67 Atlas

Had the Atlas out for some riding yesterday and had a blast! It amazed me that when I stopped anywhere, the bike drew a crowd.
Bike started easily in 2 kicks after sitting for several weeks and generally ran well during the ride. I say generally because it just flat out died a couple of times at stop lights. What was a real problem was that after a short stop to get gas, it took 20 minutes of leg-numbing kicking to get her started again. Happened a second time after stopping for a half hour, then again after another short stop.
Fuel supply seems ok- I pulled a hose and opened petcock to test. It almost seems like sh has some sort of vapor lock going on. Any thoughts?

wjrich said:

Had the Atlas out for some riding yesterday and had a blast! It amazed me that when I stopped anywhere, the bike drew a crowd.
Bike started easily in 2 kicks after sitting for several weeks and generally ran well during the ride. I say generally because it just flat out died a couple of times at stop lights. What was a real problem was that after a short stop to get gas, it took 20 minutes of leg-numbing kicking to get her started again. Happened a second time after stopping for a half hour, then again after another short stop.
Fuel supply seems ok- I pulled a hose and opened petcock to test. It almost seems like sh has some sort of vapor lock going on. Any thoughts?

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If it’s not fuel, it is almost definitely something electrical; your description describes almost all old Norton’s the world over. Which ignition system have you got- Magneto or some other type :?:

Press the ticklers next time it happens.

Hadsimilar issues with my '66 Atlas when I first got it on the road. The only problem was me - technique and familiarity mean that I have not had the issue in the last 5 years. Practice, I suspect I was flooding it when I had the problem. I give it much less throttle when starting 'warm' as opposed to cold.

It's a magneto.
I'm thinking I flood it out when warm, as I habitually tickle till my finger's wet all the time. This is the first time I've had the bike out for any length of time simce swapping out the monoblocs for concentrics. The bike misbehaved similarly with the monos, but looking back, I probably over tickled them as well on hot starts.
I'll have to revisit my technique next ride.
Still have to figure out why it sometimes just dies at a stoplight or right before as I'm throttling down. Usually fires up on 1 kick when that happens, which shows that my problem above may be flooding.
In the meantime, I'm starting to look funny in shorts with one muscular leg and a stick for the other.

wjrich said:

It's a magneto.
I'm thinking I flood it out when warm, as I habitually tickle till my finger's wet all the time. This is the first time I've had the bike out for any length of time simce swapping out the monoblocs for concentrics. The bike misbehaved similarly with the monos, but looking back, I probably over tickled them as well on hot starts.
I'll have to revisit my technique next ride.
Still have to figure out why it sometimes just dies at a stoplight or right before as I'm throttling down. Usually fires up on 1 kick when that happens, which shows that my problem above may be flooding.
In the meantime, I'm starting to look funny in shorts with one muscular leg and a stick for the other.

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If you think you're flooding it, don't tickle it so much!

If you think it's flooded, kick it over a couple of times with a big throttle opening.

Have you ever had the mag's capacitor changed? They age, and will cause the mag to cut out when hot, but will start fine cold. The Lucas capacitors can be expected to do this after 30 - 40 years age, even if they are NOS.

I agree that Lucas capacitors (post war) were junk when new, heck Lucas themselves only gave new ones a 10 year shelf life! In this case, be sure to determine if your trouble is fuel, or ignition. My bet is a flooded carb, but its nearly impossible to diagnose over the internet. If you keep a plug wrench on the bike, the next time you have trouble starting it, pull the plug, is it soaking wet? If it is, its flooded. Hold the plug against the head (to ground it) and give a kick, is there spark? This simple easy test will tell you a lot& its free.
If you find a weak spark, PM me about your mag & I will walk you through what you can do to narrow down a mag problem , but because you can restart it while everything is still hot, I would think the mag is OK & the plugs are either flooded, or fouled with black soot.

