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Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 9:07 am
by Gui.dorey
Hi there everyone,

I've finally finished rebuilding my Square Four from a basket case - only possible with a lot of help from all of you here in the forum. Many thanks for that!

This weekend I did the first start attempt, and she starts briefly for a few seconds and goes out. It almost seems she floods because afterwards she gives me no signs of wanting to start again. Taking the plugs out they are a bit wet, I then turn the engine a few times to clear it, do another attempt, she fires briefly and goes out. The engine is still very tight, and after a while I give up, as there's no strength left to kick it further.

My settings for starting are:
Bi starter pulled all the way out
Throttle fully shut
Ign on
And kick away

Any advice on what to check or adjust for the first start? I have a solex carburetter. How many turns out does one set the air screw? Is there anything else one can adjust on the carb?

Cheers
Gui
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PS for the one who followed my latest tribulations, in the end I had to purchase a new head. The head that came with the bike had been indeed skimmed down by the previous owner. He took out so much that I was missing 3-4mm which was why I had no valve gap left.... fortunately I was able to find a head I could use from a member of the Danish AOMCC.

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 10:42 am
by simon.holyfield
Congratulations Gui, you are almost there. Now the riding & fettling fun begins.

Be wary of the bistarter after the winter cold is gone. If my bike is stone cold, maximum two kicks on the "full" position will see it start - but any more kicks and it will flood. It goes on to the "half" position as soon as the engine runs. It's much more difficult with a stiff new engine.

Idle screw - 1.5 turns out, with one fibre washer under the float valve. I am currently testing two fibre washers under the float valve, and the bike performs much more cleanly at low speed with the idle screw 2 turns out.

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 10:45 am
by simon.holyfield
By the way, do you have a small front wheel? The mudguard looks very high at the front.

Here's a picture I took yesterday:

IMG_20190426_105242.jpg


I've still got the KH tank fitted.

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 11:42 am
by Gui.dorey
Thanks Simes,

I'll try that. I had the air screw 3 turns out. I'll also try the washer under the float valve. Silly question,but how do you attach the washer under the float valve? The top of the float has a dimple where it pushes the small valve rod... I'm probably just missing the picture.... the idea is to shut the petrol supply earlier, right?

Yes my front mudguard looks strange. I have a 19" wheel so it should be correct, but whatever I tried the mudguard seems to be angled backwards. Of course the front suspension is still high up as it hasn't been touched after assembly. I expect it will settle somewhat after the first ride,but it won't cure the strange appearance I'm afraid.

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 12:08 pm
by simon.holyfield
When I say under the float valve, I mean between the float valve and the carburetter top - to the valve closes with the float lower, drops the fuel level and weakens the mixture. Be careful though, you don't want to weaken it too much.

What about if I measure my stays and compare them with yours? We can also look at how your front stand is fitted to the guard.

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 1:05 pm
by Gui.dorey
Got it :).
There was a fibre washer already under there, but I added a second one just to try it out.

The front stays measure about 29mm from the fastner‘s centres. Here‘s a pic of the front stand‘s attachment. However the angle of the mudguard is set by the center stay beween the fork legs isn‘t it?

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 1:11 pm
by chris.shearwood
Gui.dorey wrote: do another attempt, she fires briefly and goes out.


Hello Gui,
Your bike looks good - don't get discouraged, it is going to start eventually. You don't have your timing set 180° out do you?
Regards, Chris

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 2:55 pm
by Gui.dorey
Hi Chris,
I don‘t think so. Triple checked the timing and all that, but I‘ll recheck if nothing else works. Anyway, if the timing was off 180deg, would she even fire up and run a few seconds?

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 8:34 pm
by paul.jameson
Try pulling the bi-starter fully out then depressing the kick start until all four cylinders have gone over compression once with the ignition off. Move the bi-starter to half way out, turn the ignition on and kick to try and start the bike. When she starts, open the throttle and push the bi-starter right in.

Re: Square Four MkI restoration complete - almost....

Posted: Sun Apr 28, 2019 8:39 pm
by simon.holyfield
My bike will go off the bistarter completely after about a minute in this weather. Idle screw 2 turns out.