Engine rebuild - W/NG

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simon.holyfield
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Engine rebuild - W/NG

Postby simon.holyfield » Mon Aug 03, 2020 8:08 pm

As some of you may know, the W/NG hasn't been too happy recently - it's been consuming spark plugs at an alarming rate and has caused several unscheduled stops by the roadside - particularly annoying, because I'm lucky enough to live by the sea and a bike is the best choice of transport in the summer - you will never park your truck again if you choose to move it.

So, the W/NG is the go-to machine for local use, until it decides it isn't going to play nice any more. Next up is the SQ4... which has a flat battery and knackered points (my fault - embarassing story). Now I know what a garage full of dead Ariels looks like:

IMG_20200803_160633.jpg


So I've pulled the W/NG apart. The piston is an oily mess and the top ring is in three pieces:

IMG_20200803_165022.jpg


The small end is cratered but is dimensionally OK. I've not measured the pin or the piston yet, but the bore is 2.871 in the midle of the stroke (fore and aft direction) which is getting on for 40 thou over factory standard. There is no ridge at the top, so we will have to see what the piston dimensions are.

IMG_20200803_165533.jpg


The valve guides are awful. I've not measured the valves yet, and I have no way to accurately measure the guides but the exhaust valve rocks maybe 1-2 mm at full open, the inlet maybe half that. The inlet guide is loose.

IMG_20200803_172524.jpg


Then there is the big end. I can feel up and down play of maybe 0.5 mm; side to side rock is maybe 3 mm at the small end.

All in all, a good afternoon's work. A lot nicer than the morning, which was spent pulling one of these apart:

IMG_20200803_105502.jpg
cheers

Simes

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

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paul.jameson
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Re: Engine rebuild - W/NG

Postby paul.jameson » Mon Aug 03, 2020 8:48 pm

What that piston is - goodness alone knows.

I have sent you a PM.
Paul Jameson
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (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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simon.holyfield
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Re: Engine rebuild - W/NG

Postby simon.holyfield » Mon Aug 03, 2020 9:59 pm

Thanks for your guidance and offer of help Paul.

I'll contact Alpha - do you have a name?

Peter Kemp says he has NOS W/NG pistons at +40 which may be good enough - I am going to clean up the head and barrel and have a better go at measuring up. I'll get a new set of guides and see if they will go in reasonably well. Here's the inlet guide - is the stock one square like that, with no taper? It's hanging out in this picture - with the springs in it protrudes normally.

IMG_20200803_172530.jpg


Last point. If you look at the exhaust rocker bolt boss in the far side of this picture, it has a 1/4" chip out of it. Is it worth the risk of building this up? It's not been causing a problem.

IMG_20200803_161821.jpg
cheers

Simes

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

nevhunter
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Re: Engine rebuild - W/NG

Postby nevhunter » Tue Aug 04, 2020 12:22 am

Carefully drill that hole a bit deeper and tap a little more thread and make a slightly longer bolt for it. Use a drill press so you don't damage the existing threads AT ALL. Dirt (and carbon) in these blind holes causes a lot of splitting of the bosses one sees with these heads. Nev

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Eero.Korhonen
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Re: Engine rebuild - W/NG

Postby Eero.Korhonen » Tue Aug 04, 2020 4:57 am

Do you have resistance plug or do i see wrong?
Br, Eero
Ariel VH 1954, IZH 350 1962, H-D Sportster Hugger 1992, AOMCC Member 133

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Steven.Carter
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Re: Engine rebuild - W/NG

Postby Steven.Carter » Tue Aug 04, 2020 6:49 am

Two shitie jobs on your hands then :D
My WNG has some bits chipped out on the head, also seems not to have caused any trouble. Yes you've got to get her going again, they are perfect goto bike.

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simon.holyfield
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Re: Engine rebuild - W/NG

Postby simon.holyfield » Tue Aug 04, 2020 8:23 am

Eero.Korhonen wrote:Do you have resistance plug or do i see wrong?
Br, Eero


It's a Bosch W8BC. No resistor plugs in my shed!
cheers

Simes

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

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chris.shearwood
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Re: Engine rebuild - W/NG

Postby chris.shearwood » Tue Aug 04, 2020 12:37 pm

simon.holyfield wrote:Last point. If you look at the exhaust rocker bolt boss in the far side of this picture, it has a 1/4" chip out of it. Is it worth the risk of building this up? It's not been causing a problem.


Simon,
Isn't that damage caused by someone removing the rocker box with the valve fully open i.e. the spring fully compressed? I wouldn't bother trying to repair it. My VH has the same sort of damage with no ill effects.
Regards, Chris
1946 4G, 1950 NG and 1951 VH

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simon.holyfield
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Re: Engine rebuild - W/NG

Postby simon.holyfield » Tue Aug 04, 2020 3:28 pm

chris.shearwood wrote:
simon.holyfield wrote:Last point. If you look at the exhaust rocker bolt boss in the far side of this picture, it has a 1/4" chip out of it. Is it worth the risk of building this up? It's not been causing a problem.


Simon,
Isn't that damage caused by someone removing the rocker box with the valve fully open i.e. the spring fully compressed? I wouldn't bother trying to repair it. My VH has the same sort of damage with no ill effects.
Regards, Chris


Possibly, not me though - looks old and has a different bolt. I'll leave it.

Thanks for the advice Chris, Nev and Steve.
cheers

Simes

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

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Eero.Korhonen
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Re: Engine rebuild - W/NG

Postby Eero.Korhonen » Wed Aug 05, 2020 4:37 am

simon.holyfield wrote:
Eero.Korhonen wrote:Do you have resistance plug or do i see wrong?
Br, Eero


It's a Bosch W8BC. No resistor plugs in my shed!


Should have my better reading glassess on. :D

Br, Eero
Ariel VH 1954, IZH 350 1962, H-D Sportster Hugger 1992, AOMCC Member 133


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