T140 E Ignition timing

[brooksy]

Hi,
This is my first post. I stumbled on this brilliant website whilst trying to solve a problem with my 1978 Triumph T140E. I have looked at the other posts which don't answer my question. I am reassembling the engine and am about to do the ignition timing. I have located the notch (slot) on the crankshaft but this appears in the crank case breather hole at the back, when the the pistons are at the bottom. Is this right? and if so how do I time the ignition using this method when the pistons are down at BDC.

Grateful for any help.

Brooksy

Broosy

[L.A.B.]

I have located the notch (slot) on the crankshaft but this appears in the crank case breather hole at the back, when the the pistons are at the bottom. Is this right? and if so how do I time the ignition using this method when the pistons are down at BDC.

Hello Brooksy

I own a 1978 model, and something is definitely not right there if you are finding a slot near BDC?

If what you are describing as a breather hole is the timing hole in the top of the crankcase, then you should find two slots in the crank, one at TDC, and the other at 38 degrees BTDC.

With the crankshaft set to the 38 degree slot the timing indicator pointer in the primary case window should align with the rotor timing mark. Note that there should be two rotor timing marks 180 degrees apart and the one near BDC can be ignored.

The hexagon seen in the photo below is the removable plug for the timing hole.

[L.A.B.]

Timing tool:

[L.A.B.]

This is where the crankshaft flywheel slots should be in relation to the crankshaft. If the slots are elsewhere then possibly somebody has removed the flywheel and replaced it at the [size=16]wrong position[/size] on the crankshaft:

If so, then it would certainly not be wise to attempt to run the engine as the crankshaft assembly will be totally out of balance.

[L.A.B.]

Another view showing the slots more clearly:

[brooksy]

L.A.B,

First of all thank you for your assistance. I have just been and looked again following your comprehensive information, for which I am very grateful. I have located the 2nd slot however, the pistons are still at bdc on the compression stroke (inlet valve just closed). The bike was a runner when I bought it and has a Boyer mk3 fitted. The reason I called this a breather is because it has a breather fitted through a bolt which extends into a tube with a hose on. I guess that's not correct so I'll get the right bolt.  The thing that confuses me most is that the bike was a runner when I bought it. Apart from some really bad oil leaks it. Could I time it from the pistons with a dti and timing disk and disregard these marks.

Thanks for your help.

[L.A.B.]

The reason I called this a breather is because it has a breather fitted through a bolt which extends into a tube with a hose on.

I have seen this modification, normally the T140 breathes through the open drive side bearing into the primary case.

Has the primary been close off from the engine crankcase with a seal?

Has it got a belt primary drive, as that would explain why the primary case might have been isolated from the engine, and the timing hole breather modification done?

 If so, then you need to leave that breather where it is and an "extra" breather won't do any harm anyway.    

The thing that confuses me most is that the bike was a runner when I bought it. Apart from some really bad oil leaks it. Could I time it from the pistons with a dti and timing disk and disregard these marks.

Yes you could check it with a timing disc.
The alternator rotor timing mark should at least line up with the pointer at 38 deg BTDC regardless of the crank slot positions? Have you checked that?  

If it was a runner before, then it could be OK I don't know? Possibly somebody has done some modifications to the engine, but if the flywheel has just been bolted back (120 deg.) out of position I'd think there would be some serious vibration problems.

[brooksy]

L.A.B,

Yes it did have a belt drive fitted although I changed it a few years ago. (The bike was owned by a work colleague for about 10 years before I bought it from him). The rotor lines up at 38 degrees btdc, it was just the crank marks that fooled me. The motor didn't vibrate at all before  which really surprises me now. Just goes to show you don't know what you are getting.  If I had known before I put it back together, I might have done something about it. I'll see if it runs next.

Thanks for your assistance.

Brooksy

[L.A.B.]

If its been running as you've said, then I suppose it's OK as it is.

Oh well, that's a mystery that may only be solved by getting a look at the crankshaft, or by speaking to the previous owner, if he's still around?