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Re: Correct needle for 1000-series Concentrics? [Re: Kerry W] #776064
06/10/19 6:31 pm
06/10/19 6:31 pm
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Magnetoman Online content OP

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Originally Posted by Kerry W
10:1 is certainly 'adventurous' on 92...I'd have expected not more than 9:1 and probably more like 8.5...
'Competition' Gold Stars came with 10:1 pistons and when I rebuilt the engine 25 years ago just about every station carried high octane fuel so it wasn't a problem. Now it is.

If it worked as advertised the Lucas octane booster I used increased the octane to 95. Since the engine still knocks at 95 it needs more octane than that. Eight oz. of the stuff that's on its way to me now will increase it to 100 and, if that's not enough, 12 oz. is supposed to be good for 104. If it still knocks with 104 then rebuilding the engine as a side valve may be my only remaining option...

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Re: Correct needle for 1000-series Concentrics? [Re: Kerry W] #776067
06/10/19 7:31 pm
06/10/19 7:31 pm
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George Kaplan Online content
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Originally Posted by Kerry W
10:1 is certainly 'adventurous' on 92...I'd have expected not more than 9:1 and probably more like 8.5...
KW


My XR400 has a standard 10:1 compression ratio and my friends KTM 640 has a higher ratio (I forget if its 11:1 or 12:1).

In the UK, standard pump fuel is 95 or "Super" is 97/98.

Neither of us have had problems using standard pump fuel so why should a GS need a higher octane rating.

Now I know that there is a 50 year age difference but surely its not just compression causing the knocking? I am not asking a question per se but just remarking on how two different bikes with similar CR's seem to react differently on pump fuel.

John

Re: Correct needle for 1000-series Concentrics? [Re: George Kaplan] #776068
06/10/19 7:48 pm
06/10/19 7:48 pm
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Magnetoman Online content OP

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Originally Posted by George Kaplan
why should a GS need a higher octane rating.
A half-century worth of work into combustion chamber design is what allows modern bikes to have those high CRs.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776084
06/10/19 11:21 pm
06/10/19 11:21 pm
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A great read MM, most interesting . You got me googlin for Air Fuel ratio meters. The magneto spring eh, who would have thought, great catch, and the pivot shim . Snap that stuff up at 8$ a gallon, here 98 is £1.40 a litre, 91 is £1.30, my bike cost 10 pence a mile to run fuel alone.


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Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776087
06/11/19 12:18 am
06/11/19 12:18 am
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Originally Posted by gavin eisler
A great read MM, most interesting .
Thanks very much for the comment. The technical content often isn't typical Britbike fare so it's nice to hear it's appreciated.

Originally Posted by gavin eisler
The magneto spring ... and the pivot shim .
A larger pulley arrived today and from now on I'll test my magnetos at lower speed and then at the equivalent of 6200 rpm engine.

Originally Posted by gavin eisler
here 98 is £1.40 a litre, 91 is £1.30, my bike cost 10 pence a mile to run fuel alone.
I knew Europeans wouldn't have much sympathy for $8/gallon. Today's price of 92, the highest at the pump where I live, is $3.07/gal = £0.64/l. The cheap stuff, 87, goes for $2.63/gal =£0.55/l. The difference is "only" a factor of ~2, but gasoline to ride a motorcycle in the U.S. feels pretty much like an incidental expense, but every time I replace the nozzle after filling the tank in Ireland a serious number is staring at me on the pump.

I mentioned a few days ago that I managed to grab a second Innovate LM-1 that had been mis-listed on eBay. I decided that given the usefulness of the device, along with my modified Gold Star pipe, it would be good to have a backup. However, I realized I hadn't fully tested it so today I hooked it up, connected the cables to the DocZ, but then was overcome with the urge to try to start the bike the old fashioned way. I'm happy to report it only took a couple of kicks and I'm still able to walk afterwards. I made three laps of the driveway and downloaded the data. The new LM-1 works fine.

Interestingly, the new LM-1 is a different color than my original one and has a much higher serial number so I must have been a fairly early adopter. Assuming they started their numbering with 1000, my original one would have been one of the first 2800, with the second one some 15,000 later. On the other hand, did they really sell at least ~18,000 of these specialized units in the less than a decade before it was replaced by the LM-2?


Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776093
06/11/19 2:06 am
06/11/19 2:06 am
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Sydney, Oz
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Originally Posted by Magnetoman
If it worked as advertised the Lucas octane booster I used increased the octane to 95. Since the engine still knocks at 95 it needs more octane than that. Eight oz. of the stuff that's on its way to me now will increase it to 100 and, if that's not enough, 12 oz. is supposed to be good for 104. If it still knocks with 104 then rebuilding the engine as a side valve may be my only remaining option...
FWIW, 1960s Land Rover workshop manuals recommended retarding the ignition timing for lower octane fuels, and from memory there was a table of ignition advance vs octane rating. Some of the places where those things were used had very low octane fuels, too.
I think I have a manual in the shed, which I can dig out next weekend if somebody hasn't provided useful information beforehand

Re: Correct needle for 1000-series Concentrics? [Re: Shane in Oz] #776096
06/11/19 2:49 am
06/11/19 2:49 am
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Originally Posted by Shane in Oz
I think I have a manual in the shed, which I can dig out next weekend
That could be quite interesting. After I read your post searched for such information online but couldn't find anything.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776102
06/11/19 7:17 am
06/11/19 7:17 am
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Originally Posted by Magnetoman
I knew Europeans wouldn't have much sympathy for $8/gallon. Today's price of 92, the highest at the pump where I live, is $3.07/gal = £0.64/l. The cheap stuff, 87, goes for $2.63/gal =£0.55/l. The difference is "only" a factor of ~2, but gasoline to ride a motorcycle in the U.S. feels pretty much like an incidental expense, but every time I replace the nozzle after filling the tank in Ireland a serious number is staring at me on the pump.


Looking at your numbers it would seem that $8/gallon is about £1.67/litre which is about 28% more than the UK so you do have "some" sympathy.

Further to my earlier comments I didn't realise (even though I have driven in the USA many times) that standard gas was only 87 and the better stuff only 92. Compared to the UK where it is 95 & 98 respectively.

John

Re: Correct needle for 1000-series Concentrics? [Re: George Kaplan] #776126
06/11/19 3:39 pm
06/11/19 3:39 pm
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Originally Posted by George Kaplan
Further to my earlier comments I didn't realise (even though I have driven in the USA many times) that standard gas was only 87 and the better stuff only 92. Compared to the UK where it is 95 & 98 respectively.
Don't start feeling superior for having higher octane number than us. Like 'The Three Bears' there are three common rating systems for the anti-knock properties of gasoline: Motor, which gives a somewhat low number, Research, which gives a somewhat high number, and (R+M)/2 that gives a number that's in the middle (I'll call that number 'G' for Goldilocks). England uses R while the U.S. uses 'G'.

As far as I can tell the U.S. used R to rate octane at the pump until the early '70s, then switched to the present 'G' system. So our old 98 'premium' of the 1960s was roughly the same as your current 98 and probably is equivalent to something like 'G'= 93. Although slightly higher octane is available in some places in the U.S., California, Nevada and Arizona all get the same blends, which gives me a maximum of 'G'=92. In the 1960s we also had R=102 'super-premium' which my 10:1 Gold Star likely would be happy with. Assuming the octane booster I used increased my 'G'=92 up to 'G'=~95, and given that it still knocked, it means I need to boost the octane to G=~98-100 to give it the equivalent of R=~102.

p.s. I meant to write more about octane. Last night Shane in Oz sent me the link to a Land Rover manual that describes how to change the timing of two of their engines to deal with lower octane fuel. The manual gives two timing figures for one of the engines when it has the "high compression" 8.0:1 piston, but only one figure for the other engine with its 7.8:1. However, it gives several timing figures for both when using "low compression" 7:0 pistons.

Starting with 90 octane as the "normal" fuel (which I assume is the Research octane no.) and with the 8:1 piston, the 6-cyliner engine is to be retarded by 3-deg. when using 85 octane. Only the timing value for 90 octane is given for the 7.8:1 piston in the 4-cyclinder engine.

