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Re: Correct needle for 1000-series Concentrics? [Re: Kerry W] #771087 04/15/19 4:23 am
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Magnetoman Offline OP
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Originally Posted by Kerry W
the big-end cage melted, soldering the pin and rollers to the outer race,
Thanks for pointing out that possibility but, of course, I hope your're wrong and GreggK is right. If I do end up having to take the engine completely apart I'll be changing the 10:1 piston for something more suited to today's fuels. Conveniently, I have a Pearson crank assembly sitting on the shelf that I bought when the pound sank after the Brexit vote. I thought I was clever buying it then but little did I know the Brits were determined to do everything in their power to make the exchange rate even better.

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Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771089 04/15/19 4:55 am
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Kerry W Offline
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..every big-end seizure cloned has a silver-plated cage lining!


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771123 04/15/19 1:46 pm
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Kerry has a good point: I recall a section in Golland's book entitled the "Development History of the Gold Star" discussing the measures BSA took to adequately lubricate the big end, and especially where the cage might rub. Their later efforts included "clocking" the oil feed holes in the pin relative to the crank position, and also adding feed holes in the pin to alleviate friction between the cage and the pin shoulders.

I too, hope my earlier suggestions prove correct, but Kerry may well have nailed it.

In any case, checking the simpler causes will be easy, and would be done "on the way in" to checking for a more serious defect in the big end.

.. Gregg


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Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771149 04/15/19 6:23 pm
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Magnetoman Offline OP
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Originally Posted by gREgg-K
how about the bush in the timing side support plate?
Originally Posted by Kerry W
seized big-end..
Of those two possibilities the answer turns out to be possibility #3 -- seized breather. Hallelujah, this looks like a 30 min. job at the cost of a gasket rather than several days and major dollars.

As the first photograph shows, when I pulled the timing cover off oil dripped from the crankshaft feed, so that was a good sign that oil had been flowing. Next I could rock each of the cam gears back and forth against the backlash, indicating they were free in their bushes. At that point I noticed flecks of Al near the magneto gear, as shown in the second photograph. I couldn't get the breather out of the timing case that I had left hanging from the cable, so I removed the tach drive and had to drift the breather out of the case using a socket. The third photograph shows the scoring of the cover caused by the seized breather.

And, yes, with the timing cover off the engine turns over without problem. I've never been so happy to find a seized part. If only I had a Sunnen hone... oh, wait, I do.

Attached Files
Breather02.jpg (93.75 KB, 400 downloads)
Breather01.jpg (102.56 KB, 402 downloads)
Breather03.jpg (61.84 KB, 401 downloads)
Breather04.jpg (96.87 KB, 372 downloads)
Last edited by Magnetoman; 04/15/19 10:07 pm. Reason: added photo of timing cover on the hone
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771188 04/16/19 2:42 am
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Excellent, if surprising result! Happy to be wrong! Jetting will be done by Sunday then!


No generalisation is wholly true, not even this one.
Oliver Wendell Holmes
Re: Correct needle for 1000-series Concentrics? [Re: Kerry W] #771189 04/16/19 4:08 am
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Magnetoman Offline OP
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Originally Posted by Kerry W
Happy to be wrong!
No one is happier than me. When I found the breather wouldn't rotate and then tried the kickstart lever, the clouds parted, the fog lifted, and a flock of songbirds appeared chirping with joy.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771195 04/16/19 6:59 am
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hunter h Offline
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cheers that's good news . but looks like from your photos there is not any oil coming down from top end .The timing gears look dry in photos? hunter

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771207 04/16/19 12:59 pm
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Oh happy day!

Now we have to answer the question: "Why did the breather seize in a timing chest which should have returning oil splashing around in it?" Is not enough oil coming into the chest, or is it being drained away too quickly, so that there is not enough oil for the timing gears to pick it up and distribute it upward?

I wonder if this failure has a cause similar to what results in the crank's oil feed stub seizing in the support plate bush?

