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E: Engine Timing Gear Set Up

Steve Morris

Well Known and Active Website User
VOC Member
Hi all. I have removed the timing chest on my Comet series C and am fitting a new ATD. On inspection i noticed that the half time pinion nut was loose with no lock washer...

So, decided that i really needed to remove all the pinions and check as i also had an issue with the bike using oil/smoking. On inspection there were a couple of thrust washers missing/in the wrong place, so i have now removed all the pinions with the exception of the dynamo one, and the pins, and thoroughly check/cleaned all the above. I have done a dry fit (have ordered a new thrust washer kit) and with the correct shims/thrust washers in the correct places (as per P.Richardsons book) i have what i consider to be quite a lot of play in the pinions, id say on average 30-50thou on each one?

I have made a video showing the play. Can anyone tell me if this is correct as i cannot seem to find in Pauls book OR KTB any reference to the correct movement/gaps?

Many thanks,

Steve.

https://youtu.be/ltleq8i8HXs
 

Steve Morris

Well Known and Active Website User
VOC Member
Thanks Eric, Where is this oilway? Like i said i have an oil consumption/smoking issue so maybe have more oil going to the bore than is necessary? There is or seemed to be plenty of oil in the chest and cam area..
 

vibrac

Well Known and Active Website User
VOC Member
As has been recently discussed on here religious adherence to the recomended arrangement of washers on the timing gear is not all ways the best way, in fact know thy Beast actually has a rare error in my edition
 

Bill Thomas

Well Known and Active Website User
VOC Member
They may be a little loose , But better than too tight,
The Breather needs more play than the others.

The half time nut , I still do like the factory and pin punch,
But to do it up tight, You need to hold the outside of the engine shocker with a chain wrench.
 

Marcus Bowden

VOC Hon. Overseas Representative
VOC Member
A much more positive method I use is drilling and tapping the locking nuts on gear/boxes engine shafts etc.
HALF TIME LOCK NUT IS FROM A SERIES "A" WHEEL HOLLOW AXEL NUT AS THE HEXAGON IS THE NEXT SIZE WHIT-WORTH UP AND GIVES ONE MORE SPACE TO DRILL AND TAP ENABLING TO LINE UP WITH THE TAPPED EXTRACTION HOLES OF THE HARDENED PINION AND AN ALLAN SCREW LOCTITED IN

P1040104.jpg
 

craig

Well Known and Active Website User
VOC Member
HALF TIME LOCK NUT IS FROM A SERIES "A" WHEEL HOLLOW AXEL NUT AS THE HEXAGON IS THE NEXT SIZE WHIT-WORTH UP AND GIVES ONE MORE SPACE TO DRILL AND TAP ENABLING TO LINE UP WITH THE TAPPED EXTRACTION HOLES OF THE HARDENED PINION AND AN ALLAN SCREW LOCTITED IN.

Thank you , This looks like a great option.
What is the part number to be ordered for this larger nut please?
Craig
 

greg brillus

Well Known and Active Website User
VOC Member
If it's a series "A" axle nut you wont be able to buy one, only make one.......If the gear itself is a good fit on the shaft with a new key a nice tight fit, the nut should not come loose.........As I've pointed out in other posts, if the fitting itself comes loose due to play in the spline or keyway, then the nut will always loosen itself. I've had several engines where the pinion starts rotating on the shaft with a loose key, at low engine speed it sounds like the big end is gone.
 

craig

Well Known and Active Website User
VOC Member
I would like to see the tooling in action checking the dimensions of clearance prior to fitting the steady plate. Choice of dimension tool, choice of reference tool. Follower shafts, cam shafts , the three mount shafts, etc.
 

Martyn Goodwin

Well Known and Active Website User
VOC Member
Thanks Martyn, your a star mate. I did think there was a bit too much end float, ill have a proper read and play over the weekend.

Best regards,

Steve,
Here is an item from OVR #43 that provides some insight into improving Comet Timing Case lubrication.
 

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Steve Morris

Well Known and Active Website User
VOC Member
OK. Ive been in the garage all day, 'Good for you' i hear you all saying, however............

I very stupidly, and only to see if i could move the spindle, removed the 3 nuts that hold the large idler boss on and removed the boss, huge mistake, i have just about got the alignment correct (re backlash) or at a point where i am kind of happy that its not going to whine/rattle like a b*stard on the road...

Anyway, I have another question for the learned.

On stripping down the timing gear, the camshaft spindle (ET156 I think as isn't the Comet cam spindle the same as a twin rear?) came out. On close inspection there is some wear on the spindle where it goes into the crankcase. So, first question, Is this normal? It goes back in and is quite tight, but i have no real way of telling how far in it should go, plus (and this is the reason i first took it apart) setting up the end float on the cam is difficult as the depth of the spindle has an effect on the end float of the cam. I noted on VOC spares that they sell o/size spindles, is this a common thing?

I have considered either peening the spindle and loctiting it in, has anyone done this before?