With the optional "low compression" 7:1 pistons Land Rover seems to assume the best either engine ever will see is 83 octane, and with respect to that fuel they're to be retarded by:

4-cylinder engine (with respect to 83 octane):
3-deg. with 75 octane

6-cylinder engine (with respect to 83 octane):
2-deg. with 80 octane
4-deg. with 78 octane

Although these values can't be applied to a Gold Star engine, they do show that a fairly large drop in octane (e.g. from 83 to 78 or 75) doesn't require the timing to be retarded by a huge value. On the other hand, not knowing what the fully advanced timing values are for these engines, these 3-4 deg. changes could represent a pretty significant fractions of those values.


Last edited by Magnetoman; 06/11/19 4:27 pm. Reason: added p.s.
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776131
06/11/19 5:26 pm
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Thanks for this MM, i have learnt something. As they say we are two countries separated by a common language. (I am stretching it a bit by applying "language" to other ways that we describe things like octane ratings or gallons)

In the interest of knowing a little more I found some articles online including a Masters Dissertation titled Effect of spark advance and fuel on knocking tendency of spark ignited engine

John



Last edited by George Kaplan; 06/11/19 5:31 pm.
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776203
06/12/19 4:57 am
06/12/19 4:57 am
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Magnetoman Online content OP

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Originally Posted by George Kaplan
... knocking tendency of spark ignited engine
The expensive stuff that I'm waiting for to arrive is called Race Gas and on their site I found the attached chart. As can be seen they estimate 10:1 needs 100 octane, and also that I would have to drop down to 8:1 if I hoped to use straight 92 pump fuel. If the Race Gas works, that will be my Plan A.

Attached Files
RaceGas_CR_octane.jpg (161 downloads)
RaceGas_CR_octane_2.jpg (160 downloads)
Last edited by Magnetoman; 06/12/19 5:03 am. Reason: added edited version of chart to make it more readable
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776210
06/12/19 6:50 am
06/12/19 6:50 am
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Have worked with MON and RON and the average of the two over the years, when considering high performance competition 2 strokes..easy to get the fuel/compression wrong and you will have an expensive seizure..

Broad-brush 'conventional' wisdom says compression needs to be no more than 10% of the octane rating (being non-specific about which version of octane rating)...hence my earlier post about a max of 9:1 on 92 and probably less (especially given the old-style combustion chamber design).

It is also my experience that some/many octane improvers don't achieve much, especially where they don't contain lead. As they don't, if they want to be acceptable in street engines in most of the western world these days.

Fuel quality, as a function of time and handling, is also a factor: that tin of gas that goes 'whoosh' when you take the lid off is less of a fuel than you might think..the whooshing bit is all the stuff that makes it good. We've all heard how the fuel goes off over time, with the light ends (the whoosh) evaporating and reducing the fuel quality. It's true - read up on Reed Vapour Pressure. Had this experience driven home to me in recent times, where the fuel had lost all it's whoosh and was consequently harder to vaporize in the engine (effectively coming out of the needle jet in bigger 'globs' than normal, which are consequently harder to vaporise). The end result is that the spark plug (and presumably any air-fuel sampling device) sees rich, though the combustion is actually lean...so the tuner goes smaller in the jetting..worsening the problem.

Kerry W

PS: sometimes simply backing the spark off is no more than a band-aid..the compression needs to be right for the fuel

Last edited by Kerry W; 06/12/19 6:54 am.

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Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776248
06/12/19 5:06 pm
06/12/19 5:06 pm
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Originally Posted by Kerry W
my experience that some/many octane improvers don't achieve much, especially where they don't contain lead. As they don't, if they want to be acceptable in street engines in most of the western world these days.
Right. I'm generally skeptical of snake oil, although overall I'm a believer in Monsanto's old slogan of "better living through chemistry." That's why I've tried to qualify my comments about the octane booster I used by writing 'if it worked', and the stuff I have on order with 'if it works'.

Originally Posted by Kerry W
high performance competition 2 strokes..easy to get the fuel/compression wrong and you will have an expensive seizure..
Another important factor is temperature. I reported my jetting results as having been made at an ambient temperature of 95 oF because that matters. My friend whose shop burned down was an active AHRMA competitor in the '90s and '00s on his now-destroyed Yamaha 350. Since in principle he might race one weekend at Willow Springs, California at 95oF and the next weekend at Steamboat Springs, Colorado at 65 oF, I realized he would get more practice time at the second higher, colder track if he needed to spend less time sorting out the new jetting.

