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Matthew Manton
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![[*]](./images/corporate/default_icon.gif) posted on 6-25-2009 at 06:07 AM |
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Fly Wheel Tight 1967 T20SM
Hi Guys,
Things are not good in Cub Land.
This is the problem:
The flywheel moves freely until I tighten the nut on the end of the rotor. It does not completely seize up, but definitely does not feel good and
free.
I have a wrench on the rotor nut and one on the other side of the flywheel next to the timing pinion.
I have upgrade to 12 volts and have the Sparx rotor.
In the Parts Catalogue #1 it shows the spacer bolt setup for a T20SM (which I have) and a T20SH. I have everything assembled as per the T20SM Setup,
I do not use #34 and #39.
When I assemble the engine sprocket I can feel it going though the oil seal and seating on the bearing face.
Any suggestions folks?
Cheers
Matthew
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T100
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| posted on 6-25-2009 at 06:21 AM |
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Matthew
What actually binds?
Is it the engine sprocket that gets pushed against the crankcase?
Perhaps washer/distance piece No 34 is necessary to allow more clearance between sprocket, rotor and crankcase.
Other than that - is the crank being pulled through by tightening the rotor nut?
I must plead ignorance with regard to Cub innards - mine's behaved quite rationally and not needed stripping (YET)
Good luck - keep us posted.
Martyn
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Raggles39
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| posted on 6-25-2009 at 06:37 AM |
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Matthew
Like Martyn I'm not conversant with the Sparx set up but would also think that the spacer No34 would be necessary as it sounds very much like a
clearance problem that you're experiencing
Jim |
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dollah52
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| posted on 6-25-2009 at 07:47 AM |
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Dear Matthew,
Do not use #34, it is meant for RM18 rotor which is slimmer. The Spark rotor is thicker (same as RM13), do not use #34.
When you tightened the rotor nut and another ring spanner on the other side of the flywheel, the alignment of the flywheel is out and when you rotate
the FW it is not that smooth. You need to align back the flywheel.
Use the copper rod as a punch, a hammer and set square. At the opening of the block, you use the set square (or small ruler) and check the alignment
of the flywheel, if it is not aligned properly, you tap the flywheel to straigten it. Tap it gently, definitely it will be smooth again. I had
experienced it before.
The best way to tighten the rotor just refer to the Haynes manual or search in the forum.
Regards,
Abdullah |
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T100
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| posted on 6-25-2009 at 08:18 AM |
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Good point, Abdullah.
Matthew, as Abdullah says, with a spanner at both ends of the crankshaft you are torquing the crank out of alignment.
Re true the crankshaft and then tighten the rotor nut by spragging the final drive sprocket - which means the clutch will need assembling.
Martyn
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Raggles39
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| posted on 6-25-2009 at 09:08 AM |
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Well done Abdullah - I forgot you had similar problem when you fitted your Sparx system
Martyn - spragging the final drive sprocket would be the best method thus preventing the truing problem with the flywheel
Jim |
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Matthew Manton
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| posted on 6-25-2009 at 10:52 AM |
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Thanks for all your great suggestions Guys, many thanks.
I just checked the fly wheel for alignment and it is bang on.
I will get the clutch together and then tighten the nut.
Cheers
Matthew |
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GBC
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| posted on 6-25-2009 at 02:39 PM |
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Spragging? Fits 'at? Is that like sticking a bit of wood between the primary chain and the bit sproketty thing around the clutch?
I'm sure sometimes you must despair of me! 
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t20c
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| posted on 6-25-2009 at 11:51 PM |
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'Spragging? Fits 'at? Is that like sticking a bit of wood between the primary chain and the bit sproketty thing around the clutch?'
Er I think so GBC, I think your description is more helpfull to people like me.
Mind standard mechanical practice dictates that the bit of wood will jump out just at the wrong moment and either hit you in the shin or break
sonthing in the garage. Beware.
Andreas
T20C
1958 T20c
1983 XJ550 x 2
1985 MT500 |
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T100
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| posted on 6-25-2009 at 11:55 PM |
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GBC - to sprag it means really just to stop it turning - anchor it fast.
The way to do it is to pass a gash length of chain around the sprocket and hold the spare length of chain VERY tightly by holding the loose end in a
vice or clamped to a long pole or wedged in a door jamb!
If the engine was in the bike then the sprocket could be "spragged" by putting the rear brake on.
It's just a means to tighten the crank nut by stopping the crank rotating and not putting a torque on the shaft - the clutch, gears and final drive
sprocket all being on the left will not transmit the turning effect through the crankshaft to the timing side.
Convoluted way of explaining a simple thing! 
It could be spragged as you suggest but you'd need a fairly hefty lump of wood which may not fit adequately twixt chain and clutch sprocket.
