Square 4 MKI - more troubles

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simon.holyfield
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Re: Square 4 MKI - more troubles

Postby simon.holyfield » Sun May 10, 2020 7:45 pm

Check the tap seal has not swelled and partially blocked the flow - I've seen that on one of those taps..

I use a single stage ewarts tap with cork seals on mine. A few years ago, when I had a rather restricted flow path, mine was very sensitive to fuel level as well.

Sounds like you are on the right track.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
http://ariel-square-four.blogspot.com

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Re: Square 4 MKI - more troubles

Postby john.bebb » Mon May 11, 2020 10:24 am

Hi Peoples, - the comments string seems convinced the issue is fuel flow - so a few thoughts; - whilst faffing around with the "plumbing"
1/ Have you checked that the tank is able to breathe? - I have not had the problem specifically on my Square; - but I recall a Tiger Cub from longtime past which would run perfect for ages... then cough & choke until I took the filler cap off - then back to perfect...
It doesn't matter how clear the tap & fuel lines may seem - if air can't get in too well then likewise the fuel don't come out so good!
2/ Have you had the fuel tap out of the tank? - some of these are fitted with a mesh filter which cannot be observed whilst the tap is fitted... maybes worth a check.
3/ Fully support the filter in the (clear) fuel line ideas - the bottom of the "U" in the tube should be below the float bowl lowest point.
4/ Water in the fuel? water globules can cause havoc in float bowls - fond memories of Beemer's Bing CV with the QD sprung wire clip, also certain Amals with a screwed side plate - however, not so QD on a Square's Solex (I run my Sq. with an Amal 626).
5/ Assuming it is original - your tank is over 60 yrs old - surely some corrosion on the inside - so when was last flushed?
(If it is a "made in India" copy - then a/ heaven knows what is inside, & b/ congratulations on getting it to fit!).
Cheers, John

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Re: Square 4 MKI - more troubles

Postby Gui.dorey » Mon May 11, 2020 12:16 pm

john.bebb wrote:Hi Peoples, - the comments string seems convinced the issue is fuel flow - so a few thoughts; - whilst faffing around with the "plumbing"
1/ Have you checked that the tank is able to breathe? - I have not had the problem specifically on my Square; - but I recall a Tiger Cub from longtime past which would run perfect for ages... then cough & choke until I took the filler cap off - then back to perfect...
It doesn't matter how clear the tap & fuel lines may seem - if air can't get in too well then likewise the fuel don't come out so good!
2/ Have you had the fuel tap out of the tank? - some of these are fitted with a mesh filter which cannot be observed whilst the tap is fitted... maybes worth a check.
3/ Fully support the filter in the (clear) fuel line ideas - the bottom of the "U" in the tube should be below the float bowl lowest point.
4/ Water in the fuel? water globules can cause havoc in float bowls - fond memories of Beemer's Bing CV with the QD sprung wire clip, also certain Amals with a screwed side plate - however, not so QD on a Square's Solex (I run my Sq. with an Amal 626).
5/ Assuming it is original - your tank is over 60 yrs old - surely some corrosion on the inside - so when was last flushed?
(If it is a "made in India" copy - then a/ heaven knows what is inside, & b/ congratulations on getting it to fit!).
Cheers, John


Hi John,
All valid points and worth checking with problems like this. In my case:
1) yes, one of the first checks I did and the breather on the filler cap is free.
2) Yes and as described on my previous post there was some debris on the bottom part of the mesh. This seems to match the rest of the symptoms - lower petrol level and likely blocking the flow.
3) Bottom of the U is below the bowl's lowest point.
4) It's fresh petrol.
5) it's an original tank. It was flushed and cleaned last year. There is still some debris left as shown by the by point 2, and might have been dislodged with all the disassembly/assembly in the past 2 weeks.

We'll see if it's sorted now with this last cleaning of the whole system...

Cheers,
Gui

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Re: Square 4 MKI - more troubles

Postby john.whiting » Tue May 12, 2020 4:51 am

When I bought my first Sq4,I had no car ,and no licence (wasnt old enough).....and it conked out after about 15 miles on the way home .....I went to remove the fuel pipe ,it was a sort of braided wire stuff,anyway ,soon as I touched a spanner to the nut,the pipe lining broke apart ,and petrol went everywhere.....I propped the bike up against a fence ,and walked and hitch hiked home ...The bike was left leaning on a fence for a few days ,when I got a phone call from the ex owner ...still had the plates on it ,and the cops had been to see them about dumping the bike .....Anyway ,I got a lift back by fibbing about how far it was ,and got it fixed and rode home ,breaking down about every five miles.,with rust from the tank.