.. Gregg


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Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771216 04/16/19 3:41 pm
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Magnetoman Offline OP
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Originally Posted by hunter h
looks like from your photos there is not any oil coming down from top end
Originally Posted by gREgg-K
Is not enough oil coming into the chest,
I'm reminded what my friend, whose shop burned down two weeks ago, says when asked what is the "best" oil to use -- "Any oil is way better than no oil." The seized breather illustrates this fact.

I hadn't run that bike in a long time so the cause could be simple, such as just taking longer than the ~30 sec. it ran to fill the cavities and wet the surfaces before oil could make it back to the timing chest. Or it could be more complex, such as having developed an air leak in the lines, or the oil pump has gone bad with time.

When I assembled it yesterday I used cam lube on the breather to keep it happy until oil takes over the job, but I will investigate the other possibilities today before I start the bike. And, once I do start it, I'll have the oil cap off so I can confirm that oil is returning to the tank before I peg the rev limiter.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771222 04/16/19 5:06 pm
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MM: Your adventure points to the whole area of splash/mist lubrication which I think is a major cause for engine start up wear. Most of us keenly pre-lube these areas when we build an engine but that is where it normally ends. One only needs to think of the pressure put onto a dry cam lobe and cam follower when cranking over an engine that has not run for a long time. Until the engine starts and oil starts to flow it will be metal to metal after a few kicks. Imagine the dry engine that took dozens or even hundreds of kicks to get going. Kicking will quickly pump oil into the crank but that will be about it. The GS will at least be pumping oil into the cam spindles but it will not immediately get to the lobes or other area needing splash or mist lubrication.

I always attempt to lubricate as much as possible before I start up a sleeping engine.

It varies from engine to engine but most have some easy way to get some oil trickling down towards the cams before starting. The A65 has the rocker cover for access, the Triumphs have the four rocker inspection caps, the unit singles have the two rocker inspection caps and the pre-unit BSA singles have either the tappet recess cover or rocker inspection cover. The later timed breather GS engines have either a cover or a tach drive that can be removed to access that area for a little pre-start lube. Most of the rockers covers I have seen have real wear in the area of the timed breather.

Gordo



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Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771240 04/16/19 8:11 pm
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Magnetoman Offline OP
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Originally Posted by Gordo in Comox
I always attempt to lubricate as much as possible before I start up a sleeping engine.
I knew that. But, if only I had acted on it. Sigh...

As the first photograph shows, the oil from the tank has to flow 750 miles (estimated) before it finally gets to the small pipe that leads to the rocker cover, then drip down to the timing chest, where it finally can lubricate the breather. It took me all of 15 minutes this morning to pump roughly a pint of oil everywhere in the rocker box that the stream from the oil can could reach, along with straight down the pushrod tunnel to the timing chest. This included removing the two bolts from the rocker feed and pumping oil directly into both rockers.

The 15 min. I "saved" by not doing what I "knew" I should have done resulted in unnecessary engine wear as well as much more than 15 min. of frustration spent trying to start an engine with a breather that seized because I hadn't taken the time to add the oil.

With that out of the way, I put fuel in the tank, the magneto on half-retard, tickled the carburetor, and it started immediately on the DocZ. Oil from the return line was flowing so I took a couple of laps of the driveway. Given that it wasn't fully warmed up and the driveway limited in what I could do, it feels like the slide cutaway could be correct. Also, when I tried to set the idle (again, not fully warmed up), I had to have the pilot screw almost all the way in so I'll switch from the #30 jet to a #25 when I get a chance.

The extra pint or so of oil I squirted into the engine today caused the oil tank to become too full (accentuated in the photograph by the bike being on its side stand) so I sucked 350 cc out. This makes the level lower than I originally had it but makes it easier to see oil squirting back from the return line. After I gain confidence in the oil pump I might add a bit of oil to the tank, but I might not.

Sadly, that's all the testing for today. My granddaughters got a new pony and they want to show it to us when they get out of school. I'm sorry to admit it to the true bike junkies, but jetting a Gold Star falls lower on the priority list than making my granddaughters happy.