Martyn
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GBC
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| posted on 6-26-2009 at 01:04 AM |
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Ah, I see, thank you Martyn. I used the bit of wood method when I had to keep removing and replacing the rotor for various reasons. As you say,
works ok with the engine in the frame but if it had been on the bench I might have struggled.
T20C, I'm glad someone else knows what I'm on about, occasionally! 
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Matthew Manton
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| posted on 6-26-2009 at 09:22 AM |
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Hi Guys,
I have been fiddling around with this problem for a while and I am up a creek without a paddle, my canoe is sinking.
As you can see by the photo below I took the primary chain and rotor off. I then put a sleeve on, a bunch of washers and installed the nut on the
engine sprocket.
Even holding the sprocket with my hand and gently doing up the nut with my fingers I can feel the fly wheel rotation tighten up. The sprocket is not
fouling on the crankcase, plenty of clearance.
When I push the sprocket through the seal I can feel it bottom out on the bearing, I take it is supposed to bottom out on the main bearing? With out
tightening the nut it moves freely.
Anybody have any ideas?
I really do not want to split the crankcase.
Cheers
Matthew |
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t20c
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| posted on 6-26-2009 at 11:03 AM |
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Hi Matthew,
I assume you have replaced the bearings? are bothe the mains ball bearings?
If I remember correctly (it s a while since I had mine apart) the ball bearing mains press in from the inside of the crank case half, and it is the
shoulders on the crank which centre the crank against the inside edge of the mains.
The sprocket slides on the splines on the crank against the other side of the main bearing.
The sprocket and the shoulder on the crank should only cotact the main bearing at the centre ring ( the bit that turns).
Tightening the sprocket should only pull all the components together against this bit of the bearing and should not cause any problems like you are
having.......unless
The new bearings fitted are incorrect and the sprocket is somehow interfering with the cage part of the bearing.
or (more likley)
There is a small amount of lateral play betwwen the inside of the bearings and the crank shoulder. tightening the sprocket on is pulling the crank
slightly to one side. If the fit into the timing side bearing is realy tight it could cause the bearing to nip up. this could be made worse by
tightening the nut on the timing side although normaly the bearing would move a little in the crankcase half to accomodate.
I think the plain type of bearing alows for this movement and has a thrust face so if you have a plain bearing the above is wrong, as indeed id could
be anyway, but it might help.
Andreas
Andreas
T20C
1958 T20c
1983 XJ550 x 2
1985 MT500 |
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Matthew Manton
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| posted on 6-26-2009 at 11:20 AM |
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Thanks Andreas,
Installed new ball bearings, same type that came out.
Bit of an update:
Loosened off the timing gear nut and then tightened up the rotor nut, moved free as a bird. I snagged the setup using an old clutch bonded plate
bolted to a flat piece of steel.
Moved over to the other side and tightened the timing gear nut and the flywheel stiffens up. After tightening both nuts I could still rotate the
flywheel by hand using the rotor, but it definitely stiffens up as soon as I wrench up the final nut.
Matthew |
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Chris Foster
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| posted on 6-26-2009 at 12:17 PM |
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Hi Matthew,
A bit of a puzzler! Can you let the "team" know:-
- Did the crank turn freely before you commenced overhaul of engine?
- Has your engine a ballrace or plain bush timing side main bearing?
- Has the big end bearing been replaced during the overhaul and, if so, are you confident that the assembly has been pressed together correctly?
[didn't you have issue with piston skirt hitting flywheels --- any devious clues here?].
- are the crankcases a matching pair?
- is the oil seal behid crankshaft sprocket fitted correctly?
My gut feel is that crank incorrectly assembled or main bearings incorrectly fitted. Either way, I suspect you may have to split the crankcase to
check the basics. Hope I am wrong !
Chris |
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Matthew Manton
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| posted on 6-26-2009 at 12:36 PM |
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Hi Gang,
The engine has been completely been stripped down by me, it was a mess.
Answers:
- Did the crank turn freely before you commenced overhaul of engine?
No piston was seized in barrel.
- Has your engine a ballrace or plain bush timing side main bearing?
Ball race
- Has the big end bearing been replaced during the overhaul and, if so, are you confident that the assembly has been pressed together correctly?
[didn't you have issue with piston skirt hitting flywheels --- any devious clues here?].
Big end bearing has been replaced. Confident I assembled everything correctly, checked alignment of flywheel halves.
Pistons are fixed now, but do not have them assembled to the crankssaht.
- are the crankcases a matching pair?
Yes
- is the oil seal behid crankshaft sprocket fitted correctly?
Yes
I will sleep on for a bit before I spilt the crankcases.
