Mystery oil leak

[vsboxerboy]

So I'm having some trouble figuring out where this oil leak is on my engine.  It seems to be a result of the upper left (when sitting on the bike) bolt that holds the cam cover in place not tightening, it just spins with some resistance making it impossible to tighten and difficult to remove.

I would assume that this is where the oil leak is coming from but is there a better way to figure out where its from?

Additionally, if that is the issue, what can I use to get the bolt to stay.  I was thinking something like teflon tape but I want to be sure that nothing is going to melt and get into the engine. 

Also  I went ahead and ordered a new seal for the bolt along with a few other misc items a few days ago from bikebandit.

[trumpetguy]

That stripped bolt would be a likely candidate to cause a leak.  If it's the top one (one of the ones with an O-ring underneath the large head), the threads are in the top half of the cam bearing.  That would be easy to remove and install a helicoil (thread repair insert).  If you're lucky, maybe the previous owner just put the wrong bolts in the wrong locations (I don't even know if this is possible, but it would be preferable to having a stripped thread!)

As far as determining the location of the leak, clean the engine and then watch after a long ride to see where the wet oil is starting.  In my engine, the valve cover gasket was leaking.  I replaced it and didn't over-tighten the bolts.  It's oil-tight now.

[vsboxerboy]

Okay so I checked out the bolts on the top of the valve cover and the top left seems to be way loose.  I tried putting different bolts into that hole and they all just kinda fall into the hole if i push on it a little bit.

I have no idea how to repair this so whats a helicoil and where can I get one?

[trumpetguy]

A helicoil is a stainless steel thread repair insert (details http://www.emhart.com/products/helicoil.asp).  It requires a special installation kit consisting of a tap larger than the stripped hole and a tool that installs the insert into the newly tapped, larger hole and restores the original size threads.  A machine shop could do the job for you relatively cheaply.  It allows good threads to be restored to an aluminum part that has been stripped out.  There are also other brands and it doesn't matter what brand -- helicoil was the first big name in that area and the name has become somewhat generic for thread repair insert.

Read the wiki (or watch the first part of Kerry's valve adjustment video linked on the wiki) about removing your valve cover.  Then remove the top half of the cam bearing containing the stripped threads (noting which way around it is installed so you can put it back the same way) and head to the machine shop with the bolt that goes in it.  With the part off the bike, they should be able to repair it easily and quickly.

If I'm not understanding you correctly about which bolt it is, you might have the one that goes into the head.  That will be a more time-consuming disassembly (or would have to done on the bike) and one that you probably want to take to the shop, unless you have a lot of mechanic experience.

[vsboxerboy]

I believe we're both talking about this guy:



right infront of the A.  Time to look for a machine shop then!  thanks

[vsboxerboy]

So the machine shop just called me back and said that the thread is an odd size (7.5) and they don't even have the right helicoil in stock to fix it although they could order it and it would cost ~60 bucks!

I was wondering if I could just get a new one of those for less or are they machined as a matched pair to the rest of the head or what cause there isn't a part number next to this guy on the parts fiche...

Not really sure what to do about this

edit:  oh yeah and he confirmed that the threading inside of the piece is definitely stripped away

[trumpetguy]

That's the top half of the cam bearing.  It's machined in place, so another one is not going to be an exact fit.  It is easy to get off and easy to transport to the shop.  I didn't realize it was an odd thread -- yikes.

You have a few options, none of them cheap:

1.  Try to find a part off a wrecked or (more likely) engine-seized GS500.  It won't be an exact match, and the manual will say not to, but I'd be willing to bet a pizza it won't be off enough to matter.

2.  Pay the machine shop.

3.  Buy the helicoil (or other) kit yourself, and do the work yourself.

It's too bad it isn't a standard thread -- that would be much cheaper/easier!

[GeeP]

1.  Try to find a part off a wrecked or (more likely) engine-seized GS500.  It won't be an exact match, and the manual will say not to, but I'd be willing to bet a pizza it won't be off enough to matter.

Won't work, and it will matter.  The position of the center of the bearing depends completely on the fixture used to hold the cylinder head in positon on the line boring machine.  Considering the bearing clearance is about .0008", it is not safe to assume that the fixture will repeat within an acceptable tolerance (say .0002" or less) cylinder head to cylinder head.  A positional error of .0004" or more could cause the cam to seize.  A positional tolerance of .0006" or more will seize the cam.

All that said, it is possible you could find a suitable match.  However, you would need access to several cam caps and a few sticks of Plastigauge.  Try all the cam caps and find which one fits within a few ten thousandths.

If you have never tapped before, pay the machine shop to put a heli coil in it.  It is possible you could scrap the part.  If that happens you'll be looking for a new head. 

Make sure to use a torque wrench when you reinstall it!

[coll0412]

Try a different machine shop, or cough up the $60 bucks, its sure is alot cheaper than a new head after the cam seizes   

[trumpetguy]

I will bow to the greater motorcycle mechanic experience here.  My comment on substituting a cam bearing half was based on experience with OHC Datsun engines, of which I have MANY years of experience (probably more than the average age of GSTwin readers!).  I have removed and replaced cam towers on those engines (also aluminum), in spite of the fact that the factory manual says to never remove them because they will never be aligned properly afterwards.  However, if you ever warp a head, you HAVE to remove them to surface the top and bottom of the head to get the surfaces parallel again.  Then you use cam tower shims to replace the thickness of the material that was machined off.

Anyway, it is obvious that I am wrong here -- the tolerances involved are WAY different than my similar automotive experience.  I owe SOMEBODY a pizza!

[GeeP]

No worries Trumpetguy.  I have a habit of being brief, which can sound harsh.  No harshness intended.   

As I say, worst case you could likely swap out cam caps if there was no other choice.  However, I suspect you'll have to sift through a small stack to find one that Plastigauges within factory limits.  All this depends on the locational tolerance of Suzuki's lineboring fixture.  I would expect that the positional error distribution would be more or less random.

As to aligning multiple journal bearings, a piece of precision ground drill rod a few tenths smaller than the ID on the bearing surfaces works very well.  Lightly oil the rod with WD40, put it in the bearing saddles and lightly torque the bearing caps.  Then torque down the journal fixing bolts and remove the journal caps.  Check with the shaft and Plastigauge to be certain everything is in alignment.   

Make sure to test the rod between a set of bench centers or a pair of V-blocks to see that it wasn't bent in shipping!  (Not that I've aligned anything with a piece of UPS-bent drill rod before.)   

[trumpetguy]

As to aligning multiple journal bearings, a piece of precision ground drill rod a few tenths smaller than the ID on the bearing surfaces works very well.  Lightly oil the rod with WD40, put it in the bearing saddles and lightly torque the bearing caps.  Then torque down the journal fixing bolts and remove the journal caps.  Check with the shaft and Plastigauge to be certain everything is in alignment.   

Actually, with the Datsun Cam journals, I used the cam itself.  Installed and lightly tightened the bearing towers (journals), then put in the cam (no followers so it could turn freely).  By tapping with a rubber mallet I found the position of each tower that offered the least resistance.  Got over 200K miles from that engine.