Gear up..

[Moparnut72]

There is a company that makes timing gears for 88" Harleys to replace the problematic chains. One requirement is that the crank must not have more than .003" runout. They also make a standard gear and a + and a - to account for differences in shaft placement. The last I knew they were over $800. When I had my 88 I figured I could replace the tensioner shoes every 30,000 mi for that kind of money, not a terrible job. I had the bike for only six months, lost in a fire, so I never had to do the job.
kk

[Huzo]

When I had my 88 I figured I could replace the tensioner shoes every 30,000 mi for that kind of money, not a terrible job.

Well yes that’s true.
But I didn’t get them to save money, so it’s of no consequence.

[Alfetta]

I can see no reason why the shaft centres would not be as per spec,

A manufacture prefers to have a specification of +/- .010 over +/-.002 (Imperial tolerances...sorry)
A chain drive system can live life well with either tolerance, but gears require the latter.

One may argue that the use of chain indicates that the manufacture took the cheap approach, Another can argue that the manufacture saved him some hard earned cash...
the truth is both system are more that acceptable for 99.9% of IC engine applications...

[Huzo]

Got these.


 A new set of bearings for the oil pump are on their way, so I’ll do the swap when I get back from my Oz lap on the 110.

[Huzo]

https://northernbuckeye.com/2021/05/12/lincoln-casino-no-deposit-bonuses-2021/

Ummmmm.....

[Huzo]

I got my Norge home yesterday from England and have the front end out and timing chest off. I’m going to install the new oil pump and timing gears.


I noticed that the oil pump had discernible play in the bearings last time it was out and was given to wonder if that is a contributory cause for the failure of some pumps in red ‘07 Norges. Mine has done the time, but it is a red ‘07 and only just missed the suspect batch. Any play in the pump bearings (and there is some), will be forcing the mating parts of the pump internals together cruelly.
The bearings are two side by side races of total width about 10 mm and the sprocket is something like 25 mm away from them. The pull of the chain tensioner is putting a brutal bending load on them and it bugs me…
There is no such load with gears.
I will have the pump out today and will post a shot for illustration purposes.

The issue of the shaft centres still haunts me but when I fitted them the first time, it occurred to me on start up that I had not checked for adequate lash upon assembly, so I shut it down and removed them.
This time I will.
If I determine that they are not running with zero lash cold, I’ll give them 1000 km to settle.
I’m convinced that as the engine warms it will grow vertically to some degree and will therefore open up the dimension of the shaft centres thus increasing lash not the opposite, which would mean end of engine.
We’ll see.

[Ncdan]

I replaced mine at 40 thousand and not a mile too soon, they were worn slap out.
However the gears make a log of noise whining from what I here.

[n3303j]

My R60/2 ('66) had an aluminum cam gear mated to a steel crank gear. I sold the machine at 100K miles. Gears still looked and sounded okay. There's a reason antique clock makers ran metal against wood and had good service life.

I seem to remember that BMW made their blocks and measured the crank to cam center distance when finished. The blocks were marked with a code indicating the deviation from perfect. I think there were 6 steps.

BMW made the timing gears in matched sets and measured their center distance deviation from perfect. The gears were marked with the same code as the engine. The gears and engine blocks were paired by code at assembly.

After a lot of running the compress / explosion pressures widened and shortened the block. So replacement gears had to be ordered smaller than original numbers indicated.

Ural tried a similar approach with the numbered blocks and gears but the Russian product wasn't precision in any way. Russian gears were hardly round so clearance was set to the tight spots. Their Herzog gear upgrade was a great improvement.

From my FWIW department I ran my Valtek chain tensioner for 80K miles before replacement. It was still functioning but probably would have worn through at 120K miles. I replaced the timing chain and crank timing cog as long as I was in there. It was a bit past 100K miles. It got a bit quieter and timing a bit more stable after the attention.

[Huzo]

After a lot of running the compress / explosion pressures widened and shortened the block.