Cheers
Matthew |
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Raggles39
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| posted on 6-26-2009 at 01:24 PM |
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Hi Matthew
I tend to agree with Chris that you will have to split the crankcase halves and re examine everything
You mention that the engine was seized - just wondering if the crankshaft isn't true and has been slightly bent owing to the seizure
I would also check the thickness of the new bearings against the old ones if you haven't already done so as so many aftermarket parts don't measure
up
Jim |
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Matthew Manton
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| posted on 6-26-2009 at 05:51 PM |
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New bearings, same as the old guys. New con rod.
Did a bang up job on truing up the flywheel.
Splitsville next week.
Cheers
Matthew |
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t20c
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| posted on 6-27-2009 at 12:21 AM |
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I agree with the guys, as it turns ok when only the rotor side is tightened it sugests that all is ok on that side, if tightening the timing side nut
stiffens rotation either that action is trying to move the bearing inover or the crank out over putting lateral pressure on the bearings which is not
good for deep groove ball races.
was there any kind of shim/washer between the bearing and crank journal shoulder when you took it all apart???
Usualy ball races are made to exact tolerances and if your crank was out of true you would hace great dificulty assembeing the crank case halves, so i
would be inclined to rule that out.
Think you need to split the crank case.
I might be an Idea for diagnosis only to nip up the timing ste nut until it stifens the crank, and then tap that nut with a hammer, if the crank frees
(ie the bearing moves) you need some sort of shim. If not time for yet another re think!!
Andreas
Andreas
T20C
1958 T20c
1983 XJ550 x 2
1985 MT500 |
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Matthew Manton
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| posted on 6-27-2009 at 04:44 AM |
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Thanks Andreas.
On Monday I will split the cases and investigate.
Cheers
Matthew |
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Matthew Manton
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| posted on 6-29-2009 at 01:04 PM |
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Hi Guys,
Spent all day getting the crankcase split and tried to figure out my problem concerning the flywheel rotation stiffening up when I tighten the nuts on
either end of the crankshaft.
Spent a lot of time staring at the problem hoping for divine intervention but nothing happened.
Checked the bearings were correctly seated in both the left and right crankcase and everything seemed fine, checked the alignment of the flywheel as
per the Triumph manual and every thing looked good.
The only problem I could determine is this:
The bronze drive gear slides up the shaft followed by the timing pinion and seats on the shaft shoulder shown below. The nut can then be tightened
and every thing is fine, free movement of the flywheel. The shoulder of the shaft protrudes above the crankcase face so the bronze drive gear bears
down on the shaft not the crankcase, how it should be I believe.
Move over to the other side of the crankcase and tighten the nut and what happens is the shaft shoulder (shown below) disappears up the hole and now
the bronze gear fouls the crankcase face as shown below.
Do you have any ideas on how to fix this problem? A shim seems a bit of a bodge?
Its and adventure if I say the enough times to myself I will be
fine.
Cheers
Matthew |
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T100
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| posted on 6-30-2009 at 12:26 AM |
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A simple solution would be to "shim" the bronze gear from the crankcase to obtain clearance. Not a pukka Triumph item but so what?
Is the drive side bearing the correct size? If the bearing was a few thou narrower, thereby allowing the whole crank to be pulled to the left as the
nut is tightened, it would have the same effect that you experience.
There is obviously some discrepancy in the dimensions of shaft, bearing, bronze drive gear or anything associated with these items.
You can either make the bits you have fit, or change the bits that are out of spec. The problem is in determining which bits are which!
If I was faced with this dilemma then I'd look at the easiest and cost effective solution.
To me, the answer would be to "shim" the bronze drive gear away from the crankcase where it fouls. A suitably sized washer or distance piece would
suffice.
Good luck..........
Martyn
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ronmcl
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| posted on 6-30-2009 at 12:34 AM |
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Are the crankcases mating properly? Are you fitting a gasket between them? - if so remove it.
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t20c
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| posted on 6-30-2009 at 01:40 AM |
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Good to see you are making progress, I would do as ronmcl suggests, once cases are checked / gasget removed if the problem persists I would fit a shim
washer on the most apropriate side for ease of opeation.
Andreas
Andreas
T20C
1958 T20c
1983 XJ550 x 2
1985 MT500 |
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Chris Foster
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| posted on 6-30-2009 at 03:45 AM |
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I would be wary of shimming until you understand just what is going on ---- you don't want to end up with skew gear incorrectly meshing with skew on
oil pump drive or some messy chewing may occur!
I very much doubt if this problem is a one off so would be tempted to Email the symptoms to Mike Estall to see if he has any relevant experience.
Also, a phone call to Derek at Greystones may be worthwhile.
To rule out the changes made by fitting Sparx rotor, spacers etc as the cause, have you tried refitting the original items to see if problem
persists?
Just looked at photo again ---- notice oil pump shaft and camshaft drive pinion not fitted. If they were, would the skew gear be held clear of
crankcase?? Just a wild thought. |
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