• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

E: Engine Modern Fuel & Ignition Advance



Pete Appleton

Well Known and Active Website User
VOC Member
VOC Forum Administrator
VOC Forum Moderator
#41
There is nothing that seems to be seized up on that distributor. If you grab hold of the rotor arm you can move it back and forth against the springs easily. I wondered if it was caused by one, or both, of the springs not being tight initially and coming into play later. It is all very clunky.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
#43
I don't think a Vincent needs much, I have a Comet on Manual and had a Twin on Manual, Once started I don't mess with it much. Cheers Bill.
In the sixties I had a 350 DB32 Gold star and later fitted a DBD34 500 engine. I retarded a bit with the lever for starting but advanced it after it fired up. Like Bill I don't think I used the lever much once I was riding.
If your engine is pretty standard I don't think that you need to mess about with your ignition timing much other than maybe knock the advance back a few degrees to find a sweet spot. I've had a BT-H magneto with electronic advance on my Rapide for around 10 years. The advance characteristics aren't wildly different to what you will get from a properly functioning mechanical ATD. It has been dead reliable and provided 1st or 2nd kick starting (1st press of the button now:)) for over 40,000 miles. I use whatever fuel that comes out of the pump and haven't noticed any problem with the inclusion of alcohol in the petrol. Depending on where you are in the world you may be using fuel with a higher alcohol content than the up to 10% we have in the UK so I can't comment on higher alcohol percentage fuels. If you have a modified engine then that may also be a different story.
I think if you have a good standard magneto then you shouldn't really have any trouble. The problem is that most original magnetos are no longer performing how they did when they were new. Even some newly rebuilt magnetos are not really that good or don't work properly for very long. The problem with many old bikes that the owner can't get to run right may be that they won't get their money out and buy a good ignition system whether it be electronic, coil and points or a properly refurbished standard magneto.
 
Last edited by a moderator:

LoneStar

New Website User
VOC Member
#44
Hi Vince,

See OVR #42 for a detailed analysis and info on how to set up a mechanical (Lucas) ATD: Here are the conclusions: Full Advance - single plug heads is 34 BTDC and twin plug heads 26 BTDC. Full Retard - kick start motors 4 BTDC and electric start motors 2 ATDC.

Martyn
Martyn,

This was one of the inspirations for my original post, in that the figures are given without a discussion of how they were arrived at. It's said that modern fuel is the relevant factor, suggesting it burns faster than when the factory specified 39 degrees, but no one here seems to know why or to what extent (despite a great deal of informative technical discussion on ignition advance).

Assuming a standard Vincent twin, with compression ratio in the range the factory used (6.7 - 8:1) and original magneto/ATD, fuel composition is the only factor I can think of that would invalidate the factory's original specification. To see if it does, we could look at fuel burn characteristics (seemingly unavailable) or dyno tests on actual standard bikes running various fuels (race gas, pump unleaded, maybe some leaded premium if available) - but it seems no one has done this either.

Lacking hard data, we can fall back on "it seems to run best at x degrees" - but as davidd points out, seat-of-pants impressions are notoriously unreliable.
 

MartynG

Well Known and Active Website User
VOC Member
#45
Martyn,

This was one of the inspirations for my original post, in that the figures are given without a discussion of how they were arrived at. It's said that modern fuel is the relevant factor, suggesting it burns faster than when the factory specified 39 degrees, but no one here seems to know why or to what extent (despite a great deal of informative technical discussion on ignition advance).

Assuming a standard Vincent twin, with compression ratio in the range the factory used (6.7 - 8:1) and original magneto/ATD, fuel composition is the only factor I can think of that would invalidate the factory's original specification. To see if it does, we could look at fuel burn characteristics (seemingly unavailable) or dyno tests on actual standard bikes running various fuels (race gas, pump unleaded, maybe some leaded premium if available) - but it seems no one has done this either.

Lacking hard data, we can fall back on "it seems to run best at x degrees" - but as davidd points out, seat-of-pants impressions are notoriously unreliable.
In my case figures for maximum ignition advance were arrived at with a combination of on-road testing, feedback from a number of Vincent riders (you would be surprised at just how many Vincent owners don't ride their Garage Queens) and observing the effect of too much advance.

The advance recommendation at maximum retard for starting - 4 BTDC - is the factory number and has been repeated a number of times in publications written by Phil Irving - the designer of our engines.

I had an original Lucas ATD fail when out touring at speed. It was early in my 'vincent' life and the ATD had been tuned by bending the stop ears on it. Well unbeknown to me BOTH the stop ears eventually broke away and I subsequently found - after the pull down that it was providing 4 BTDC to start and 46 BTCD fully advanced. I did notice some pinking noise on the hills but cruising at 75-80 mph it did not seem too bad. Here was the result it had on a CP Forged piston, and yes suddenly I lost a bit of power.

