Ignition timing vh500

[Alan G]

I have never had a manually advance/retard bike before, but understand how it is meant to be used. But bearing in mind I have no experience.....

How is ignition timing set - I am assuming there is a way to set the optimal timing so that the adjusting lever has the correct range of adjustment? Or is it simply roughly set at the magneto and the lever gives sufficient range to seek the sweet spot for starting, tickover and running?

I am wondering if there are timing marks for either static or dynamic setup?

Engine is a 1958 bottom end with earlier top end.

[simon.holyfield]

What you do is set the engine to the appropriate position - for a VH it is 1/2" - 5/8" BTDC, and then set the magneto fully advanced using the lever - Ariels are usually tight wire advance, which means the timing is set with the cable taut. If the points are just opening at this position then you are good to go; if not, you remove the sprocket driving the magneto, move the magneto armature so the points are just opening, then put the sprocket back on without moving the engine.

That should leave you with the ignition timing set correctly.

Day to day, you would usually ride around with it fully advanced. You will need to retard the timing for starting and you use the handlebar lever to do this - how much depends on how it kicks back, but half way perhaps? you get a feel for it.

[Alan G]

Thanks Simon - for the avoidance of doubt, when you say1/2 to 5/8 before tdc, I am reading this as 1/2 vertical travel on the piston, and not 1/2inch rotational travel on a flywheel. Correct? There are no timing marks, just use a 'dipstick' through the plug hole to measure?

Tight wire advance? I think mine is the opposite.... lever all the way forward being full advance, pulled back (tight wire) retards. And confusingly, the choke lever is tight for fully off.

At least that how it appears to me with the bike running. But only had it running for maybe five minutes so far. Bad plug cap replaced with all I could get locally which was a resistor cap - non resister one is in the post. And a spark plug that is arcing weakly to the rim rather than jumping between the electrodes. New plug(s) on order.

I have not yet gone in search of the points, or looked at how to adjust timing. Might get a chance tomorrow. But plan to wait until I have a good plug and non resistor cap installed before I start adjusting anything else.

[Simon.Gardiner]

Vertical travel on piston. Ariel only ever specified 1/2 BTDC as standard but 5/8 BTDC for high compression. The latter seemed to include everything from 'fast touring' high compression to the out-and-out scrambler.
As Simes says most folk probably just get a feel for which settings work best.

SG

[nevhunter]

I prefer to use a timing disc when doing it initially. IF it will idle cleanly on full advance you need more advance. I use 35 degrees as full advance and reduce it on the cable if needed or just advance it less at the Lever when on the road. You get to remember the Correct Lever position quickly enough. Advance is an RPM thing. Not a going up hills thing. If your pipe Blues up way along it's length, get more advance. . Nev

[simon.holyfield]

I wrote this up a few years ago. It might be useful to you:

https://ariel-square-four.blogspot.com/ ... s.html?m=0

I might slim it down for a CdF article!

[Alan G]

Perfect. Thanks everyone.

[ian williams]

hi alan ;
first thing make sure you have the spring on end of the advance/retard cable where it is in the magneto housing ,so that the cam ring moves when you push and pull the adv/retard lever , mine had spring missing and caused me a few headaches ..

easiest way to time it is to put a block under the nearside leg of centre stand so that rear wheel is free to spin , kneel on floor , stick it in 3rd gear and you can push and pull the wheel back and forth by hand whilst engine turns over .
stick it on full advance [lever forward] , put fag paper in between points , turn engine over till piston comes up to 5/8" before top dead centre position , fag paper should fall out at 5/8" btdc if its timed right .
there is a choice of timing position with these engines though according to how you ride them , the manual shows timing settings that vary between about 3/8 to 5/8" before top dead so it means you can set it somewhere in this area according to how much advance you want and how you ride the bike , ie fast road or touring etc .

be careful of the screw/locknut for adjusting point gap , dont tighten it up too tight that it strips the thread in the zinc casting .

when you start the engine just stick the advance lever about 1/2 way , in line with centre of handlebar , and it should do the job for starting .

on tickover if you move advance lever back and forth you should hear engine speed rise and fall , it will actually tick over at a very slow speed if you retard it right back .

when out on bike i run full advance most of time but when i hit a hill i may pull advance lever back a bit if i find engine noise changes and i am worried about it "pinking" .

[Julian Murphy]

I found this useful:

https://www.kingpincomponents.co.uk/pro ... ming-light

I also fitted one of these:
https://www.kingpincomponents.co.uk/pro ... r-sprocket

Ran the bike for a while, and then retarded the timing by one notch, as the product detail says 2.35 deg. Bike did run 'smoother'.
(Or was that just in my mind?)