Also the exhaust cam follower spindle comes out as well, it has a screwdriver slot in the top of it, and when i mentioned this to Bob at VOC he seemed to feel/suggest that his isn't normal??

Any help would/will be greatly appreciated!

Best regards,

Steve.
 

timetraveller

Well Known and Active Website User
VOC Member
I don't know if the spindles are the same on a Comet as for the front cylinder on a twin but if they are then the exhaust cam follower spindle does have a screw driver slot. After 70 years it is quite common for cam spindles to be loose in the crank case. I think you will find that there are different amounts of oversize available to be used depending how loose the spindle is. Ideally the spindles should be put into a hot crank case but if you can get a new one cold (water pipe freezing can) then that is an alternative, You can gauge the height from the steady plate when it is seated on the other spindles.
 

bmetcalf

Well Known and Active Website User
VOC Member
It is a lot easier putting a new spindle in if the engine is stripped and on the bench. Doing the job in situ requires a lot of preparation, planning, and ideally with someone who has done it before. It isn’t an easy job.
 

davidd

Well Known and Active Website User
VOC Member
Timing Chest Stock Desc.PNG

On stripping down the timing gear, the camshaft spindle (ET156 I think as isn't the Comet cam spindle the same as a twin rear?) came out. On close inspection there is some wear on the spindle where it goes into the crankcase. So, first question, Is this normal?

The rear cam of the twin is the short one, which is used in the Comet. I replace spindles that are worn. It is reasonably common to replace a spindle with the first oversize spindle. If a larger oversize is required the installation can become complicated because the bigger the hole the more that it is likely it has lost its round shape. It then may take a little skill to install the spindle correctly.

No peening allowed. Loctite itself will not hold a loose spindle in place. The case should need lots of heating before the cam spindle (or the others) should slide into the hole.

There is no screwdriver slot in the Comet spindles as can be seen above. Someone probably put a slot in so they could tighten the spindle onto the steady plate to keep it from backing out of the nut because the crankcase had lost its grip on the spindle.

David
 

greg brillus

Well Known and Active Website User
VOC Member
Oh dear.......And generally oversize spindles are too oversize........This is not a bad thing, but you have to linish it down to the correct size.......If the spindle just goes into the hole with no up and down movement, then you need another 0.001" more on the OD of the new spindle.......0.0015" is probably too much and would be a very tight fit to install. This will be a "Work in progress".........
 

Steve Morris

Well Known and Active Website User
VOC Member
OK, the plot thickens....

Last night i thought 'enough's enough', and retired for a cogitate.

On waking this morning i could maybe see things a little clearer and was thinking that the spindle is only about 0.001" off being a really tight cold fit and probably sufficient. So off i went to the garage for a review of yesterdays work and to take stock once again. I did notice on the end of the Cam spindle that is inserted there looked like what were wear marks, but on much closer inspection the were not...

I managed to 'scratch' a bit of what looked like the wear mark off, and then the sudden realisation set in the this was not a wear mark but a 'raised' marking, yes, it was the residue of what was probably loctite or some sort of glue.. A quick 'linnish' in the lathe using 1200 paper confirmed my fears, it was loctite, someones been here before...

So, cleaned off i inserted the cam spindle into the casing and it now wiggles around like the proverbial c*ck in a shirt sleeve......

So, Looking at a couple of other posts i have decided i need to replace the cam spindle and the exhaust follower spindle which is loose but not as much, with oversized replacements. Worse case scenario is i have to remove the engine and split the cases, best case scenario is i can get the whole engine up to a decent temp using a small space heater about 4ft away then using a hot air gun 'locally' heat the spindle area to try to obtain about 150 degrees or above after doing a dry run with the original spindles and the steady plate to get my reference markings etc, and leaving the spindles in the freezer overnight, i have a fair to slim chance. I know i will need to be fairly quick as the casing will cool down quite quickly as will the spindle heat up, but I'm sure that with a couple of practice runs and someone else to ride shotgun with me, i could be done.

Whilst I have everyones ear, I have measured the cam and exhaust cam follower spindles i have, which i have to assume are standard, and they measures 0.501" and 0.374" respectively. Can anyone please confirm is these are correct as standard?

Can anyone else confirm they have managed this repair also?

Looking at the worst case scenario, it wouldn't be the end of the world, as it is using a bit of oil and i suspect either guides/valve seals or rings sticking where the bike has been sat for years, plus there are a few minor oil leaks which i could do all in one hit, and i have the time at the moment...

Ill keep you all posted!
 

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davidd

Well Known and Active Website User
VOC Member
Standard is 0.501" for the cam spindle. I think the oversized spindles go up by 0.002". Thus, the first oversize is 0.503".

Standard is 0.375" for the ex spindle. I believe the first oversize would be 0.377".

Maughans makes them if you have problems, but the Club Spares should have them in stock.

I have used a space heater to warm up the engine because it is easier to get high localized heat if the heat is not being drawn off quickly by the rest of the case being cold.

David
 

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