29 replies to this topic

[b80ven]

Hi all,

I have recently had issues starting and have put all the blame on the timing. The starter motor was playing up to a point where it needed a complete overhaul. my best guess is that it was trying to fire as the pistons were still coming up (way too advanced), hence the problem with the starter motor.

After finding what seemed to be the TDC mark on the flywheel, and putting a nice fat white line, I was unable to find it using a strobe light when the engine was running. Would anybody have any pictures of the actual TDC notch on their flywheel so I have something to compare with ?

I understand different Mini's run at different angles in regards to firing (°BTDC) so for a bit of background, my mini is a 1100S block on a 1275GT engine, not sure what the serial is on the distributor. According to the Haynes manual, 1275 GT engines run at 10°BTDC, which would explain why I couldn't see the notch during running. I have no timing marks either, which doesn't help me when doing the timing..

If anybody could tell me how many mm's 10° is equivalent to, in regards to distance on the flywheel, I would appreciate it.

B

[jagman.2003]

Just a quick comment as I was passing by, may not be exactly what your after. It is possible to have the distributor drive 180 degrees out & still run. Might be worth a look.

[lrostoke]

 timingearl.bmp   675.99K   123 downloads

This is the picture from Haynes.

Have you tried following

Turn the engine until No 1 piston is at the top, can check this through the spark plug hole...No 1 being furthest right plug.
Then check the valve rockers...If you can wiggle both rockers then that is approx TDC and you should see the mark through the inspection hole.
if you can't wiggle the rockers you need turn the crank another full turn

Also you rotor arm should be pointing to roughly a 2 oclock position

Edited by lrostoke, 28 June 2012 - 08:10 AM.

[b80ven]

Jagman - nope, distributor is definitely not 180° out, rotor is pointing to #1Lcylinder.
Steve / LROStoke / Not IROStoke - I haven't taken the rocker cover off to see that both inlet and exhaust valves are open but as stated above, rotor is pointing to #1 cylinder.
The notch shown in the picture looks identical, where the notch is fairly long, vertically. I just don't have the '1 4' mark, or any other numbering shown for that matter. So I can't determine my angle. Currently, I've done the static timing, where the coil is just about to fire at TDC (not BTDC).

[Ethel]

Flywheels off later cars, with marks on the crank pulley, may not have flywheel markings as well - they'll also be lost if the fly has been lightened. If they are there, they'll be above one of the diaphragm bolts. TDC is the same for 1 & 4, don't confuse yourself with the camshaft / dizzy - they turn at half the speed. Even if you are 180 degrees out with them, the crank will have done a full lap back to TDC.

I can't help with the mm to degrees bit, you might get an idea from the starter ring gear, 107 teeth inertia - 129 for pre engaged. Dividing 360 by those gives 3ish degrees per tooth. Alternatively stick a protactor on the crank pulley, there are several online to download & print & a CD is a good size to stick one to.

[b80ven]

Thanks Ethel,
Not sure what kind of flywheel I have, apparently it is a competition one so yes, perhaps it has been lightened.
Yes, there is a bolt I can see, with what looks like a wedge in the shape of an up arrow, which is different to where my notch cutout is..
ahhh, ok that makes sense. The BMC A-series engine, being a 2 x 2 cylinder engine, rather than a 4 cylinder, #1 and #4 is at TDC exactly the same time ? That explains the '1 4' marking.
agreed, dizzy turns half the rate of the engine.

[Ethel]

It'd be the same on any 4 inline. Is "A" on the diaphragm (inside the rim around the bolt head)? It's an alignment mark to match the diaphragm to the back plate, for balance. I think that makes yours pre-Verto, the clutch arm and slave cylinder location are a bigger give away.

[b80ven]

I don't know if "A" is inside the rim around the bolt head. That's about as far as my knowledge of the parts inside goes.

[lrostoke]

Alternatively you could just start the car and advance the dizzy untill you have the highest revs...then retard it slightly till the revs drop a bit..and test run it.
If you get pinking then back off a little more.

Any factory timing figures will be for old leaded fuel and unmodified engines fresh out the box.

[bmcecosse]

Forget the flywheel and the strobe - kicking against the starter indicates FAR too far advanced timing - take it back till it does not kick. But the fact you were running that much advance suggests other problems inside the dizzy - mechanical advance stuck or vacuum advance failed.

[b80ven]

thanks BMC. Yeh I agree it must have been too advanced. using the strobe is proving to be impossible. It wasn't running well at all today.
This is the technique I used for static timing prior to using the strobe:
http://home.mindspri...taticTiming.pdf

I took photos of the notch mentioned above and of the clutch arm for you to assess Ethel, not sure how to include them here.

ON a different note, and i'm not sure if this is the right section, but i'll include it here anyway. Technique of adjusting mixture on a HS6 carburettor. When adjusting the mixture, I'm basically pressing the lever which brings the piston up slightly, and I've been listening to whether the revs drop (which indicates too lean a mixture), or if the revs rise (which indicates too rich) - can anybody confirm that this is the correct way of adjusting mixture ? Taking the air filter off, it turned out when I raised the piston by hand, the change in revs were more noticable. What is the recommended method ?

The exhaust is sounding louder than normal. I think, actually, I know, I have a crack in my 2nd cylinder. Taking the spark plug out, I see green drops of my coolant!
This explains why I haven't been able to tune it, why it's been running like a dog, and why when it's cold, I get excess smoke, which dies down completely when warm.. Is this a common problem on A-series engines, and is it repairable ?

sorry for all the questions in this one post. it's been a rough day with my Mini.. SO FRUSTRATED!

[b80ven]

well, here are a couple of photos.
the notch appears to have a smaller circular notch also etched fairly close to the bigger one.
BMC - i'll take your comment on board, if it is a lightened flywheel, my strobe will never work as the notch will be incorrect anyway..

 notch.JPG   45.18K   40 downloads

 clutch arm.JPG   35.99K   27 downloads

[b80ven]

lrostoke - regarding your comment about advancing until reaching the highest revs. This is fairly difficult because each time you adjust the timing, the mixture and the idling point needs to change as the vacuum created in the cylinders changes. I can't see how this will work unless you keep adjusting the mixture and idling at each point.

[Ethel]

don't think that's a timing mark.

[b80ven]

no, neither do I, so my dilemma, how do I find true TDC ?