point..........they have been overtightened  big time.

You have used the wrong scale or the tool is miles out of calibration............given the tool is brand new the first option is favourite.

No reason why the remenants would be tight in the holes and I would expect them to come out relatively easily with a screw-extracter.

[piresito]

There's a difference between:

inch pounds

foot pounds

newton meters


Most likely you had the torque wrench on a difference scale that what you read in the book.

I am not sure what to do now.


manual says:
Camshaft journal: 8 - 12 N'm

Looks like you went all the way to 25nmn. Over twice the max torque.

+1...in your picture shows that you set your torque wrench to 25nm. Thank to Suzuki for making stiff threads in there.
Remove all 4 with a screw extractor, buy 4 new screws and set you torque wrench to the bottom of the scale! BTW, torque wrenches in the beginning of the scale aren't very precise!

[sledge]

torque wrenches in the beginning of the scale aren't very precise!

I will dispute that comment, + or - 3% of the indicated figure across the range is generaly the accepted standard and the more expensive makes can easily achieve a tighter tolerance. If you are having problems with yours I suggest it needs calibrating or repair

For anyone that is interested a neat desktop torque convertor can be downloaded free here

http://www.boltscience.com/pages/convert.htm

[bombsquad83]

I had the same thing happen to me with one of my camshaft journal cap bolts.  I was able to get it out with a left-handed drill bit alone.  I also bought a small screw extractor that I had planned on using once the hole was drilled, but I didn't end up needing it.  I also had to take the engine out of the bike to get the right angle at drilling it out.

I ordered a 1/16" bit, a 3/32" bit, and a #1 Screw Extractor from Mcmaster-Carr.  I think I actually ordered 2 of each bit in case one broke.  Be careful to clean out the drill shavings from your head when you are done.

[craigs449]

Tidbit of info, to convert NM to Ft/Lbs, multiply the recommended NM X .737 = Ft/Lbs.


I have found that most of the specs in my Haynes manual are extreme, if a torque scale is given (such as 10-14 NM), I always go closer to the bottom of the scale like 10 nm. I always use Blue Loctite on my outer case bolts to ensure they stay in place also......

[angusgst]

hi all, thanks for the replies and suggestions. I bought new bolts today along with a thread-extractor kit and am beginning to attack the old bolts. How bad will small amounts of tiny metal filings be for the engine if they get in there? I'm covering up the rest of the head with a cloth but some are bound to end up in it.

[sledge]

Cover the top end with a cloth then seal the edges with duct tape.

[bombsquad83]

Cover the top end with a cloth then seal the edges with duct tape.

Good idea, but I would use painter's tape so you don't leave stick residue.

[dgyver]

Hopefully you bought the correct bolts from Suzuki not from a hardware store. They are soft and designed to fail before stripping out the aluminium.

Don't feel bad about it. I did the same thing on the oil pan...read the torque from line above... 14 instead of 7.

[Bluesmudge]

I have done the same thing as well with a cheap torque wrench. I even remember thinking, "hmmm this feels like the correct amount of pressure but it hasn't clicked so I guess I will keep going..." Next thing I know I've stripped the bolt.

Luckily those are soft bolts so they are fairly easy to drill in to. I found that I couldn't get the correct angle with the head still on the bike so I removed the head and did the drilling and extracting on the work bench. I might have some photos of the process, if I find them I'll post them later.

EDIT:
Sorry, these images are not that useful. I used a vice grip on the bolt extractor, but that is not the proper tool. You can buy a handle for the extractors that give you better leverage.



The second image shows the extracted bolt next to the hole it came out of.

[angusgst]

Wow, nice work. I've been giving it a go, and am finding it really difficult to drill the holes into the centre of the bolts. The problem is that when the bolts sheared off, the surface on top because anything but flat. I've got a centre punch and smaller drill bits etc, but it still seems impossible. =/  Any suggestions?

The bolts are the correct ones, fresh out of a GS500 from the local wreckers. At least that's what they said... the bolts look identical but are black. Has anyone ever seen black journal cap bolts on a GS500?

[adidasguy]

Yes - black is OK.Color doesn't makeany difference.

Use a little grinding wheel on a dremel tool to level off the tops of the sheared bolts.

[Bluesmudge]

I think black is the older engines and silver the newer, or vice versa. I don't know when they switched but either should be fine.

I purchased the best automatic center punch I could find when I did this. After stripping the bolt because of cheap tools, I wasn't going to mess up the extracting for the same reason because you only get one or maybe two chances to get the drill bit centered.

This is the center punch I used:
http://www.amazon.com/Starrett-18C-Automatic-Heavy-Duty-Adjustable/dp/B000VDVR6W/ref=sr_1_4?s=hi&ie=UTF8&qid=1354316559&sr=1-4&keywords=spring+punch

My bolt didn't snap off flat either, as you can see. That first picture is deceiving because it is after I have started to extract the bolt. If yours is like mine, the bolt broke off below the plane of the head so there is no chance to dremel a better surface.

I also bought the best left hand drill/extractor set I could find because I have seen cheap ones break off inside the bolt and then you are SOL.mi ended up spending a lot of money to get that one bolt out, but with the right tools it was actually easy and I have been happy to have the nicer tools since then.

[burning1]

You are far more likely to ruin a bolt with a torque wrench, than you are without one. Part of the problem is that they don't provide much feel, and part of the problem is that they tend to cause us to over-ride our own judgement.

A major problem is that big wrenches are not sensitive at low torque values. Your 90 foot pound wrench isn't going to click on a little 12 foot pound bolt. Period. The bolt starts to fail before it clicks, and you end up twisting the head off the bolt.

Torque wrenches are absolutely a necessary evil on engine work. But you have to use the right one. Use a small wrench on small engine parts. That big wrench is only good for cam sprockets, head bolts, and lug nuts.

[Bluesmudge]

Yup! I bought an inch pounds torque wrench after my mishap. Now I have 3 different torque wrenches.

[angusgst]

Thanks again for all the suggestions. I eventually got all the bolts out without too much hassle. Having a little problem with a camshaft now though...

When installing the exhaust cam, it's supposed to be placed so that the "1" on the gear points forward, level with the top of the engine case. However in this position I can't get the camshaft to sit flat because the left cam is pressing on the shim.

I looked at this video and in it the mechanic places the camshaft straight on without a problem (at 6:20ish). Any suggestions as to what's going on?

http://www.youtube.com/watch?v=KmfkhLE0Cog