General Category >> Technical Documents/Reference >> Simplified refitting of Cam Bearing Journals

Message started by Oldfeller on 03/12/10 at 19:49:10

Title: Simplified refitting of Cam Bearing Journals
Post by Oldfeller on 03/12/10 at 19:49:10

I promised Serenity I would post a fully durable fix for worn Cam Bearing Journals.  

The surface used by this fix is raw sanded aluminum, in essence the same durable surface that the factory used on the new bike.  The surface is rougher, but oil film will be over that surface and the roughness should not matter as long as the oil film is present.

It has been about 8 months now so here is the second, much simplified method to fix a torn up set of cam journals.

patience and a fair set of manual fitting skills.  Also assumed is you know what plastigage is and how to use it.

Warning:  I make it seem easy.  This particular method was 8 months in development and it is the accumulation of lots of other's tries and methods, so all the credit goes to my predecessors who smoothed out the path by all their efforts.


OK, you have GOT TO FIND OUT WHAT CAUSED YOU TO HAVE LOW OIL PRESSURE.  You have to fix what caused this issue to happen, or it will happen again.  Some known causes are:

1) low idle speed.  You must idle above 1,000 rpm to have anywhere near good oil pressure with normal bearing gaps.   If you have worn gaps you should raise idle speed accordingly.

2) disengaged oil pump gear due to repairs that required removing the clutch basket.  There is a flange washer behind the basket and a small pin, putting them back in incorrectly allows the oil pump gear to move forward out of engagement.

3) errors in putting gaskets back in, clutch side cover gasket, head base gasket, main head gasket, head "O" ring gasket are especially favorite points to interrupt the necessary oil flow/pressure.

4) not putting the transmission oil metering jet back in place after taking off the clutch side cover.  Yeah, it sits out there not held in by much when you take the side cover off, if it gets out and on the floor it will likely stay there ...

5) blocking up any of the above by incorrectly using silicone gasket sealants .... (duh, but a popular cause though)

Title: Re: Simplified refitting of Cam Bearing Journals
Post by Oldfeller on 03/12/10 at 20:30:28

You have taken the head off and taken it apart.  You have a suitable cam that you are going to use to fit the head back together with (you must have a useable cam to work to as this is a fitting exercise to actual cam journal diameters using plastigage).


Look at the wear that has taken place in the head half.  You have 3 torn up journal halves in this part -- know that they are
1) true wear fits to a cam journal diameter and
2) they are in-line with each other within the "variation of damage" factor.

They are what you are going to fit to (yep, they sure are ugly but they are your starting point).

Install the cam in the head half, verify by feel that the 3 bearing half circles contain that cam without any rock or error -- that the 3 worn, torn up seats really do make a perfect line up.

Take solvents and get the 3 head seats clean.  If you can feel metal trash embedded in the aluminum, take a sharp point and flick the trash out of the metal pit.  Finally, take a tiny piece of 220 grit wet or dry sandpaper and lightly roughen the surface taking great care not to change the radius any at all.  Your goal here is to mute the tops of the gouges and scratch marks down a bit and get rid of the nasty black stuff that has been rubbed into the metal.

Clean it with solvents again.

Install the cam again and verify the line up is still solid and perfect.


Put the head and cam and cover together with bolts.  Leave off the half moon clip, you want to feel the motion back & forth too.  Stick (lightly jam) your finger into the hole in the middle of the cam and feel what sort of level of damage has taken place by moving the cam back & forth (up down) with your stuck-in-place finger.  We are mainly interested in "shake" -- motions in line with the valve action.

Plonka plonka, ain't it?  Generally it is a linear displacement of the cam down into the head by about .010" or so and boy you sure can feel it and see it and HEAR it.   Imagine that going on 4,000 times a minute as the cam slammed around in that gap.  Ugly to think about, but that was your nasty head knocking sound.

Just sit there and play with it and get a notion of what went on and get a feel for how you are going to have to shave the cover half to recover the slop.  Make a mental image of what has to move where to make it go away.

Yep, you are going to reseat the cover half to remove all the slop and leave the cam sitting where it is in the worn head half with no remaining slop & looseness -- this isn't a perfect method, it is a simple fitting type repair to get back to a functional engine again.  

Not perfectly new, but perfectly functional -- that's the goal.  


Clymer/Suzuki gives stock bearing clearance as .0013"-.0026" with a total service limit of .0059" which is way way sloppy and we can and will fit to better than that.  This isn't really tight fitting, so you can do it with flat sanding on your wife's kitchen tabletop.

Remember, we fit to dry conditions but we add the silicone sealant thickness to our bearing journal oil gaps, so we will have even more gap than this when we are done putting the engine together.

Title: Re: Simplified refitting of Cam Bearing Journals
Post by Oldfeller on 03/12/10 at 22:24:04


Ok, got your ideas in your head straight, time to take out the hollow locating pins.  They stick in one half or the other and can sometimes be simply pulled out with needle nose pliers.  If stuck harder, don't grip them hard and try to pull them, use a tap instead.  Pick a tap that will just barely engage the ID (english or metric, makes no difference).  Just barely get the teeth biting on the tap then use the tap as a striking surface (from the other side of the cover of course) with a long punch to tap the pin out.  