Attached Files
Breather05.jpg (83.74 KB, 279 downloads)
Breather06.jpg (86.52 KB, 281 downloads)
Breather07.jpg (84.43 KB, 277 downloads)
Breather08.jpg (67.77 KB, 276 downloads)
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771241 04/16/19 8:22 pm
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gREgg-K Offline
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Originally Posted by Magnetoman
Originally Posted by Gordo in Comox
I always attempt to lubricate as much as possible before I start up a sleeping engine.
I knew that. But, if only I had acted on it. Sigh...
<SNIP>
The 15 min. I "saved" by not doing what I "knew" <SNIP>.

You're not alone of course, and it's so common that someone even came up with a saying to cover it:
"There's never enough time to do it right, but there's always time to do it over ..."

Sounds like you now have it under control. Congratulations MM, for wrestling the old beast to the ground!
.. Gregg


Spyder Integrated Technologies
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SMITHS Chronometric Restoration
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Re: Correct needle for 1000-series Concentrics? [Re: gREgg-K] #771256 04/16/19 11:00 pm
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Magnetoman Offline OP
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Originally Posted by gREgg-K
"There's never enough time to do it right, but there's always time to do it over ..."
Sigh...

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771353 04/18/19 4:17 am
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Magnetoman Offline OP
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I did a short loop in the neighborhood this morning and the jetting seemed great (at least up to ~40 mph) so I decided to attach the air/fuel sensor and data logger. I proceeded slowly, trying to make sure nothing could fall off, or get caught in the spokes, so that took about 90 min. The photograph shows the final result.

Everything is held in place by nylon straps or zip ties, but I also used blue tape to keep a few things from wiggling. Starting from the back of the bike there's a sealed 12 V battery. Next is the inductive clamp around the spark plug lead for determining rpm. Located at the bend in the pipe is the wideband sensor. Clamped to the handlebars is the throttle position sensor based on a potentiometer and AA battery. And on top of the headlamp, along with all the extra wire, is the Innovate LM-1 and an accessory called the LMA-2 that accepts the input from the inductive clamp along with five 0-5 Volt channels. I'm only using one of the channels, for the throttle position sensor.

I started the bike, fired up the Innovate LM-1 (which takes ~30 sec. to warm the sensor), hit 'R'(ecord), and headed out on a planned ~10-mile loop. Unfortunately, I hadn't emptied the memory since I last used it and failed to see the brief message telling me it was full. Actually, I did see a message come up on the screen but didn't pay attention to it so I can't blame the unit.

The bike ran fairly well as I exited the neighborhood but the A/F readings were pretty low, i.e. rich. I didn't pay a lot of attention to the numbers (but they were often in the 11s and 12s, and almost never hit 14) since it all was, ahem, being recorded for later viewing. When I returned to the neighborhood I was behind a car going slowly and the bike started loading up. I was afraid it would die on me so I reved the engine to get it running well and passed the guy on a blind curve going maybe 20 mph at 4000 rpm. I'm sure he rightfully was swearing at me for being such a [***].

I made it back home and up the steep driveway only to discover when I was back under the carport that there was no flashing 'R' in the display to indicate it was recording. So, the DocZ started the bike again but I didn't get any further than the gate before it was 8-stroking at anything other than idle. That ended the day.

The current configuration is:
-- 30 pilot
-- .106 needle jet (measured 0.1065"-0.1066")
-- 4-stroke needle on top notch
-- 2-stroke spray tube
-- cutaway #3
-- 340 main

Since the richness is most pronounced at low throttle settings I'll change to a 25 pilot in the morning and hope that makes a big difference. Dropping the needle isn't an option since it's already on the top notch. Now that I've cleared the LM-1's memory tomorrow's run should be more enlightening than today's.

Attached Files
InnovateAF.jpg (124.36 KB, 213 downloads)
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771546 04/19/19 10:37 pm
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Magnetoman Offline OP
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A mini heat wave already had us at 96 oF at 1pm and it's now 3:30 pm and 98 oF so I only was able to make one ride today. OK, I could make more, but did I mention it's 98 oF?