Can I have this bit again please mate.
You make good sense, but this bit has got me baffled.

[n3303j]

Can I have this bit again please mate.
You make good sense, but this bit has got me baffled.

The combustion pushes down on the pistons and pushes up on the combustion chamber. In turn the cylinders are tugging outward on the block on the left and right sides. After many miles this does widen the block a bit. The extra width is subtracted from the height. Hence the crank to cam distance is shortened and replacement timing gears are normally one to two deviations smaller then the originals. Duane Ausherman went into this in detail in his vintage BMW site.

[Huzo]

Ok.
Out I went and began to take the timing internals from where they currently reside. I never really liked the way it was and here’s why… https://youtu.be/WpUtgmANr3I
All that went ok and I got to here https://youtu.be/ZBFVQWB4jnw
But here’s the thing…
I felt that the crankshaft to oil pump gear mesh was a bit tight, I still had the old oil pump in situ but set out to find why.
The edges of the oil pump teeth were still a bit sharp where the angles were machined and although doubtless correct, I saw that this was where the tip of the teeth were meshing, so I LIGHTLY wire brushed them to enhance the meshing process.
But.
The cam and crank gears both have a white dot to facilitate timing and these dots is are supposedly in small depressions on the gears. At least that’s the plan…
But while I was carefully brushing the crank gear, due to the fact that there is no indentation where the white spot is on the crank gear, the brush removed the timing mark.
The crank gear mark should look like this.


But mine now looked like this..


The eagle eyed among y’all will notice the (now) absent timing mark….
After I had finished soiling my pants and wondering why I put the gear on the brush, I referred back to this photo again


And I ascertained that the timing mark is 4 teeth inclusive, from the one that the key way is aligned to.


If anyone disagrees with me, please say so before I button it up, but I think I’m ok.
So I counted 4 teeth anticlockwise and put a dot on the correct tooth…


And it’s red for a VERY good reason…I didn’t have any white paint..!

It turns out that the crank to oil pump set were tight, because the oil pump was bolted up just a touch too close to the crank gear.
When installing the new pump, I LIGHTLY wedged the oil pump away from the crank gear and tightened it all up.
As you see in the video, it spins nicely…!
BTW…
I snuck a feeler in between the teeth in the gear sets and there is 4 thou’ lash..(0.004”)
I think I dodged a bullet.

[Scout63]

Interesting but frightening Huzo.  I bought a steel idler gear to replace the alloy one in my Rapide, took one look at it and put it back in the bag.  Peter Talabach is installing it. He has the tools and experience to handle this and I don’t.

[n3303j]

At 0.004" clearance you are a bit loose on the clearance. But it won't hurt anything. The BMW standard was half that at 0.002". That gave you 0.001" per side for oil film. BMW was a slightly angled tooth which decreased sound output. There wasn't a lot of angle, as it would generate axial thrust on the crank and cam.

[pressureangle]

Gear tooth lash is a voodoo science. Tooth profile, pitch and wheel diameter have all to be taken into account, as there is always some amount of sliding between tooth faces. I suppose there is some perfect set of circumstances where a gearset could roll between faces but nearly never. One consideration in clearance is the necessary clearance not between the pressure faces, but between the tip of the tooth passing by the body of the intersecting teeth. 'square' teeth tend to need more face clearance to accomodate tip clearance. Modern gears are often of a curved profile which allows a tighter face clearance and less noise. The load carrying ability of the gears are little affected by these parameters until the heat of loading and sliding becomes problematic.

Back in Harley-Davidson flathead racing days, gearsets were installed intentionally tight and mated with valve lapping compound and jeweler's rouge to keep the lash as tight as possible.

[lucian]

Best way to set gear lash is on a cold engine using a standard piece of lined writing paper. Typically .003 in. (mic first to confirm,) install the gears and run the paper strip through the gear set while turning the engine by hand.  If the paper passes through your good to go, if it jambs the gears up they are too tight. If you can run the paper through doubled up , your still ok, ( .006 thou). If three folds pass through and don't jamb the gears up your too loose. The good news is , if the fit is tight it's pretty easy for a machinist to take a thou or two off a straight cut gear.  Not so easy to make them larger.