P1110566.JPG

As you can see from the carbon deposits - it was not running lean - in fact it was (intentionally) a wisker rich. New piston, bore cleaned up and a new ATD was the main work needed.

Modern motors are fitted with knock sensors and while i'm no expert I figure that they work by retarding the ignition if knocking is detected. Knocking or pinking is the noises the motor produces when the fuel charge burn reaches maximum pressure BEFORE the piston gets to TDC and in doing so tries to force the piston to go back down the bore BEFORE it is at or past TDC. Produces noise, excessive heat on the piston crown and also beats up on the little and big end bearings.

The only knock or pinking detectors we have with our old bikes is our own senses - mainly hearing. If at any time you hear those sounds then you know the charge is being ignited/burnt too early and the only way to stop it is by 1. closing the throttle so there is no fuel to get burnt or 2. ensure that the charge gets burnt a bit later - ie by retarding the ignition. And that was the basis of my recommendations after lots of road testing by myself and a lot of other Vincent owners.

Purists may suggest I have been too conservative however the consequences of too much advance is in my experience catastrophic and expensive.

But then again as David D has earlier suggested (post 24) , the ONLY definitive method is to use a dyno to determine the setting for maximum performance which by the way may well NOT equate to maximum reliability.

Martyn
 

Nigel Spaxman

Well Known and Active Website User
VOC Member
#47
I have been doing a lot of experimenting with timing recently. My bike is a Rapide with MKII 105 cams and 8:1 pistons. It is not very fussy about the timing. I run the bike usually on 94 Octane gas and it is almost impossible to get the bike to knock or pink even lugging it in to low a gear up hill when it's hot. The only time I have heard the bike pink at all was on timing that was very over advanced. Probably the timing was set around 42 degrees BTDC when I heard this pinking, and it was very slight. When the timing is really late the engine feels very soft and opening the throttle results in more noise and not so much acceleration. I have a Dyna 2000 ignition (for a Harley) modified for the Vincent. A lot of people around Vancouver use this system. It can be programed for two advance curves any way you want by connecting it to a computer by a usb cable. There is a vacuum operated switch. One curve is used at high vacuum and one for lower vacuum. On my bike all these extra functions seem a bit unnecessary. My bike seems to like full advance by about 2000 RPMs. I can ground the vacuum operated switch or leave it open to select from the two curves to experiment with the timing. I bought a very nice new timing light from MSD that is really bright. It is one of only a few lights you can get that will work well with a multi spark ignition like the Dyna. Also this light flashes even at kick over speeds so you can even check the timing at kick over speeds (I haven't bothered doing that yet) I have a mark on the plastic gear that drives my ignition. I put that mark at 34 degrees btdc because that was the timing that many people recommend now days. I have tried everything over the last few weeks and I have decided I prefer a full advance timing of 38 degrees BTDC. When I have the timing set this way my bike has the best acceleration and gets the best gas mileage. I get between 55 to 58 MPG (Imperial) and when the timing is retarded to below 32 degrees the mileage drops below 50. I am going to keep experimenting, but that is what I am settled on now. The trouble is with the two advance curves and the vacuum switch there are to many possibilities. I haven't even started on that yet. I think some other engines with squish heads or higher compression probably would prefer less advance but not this engine. My engine is pretty mildly tuned, I think that many bikes are even more mildly tuned than mine and would probably run with the timing pretty close to the original recommendations like mine does.
 

Magnetoman

Well Known and Active Website User
VOC Member
#48
34 degrees btdc because that was the timing that many people recommend now days. ... I have decided I prefer a full advance timing of 38 degrees BTDC.
For what it's worth, I have my BB and DBD Gold Stars set very near the factory recommended values of 40.5-deg. (actual setting 40.2-deg.) and 39-deg. (actual setting 37.8-deg.), respectively. With 91 octane fuel, the highest available from the pump in my State, if I lug the Catalina going into an uphill curve it will ping unless I retard the timing somewhat (both bikes have manual advance levers). Both bikes came to me pre-built by someone else so I don't know their compression ratios, although the kick starters tell me they're not low. This fall on a ~1200 mile ride in Texas (where the octane may be a bit higher than 91?) there were no apparent issues with the timing.

Anyway, I don't know where the recommendation for using less advance with modern fuels comes from, or what data it may be based on but, like Nigel, I find the factory values from 50+ years ago to be just fine. At least for my Gold Stars.
 