A few notes in reading the attached two graphs from my data logger. The values for AFR (magenta), rpm (black), and voltage from the throttle position sensor (red) at the upper right are from the time into today's run (11 min. 29.33 sec. for the first graph) where I had the cursor set when I took the screen shot. The rpm values shown in black are 2x what they should be, apparently because the inductive clamp I have laying directly on the magneto is picking up a signal from there as well as the wire. The voltage values are 1.5/5.0 of what they should be because I incorrectly tricked the program when it imported the data -- I should have used a factor of 5.0/1.5. The appropriate scales for these three quantities are shown in the same colors on the Y axis. As background, the stoichiometric ration for old fashioned gasoline is 14.7, and maximum power from most engines obtained around 12-13.

Referring to the first graph, during the interval between 11:22 and 11:48 it can be seen that I had the throttle at a fairly constant ~0.1 so it was mostly running on the pilot circuit. The AFR can be seen to have been a very rich 11 or so. The four sharp spikes in this time interval are because the engine missed, allowing raw fuel and oxygen to pass through to the exhaust. Engine rpm was ~7800/2 = 3900 so each combustion cycle was (3900/2)-1 = 0.5 msec. The fact these spikes are seen tells us the response time of the sensor is at least this fast.

The three regions near 11:12, 11:20 and 11:52 show that when I completely rolled off the throttle the exhaust mixture got very lean because only air and a little unburned fuel was passing through under that circumstance.

Turning to the second graph, I had the cursor placed at 8 min. 19.3 sec. for the screen shot, at which point the throttle was wide open. Note that the AFR is a very rich 9.35.

Starting at the far left of this graph it can be seen that over a time of ~1¾ sec. I increased it to ~½ throttle. Up to ~¼ throttle the AFR stayed around 13, but then started dropping as the throttle opened wider, dropping to ~10. I briefly let off the throttle, then rolled it back on to full throttle. Again up to partial throttle the AFR went back to ~13, but again it dropped to below 10 by full throttle. Note that these are "transient" behaviors, not steady state, so there's a lag between changing the throttle position and the engine catching up with the change.

It's not worthwhile analyzing this data any further. The bike was very rich and, as a result, it would load up at low throttle settings and I'd have to rev the engine to clean it out enough that it would again run smoothly. So, there's a lot of bad behavior reflected in various time intervals.

This morning I replaced the #30 pilot with a #25 but did not adjust it before today's run for reasons not worth going into. Had it been adjusted I assume the AFR at low throttle settings would have been more reasonable than the super-rich <10 that caused the bike to load up today. I'll drop the main jet by a couple of sizes and adjust the idle mixture before setting off on a similar run tomorrow.

Attached Files
Innovate01.jpg (73.96 KB, 190 downloads)
Innovate02.jpg (63.64 KB, 190 downloads)
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771630 04/20/19 6:34 pm
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Magnetoman Offline OP
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I made some progress on my jetting this morning. I found that turning the pilot mixture screw all the way in had no effect on the rpm. The last time I had that problem, coincidentally on a Gold Star but with a Monobloc, I found the float level was very low. So, although I checked it long ago, after lunch I'll check the float level again.

With the pilot screw all the way in I made another 8-mile run. Halfway through the run, when the engine was fully up to temperature, I stopped and watched the AFR as I adjusted the pilot screw. It got richer as I backed it out a half turn, and got leaner as I turned it back in, so all the way in was leaner than yesterday (but still not correct). Anyway, with the somewhat leaner pilot mixture the bike behaved better than yesterday. The mixture was still too rich but it never dropped below 10 where igniting it seems to be problematic.

The DocZ rollers are earning their keep. Bikes like rich mixtures to start but my AMAL 1036 doesn't have a choke (the cap only has a hole for the throttle cable and thus far I haven't located the appropriate 1000-series cap). But, no choke is no problem with rollers. One problem I am having, though, is I'm way too used to the up-for-down shift pattern of my other Gold Stars. This one has rear sets, but not a reverse cam plate, so it has a Triumph-like up-for-up shift pattern. I have a reverse cam plate I could install but I'm not sufficiently motivated (or, the least bit motivated) to do so.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771634 04/20/19 7:00 pm
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koncretekid Offline
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Have you got a 105 needle jet to try?