It turns out that fuel flow depends on the ratio of density to viscosity, and both of these properties change with temperature. So, using a Cannon-Femke viscosimeter and Ertco hydrometer I determined these to 0.2% between 32 oF and 120 oF for VP C12 racing fuel. Making a long story short, I then created a kit containing the instruments for measuring the necessary parameters (relative air density, temperature, humidity, etc.) and devised a program for a portable calculator that used all of these inputs to convert the presumably-perfect main jet determined at one race to the required main jet for the current track.

Returning to my Competition, fuel flow at 95 oF is ~35% greater than at 65 oF which, of course, will affect the jetting. Unfortunately, it's more complicated than simply measuring the ambient temperature since what matters is the temperature of the fuel in the float bowl (which can be measured, but with more effort). But, without being quantitative, it's safe to say that, all other things being equal, more fuel will flow on a hot day than on a cold day. It's also safe to say the air density will be lower on a hot day than a cold day, which means that both the total amount of air ingested by the engine, and the "vacuum signal" at the top of the spray tube that draws fuel in, depend on temperature. As I said, it's complicated.

Originally Posted by Kerry W
Fuel quality, as a function of time and handling, is also a factor: that tin of gas that goes 'whoosh' when you take the lid off is less of a fuel than you might think.
I was interested in 'the whoosh effect' in the context of determining whether or not fuel stabilizers made any difference. So, in the '00s one long-term test I conducted was of the volume of fuel lost as a function of time. In an open container at 72 oF fully 50% was gone in just three days. While that's not too surprising, 1.9 years later -- hey, I said it was a long-term test -- a small quantity still remained of a very viscous liquid.

Originally Posted by Kerry W
the spark plug (and presumably any air-fuel sampling device) sees rich, though the combustion is actually lean...
Bosch wideband sensors are sensitive only to the oxygen and they produce a voltage proportional to the difference between the percentage of oxygen in the exhaust pipe and that in the outside air. All the sensor "knows" is how much oxygen is present, not how it got there, so there are circumstances when interpretation of that result as rich/lean mixtures can go awry. For example, if an engine misses, oxygen doesn't get combined with the hydrocarbon so the sensor sees too much 02 which the meter incorrectly displays as a lean mixture.

No matter how bad the fuel is, if it burns, the oxygen sensor contains information about the rich/lean mixture strength. That said, "classic" gasoline combines with all the oxygen if the AFR is 14.7, but I don't know if that same 14.7 applies if, say, a lot of the 'whoosh' was gone from the fuel that burned. If the stoichometric ratio of de-whooshed classic gasoline is different than 14.7 then interpretation of the mixture strength from the output of the sensor will be affected.

Octane, compression ratio, ethanol content, timing, temperature, density, air/fuel ratio,... It's remarkable carburetors and engines work at all, let alone that they work so well.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776567
06/16/19 5:20 am
06/16/19 5:20 am
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Maine
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You have "optimized" the AFR for efficient combustion, but running under load using pump fuel in our deep chambered, low energy ignition dinosaurs presents another challenge . Enriching the AFR beyond the modern norm might reduce pinging under load.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776572
06/16/19 6:51 am
06/16/19 6:51 am
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I have no definitive data, but the norm seems to be to retard a few degrees (say, 3 or 4) when running modern, fast(er) burning unleaded fuels.

My lack of data relates more to how much 'too far advanced' and engine would be to pink/ping (depending on where you grew up). I'd suggest that it's probably more than 3 to 4 deg, though while retarding by a few degrees might raise the 'ping threshold', adding fuel, as suggested above, would definitely help - though a compression plate or a few mm off the piston crown is the real answer.

My father and I were in exactly this position with a little air-cooled twin cylinder 125cc Yamaha factory-produced road-racer about 35 years ago - the PO could not stop it seizing and concluded compression was a problem, so fitted 2 head gaskets (it used a little copper gasket). This din't help much. Preference at the time was to use 96 octane pump gas, which you could get away with in up to a 125cc cylinder, because it mixed easily with the preferred Castrol R bean oil. The better fuel (though slow burning) was 100/130 green avgas, readily available, more expensive and didn't like mixing with the Castrol R without a large dose of acetone..which was more of a problem to find.