Do not warp the pins -- they need to be true & round to put things back together with a good alignment.


Tape a full size sheet of 120-180 grit sand paper to your wife's formica kitchen counter.   Normal sandpaper tears too easy, go get some stiff backed sandpaper.  Lowes sells 3M Sandblaster paper which is stiff backed enough for about the same price as normal sandpaper -- looks like wet or dry on steriods and it does the job jest dandy.

(Hey, did you notice the rubber band used to keep your adjuster tips up off the sandpaper?)

You want a "medium grit open coat" sandpaper, you need it to not load up and you DO NOT WANT THE GRITS TO COME OFF THE PAPER.  Using 120 grit Sandblaster I just brushed the copious aluminum dust off of it with a new paint brush periodically and it was unfazed by the hard aluminum it was removing.  You will NOT press hard so your sanding marks won't be all that gross but you don't want it to take 3-4 forevers to remove the needed .010" of material either.  

You are going to flat sand that cover "crooked" on purpose.  The long narrow bearing does not need nearly as much material removed as the larger bearing end does.   Also, there is no 3rd bearing journal on the cover, so you are just sanding to true the narrow and fat middle journal so keep your head on straight as you begin stroking the cover on the sand paper.


Stop and do a trial fit just as soon as you have clean up (sanding marks) over the entire surface.  You don't have to put the pins back in at this rough stage, you are nowhere near close enough for them to matter much yet.  

You need this very early reality check as you likely are not tilting the cover enough.  You sand it "tilted" by putting all the finger pressure on the one side.  If you need even more tilt put some scotch tape on the edge of the narrow end that you don't want sanded -- you may have to replace the tape several times as it is removed while maintaining your tilt.

Scotch tape in place NOW, please !!!

As you do the finger motion checks note the slop is decreasing effectively much more on the long narrow end of the cam journals -- this is your danger zone and why you must use tape and tilt to remove the big end slop while NOT removing all the clearance at the narrow long end.

When your finger checks tell you that you are getting close, stop, clean everything up, put the hollow locator pins back in place and do a full torque on all bolts plastigage assembly check.

Amazing, using finger sensations alone you actually got it almost inside factory specifications and WAY WAY inside the maximum wear limits ....  fairly quick and easy too.

Ugh .... it is tough not to take off too much on this narrow long end !!!


This is the outside single half bearing end on the outside of the cam chain -- it always carries load on a refitted journal set and must be considered and measured too.  The narrow long end and this end will be what goes into engagement first on any tilt fit job, so consider them carefully as the middle bearing can actually run in air (no engagement) if these two tell it to do so.


Ok, due to damage this middle journal (the one with the half moon clip) is running in air right now.  It is also slightly out of factory spec too.  This situation indicates that my sanding tilt on the top cover wasn't quite enough, so when I go for final fitting I need to try to fix this situation somewhat.  I will need to take the clearance of the outer two saddle blocks down to .001" or slightly below to get that middle block into factory print range (this means slightly more tilt and just about no more removal on the narrow end)

This is hard to explain verbally -- there is no top half to that outside bearing saddle, so by tilting the sand job you are lowering the middle top half to remove the remaining slop while keeping the narrow long bearing up enough for it to continue spinning.

Go slow here -- going too far means scraping curved bearing journals to fix it and that is way much harder than simply not going that far in the first place.

Next, at this stage and beyond all fitting needs to be done with hollow locator pins in place and all bolts tightened to factory torque specs.   Not doing this will cause errors and you having to scrape at curved journals to fix the goof ups.


Or, since you are WAY WAY well within Clymer/Suzuki .0059" acceptable wear limits and only one thousandth off factory specs on only the one middle journal you could just quit while you were ahead !!!


I'm done ....  

You can fart around and spend a whole lot of time fixing your attempts to make this thing 100% perfect, or you can be happy with "functionally good" and just go on with your life.  

You got other things to fix about this engine, so go on about it -- just be happy you got lucky on your first try.   8-)

Title: Re: Simplified refitting of Cam Bearing Journals
Post by Oldfeller on 03/12/10 at 22:53:13

What about this fix is less than perfect?  What are the downsides?

Biggest downside is you can screw it up while trying to fix it.  But then again, you have nothing to lose at this stage either.

Your cam chain is "slack" by whatever the initial wear amount was, so your cam chain life is slightly lessened.

Your cam is running slightly crooked to the rocker arms, so expect some uneven wear on the tappet surface.  

Actually, you re-aligned the cover to the crooked cam somewhat by sanding the cover tilted, so you already minimized this mismatch to a degree but you can still expect to see it reflected on the wear pattern on the tappet surface.  Once seated, this is effectively taken care of from then on ....

A minor upside is that all this fiddling falls within the adjustment range on the rocker arm screws and nuts, so you can still get good valve adjustments out of the system.  

Before you worry about actuating the valves "crooked" side to side because of the cover sanding tilt, consider the loading already put on them by the rocker's arc of actuation -- the side to side thing you sanded into it isn't even in the same order of magnitude to what it deals with already.

