Cam endfloat mod - update

[GregT]

I've just done the mod as detailed in the old Suzuki forum posts - and still up on Bwringer's site.

I have a couple of possibly useful updates.

It is possible to do it with the head still on the engine - and still in the frame. With the buckets removed, the cams can sit down in the bearings with enough clearance for a small amount of rotation.
For those who worry about marking the lobes on the valve stem tops, cut cardboard circles and drop them on top of the valves.
Leave the spark plugs in. At some point in the process you will drop a cam cap dowel. Best if not inside the engine....

I found that on this engine all the wear was on the left - or downhill side when on the sidestand. So only inserted that side. Clearances before starting were .0055in inlet and .0075in exhaust.
Finished - -002in both cams.

I made the half moons by holesawing out blanks from 4mm 6061 alloy sheet then machining. Parting off accurately at what is a fairly large diameter for a home lathe, I try and avoid.
Measuring showed I needed inserts approx 3.9mm thick so the 4mm sheet was ideal.

When doing the final clearancing - hand rubbing the inserts to thickness - it's worth ensuring the inserts are fully seated in the machined recesses.
I used a block of wood and a small hammer to tap the end of the cam across to push the inserts fully home.
When doing this, you of course only need fit the cap which holds the insert.

If I did another one, I think I'd use bronze rather than alloy for the inserts. That's a very narrow thrust face. No expansion probs either, and the insert is locked in place anyway.

I'd be curious to see if anyone else has done it and if there are any other solutions out there. Most modern engines now use a narrow steel half moon running in a slot in a cam bearing journal for location. Can't do that on the 8V GS basically because of the overhung end cam lobes. Don't want to break a cam.
Another way which came to mind is using a hard overlay on the cam locating flange to build it up. Not difficult I'd think but the risk is cam distortion if it's overheated putting the overlay on.

 

[Gorminrider]

Right on,GregT-I'll be trying similar when the shed warms up. My experiment of simply flipping the cam-end seals inward worked great!... but not for long. New ones are cheap but a shim of bushing-bronze would be the waytogo... and without actually staring at the cams right now, I'm still imagining it'd be possible to simply slip a shim (or shims) in between the rubber seals and camends...Where could they escape to? a drop of epoxy or a "fencing" seems like it should do.

Add hmm, what bushings do I have around..could I just cut a section off one and use it for a shim..? But perhaps it'd be harder to hold in place and not last as long either...)OR it could nest in that plastic end cap?..........)

 

[bwringer]

I still have Ian Grant's old PDF floating around my server:
https://www.bwringer.com/gs/cam_end_float_mod.pdf



FWIW, my GS850G is wearing what I think may be a 1981 GS850GL engine. It's quiet when cold, knocks like hell in between. and gets quiet again once it's nice and hot. It's done this for the whole 50,000 or so miles I've had this engine in the bike, and I hardly notice any more. Besides, I'm always wearing ear plugs. Although it is a little embarrassing at stop lights until it warms up. In any case, I have zero access to the tooling required, and ignoring it is free...



One thing that has entered my mind is a contraption that replaces both "half moon" seals on each camshaft with a solid metal insert containing a screw and locknut arrangement. On the inside, you'd have a round flat "head" on the screw that contacts the camshaft. Turn the other end of the screw until the annoying noise stops, set the locknut, and forget about it.

Since the end of the camshaft is notched on the right, this might not be very viable.

I could also envision some sort of really thick half-moon, or half-moons in different thicknesses or that you can sand down as needed to control the camshaft. I've found that if you shove the camshafts back and forth with the valve cover off, you can replicate the motion and the noise and figure out what's smacking into what.

Again, I'm not sure how viable using the end face of the camshaft might be. Maybe these need little protective caps or something.

 

[GregT]

One thing that has entered my mind is a contraption that replaces both "half moon" seals on each camshaft with a solid metal insert containing a screw and locknut arrangement. On the inside, you'd have a round flat "head" on the screw that contacts the camshaft. Turn the other end of the screw until the annoying noise stops, set the locknut, and forget about it.