Life's uncertain - go fast now!
Re: Correct needle for 1000-series Concentrics? [Re: koncretekid] #771635 04/20/19 7:07 pm
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Magnetoman Offline OP
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Originally Posted by koncretekid
Have you got a 105 needle jet to try?
Indeed I do. It certainly could be that the additional suction power of the 2-stroke body will require a smaller needle jet. But, one thing at a time. First I have to deal with the pilot circuit and possible issue with the fuel level.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771636 04/20/19 7:25 pm
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MM would you like a 4 stroke (straight) spray tube?


Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771639 04/20/19 8:31 pm
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Originally Posted by John Healy
MM would you like a 4 stroke (straight) spray tube?
John, thank you very much for the generous offer. However, I made a drift and pressed one out of an old body a few weeks ago. But, in the interests of science, and motivated by my flow bench testing, I decided to see how well I could do with the 2-stroke spray tube and with the 2-stroke constriction in the air correction passage. If I can't wrestle it into submission with this configuration I'll convert it to fully 4-stroke.

Originally Posted by Magnetoman
The last time I had that problem, ... I found the float level was very low.
The float is supposed to be 0.060"-0.080" below the top surface of the bowl. Do you suppose it's close enough now?

It's interesting that this bike, as well as the Catalina that previously had the same problem with its Monobloc, ran at all, let alone not horribly, with the fuel level fully 1" below where it's supposed to be. All I did before taking the photograph was drain the bowl as a result of switching plugs at the bottom, then turn the petcocks on. Tapping the bowl with a screwdriver handle didn't cause the level to change. It's easy to image the float hanging up on something as the bowl filled, causing the needle not to seat and therefore to overflow. But, how it can stop the flow where it did is a puzzle, especially since at some point in the past it was fine when I did the same test on the bench. However, since then the bowl has been off several time. The carburetor will now come off the bike for close inspection and repair. This "discovery" counts as significant progress.

Addendum: actually, the top of the float is supposed to be ~0.080" below the top of the bowl, but I can't seem to find any description of where the fuel level is supposed to be. John?...
I'm not saying I made the following mistake, but I'm not saying I didn't, either. By the time I got the float bowl into the garage and looked at it the tang on the float was above the needle. If this is how it was when it was in the carburetor it would have stopped the flow too soon, resulting in a too-low level. After carefully checking the height when the tang, not the end of the needle, was depressed I re-installed it and the second photograph shows where the fuel is now. Still, where should the level be?

p.s. The new, higher fuel level made somewhat of a difference, although it still idles best with the pilot mixture screw turned all the way in (#25 pilot jet). If I back the screw out 1/2 turn the idle drops to where I fear it could die. I could change to a #20 but first I'd really, really like to know where the fuel level should be.

p.p.s. I found a couple of references that say the fuel level should be 4.5-6 mm below the top of the float bowl. Assuming this is correct (¿is it?), my fuel level is still too low at ~10 mm below the top of the float bowl in the center, i.e. in the middle of the jets.

Attached Files
FloatLevel.jpg (117.95 KB, 144 downloads)
FloatLevel2.jpg (84.08 KB, 140 downloads)
FloatLevel3.jpg (74.39 KB, 121 downloads)
Last edited by Magnetoman; 04/20/19 10:39 pm. Reason: addendum, p.s. and p.p.s.
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771649 04/20/19 10:47 pm
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Wouldn't the important level be at the inlet to the main jet, as the carb is not level? And if the level was too low, how would it cause a rich condition?
Tom


Life's uncertain - go fast now!
Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771651 04/20/19 11:01 pm
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Hi MM.
Quote
I stopped and watched the AFR as I adjusted the pilot screw. It got richer as I backed it out a half turn, and got leaner as I turned it back in,


This is 100% the opposite of what should happen ????
Opening the air screw should lean the mixture
in an earlier post you also said the opposite of what is correct on selecting pilot jet size. ??
Carbs in general that behave like this usually have blocked internal passages, the two tiny drillings one under the engine side of the slide and the other further inwards
I am presuming the 1000 series did not have the pressed in pilot bush as on other Concentrics? adding a screwed in pilot to one of those really
messes things up
The Concentrics also do not like being mounted at a downdraft angle this makes setting the fuel level a matter of trial and error to find the best results,
The factory level recommendations are for horizontally mounted carbs
Set at the factory level the pilot circuit floods when the carb is tilted forwards
As a base guide I would aim to set the fuel level to the bottom edge of the thread of the pilot air screw

Which Sunday did You say ?????
John





Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771652 04/20/19 11:08 pm
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When the body is level it is .170" to .240" below top edge. With the MKII there are considerations about the location of the pilot jet when the body angle is more than 15°. Have had little experience with this carb. They move it from the outlet side to the inlet side.


Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771662 04/21/19 12:38 am
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Magnetoman Offline OP
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Originally Posted by koncretekid
Wouldn't the important level be at the inlet to the main jet, as the carb is not level? And if the level was too low, how would it cause a rich condition?
What matters is the height of the fuel below the spray tube, inside the jet chamber. Even if the main jet were mounted at 45-deg. so its inlet were higher than it normally would be, all that matters is the height of the fuel inside the jet chamber, not at the submerged inlet to the main jet.

As for whether it should be too rich or too lean when the fuel level is too low, it is behaving in the same way the Monobloc on my Catalina behaved a year ago when the fuel level in the float bowl was much too low, i.e. it was nearly unresponsive to the pilot mixture screw but ran best with the screw all the way in.

Note that after I managed to raise the level to the current ~10 mm the engine started to actually respond to the pilot mixture screw, whereas before it didn't (I could see the AFR change a little but the effect on the running was quite a bit less than it is now).

Originally Posted by chaterlea25
Quote
I stopped and watched the AFR as I adjusted the pilot screw. It got richer as I backed it out a half turn, and got leaner as I turned it back in,
This is 100% the opposite of what should happen ????
Opening the air screw should lean the mixture
Yes, that's certainly true when the fuel level in the bowl is close to correct. Which it isn't. As I wrote above, whether or not it should have acted this way, this is also how the Monobloc on the Catalina behaved when its fuel level was very low.

Originally Posted by chaterlea25
Carbs in general that behave like this usually have blocked internal passages, ...
I am presuming the 1000 series did not have the pressed in pilot bush as on other Concentrics?
The Concentrics also do not like being mounted at a downdraft angle this makes setting the fuel level a matter of trial and error to find the best results,
The factory level recommendations are for horizontally mounted carbs
Set at the factory level the pilot circuit floods when the carb is tilted forwards
As a base guide I would aim to set the fuel level to the bottom edge of the thread of the pilot air screw
This is a 2-stroke carburetor so has the replaceable pilot jet. However, the pilot circuit draws from the bottom of the bowl, and the jet is surrounded by the float bowl gasket so fuel only can get to it from the bottom of the bowl, and anyway as the photographs in my previous post show, the fuel level is too low to reach the gasket even though there is a downdraft angle.

I think the bottom of the of the pilot air screw would be way too high. If you think it is flooding now, it really would flood then. I'm going for the factory-recommended 4.5-6 mm (John's 0.170" - 0.240"). Unfortunately, all I have at the moment are a few original (non-adjustable) floats. I know the level can be tweaked by pressing on the needle seat, but even with a float in it that comes to the top of the float bowl the level is still ~10 mm too low so pushing the seat lower would result in the float topping out and the needle not sealing. I've ordered an adjustable "stay-up" float but it won't be here until the middle of the week.

Originally Posted by chaterlea25
Which Sunday did You say ?????
If the 'Competition' is fully resurrected tomorrow it will be an Easter Miracle.

Originally Posted by John Healy
When the body is level it is .170" to .240" below top edge.
Thanks for that. That's what I'll set when the adjustable float arrives.

Re: Correct needle for 1000-series Concentrics? [Re: Magnetoman] #771678 04/21/19 11:25 am
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Kerry W Offline
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Reference the comment above about 2 stroke Concentrics having replaceable pilot jets, my experience is that the 1000 series ALL had replaceable pilot jets.

Also, I've never seen a 1000 series Concentric top that had a hole for the choke cable, nor a slide with the hole for the choke slide, but that's just me.


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