Lash on bevel drive Oldhams couplings query

[machten]

Hi bruce. Yes, done that.

After some more work tonight I've arrived at the following:

After bore dialing the sleeve, it is not worn and sits well within spec for the internal diameter.

There is about 1 thou of lineal curvature on the upper bevel load surface at each end of the coupling surface. I assume the same applies to the lower bevel surface. That amounts to a total of 4 thou of circumferal lash across the coupling drive surface. That will do it to create the lash I'm seeing between the upper and lower bevel drives by my calcs.

This has had a recent (sub 6000 miles) bottom end, bore, piston, rings, etc.

I'm going to take a pragmatic approach and get the upper bevel shaft hard chromed to at least halve the lash. That way I don't need to split the engine. Worst case, I need to do this bit anyway, so nothing is lost by doing this other than the effort already spent and a little bit of work to reassemble and test. It may be that I need to do the same on the lower bevel. Or it may also see me past my riding days.

Kevin

[machten]

Just as a follow up to this....

Nigel said...

Your bevels actually look quite good compared to a lot, so maybe your sleeve is worn or oversize. I've never found any undersize sleeves myself but I would think their use would be limited if you did get one. However there is a lot of variation in used sleeves so worth a look first.

and then I said...

After bore dialing the sleeve, it is not worn and sits well within spec for the internal diameter.

...and...

I'm going to take a pragmatic approach and get the upper bevel shaft hard chromed to at least halve the lash. That way I don't need to split the engine. Worst case, I need to do this bit anyway, so nothing is lost by doing this other than the effort already spent and a little bit of work to reassemble and test. It may be that I need to do the same on the lower bevel. Or it may also see me past my riding days.

On later reflection and finding that I could source a few unused standard sleeves, I thought I should take Nigel's advice and try a decent sleeve. Much to my suprise, a new sleeve fits very snugly over the coupling and I can't by hand generate any of the lash that was there previously. I expect with some bedding in to see some lesser lash later, but I'm pretty confident that any that rematerialises will be perfectly acceptable - so I think I can avoid the whole chrome/grind of the bevel event at least for quite some time. I'm going to run with that, anyway, and see how it goes.

I think Nigel's "by photo" assessment and recommendation has proved to be spot on.

My lessons out out of this:

1. Get some more practice with the bore dialer
2. Listen to those with real practical experience (thanks Nigel!)

Kev

[graeme]

Hello Ken

I'm in the process of getting a late model 450 scrambler running.
It has a terrible tappet noise that sounds to be comming from the exhaust side.
The shim clearance is 0.18mm , a little loose but the noise sounds like the clearance is 1mm.
Did your slack Oldham coupling have a similar noise?

Graeme

[Jordan]

Did you eliminate the top bearing sleeve fit as the source of noise?

Jordan

[graeme]

Hello Jodan,
No, I've only checked the rocker clearance so far.
I haven't removed the head or the timing covers yet.
The left cam bearing holder (with 450 on it) is tight in the head when I removed it.
But that's as far as I've gone so far.
The rocker bush's feel worn too.

Graeme

[machten]

It has a terrible tappet noise that sounds to be comming from the exhaust side.
The shim clearance is 0.18mm , a little loose but the noise sounds like the clearance is 1mm.
Did your slack Oldham coupling have a similar noise?

Hi Graeme,

The first thing I'd say is that I often find it very difficult to accurately isolate the source of noises within a running 450 springer. Perhaps the thinner barrel as a result of the increased bore reverberates the noise around a lot more. Even a new build has no shortage of mechanical noises happening in there!

The O/C noise is not unlike loose tappets.

In any case, it easy to test if the oldhams coupling is a problem.

All you need to do take off the top bevel cover, position the engine at or about TDC, put it in gear then and see how much free play you have if you try to rotate the upper bevel back and forth (the horizontal gear, not the bevel gear mounted on the camshaft). In my case, I had sufficent free play to be able to make the olding coupling "tap". If you do this test, it is worth doing with a warm engine, as the viscosity of cold oil can mask the problem somewhat. If you do find an uncomfortable amount of free play, then it is worth removing the timing side cover to check that the play is not also contributed to by the lower bevel. In my case, it was all in the oldhams coupling.

New coupling sleeve from Italspares (standard size available only) was about $16. (Which makes it about the cheapest fix I've made to this thing )

I was so impressed by the outcome on the 450 that I treated my 750 Sport to some new sleeves on the weekend with the same result. My 750 GT will get the same treatment shortly.

Regards,

kev

[graeme]

Hello Kev,

I'll look further on the weekend.
I only had time to check the rocker clearance and remove the cam bearing cover/retainer to have a look.
It's heaps noiser than I've heard before.
Noisey with a cold engine and noisier with a hot engine.
I don't have time or space to restore this bike before we move to Tasmania, so I thought I'd just get it running for now.
Will let you know what I find.

graeme

[machten]

Btw Graeme,

Jordan's heads up on the upper bearing sleeve is worth a look too just as a matter of course. Not being set up correctly for the upper bevel housing gasket can allow the sleeve to rotate.

The other thing I've seen on twins that addes to noise is the rocker spindle holes in the head getting worn oval. The spindles should be a snug fit into the head.

Watch out for wombats and devils on the road in Tassie! (you lucky fellow. Nice riding there!)

Kev

[graeme]

Kev, I recon there is something moving.
Tonight I checked the clearances again and now they are tighter.
There seems to be no slack in the Oldham or anything else I can see without delving further on the weekend.

[Bevel bob]

HI,No play anywhere does not sound good, its possible to mess around with the bottom bevel shims and finish up with the Oldhams joint axially loaded up which will damage the bearings and stop the head from seating.Its also possible for the bushing which holds the bearings to be incorrectly packed down,allowing a seemingly correctly shimmed set of bevels to develop lots of play. Been there,done that!!!.