I the end, we ran the pump gas, backed the timing off from 2.0mm BTDC to 1.85mm (0.006" at the piston), ran the stock single copper head gasket and pushed the jetting up a couple of sizes. On the coldest plugs we could find at the time, (Champion N55G's - approx the same as an NGK B10 or 10.5) it ran like a train..the only time I ever seized it was own I ran it on some soft plugs and forgot to change them for the race..

In this case, the compression was workable for the fuel, but needed less timing and richer jetting to keep it in one piece. It would probably have run better with better fuel and more advance/leaner jetting..though it did get me to score some points in the national 125 series at the time..probably the last time it was done on drum brakes and 5 speed with air-cooling! (about 1984..the bike was 1974..)


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Oliver Wendell Holmes
Re: Correct needle for 1000-series Concentrics? [Re: Kerry W] #776592
06/16/19 2:10 pm
06/16/19 2:10 pm
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Originally Posted by Belfast Bikes
Enriching the AFR beyond the modern norm might reduce pinging under load.
Originally Posted by Kerry W
a compression plate or a few mm off the piston crown is the real answer.
I hope to have the chance later today to try the bike with the new, costly octane booster. I'll also swap the main jet for a different one of the same nominal size to try to sort out the issue with variations in marked size.

What I won't do this morning is rebuild the engine with a lower compression piston. Instead, I'll ride with crossed fingers hoping that, plus the octane booster, provides a workable solution.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776594
06/16/19 2:18 pm
06/16/19 2:18 pm
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Ahh..the old fingers crossed option!

You'll be back..


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Correct needle for 1000-series Concentrics? [Re: Kerry W] #776595
06/16/19 2:20 pm
06/16/19 2:20 pm
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Originally Posted by Kerry W
Ahh..the old fingers crossed option!
Desperate times call for desperate measures...

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776628
06/17/19 12:12 am
06/17/19 12:12 am
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Today's very good, albeit expensive, news is the 'Race Gas' octane additive actually works. I mixed 8 oz. into 2-gal. of 92 octane, which is supposed to boost it to 100. The only times I heard slight pinging/pinking was for the first half-sec. or so when pulling away from a stop sign going uphill without retarding the ignition, and for a half-sec. or so after making a slow-speed U-turn and pulling away in 2nd and again without retarding the ignition. It was 97 oF when I made today's jetting run, which pretty much counts as worst-case conditions for pre-ignition. This additive, although expensive, saves me from having to rebuild the engine and install an 8:1 piston in order to use 92 octane pump fuel.

The downside to 'Race Gas' is it costs $1/oz. ($32.49/32 oz.) so it adds $4 to each gal. of gasoline to bring it up to 100 octane, resulting in a total of ~$7/gal. at today's price at the pump (£1.47/l, AU$2.69/l). On the other hand, at ~50 mpg the additional cost to go 2000 miles only will be ~$160, which is a lot cheaper than rebuilding the engine. Another downside is when I know I won't be able to ride bikes for a while I empty the tank and dump it into one of the cars. That now becomes a much more expensive disposal.

Returning to jetting, you might remember that a jet marked '220' resulted in an AFR of ~12.3.:1 at full throttle, while one marked with a smaller '200' gave a slightly richer mixture of 12.0:1. I didn't have another '200' to try today so I installed a '190'. This resulted in a leaner mixture, as it should, but the 13.0:1 isn't quantitatively consistent with either the '220' or the '200' having been accurately marked (nb. none of them might be correct). That is, if the '190' happens to be a truly accurate 190, an accurate '200' should have given 190/200 x 13.0 = 12.3 instead of 12.0, and an accurate '220' should have given 190/220 x 12.3 = 10.2 instead of 12.3. However, as the saying goes, close counts in horseshoes, hand grenades, and AMAL jet markings, so I conclude from this that the markings on the '190' and '200' are "essentially correct,", but the '220' is off by several sizes. Unfortunately, I had tossed it back in the '220' compartment a week ago where it is now mixed with others that might (or might not) actually be true 220s.