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Re: Square 4 MKI - more troubles

Postby Gui.dorey » Wed May 13, 2020 5:09 pm

Well, managed to do a short ride today, and I'm happy to report that the problem seems to be solved. The Square 4 ran smoothly so the cause was apparently indeed the partly blocked mesh on the petrol tap.

I didn't try a high speed run, as I 'm still bedding her in, therefore can't say how the power is at higher rpm's. There was a missfire here and there on top gear, but very sporadic, and I'm not sure what could be causing it. Since the jets on the carburetter are fixed and the mixture can't be adjusted at higher throttle openings, I'm ruling out a too poor or too rich mixture for now. Could be the timing a bit off, so I'll have to still fettle a bit before I 'm happy. Ideas and experiences with tuning the MKI are always welcome.

Tick over is smooth and stable, and I turned the pilot screw another half turn out (now at 2 1/2 turns out - too rich, maybe?) and the throttle stop a tad out as well (slower idle speed).

Thanks again for all the helpful comments and suggestions.

Cheers,
Gui

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Re: Square 4 MKI - more troubles

Postby simon.holyfield » Wed May 13, 2020 5:40 pm

Have you got the boot on the distributor Gui? I ran without one for a while, and coupled with a fibre washer on the rocker box oil inlet I (eventually) found oil in the HT pots on top of the distributor, which caused a sporadic high speed misfire.

Copper washer and heat-shrink boot fitted and all is well.
cheers

Simes

'51 Square Four,
'58 Huntmaster,
'42 W/NG,
'30 Model A
http://ariel-square-four.blogspot.com

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Re: Square 4 MKI - more troubles

Postby Gui.dorey » Thu May 14, 2020 5:23 pm

I don't have a boot on the distributor, but I do have a copper washer on the rocker box inlet. I just checked the distributor and all the HT pots, and everything was clean and dry.

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Re: Square 4 MKI - more troubles

Postby john.bebb » Fri May 15, 2020 11:16 am

Hi Gui, -
Glad matters seem to have improved - the odd misfire is unlikely to be fuel/air induced - far more probable is to be something "not quite right" in the electrickery department...
Please; - what ignition system is involved? - the original 6V dyno, CVC box, batt and points & capacitor or something a bit more modern?
Are ALL HT leads really secure at all their ends?... is the coil casing reliably earthed?... are the screws in the terminals of the headlamp switch all secure - and clamping more than just a wire strand or two? (when I'm happy with such I apply a dob of Si RTV - giving water & dirt seal & vibration proof but easyish to remove for service/rework)... what suppressor caps are being used?, are the plug ferrules tight?
Perhaps take it for a run at night - on unlit roads - (preferably with a pillion) - such may make HT leads tracking more obvious...
Final query; - does misfire become more noticable if riding in the rain?
I know - loads of questions... more to maybes follow when I'm aware of your electrics set-up!
Cheers, John

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Re: Square 4 MKI - more troubles

Postby Gui.dorey » Sat May 16, 2020 11:29 am

Hi John,
All is possible, but I 'm reasonably sure the electrics are in good order. The wire harness is new, and I triple checked everything during the rebuild - all connections, good ground, etc.

I'm using a Thorspark electronic ignition with a new coil and converted to a 12V system with an alternator from Ironhorse Spares. I just rechecked all the HT leads, and everything is clean, tight and secure. I have no supressor caps and the plug caps are tight. I also only ride in dry weather so she hasn't seen any rain or humidity.

It really feels like an ignition timing or mixture issue, but I'll have to experiment some more. It only happens at higher rpms, when accelerating or cruising along. By higher rpms I mean mid range, as I haven't tried full open throttle yet being in the break in stages. Could be that my advance mechanism isn't advancing as it should, but I 'm not really sure how to check it or test it. Could just be that my ignition timing is too advanced or retarded, but also not sure which exactly, that would cause this.

Cheers

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Re: Square 4 MKI - more troubles

Postby Paul_Linden » Sat May 16, 2020 1:05 pm

When I had the same symptoms on my Square 4 it was a spark plug that had come slightly loose.
Ariel Square 4 mk2, Ariel Square 4 mk3 (yes, really), Ariel Colt, Matchless G12, BSA C12. Room for one more......


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