Slide needle removal on IP2.

Post Reply
redshiftrotary
moderator
Posts: 17
Joined: Sat Apr 17, 2021 8:38 pm

Slide needle removal on IP2.

Post by redshiftrotary »

Sorry for the stupid question everybody .........
Having removed the locking grub screw, how does the slide (metering) needle come out?
I've tried a gentle tap upwards and I've tried a gentle tug downwards, to no avail and before I get my really big hammer out I thought it best to ask the experts .....
Up and down are as if the carb. was on the bike.
User avatar
Interpol2471
moderator
Posts: 1282
Joined: Mon Oct 20, 2008 1:02 am

Re: Slide needle removal on IP2.

Post by Interpol2471 »

If you have removed the grub screw it should come out, give it a tap and pull the needle out from the bottom.
You have obviously drained the oil etc from the inside?
Various rubbish in various states of decay.....
redshiftrotary
moderator
Posts: 17
Joined: Sat Apr 17, 2021 8:38 pm

Re: Slide needle removal on IP2.

Post by redshiftrotary »

Yes, oil drained and slide out of carburettor on the bench.
So I'm tapping it downwards (gently) with a punch/drift down the damper rod tube?
fogrider
moderator
Posts: 118
Joined: Wed Jun 23, 2010 8:42 am

Re: Slide needle removal on IP2.

Post by fogrider »

There should'nt be access to the needle via the oil well, heat the piston up with very hot water then twist and pull the needle out from the bottom. If it still resists, you may have to carefully nip the needle right next to the piston with pliers. You may get away with not marking the brass, but needles are available if it comes to the worst.
Maybe worth trying to grip it with a bit of fine emery cloth first ? - twist and pull after the hot water.
Regards, Terry..
redshiftrotary
moderator
Posts: 17
Joined: Sat Apr 17, 2021 8:38 pm

Re: Slide needle removal on IP2.

Post by redshiftrotary »

Thank you Terry, success with your method!
Naturally, having got a step forward, this leads onto the next question .......
I discover on starting to re-assemble that the Metering Needle Guides currently fitted are giving a Needle Bias TOWARDS the engine, whilst the Norton Manual makes it clear I'm needing a bias AWAY from the engine.
My Burlen S.U. parts book gets a bit vague and gives three part numbers for an 'away from engine' bias Guide: AUD 4290, which is superceded by JZX 1038, plus there's AUD 4289 a 'reduced height' version. They're all in stock so my guess isn't limited by availability - can anybody specify which one I need?
John.
User avatar
Richard Negus
moderator
Posts: 1049
Joined: Mon Jun 18, 2007 5:11 pm
Location: Wilds of Lincolnshire

Re: Slide needle removal on IP2.

Post by Richard Negus »

John,
The correct needle for ALL Norton rotaries (except F1) is NZX 4030, stamped 'AEF'.
The needle was changed several times in production so the ones you have removed my be stamped something else.
R.
Just a bike-less old fogey now. Boo-hoo!
redshiftrotary
moderator
Posts: 17
Joined: Sat Apr 17, 2021 8:38 pm

Re: Slide needle removal on IP2.

Post by redshiftrotary »

Hello Richard,
Thank you for your reply, mine are stamped 51XA - but that wasn't the question!
What I'm interested in is the Burden/S.U. part number for the Needle GUIDE, which gives the needle it's rear bias.
Currently the ones fitted in my carbs. (I discover) are giving a forwards bias, which I'm assuming is not correct.
Burlen/S.U. list three part numbers (listed in my previous post) and ALL are available.
Kind regards,
John.
User avatar
Richard Negus
moderator
Posts: 1049
Joined: Mon Jun 18, 2007 5:11 pm
Location: Wilds of Lincolnshire

Re: Slide needle removal on IP2.

Post by Richard Negus »

John,
I wasn't avoiding the question of the correct needle guide part number. It's just that I don't know and I doubt there's anyone left that does. Burlen certainly don't have any SU records of those carbs' specification.
Perhaps you could persuade Andover Norton to strip one of their old-stock carburetors to see which way the needle is biased in the jet?
I understand why the needle is biased, but don't think that, for all practical purposes, it makes any difference which way it is biased. I'd be pleased to hear from anyone who knows which way it should be biased for a Norton rotary.

Reverting to my needle information, 51XA was the original designation of the needle, later changed by SU to AEF.
R.
Just a bike-less old fogey now. Boo-hoo!
redshiftrotary
moderator
Posts: 17
Joined: Sat Apr 17, 2021 8:38 pm

Re: Slide needle removal on IP2.

Post by redshiftrotary »

Thank you Richard,
Like you I'm not convinced WHY it needs a bias but my Norton Workshop Manual makes it clear it should have one and Burlen list Guides for a forward or rearward bias so there must be a reason?
What I'm trying to do is get back to a 'level playing field' with my carbs. and hopefully cure some niggling problems.
Sorry I can't attach a photo. of the relevant page in the manual but it's Section B7, page B22, top of the page paragraph d, for those that have a copy to refer to.
Kind regards,
John.
P.S. I've P.M.'d you about your very useful carb. spares.
User avatar
Richard Negus
moderator
Posts: 1049
Joined: Mon Jun 18, 2007 5:11 pm
Location: Wilds of Lincolnshire

Re: Slide needle removal on IP2.

Post by Richard Negus »

John,
The reason for the bias is to maintain a uniform fuel flow between needle and jet and hence a constant fuel/air mixture. There is no simple way of keeping the needle in the middle of the jet so the alternate is to have it always to one side, hence the bias.
Fuel flow from a concentric needle with an annular hole for the fuel is not the same as a crescent shape although they are the same cross-section area.
The annulus will always flow more fuel than the crescent.

As I said previously, I don't know whether a bias towards or away from the engine is preferred, although I suspect towards the engine is correct so that varying air flows ensure the needle is always pressed to the side of the jet.
R.
Just a bike-less old fogey now. Boo-hoo!
Post Reply