E: Engine Timing Gear Set Up

craig

Well Known and Active Forum 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.
 

Steve Morris

Well Known and Active Forum 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 Forum 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 Forum 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 Forum 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 Forum 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 Forum 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!
 

Attachments

  • IMG_4089.jpg
    IMG_4089.jpg
    658.9 KB · Views: 14
  • IMG_4092.jpg
    IMG_4092.jpg
    818.4 KB · Views: 14
  • IMG_4093.jpg
    IMG_4093.jpg
    778.6 KB · Views: 14
  • IMG_4091.jpg
    IMG_4091.jpg
    789.5 KB · Views: 13
  • IMG_4090.jpg
    IMG_4090.jpg
    634.8 KB · Views: 12
Last edited:

davidd

Well Known and Active Forum 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
 
Top