Adjudting idle Speed VH

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Keith.owen
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Adjudting idle Speed VH

Postby Keith.owen » Wed May 23, 2018 9:21 am

Hi,
I've done nearly five hours in the saddle since putting my completely rebuilt engine back on the road and have covered about 150 ish miles.

So far so good, running on small throttle openings and changing between 3rd and 4th gear - trying not to labour the engine.

| have set the idle with the ignition fully retarded and when hot the engine 'ticks ove'r at bout 750 RPM; I bought one of those Chinese tachometers that works by winding a sense lead around the spark plug lead. However, with the ignition advanced there is, as one would expect an increase in idle speed, it is in fact quite significant. I'm not keen on it because I'm not getting the engine braking I'd like and when at a junction with the clutch in the engine races a bit. I get round it by retarding the ignition when I come up to a junction, and then advancing it when pulling away, but this is all very fiddly and not something I'd have time to think about in the unfortunate event I had to do an emergency stop.

So, my question is 'what is the general consensus regarding setting idle speed taking in consideration ignition timing?'

Keith

PS. This would not be an issue with auto advance!
Keith Owen
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1950 Rigid Ariel VH
1951 Rigid Ariel NH (under construction)
1973 Norton 850 Commando Interstate

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Re: Adjudting idle Speed VH

Postby simon.holyfield » Wed May 23, 2018 10:36 am

My W/NG behaves exactly like that - I had put it down to a tired carburetter. What sort of shape is yours in?
cheers

Simes

'51 Square Four, Masquerading D3 Bantam, '58 Huntmaster, '42 W/NG, http://ariel-square-four.blogspot.com

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Re: Adjudting idle Speed VH

Postby Keith.owen » Wed May 23, 2018 12:01 pm

Hi Simes,
It is a very new Amal concentric with Premier slide and stay up float with Viton tipped aluminium float needle. The carb is fitted with a pancake air filter.

The engine has a7.5:1 HC piston and HS cam.

Keith
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Re: Adjudting idle Speed VH

Postby chris.shearwood » Wed May 23, 2018 1:25 pm

Hi Keith,
Although I've never tried to measure mine with a tachometer, 750 RPM at fully retarded sounds a bit fast to me. With a fully retarded, warmed up engine I like to have it such that it just barely keeps running. Just an occasional thump, so to speak. This seems to impress and amaze onlookers too sometimes! But even set like that it does rev too fast when stopped at idle - at a stop sign: so what? At a red light retard it a bit.
1946 4G, 1950 NG and 1951 VH

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Re: Adjudting idle Speed VH

Postby chris.shearwood » Wed May 23, 2018 1:57 pm

Hello again Keith,
I've posted this link before and it is showing my NG but my VH is similar (except I use the decompressor to start it) and right near the end of the video, as the bike is warming up a bit, I retard the ignition and the motor slows down. If the bike had been fully warmed up the engine speed could have been lowered much more.
https://www.youtube.com/watch?v=pmTY6Vl ... H3p0VoVxpW
1946 4G, 1950 NG and 1951 VH

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Re: Adjudting idle Speed VH

Postby dave.owen » Wed May 23, 2018 3:20 pm

My 52 vh is similar when warm on full retard the engine is barely running, but full advance speeds it up. No issues with stopping at traffic lights just retard a little when stationary and increase advance as you pull away.
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Re: Adjudting idle Speed VH

Postby ian.scott » Wed May 23, 2018 5:44 pm

On my 35 VH , I hardly touch the advance , I start and ride it on virtually the same setting, 7/16 at full advance. It doesn't kick back because I used the valve lifter to start it.

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Re: Adjudting idle Speed VH

Postby CylvaBirch » Wed May 23, 2018 6:21 pm

Where can I get a tacho that senses off of the HT lead please?
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Re: Adjudting idle Speed VH

Postby nevhunter » Wed May 23, 2018 11:03 pm

IF you idle fast on full retard ,the motor will get hot fairly quickly, with out airflow over it. FULL retard can mean different things, depending on the range the cam is moving in the magneto and what angle you have set the timing to. The lever position and thereby the advance for cruise is not suitable for idling. That's why you have the hand adjustment. On Ariel singles I've owned and worked on you practically never run or even start, on full retard which is close to firing at TDC (Just a few degrees before, is where it usually ends up. I don't usually use full retard even when idling but you should have to reduce the running setting/position of the lever, to get a good idle) the only time, apart from when at idle, that I touch the lever is when getting around a corner, rather than change down or pulling hard on a hill IN A TALL GEAR where the engine will run and pull better if you retard it a SMALL amount. You don't retard the engine if it's revving EVER. It's at revs where you need the most advance, on any motor.. You will get used to retarding slightly when pulling up completely and moving it up when you take off, or the response will be a bit dead, and you wil probably blue the pipe. The usual difference is about 5 mm of lever position.. The full retard position has the weakest spark, so that's a good reason to start with some actual advance. Nev

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Re: Adjudting idle Speed VH

Postby Eero.Korhonen » Thu May 24, 2018 5:53 am

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


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