Using the Mikuni "Main Jet Tuning Calculator," if a 190 main jet is perfect at 100 oF, one that is one size larger would be needed if riding at 75 oF and two sizes larger at 47 oF. Stated the other way, the present '190' would be two sizes too lean at 47 oF, resulting in an AFR of 14.5:1 rather than today's 13.0:1. Instead, the '200' that was in it until this morning would give 13.5:1 at that too-cold-to-ride 47 oF, and 12.6 at 75 oF. So, I'll be re-installing the '200'.

I'll shortly be posting a full 1000-Concentric jetting guide with all the relevant results of these experiments. As a preview, for a fixed needle adjustment (middle slot), and within the normal variations of the AFR, the '190', '200' and '220 all gave the same results below ~1/4 throttle, with the main jet dominating above ~1/2 throttle. The effect of the needle can be seen in the shape of the curves between ~1/4 and ~1/2.

Attached Files
AFR.jpg (106 downloads)
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776632
06/17/19 2:12 am
06/17/19 2:12 am
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Posts: 1,297
Middle East,
Kerry W Online content
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Kerry W  Online Content
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Joined: Feb 2012
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Middle East,
So MM, what you're saying is that we can all send you out AMAL main jets for you to calibrate using your AFR setup...generous! A big box on the way!


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776638
06/17/19 3:50 am
06/17/19 3:50 am
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Magnetoman Online content OP

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Originally Posted by Kerry W
what you're saying is that we can all send you out Amal main jets for you to calibrate using your AFR setup...generous! A big box on the way!
A high-born Indian colleague (younger son in the line of the only Indian ever raised to hereditary British peerage) told me a story of his time spent receiving his Ph.D. from Cambridge. His possibly apocryphal (or possibly autobiographical) story was that a high-born Indian joined a research group at Cambridge and, in what is a pretty common practice, was given an initial menial job to begin familiarizing him with the lab. He was to sort loose resistors back into appropriate drawers, but when the professor returned later in the day he saw the resistors still strewn across the table. When the professor asked why he hadn't sorted them the student replied "the boy never showed up."

Back to your box of jets. I'll be more than happy to calibrate all of them. As soon as the boy shows up...

If summer temperatures weren't coming on strong, and if I didn't have other things I wanted to get to (like re-rebuilding the Ariel), I'd be very tempted at this point to convert my 1038 to a full 4-stroke body and see how different its final jetting was from the 1036.


Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776719
06/18/19 12:41 am
06/18/19 12:41 am
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Magnetoman Online content OP

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I had a second close call with the Sheriff. After getting a data point at 3/4 throttle I didn't have enough road left to get another data point (i.e. by holding the throttle at a fixed position for at least 4 sec.), so I shut down in order to do a U-turn early at an upcoming cross road. When I already had dropped to a slow speed a Sheriff's car pulled up at that stop sign and then turned onto my road. Only once today had I quickly glanced at the speedometer and saw I was only doing 40. It certainly felt faster than that but I dismissed it as the poor quality of the road and continued accelerating. Later I realized it was the tach I had glanced at so I had been going ~70 mph. If I had been doing a full-throttle run I would have been going at least that fast when I passed that cross street.

Originally Posted by Magnetoman
I'll shortly be posting a full 1000-Concentric jetting guide...
Correction, I should have written that I'll soon be posting that guide. I always hate it when I've disassembled some setup only to then realize there is one more measurement I wish I'd made. So, since there's no urgency to have the Competition in final form, and since the 'Race Gas' is working with its 10:1 piston (another 32 oz. of which is on order), it was time for another measurement.

I had thought raising the needle another notch would make it too rich, but I decided I needed to find out for sure. So, I raised the needle to the bottom slot leaving the rest of the settings the same as yesterday. Also, what is important for fuel flow is its temperature, not that of the air, so I measured the temperature of the fuel in the tank (~100 oF) and the outside of the float bowl (~100 oF), both of which were essentially the same as the air temperature. The dashed green curve on the attached figure shows the result of today's jetting run with the needle on the richest slot. Updated Figure: the AFR will stay between the green bands with the needle in the #3 slot in the temperature range 48oF<T<98oF.

