Author Topic: Lining up the Timing wheels... What should I do?  (Read 5891 times)

Offline LJ.

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I've noticed recently my blue A10 to be sort of sluggish & juddery when in third gear at 30mph. I've been wondering if this might be a dirty air filter or weak carb etc... But on removing the outer timing cover to investigate a noise in there that others have heard. I found the breather cork to be undersized and in need of replacement. Further on, removing the inner timing cover I notice the timing wheels to be out of sync as you can see in the picture below.

Now then... What should I do here? move the wheels around to line up the dash and dots or leave well alone as it had been running mostly okay. I'm wondering if lining up correctly will allow the bike to run smoother than it is presently running.
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline Rusty nuts

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Re: Lining up the Timing wheels... What should I do?
« Reply #1 on: 15.09. 2009 11:57 »
LJ

They don't line up all the time.
Rotate the engine & they should eventually line up once every few strokes.
Should add, if they are misaligned engine would not run!

Rusty
1949 A7 Plunger
1947 A7 Rigid Star Twin
1969 Triumph T120R
1972 Triumph T120V

Offline RichardL

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Re: Lining up the Timing wheels... What should I do?
« Reply #2 on: 15.09. 2009 12:18 »
LJ,

Rusty is correct, but it is more than every few strokes, like, every 98 revs. Look here http://www.a7a10.net/forum/index.php?topic=789.msg5039#msg5039 and at the rest of the thread for similar discussion.  And, yes, in my "o'pinion", you must start with the marks in alignment, but, as you well know, others here have their "teeth" deeper into the subject.

Ricahrd L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline Rusty nuts

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Re: Lining up the Timing wheels... What should I do?
« Reply #3 on: 15.09. 2009 12:29 »
A "timely" piece of wit!
I remember turning mine over to see how long it took.
Don't think that many for my longstroke, would have got bored & gone off for a beer long before that.
Think I only had to turn it over a dozen or so times max.
Rusty
1949 A7 Plunger
1947 A7 Rigid Star Twin
1969 Triumph T120R
1972 Triumph T120V

Offline LJ.

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Re: Lining up the Timing wheels... What should I do?
« Reply #4 on: 15.09. 2009 12:34 »
Hi Just come back in from the shed, excuse the oily hands...

Thanks guys!

Rusty... I got up to 49 turns and the dots n' dashes once again lined up. How good a feeling is that?? lol. 

Richard... That is one thread that I missed, it was too mathematical and technical for me but was an interesting read in relation to my query. Such is the joy of our forms information and of you guys too!

Many thanks! (Now looks for the next problem)  *lol*
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline RichardL

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Re: Lining up the Timing wheels... What should I do?
« Reply #5 on: 15.09. 2009 13:06 »
Sorry, I guess I need to check my math. The fact that no one objected at the time made me think I was right, so I moved on.

Hide your children, I will be back with more on this, probably a display of how one can walk with tail between legs.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline LJ.

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Re: Lining up the Timing wheels... What should I do?
« Reply #6 on: 15.09. 2009 13:19 »
Your an honourable chap Richard... I'd have just re edited my post.  *lol*
Ride Safely Lads! LJ.
**********************
1940 BSA M20 500cc Girder/Rigid- (SOLD)
1947 BSA M21 600cc Girder/Rigid-Green
1949 BSA A7   500cc Girder/Plunger Star Twin-(SOLD)
1953 BSA B33  500cc Teles/Plunger-Maroon
1961 BSA A10  650cc Golden Flash-Blue
1961 BSA A10  650cc Golden Flash-Red

Offline RichardL

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Re: Lining up the Timing wheels... What should I do?
« Reply #7 on: 15.09. 2009 13:58 »
Sitting on the bus, thinking. No matter how we slice the math, the cam must do one rev for every two of the crank. Hence, 49 crank revs yields 24-1/2 cam revs and the cam dot is 1/2 rev out of position. LJ, is it possible you started your count with the crank and idler marks aligned such that the next 49 turns got everything aligned?

I await the fall of the guillotine, but, no matter, the head in the basket had long forgotten numerical analysis and differential equations.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline Beezageezauk

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Re: Lining up the Timing wheels... What should I do?
« Reply #8 on: 15.09. 2009 19:26 »
I was informed that when positioning the valve timing idler pinion, the engine is automatically positioned at TDC and this can be used as the basis for setting the ignition timing at the same time.  Can anybody confirm this.
Beezageezauk. 

Offline dpaddock

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Re: Lining up the Timing wheels... What should I do?
« Reply #9 on: 17.09. 2009 03:19 »
It doesn't matter where the marks line up after revolving from the initial timing setting (BSA Service Sheet 215). The idler can be as big as a wagon wheel because the timing will be correct since the cam pinion has twice the number of teeth as the crank pinion. Period.

David
David
'57 Spitfire


Offline RichardL

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Re: Lining up the Timing wheels... What should I do?
« Reply #10 on: 17.09. 2009 04:05 »
The original point, I take it, was to determine if LJ's crank and cam are in the correct relationship regardless of where they are at at any given time. The only way to know this, as I understand it, is to initially line up the crank and cam timing marks with respect to the idler. My point was to give an idea (really, the exact idea) as to how many turns one would have to rotate the engine before the marks once again line up. Assuming gear timing is correct, and the crank mark is lined up with the idler mark, you are either right on the marks or 49 turns of the crank away from them. When you are 49 turns away, the cam gear mark will be 180 deg. away from its rightful location opposite its corresponding idler mark. If you are not timed correctly at the gears, you might learn this by turning the crank over 98 revs and seeing that the marks never all align, but that would be ridiculously tedious versus just repositoning the idler and cam.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline A10Boy

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Re: Lining up the Timing wheels... What should I do?
« Reply #11 on: 17.09. 2009 10:36 »
I'm begining to wish BSA had made the Idler Pinion the same size as the camshaft Pinion.....
 ;)
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline RichardL

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Re: Lining up the Timing wheels... What should I do?
« Reply #12 on: 17.09. 2009 13:25 »
. . . However, the philosophy of the 'hunting tooth' - whereby an idler is nearly always a weird number of teeth - is standard practice. What we don't want is the same too/eeth on the idler always taking the load every time a valve opens. So, by giving that gear a prime number's worth of teeth (or at least, like 49, a number not divisible by any of the numbers that divide into the number of teeth of the driver and driven gear (in this case 2 and 11 and 22)), we get to a situation where the load is shared equally between all the teeth of the idler and it, theoretically, lasts a very long time. With consequent benefit to the other pinions in the train, which are not having to mesh with the same ever more worn teeth.

This bit of knowledge from Groily, which was most enlightening (to me, at least), explains why not.

Richard L.
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Offline A10Boy

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Re: Lining up the Timing wheels... What should I do?
« Reply #13 on: 17.09. 2009 19:01 »
Ok for the Idler, but what about the camshaft pinion, teeth on that would take a "regular" load ?
Regards

Andy

1960 A10 - Black Golden Flash
Plus
1974 Kawasaki Z1a
Yam XJR 1300

Offline RichardL

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Re: Lining up the Timing wheels... What should I do?
« Reply #14 on: 17.09. 2009 19:21 »
A good answer coming from me would be "dunno."

Groily was careful in saying that the idler teeth were conserved, and, in turn, did not wear the teeth of the other gears.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.