[n3303j]

20 Pound stock, standard writing paper is 0.005 average thickness.
If you are running a single thickness of paper through you have 0.005" on EACH side of the gear tooth. That's 0.010 clearance and is way too loose.
Assuming the gears are properly cut, they will not bottom out on the root diameter. So the clearance you want to measure is between the tooth faces. These are the working surfaces. This is reasonably easy to do with a 0.0005" dial indicator. Lock the crank and leave the cam unloaded. Put the point of the indicator on the face of the cam gear tooth. Rock the cam gently back and forth against the crank gear. Read the lash off the indicator.

[lucian]

Always mic the paper to confirm thickness. I find the average to be .003 , the point of using paper is that it will compress. If it makes it through without jamming or tearing you know you have acceptable clearance. You can also inspect the paper and if there is any pinched spots it's easy to see if it's the root or interface. Also , shafts , bearings and gears may not always be 100 percent concentric so running paper through an entire revolution will gauge the tightest spots in the circumference. It's important to check the the lash on all of the teeth interfaces, not just one . The paper method has never failed me in 45 years and was taught to me by a life long transmission mechanic. As long as one or two layers of paper make it through a full revolution you will be fine.

[John A]

You can get fancy and run Plastiguage through it.

[Huzo]

Okay..
The last 3 or 4 posts all make sense to me. My main concern was that they were too tight, as long as my mind is at rest on that score, I’m gunna’ go.
I am not sending them back to Scotland if they are too tight and not leaving them out if too loose.
So.
IN THEY GO…!

[n3303j]

Transmission gears are run a lot looser than timing gears as they often run on bearings or bushings on shafts in turn supported on other bearings.
Timing gears are fixed to their shafts and run a repetitive tooth contact pattern.
That said, running loose won't kill the gears. Running tight will hurt every part of the drive.

[lucian]

My curiosity led me to do a little test of the not so exact science of setting gear lash with the paper method i've used for years. I first measured some lined paper with a micrometer and found  this pads pages to measure exactly .003 of an inch. I then set the reverse tumblers of my south bend lathe to allow two layers of the paper to pass through to the very tight side. Three layers would jam the gears solid.  These gears are straight cut and fixed hard to the shafts ends just like Petes timing  gears , ,and I can adjust the lash + or-.  As you can see in the photo, it's easy to note the pattern of contact on the paper strips. The gaps between the marks show the root clearance.  I then set up a dial indicator and measured the lash by rocking the large gear back and forth while locking the tumblers solid. The end result as shown on the dial was .0035 of an inch  demonstrating the compression value of the two layers of paper with very acceptable results.  I repeated the test four times with new paper strips each time and got the exact same results.  I never doubted the wisdom of the old timer who showed me this method and and never felt the need to test the theory until now. I remember him telling us that it is not always easy to indicate gears installed in there cases and preferred this simple but telling method.




 
 

[Huzo]

Well here’s the thing…
I put the gears in after determining that there was nominally 0.004” clearance between the teeth. I was happy with that so I proceeded.
But they just make too much noise for mine, there’s absolutely NOTHING wrong with them, but I think I’ll have them out.

https://youtube.com/shorts/ZBFVQWB4jnw?feature=share

https://youtu.be/BHbm530OVhI

[lucian]

It's funny how new, unfamiliar noises on a motorbike will raise your hackles.  They quickly become the new norm once the paranoia wears off.  .004 clearance seems acceptable but will grow a bit when the cases heat up. Not enough to drastically affect the timing. Plenty of oil slinging around in there so all should be fine. Perhaps they will quite down a bit after some km's.  Also, earplugs are recommended. 