While today's jetting is "too rich" for maximum h.p. between ~1/4 and ~1/2 throttle, the bike still ran great. Keeping in mind that at 68 oF the curves will be displaced upwards by AFR ~0.8 (and by twice that at 48 oF, a temperature at which only a Scottsman would consider riding), having the needle on slot #3 would ensure the peak always would be below 14.7. Also, during the nine months of my actual riding season, when the temperature is below 90 oF, the AFR would be no richer than ~12:1. So, I'm now tempted to leave the #190 in place and the needle on the #3 slot.

Any day now two 1000-Series slides should show up from England, which will give me a #2, #3, #3.5, #4 and #5 to work with, and I found an incomplete 1036 in the U.S. that tracking shows will be here on Wednesday. If it's in reasonable shape I'll drill out the compensating air passage and install a flat-top 4-stroke spray tube. That will enable me to make direct comparisons of the jetting needed for each carburetor body. The same person using the same motorcycle for all of these jetting studies eliminates a couple of big variables so the one (estimated) other person in the world who might care about these results can have confidence in them.

Attached Files
AFR.jpg (67 downloads)
Last edited by Magnetoman; 06/18/19 5:17 pm. Reason: updated the figure
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776826
06/19/19 7:52 am
06/19/19 7:52 am
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Sydney Australia
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Quote
I had a second close call with the Sheriff. After getting a data point at 3/4 throttle I didn't have enough road left to get another data point (i.e. by holding the throttle at a fixed position for at least 4 sec.), so I shut down in order to do a U-turn early at an upcoming cross road. When I already had dropped to a slow speed a Sheriff's car pulled up at that stop sign and then turned onto my road. Only once today had I quickly glanced at the speedometer and saw I was only doing 40. It certainly felt faster than that but I dismissed it as the poor quality of the road and continued accelerating. Later I realized it was the tach I had glanced at so I had been going ~70 mph. If I had been doing a full-throttle run I would have been going at least that fast when I passed that cross street.


He was probably an old time racer & wanted to soak up the glorious sounds of the bike on full song,,,,,, we hope.


Bike Beesa
Trevor
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776894
06/19/19 11:48 pm
06/19/19 11:48 pm
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Posts: 5,265
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Magnetoman Online content OP

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Magnetoman  Online Content OP

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Originally Posted by Magnetoman
Any day now two 1000-Series slides should show up from England, which will give me a #2, #3, #3.5, #4 and #5 to work with, and I found an incomplete 1036 in the U.S. that tracking shows will be here on Wednesday.
The 1036 was delivered a few minutes ago and, not only is it in good shape, it came with a #2.5 slide. So once the ones from England arrive I'll only need a #4.5 to have a complete set by halves from #2 through #5. Slowly, but steadily, I'm implementing my version of the underwear gnomes' three-step business plan to take over the world, except by cornering the market for 1000-Series Concentrics (Step 1, collect Concentrics; Step 3, take over the world -- like the gnomes, I'm still working on Step 2).

The carburetor is a 1036/11 but my lists only go as high as /8. The slide cutaway and jetting (and jet holder) that came in it are for a 2-stroke but, as can be seen, the spray tube is notched like the ones in the 932s used on Norton 850s. Fairly little information on the 1000-Series is available so this Nortonesque spray tube raises questions for which I'm not aware of the answers. Is the spray tube stock, or a user "upgrade"?

I'll install a 4-stroke spray tube, drill out the compensating air passage, and configure it with the same settings that are listed for a Thruxton. That should get things pretty close for the Gold Star. It's going to be very interesting to compare the final AFR vs. throttle position curves of the two carburetors.

Update: the seller responded to my question saying he doesn't know what bike the carburetor came on, but that he bought it along with other parts from "an old flat tracker who ran Triumphs and Nortons." This doesn't answer the question, but does increase the odds a little that the spray tube was an "upgrade" rather than being factory-original.

Attached Files
1036SprayTube.jpg (51 downloads)
Last edited by Magnetoman; 06/20/19 12:43 am. Reason: Update
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #776907
06/20/19 3:43 am
06/20/19 3:43 am
Joined: Feb 2012
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Middle East,
Kerry W Online content
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Kerry W  Online Content
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Joined: Feb 2012
Posts: 1,297
Middle East,
This will be, thanks to MM's efforts, the real answer to the question - not whether the 2 stroke carb can be made to work on a 4 stroke, but what the differences are between 2 and 4 stroke carb setups for the same bike.

Go to it!


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
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