Mk1 Sq 4

[T.J.Falloon]

Hello again all,

Thought I would give you a bit of an update on my Mk1.
If you may recall I have been having issues with my head gasket blowing and some carb problems.

Thanks to the assistance of various people on this forum I have now hopefully manage to sort the above mentioned issues out and have now completed around 400 wonderful miles on the old girl.

I have however had two minor issues arise, firstly: quite a bad vibration from the rear wheel. I suspected an out of balance wheel but when I took the wheel to my tyre specialist to balance, he said the rim was not running true. So have taken the wheel to have the rim trued, so hopefully that will fix that.

Secondly: The bike starts first time every time and is running perfectly, pulls well etc, but ( there's always a but ) I have noticed that when she gets hot after a longer ride , say about 30 miles, the motor has a tendency to pink / ping ( what ever you want to call it ) down low or under load in a higher gear, indicating to me slightly advanced timing. Not all the time but often enough to be annoying.
I have checked and rechecked my valve timing and checked and rechecked my ignition timing. Both are correct. With the ignition timing I have set it up statically using a simple 6v light set up across the points to show when points are opening. They are opening just before TDC. On the MK 1 timing is supposed to be set at TDC. If I try to retime the distributor by retarding it a tooth then it's way out.
I am running slightly higher compression pistons. I have spoken to Gui who has the same pistons and he has said he hasn't had any pinking / pinging issues with his bike.
As always any assistance appreciated.
Cheers.
T.J

[simon.holyfield]

Congratulations T.J., sounds like you are almost there.

Couple of questions: what plugs are you using? Secondly, I assume that you are unable to adjust the timing by moving the distributor in its clamp, rather than moving it a whole tooth?

[will_curry]

For any engine the more you increase the compression the less ignition advance you need.

Most Mk1 Square 4s will have had both head and block skimmed by now which pushes up the
compression as well as fitting high compression pistons.

Another issue can be the centrifugal advance mechanism in the distributor. Weak springs allow
it to advance too quickly and the wrong action plate allows it to advance too much.

[Gui.dorey]

TJ,
All good points here. What bothers me is that you said when you retard the ignition (by turning the head, not a tooth) there is no change. There should be a change, unless something else is wrong - wrong or weak springs or springs in the wrong slots on your automatic advance.

You could always try a strobe light to see where the timing goes when at higher rpms. It’s messy but doable.

[T.J.Falloon]

Hey everyone, thanks for your replies, I appreciate you taking the time to respond.
Simon, yes I can adjust the timing on the distributor by releasing the clamp, however the amount of adjustment is minimal. I have it set as far retarded as it will go. I do get a change in engine revs / running when I rotate it.
I am using NGK B7HS, I was originally running B6HS.
Will, I hadn't considered that, I have made sure it is free and working but have not checked spring tensions etc, so will definitely look into that. Is there an easy way to check if the wrong action plate is fitted/ what should the correct one look like?
Gui;
I can adjust the timing on the distributor by undoing the clamp however the amount of adjustment is minimal and I do get a change in revs etc when the distributor is moved. Will try the strobe light and see what happens as well.
Waiting for my rear wheel to return from being trued up before I attempt to start her back up again.
Thanks again for all your assistance, appreciate it.

[simon.holyfield]

On the timing adjustment - yes, it's very tight with the condenser towards the rear. My oil tank has a fairly uniform depression across the front which may increase distributor movement, and I have also deliberately pushed it backwards as far as it will go. I have considered mounting the condenser outboard to get more adjustment, just haven't needed to.

I'm surprised at your cold plugs! I've used B6HS and B5HS. I currently have W8BC Bosch plugs in it.

[roland robinson]

T.J.
You say that when you slacken the distributor clamp bolt you only get minimal movement on the distributor body. Myself, and obviously others, do not understand this because this as full 360 degree rotation of of the distributor body is now available though of course not required in this case. Please confirm that we are all referring to the same clamp bolt.

[T.J.Falloon]

Hi Roland,
I have loosened the clamp bolt on the side of the distributor, and only get a small range of movement, not sure why. I would have thought, like you, that there should be more of a range. Not sure what's going on.
Will have to look further into this. I have tried to upload a video of the range of movement but when I checked it after uploading the post says that the video won't play as it is unsupported, so I deleted the video.

[T.J.Falloon]

Hello again folks,

Well the mystery has been solved as to why I was getting limited distributor adjustment. Put simply I was being stupid, and I am feeling somewhat embarrassed to say so.
I went out into the garage and reset the bike back up firing #1, then proceeded to pull the distributor out. In doing so noticed another bolt below where the distributor sits. Once the distributor was removed I checked to see where this bolt went. Low and behold it went into the tunnel where the distributor fits. I checked on the distributor and saw there was a small flat with a bolt end impression on it. That's when the light bulb went on, I realised that this must be a secondary way of locking the distributor using the small flat located on the side of the shaft.
So armed with this knowledge I once again reset the timing, using a dial gauge test indicator to show TDC. Inserted the distributor with rotor in correct location for #1 lead, loosened the secondary retaining bolt and popped the distributor back in.
Checked the timing statically with the light bulb again noting that I can now get a full range of movement on the distributor when I rotate it. Once satisfied with the timing locked everything up, then kicked her into life. She started first kick and sounded wonderful. Didn't run her very long as I still have the rear wheel out to be re-trued. Hopefully now all will be right.

[simon.holyfield]

That 'secondary bolt' should be very short - it's just a plug. There used to be an oiler in that hole.

Someone will tell us when it was deleted.