Break-in notes (4G Square - 1937 engine)

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Akumar
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Break-in notes (4G Square - 1937 engine)

Postby Akumar » Mon Aug 15, 2016 6:16 am

Dear fellow enthusiasts,

I created a new thread as the title of the old thread was bit outdated and not very informative.

For those of you reading my thread first time, it is a Square with 1937 4G engine in a 1948 tele/rigid frame. I did a total rebuild on the bike with new liners, new set of standard pistons (IMD), new valves and guides, old con rods, and rebuilt bottom end.

I did 150 miles (short 8 to 10 miles runs at one time). Then a week ago, I was taking the bike to my friend’s home for first re-torque. On my way, after about 8 miles, the engine stalled suddenly. I tried kicking it but it will not start. It started only with the bi-starter pulled halfway out. The engine was free with no smoke, fire, or undue noise. I hauled the bike to my friend’s home on a trailer.

I have some interesting updates from this weekend’s work.

Firstly (and apparently) the left-side rear spark plug connector was loose. It appears that cylinder was not firing all the time. At this point, it is just a guess based on oil found in that cylinder and a thick carbon build on the spark plug tip. The other 3 spark plugs appear healthy.

Secondly, the Solex float has a dent/depression where needle seats (You may remember my previous post that the carb starts leaking the moment you turn the petcocks on. The leak disappears once the engine is started and running). Could that probably mean the bike was running rich at idling (or even at low revs)?

Could that also be the cause of noticeable smoke (more so from the left side) when the bike is idling? I have already done about 150 miles so far. I am not sure if there is a cause for concern here.

I have requested David Jones to send me a new float. I should have it soon and will work on the carb next.

What I still do not understand is why the engine stalled on the road last week?

Kumar

Ariel Square Four 1937 4G.jpg
48' SQ4, 53' VB, 51' NH

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Re: Break-in notes (4G Square - 1937 engine)

Postby paul.jameson » Tue Aug 16, 2016 9:03 pm

There should be a small circular dent where the needle sits in the float - but you should see that on your new float. Your sudden stop sounds like lack of fuel to me so check the petrol flow with the float chamber removed and a cup of some sort under the float needle assembly.
Paul Jameson
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Re: Break-in notes (4G Square - 1937 engine)

Postby simon.holyfield » Tue Aug 16, 2016 9:51 pm

How is your fuel line set up? I was plagued with fuel starvation problems initially.

Are you using the magneto or have you converted to coil ignition? Short, slow runs flatten my battery pretty quickly.
cheers

Simes

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

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Akumar
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Re: Break-in notes (4G Square - 1937 engine)

Postby Akumar » Wed Aug 24, 2016 4:20 am

Dear fellow enthusiasts,

Here are some nasty looking photos of the left rear spark plug. As I mentioned before, the plug wire was loose. Thus it appears that this cylinder did not see a lot of action in the first 150 miles. The other plug is also sooty because the bike was running rich mixture.

Ariel plug comparison2.jpg

I have received the Solex float from David Jones. Thanks David.

The wear on the old float can be seen from photo. You can see that the deepening of groove on the top of float. This probably was the reason needle valve was not closing completely and carb was flooding.

Solex float comparison.jpg

If you look carefully at the photo below, you can see that the actual dome curvature of the float had flattened. This led to the bronze nut being flush with the dome. This again was probably another reason needle valve was not closing completely.

Solex float wear.jpg


Solex float against needle valve nut.jpg

So gentlemen, we all need to add a new word to our vocabulary – “re-dome” your float.

Kumar
48' SQ4, 53' VB, 51' NH

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Akumar
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Re: Break-in notes (4G Square - 1937 engine)

Postby Akumar » Tue Sep 20, 2016 4:56 am

Dear fellow enthusiasts,

The Solex is sorted out now and bike is on the road again. Another of my earlier problems was that left rear cylinder was not firing (for the simple reason that the plug wire was loose). That too has been corrected and hopefully all four cylinders are firing now.

I noticed yesterday that the clutch cable was extremely stiff. I adjusted it. I also noticed that the primary chain is very tight.

I have a question for curiosity sake. Can there be a relation between tight clutch wire and tight primary chain? I am trying to visualize how gearbox movement can affect the clutch? Any thoughts are appreciated.

Kumar
48' SQ4, 53' VB, 51' NH

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Re: Break-in notes (4G Square - 1937 engine)

Postby Dave.Barkshire » Tue Sep 20, 2016 9:44 am

I'd guess that with everything bedding in, the rear chain has pulled the gearbox backwards It would be worth looking at the gearbox position adjuster and make sure that you have enough slack in both chains (check them regularly whilst everything is bedding in). Ariel clutches are usually not that heavy so if your cable is lubricated then you should check the cable route to make sure that it is as fluid as possible.
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Re: Break-in notes (4G Square - 1937 engine)

Postby ian.scott » Tue Sep 20, 2016 10:00 am

There is always a tendancy in use for the gearbox to pull backwards, so you should always take up the slack in the adjuster, to ensure it stops i.e the last adjustment should be to move the gearbox to lessen the tension in the primary chain.


Ian

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Re: Break-in notes (4G Square - 1937 engine)

Postby nevhunter » Wed Sep 21, 2016 12:30 am

That's the only way to do the adjustment that stays where you leave it. Adjuster trying to force the box forwards. Tight chains are damaging to bearings and the chain as well Gearbox in engine plates should have the nuts pretty tight there's a lot of load on it. Nev

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Re: Break-in notes (4G Square - 1937 engine)

Postby paul.jameson » Wed Sep 21, 2016 9:02 pm

On both BA and CP boxes it is easy for the clutch lever on the end of the box itself to be the cause of a stiff clutch. There should be a "half moon" on each side of the lever which press onto the shoulders of the outer part of the adjuster which operates onto the end of the push rod. These half moons get worn away in time with the result of lost flexibility between clutch lever and adjuster. If the adjuster is a tight fit in the gearbox end cover, it can tend to jam. Ideally, you need good half moons and sensible small clearances between adjuster and end cover. The adjusters are not too difficult to make and you can bush the end cover. You can also weld up and file new half moons onto the clutch lever.
Having said all this, I did most of the above on the Square and the clutch is not as good as that on the Red Hunter which has a worn adjuster and end case, together with a total lack of remaining half moons!
Paul Jameson
36 4G, 37 VH, 53 ex ISDT KHA (project), 54 KH(A), Healey 1000/4 (project)
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.

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Re: Break-in notes (4G Square - 1937 engine)

Postby nevhunter » Thu Sep 22, 2016 3:09 am

Don't run any more pressure on the clutch springs than you need and make sure the pressure plate disengages evenly. Cork clutches don't need heavy springs like fibre ones do. Nev


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