Nigel Spaxman

Well Known and Active Website User
VOC Member
#49
I use the standard settings on my Goldstar, my Norton Commando and also on my Triumph Bonneville. I have been doing this experimenting on the Vincent because I was thinking maybe a little less advance might be better, but now I don't think so. I have one Bonneville though with a very modified engine. It has 10:1 compression, and a 4 plug head. I have found it runs best on 34 degrees advance. On that engine the extra plug changes things quite a bit. (When I only had 2 plugs it used the standard 38 degree setting.
 

Magnetoman

Well Known and Active Website User
VOC Member
#50
Also, for what it's worth, I measured the full advance range on my DBD's Competition magneto to be 33-deg., and in my routine that normally results in the bike starting on the first kick I have the lever retarded by ~1/3, i.e. by ~10-deg. to ~27-deg. BTDC. That's quite a bit more advanced than the value it would have if the magneto had an ATD.
 

vibrac

Well Known and Active Website User
VOC Member
#51
I think we can discount a lot of USA figures being the land of the free they are free to chose non ethanol for a start.
 

Magnetoman

Well Known and Active Website User
VOC Member
#52
I think we can discount a lot of USA figures being the land of the free they are free to chose non ethanol for a start.
In principle, yes, but in practice very few stations carry anything but the "normal" regional blend. I'd either have to be very lucky to come across an "alternative fuels" station when I needed fuel, or take routes I didn't want to take to destinations I didn't want to visit to go from one of these stations to the next. As a result I've not had the opportunity to put anything but "normal" fuel in any of my vehicles for well over a decade.

Irrespective of my great freedom of choice, my only actual "choice" is the 91 octane regional blend distributed throughout Arizona, California and Nevada that in the winter may or may not have 10% ethanol added.
 

Magnetoman

Well Known and Active Website User
VOC Member
#53
Offline I exchanged a few messages with another VOC member on the subject of this thread. This reminded me of some fuel experiments I did in the early 2000s that, although they don't touch on advance/retard, still aren't completely off topic.

In the early 2000s I bought an Ertco hydrometer (accuracy 0.15%) and Cannon-Fenske viscosimeter (accuracy 0.29%), both with calibrations traceable to NIST, for measuring the density and viscosity of gasoline. The flow through a jet is a function of these, and both depend on temperature. I did this so I could help a friend who was a highly ranked classic bike racer at the time. The idea behind this was that if he had, say, determined the perfect jetting for his bike on a track in Death Valley in the middle of summer, and his next race was at 10,000 ft. in winter, it would be helpful if he could calculate the main jet he needed so on his first practice run on the new track he would be very close to already having perfect jetting and so could concentrate on learning the track rather than fiddling with jetting.. I still have the "track kit" I assembled of relative air density meter, humidity meter, thermometer, etc., along with a calculator I programmed with the function I determined for the flow rate of gasoline over a wide range of temperatures.

In the course of doing those experiments I measured gasoline from several major suppliers as well as expensive "racing fuel" from a pro shop (whose formulation is always the same). What's relevant for this current thread is the gasoline from the major companies had significant variations in density and viscosity, as well as in the temperature dependence of both, and hence in flow rate. Also, irrespective of the differences between brands the flow rate of a given gasoline varies significantly with temperature, which means the air/fuel ratio also varies with temperature.

Luckily for us, although there is an optimum air/fuel ratio for maximum h.p. under a given set of conditions, internal combustion engines aren't incredibly sensitive to deviations from this ratio. As a result, our bikes still manage to run acceptably well whether we fill up with, say, Shell one time and BP the next, or if we ride our bikes in summer and winter (when the fuel blends are different), or if we are using the same tank of fuel to ride from the hot desert floor to the cool mountain top. Of course, if we gain enough altitude we'll notice a falloff in performance due to the decrease in air density.

Back to timing. If anyone has a link to a credible source of actual data on the effect, if any, of timing due to modern fuels, please post it. I've been looking for such data for several years and haven't found it, although there is plenty of authoritative-sounding but unverified speculation on the web. What makes hoping to find such data problematic is that the U.S., at least, is divided into a fairly large number of different regions with fuel blended specifically for them, as well as differences between summer and winter blends. So, even if someone correctly controlled for all other relevant variables, whatever result they found for the correct timing for, say, Shell Premium gasoline in New York in summer would not necessarily apply to the Shell Premium gasoline in Los Angeles.

Again, my bikes seem to be happy with the factory timing values so I'll continue to use them, but will keep looking for any relevant data that might affect this decision.
 

vibrac

Well Known and Active Website User
VOC Member
#54
Well at least in the UK (apart from Banana mans country) we have Esso premium with a statement from Esso that "it contains no Ethanol"
 


Latest Forum Threads

Top