Sq4 stopping after oly a short run.

[Mikeoceans]

Hi,
I thought that I would see if you guys have any suggestions. My Square4 will start really easily seems to run fine comes up to temp good oil pressure. New 6 volt coil, points, condenser, cap and leads etc. The carb was striped and rebuilt with new kit from SU. The vacum throttle valve was checked and cleaned. Fresh oil in the top.
It just stops. You have to wait for it to cool down. Then it starts up again. I'm a little bit lost on this one.
Has anyone had similar experience?
Cheers Mike

[Gui.dorey]

Check for debris clogging up your petrol tap. Especially the filter gauze inside of the petrol tank. That is just one of many possibilities…

[will_curry]

Lots of questions:

Did you replace the electrics in an attempt to fix the problem?

Does it cut out at a steady throttle opening or when slowing down or what?

Does it splutter or does it quit completely as if you'd turned the ignition off?

How much oil did you put in the top of the SU?

My first thought for what it's worth is that the coil is breaking down - have you checked
to see if there is a spark when it's cut out?

Finally, welcome to the forum.

[allan.walker]

When it stops, have you tried removing the petrol tank filler cap?
Sometimes, if there is no/insufficient venting, a partial vacuum occurs which stops the fuel flowing.

[paul.jameson]

I have had similar issues, although with misfiring rather than cutting out completely, due to problems in the low tension part of the ignition system. Check that the distributor baseplate isn't cracked and that the stud coming out of the side of the distributor is still soldered into the strap which runs round the inside of the distributor. Check also the connection of the wire to the terminal which screws onto the stud externally.

Did you replace the rotor arm?

[Mikeoceans]

Hi many thanks for all your suggestions.
I haven't been able to drive as I had a brain tumor a few years back. My wife tells me it cuts out when you're throttling back. I.e Coming into a round about.
I'll check the petrol tank vacuum. That could be a go. . I did think about the coil breaking down, hence the new one. But alas no. Yes I replaced the rotor, cap, Leeds, plugs. Even bought another distributor and dynamo had it check for a spare if need be. I will check the wiring in the distributor again though.
I just seems really strange. Last year it worked really well. I was in the side car

SQ4 idling

20220609_145220.mp4

SQ4 this year

(47.16 MiB) Downloaded 25 times

[will_curry]

What a lovely sidecar outfit. The front brake is more than a bit special too.

Cutting out like that suggests to me that there is a carburettor issue - especially
if it's been standing for a while with fuel in it and especially too if the fuel is
the E5 or E10 variety.

[klaus gerhard]

The sidecar seems to be a Steib S 500 (or similar typ). Very nice!

[Mikeoceans]

Hi yes,
The sidecar is a Stieb.very compatible...... when th bike goes!

[allan.walker]

The Rodark panniers blend-in nicely.
Also...that front brake...wow!! That should deal with the extra weight of the Steib!