[n3303j]

0.004" is already double the recommended running clearance for that size gear. Of course it whines. A proper fit has multiple teeth in contact simultaneously and the teeth slide in and out of contact with their mates. BMW (vintage) got it right.

[Sye]

Well here’s the thing…
I put the gears in after determining that there was nominally 0.004” clearance between the teeth. I was happy with that so I proceeded.
But they just make too much noise for mine, there’s absolutely NOTHING wrong with them, but I think I’ll have them out.

https://youtube.com/shorts/ZBFVQWB4jnw?feature=share

https://youtu.be/BHbm530OVhI

Sounds like a VFR750 👍

[Huzo]

Chain is back in.


I’d just like to draw attention to the photo and in particular the short run of chain that is between the crank and cam wheel sprockets.
THAT is the section that drives the camshaft and as you see it is about 2” long.
If ever the cam timing was going to drift, it would be due to the wearing (stretching) of this portion. I can tell you that my new camchain length varied 0.005” total from the 140,000 km one.
So if the total camchain length was 500 mm, then 50 mm (2”), would be .0005” and that would be the degree to which the camshaft was retarded.
The camshaft sprocket is about 150 mm diameter or 450 mm (15”)circumference, so an alteration of .0005” in the length of a short run of chain is absolutely minuscule in degrees of cam sprocket drift.
And as for fluctuations in timing, the section between the crank and cam sprockets is ALWAYS in tension as long as there is resistance to turning by the cam shaft.
The timing MAY retard a tiny amount, working it out on my thumbs it’s about 0.2 degrees, but I cannot see why it would flutter.

[jacksonracingcomau]

Ok.


I felt that the crankshaft to oil pump gear mesh was a bit tight, I still had the old oil pump in situ but set out to find why.



It turns out that the crank to oil pump set were tight, because the oil pump was bolted up just a touch too close to the crank gear.
When installing the new pump, I LIGHTLY wedged the oil pump away from the crank gear and tightened it all up.
As you see in the video, it spins nicely…!
BTW…
I snuck a feeler in between the teeth in the gear sets and there is 4 thou’ lash..(0.004”)
I think I dodged a bullet.

That was never going to end well, lightly wedging oil pump just sounds fraught with risk,

[Huzo]

That was never going to end well, lightly wedging oil pump just sounds fraught with risk,

It sounds worse than it was…

[n3303j]

I always wondered about resistance to turning the camshaft. Seemed to me that a spring loaded plunger pushing on the downhill side of a cam lobe would accelerate the camshaft beyond its driving crankshaft.

It was only the chain tensioner that kept these two components in a somewhat proper relationship?

The shifting loads imposed by the camshaft contributed to the "noise" created in a gear drive camshaft as the gears racked back and forth under the changing load.

[Huzo]

I always wondered about resistance to turning the camshaft. Seemed to me that a spring loaded plunger pushing on the downhill side of a cam lobe would accelerate the camshaft beyond its driving crankshaft.

It was only the chain tensioner that kept these two components in a somewhat proper relationship?

The shifting loads imposed by the camshaft contributed to the "noise" created in a gear drive camshaft as the gears racked back and forth under the changing load.

I accept that there would be some phase of the camshaft’s rotation where it could conceivably accelerate forwards in the direction of rotation for a minuscule time. It would be an interesting thing to see filmed at high frames per second to witness what happens.
Just thinking about it, when the exhaust lobe is on the downhill side, the inlet is on the opening side at TDC on the exhaust stroke so the effect would be cancelled, but at the completion of the intake stroke at BDC as the inlet valve is closing, the uphill ramp of the exhaust cam lobe is nowhere near touching the rocker.
At this point it’s conceivable that what you say might come into play.
Of course the more cylinders you have and the higher rpm, the less time exists between this phenomena and the next time it occurs.
In a single it’s once every 2 crank revs, in a six it’s every one third of a revolution.
You’d think it’s more prevalent in a big OHC single at 1000 rpm idle, than say a Honda CBX at 1100 rpm idle.