Since the end of the camshaft is notched on the right, this might not be very viable.


Again, I'm not sure how viable using the end face of the camshaft might be. Maybe these need little protective caps or something.

If you only need to control endfloat from the left end it's a little easier.
But really you need to hit the cam on the centerline height if you're running anything against it

Which makes it very difficult with the half-moons only coming up to centerline height themselves.
Not impossible - but an awkward piece to design and make.

 

[Gorminrider]

@GegT -I wonder if you took any pictures..?

 

[GregT]

@GegT -I wonder if you took any pictures..?

No. The original PDF has enough to work with. And with the internet I have now, I can't post pics here.
The bike I did is Kiwimacchi's 1000S and I did think about asking him to take some pics - but he was busy elsewhere while I had it.

 

[Gorminrider]

One thing I noticed yesterday when attacking this, is that the reversed "half-moon" rubber seals that I tried are not worn when the clacking began to come back. They are dished. So, after thinking about it, I decided if it isn't simple I won't do it.
Therefore, I've decided this should work: simply brass sheet cut to fit. I reason there's nowhere they can go so they are not attached to anything. Merely shaped to fit the casing.(next post) This is the test fit, dropping the valve cover down.

 

[Gorminrider]

Note the handy feeler-template tool. But I further "reason" that they needn't be a fancy fit. Note the bloody rag. (Sheet metal is more fun without gloves!) Fingers crossed, are not shown.

4 cut, all the same shape on the 650. Brass sheet is about a mm thick.
Doesn't bind at all turning by hand and a short run didn't result in grinding or screaming noises. It'll take awhile before I can really say how good or bad an idea it is...

 

[bwringer]

Gorminrider, I like that idea a lot. I'll be very interested to see what those plates look like after a few miles.

 

[Gorminrider]

Yes, me too! but I won't be insuring this bike until April so warmed up in neutral in the shop is as good as I can do 'til then.

...Just as things that I noticed and will forget if I don't note it, to comment especially upon later:

-there was no trouble replacing the cover over the shims.

-the top cover is "rounded" in the casting so the "half-circle" fit for the top cover is necessarily smaller than a template of the inside curve would be in order to sit "square" and flat.

-recall that the cam ends are different, left and right. That is, the right side has those "indents" to mark cam position when adjusting valves etc, but the left ends do not and are thereby "smoother"
(if description of "indents" not plain, refer to the manual's pictures in "valve adjust".. )

...So I am especially wondering about the right side. In previous experiment, that they did not grip and destroy the reversed rubber halfmoons there, leads me to expect this won't be a problem...Still, it may be that I'd have been as well to shim the left only. Perhaps thicker perhaps not.

added; I'll be checking the oil pretty closely for brass flakes! and the filter too, later, as the oil change is due soon enough.

 

[Gorminrider]

For people that don't know what cam-walk sounds like, here's an mp3. Its Google drive but should work without logging in...there's a download link upper right...
https://drive.google.com/file/d/1Hf3ylXqLEV7xy6DBV9rMSyUr1cINACG7/view?usp=sharing

 

[Gorminrider]

Bike on the road again...working pretty well so far. Haven't opened up and looked at it yet but rides fine and quiet.

 

[uk gs nut]

My take on the cam endfloat. Square off the caps and fit shims with small cap head bolts.
Camfloat tapping fix with shims gs 750 cylinder head by Dennis Harland, on Flickr

 

[Gorminrider]

Update: had a looksee. LEFT SIDE Cam-end shims...
.

 

[Gorminrider]

RIGHT SIDE Cam-end shims..Definitely scored by the right side camend's notches- not a lot, but I think the two thicknesses together are too much when engine run to full temp..? ... they are moving up and down a little too... I sort of expected the increased gouging from the notches. I took THESE out .The left side ones (above) stay in. Seems quiet with just them alone. The experiment continues...Possibly, a shim of some material could be slipped behind them, should these prove to clatter.

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