Will it last?   Given good oil pressure you should get something similar to what you got originally.  The outboard half bearing will wear down until the middle bearing is carrying load again, but this will all still be within "acceptable wear limits"   ......


Title: Re: Simplified refitting of Cam Bearing Journals
Post by LANCER on 03/13/10 at 03:54:37

Well done dude,  thank you for all your effort on this project.  This is a very usable/understandable tech work fix.  

Now I just need to get this moving stuff out of the way so I can start  fixing my cam journals.

Title: Re: Simplified refitting of Cam Bearing Journals
Post by Oldfeller on 03/14/10 at 04:02:22

AW SH*T !!!   <crash !!>  <slam !!>

(The standard male litany of throwing stuff and cursing when things go badly wrong)


To quote the Hitchhikers's Guide to the Galaxy  "Don't Panic !!"

The dolphins can tell you how to fix it ....


If you go undersized on the small end (yup, it is real easy to do) borrow a 20mm reamer from somebody here on the list.  
One twist of the reamer and you are back in the game again with a nice cleaned up surface too.  
This is the primo way to fix your little screw up ....

(heartily recommended by a guy who doesn't own a 20mm reamer).

Another way to fix it is to glue a thin shim strip along the offending edge (jack that end back up) and let the silicone gasket stuff cover over the foil when you put stuff back together again.  

If you can keep your mouth shut, nobody will ever know but you ....  

Aluminum foil will work for normal small errors, aluminum can body material for those who got really cave man ham handed   ( ugh ....    )


Next, those pesky hollow locator pins seem to be a variable in the equation, causing a bit of side loading when you put things back together on your final fit ups.   (I'd better go back up and fix the main reference material to include witness marking the hollow pins so you put them back in exactly the same way you took them out)

First, mark the offending area's cam shaft steel with standard magic marker, put it back together and rotate the cam while stalling it with snugging up the bolts -- disassemble and note the black spot on the aluminum cover/head journals that indicates the rub area.

You can pull the hollow locator pins out and sand them down by mounting them in a drill chuck to create a little alignment room, this seems to work most of the time as it allows the cam to control the final orientation which is then held true by the jelled silicone gasket maker around the pins and along the entire mating surface.  

Next, if this doesn't fix the alignment issue you can whack the cover with a soft mallet and just tell the pesky thing to move over a bit (this does 100% work of the time, but puts your castings at risk when the blows have to get hard and you can easily go too far in the opposite direction when it does finally move -- see "AW SH*T listed above)

Or, you can carefully hand sand the black marks off and refit it and see if it still rubs.  
This is actually the simplest, quickest way to fix it.  Just don't move them durn pins any more after you do it.


"Aw sh*t, I forgot to put the rubber band in place and I sanded some flat spots on my adjustment screws".

Take them out and put them in a drill chuck and touch them to a fine belt sander belt while spinning the drill -- try to match the original contour as much as you can.


FINAL Fair Warning for all those anal folks who try to fit all 3 bearing journals to ".001 or less ....

You are going to have to do ALL these sorts of things.   You are also an frigg'n idiot, what makes you think the Suzuki factory does this level of fit?  

Next, what makes you think it is going to stay that way for long?   I have seen normal "good bikes" with thousands and thousands worth of NORMAL WEAR on these journals from simple cold start and idling actions ....

DON'T BE ANAL, a couple of thou is fine ...

"Quit while you are ahead."

   (as recommended by the Dolphins)

Title: Re: Simplified refitting of Cam Bearing Journals
Post by MMRanch on 03/14/10 at 19:38:24

Very impressive OldFeller

While reading about taping to avoid taking too much off one side, the thought accoured to me, "just run that side off the edge of the counter and do a blend at the end".

If I ever have to do bearning again , thats the best idea I've heard of yet!!

I'm still running on JB Weld , but I know it woin't last forever.  Keep the Idle up .

Title: Re: Simplified refitting of Cam Bearing Journals
Post by Kropatchek on 03/16/10 at 08:18:44

Thanks Oldfeller. Very easy to understand.
My engine is still running with the middle bearing in the air for appr. 3000KM
Job for the next OH :D

Title: Re: Simplified refitting of Cam Bearing Journals
Post by Chief Gunner on 04/17/10 at 19:52:48

Old feller,

Stuck in the sandbox right now, but still got access to see all the crazy stuff you guys come up with. This one has me wondering if I can recover from the JB Weld job I did last year. Got 1000 miles out of it before I took it apart and found that the JB, for lack of a better term, disolved. You mentioned in this thread that with the oil barrier the bearing surface doesn't need to be perfectly smooth as long as you keep the oil pressure up.
Guess I'll have to give this a try when I return. If it doesn't work I'll have to get with you guys and make a deal on a (better than mine) head and top cover. Really don't want to drop 700-900 dollars on an '87 I only have 400 dollars invested in. Plus tinkering with old parts are more fun!! ;D
You guys are great. I'll keep watching what you come up with while I'm over here and when I get back, the tools and beers will be flying. » Powered by YaBB 2.2!
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