Skip

skipsoldbikes said:

I agree that Lucas capacitors (post war) were junk when new, heck Lucas themselves only gave new ones a 10 year shelf life! In this case, be sure to determine if your trouble is fuel, or ignition. My bet is a flooded carb, but its nearly impossible to diagnose over the internet. If you keep a plug wrench on the bike, the next time you have trouble starting it, pull the plug, is it soaking wet? If it is, its flooded. Hold the plug against the head (to ground it) and give a kick, is there spark? This simple easy test will tell you a lot& its free.
If you find a weak spark, PM me about your mag & I will walk you through what you can do to narrow down a mag problem , but because you can restart it while everything is still hot, I would think the mag is OK & the plugs are either flooded, or fouled with black soot.

Skip

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Thanks Skip.
It'll be 2 weeks before I will be able to take her out again, and will do the plug check. Not sure if the capacitator has ever been changed- only had the bike over 2 years now, so not sure what PO did or didn't do. Motor has been rebuilt since tun, but don't know if attention was paid to the magneto.
Will report back when I get a chance to test it...

Check to see if oil has got into magneto, remove one HT connector on Mag, and both spark plugs, get someone to gently turn over engine while you insert ear wax cleaners into slip ring. Clean all oil off, use electrical contact cleaner to get really clean and assemble and start. If oil seal has gone, replace, but use a degree disc on crankshaft and check that magneto fires 0 & 180 degrees exactly. I cannot stress how important this is; ignore this advice at your own risk.
(Jam Advance/retard fully open with suitable size nut when carrying out above)

Went back to basics with the carbs and re-set everything following the advice on the Bushman Amal page. Thouroughly cleaned the pilot jet with a #78 drill bit, synchronized the slides as per instructions, set the idle screw and screwed the pilot screw out 1.5 turns.
Fired up the mortor and readjusted the idle screw as directed, readjusted again once the mortor was completely warmed up. The bike ran smoothly and idled well at about 11oo rpm once fully warmed up. I was confused a bnit, as this was the same thing I had done before that produced the problems outlined above. What I did do differently was in the adjustment of the pilot screws. Originally, I turned both screws out 1.5 turns, which I interpreted as 540 degrees (360 + 180). This time, I turned the screws out 270 degrees (180 + 90), and at leaset on my brief ride yesterdat, made all the difference. Will test again with a ride this evening, but could something that simple have made the difference? Air screw turned out too far causing my leaned out idle issue once warmed up?

Glad to hear that your recent adjustment has made a world of difference in the running of your Atlas.
It's interesting what you said about 1.5 turns out (difference between 360 + 180 and 180 + 90). I've always known / assumed that "1 turn out" would be 360 degrees. Either way, the settings for your new adjustment would definitely be a richer setting than the previous one. What's the difference in air temperature between now and when you first were having problems? I too live in the Chicago suburbs and was getting a very lean reading a while ago when the temperature was very hot and dry.
Please keep us posted as to how your recent tune holds. Could easily have been the pilot jet cleaning or the setting. Or a combination of both. Either way, would love to know how you get along with it. I've got a 66 Atlas, and live close to you, so always good to compare notes.

Took her out for a 30-40 minute ride last night which would be enough time to start producing some of the problems I mentioned earlier, and the bike ran fine. Idled at about 11-1200 after warming up fully, only stalled once, and started with 3 kicks after a 10-15 minute stop. Have to say it was cooler last night than the last time i took it out in mid August, and don't know if that had any impact, but I'll be happy if she keeps on running like this. Thanks all fo the good advice.

wilkey113 said:

Glad to hear that your recent adjustment has made a world of difference in the running of your Atlas.
It's interesting what you said about 1.5 turns out (difference between 360 + 180 and 180 + 90). I've always known / assumed that "1 turn out" would be 360 degrees. Either way, the settings for your new adjustment would definitely be a richer setting than the previous one. What's the difference in air temperature between now and when you first were having problems? I too live in the Chicago suburbs and was getting a very lean reading a while ago when the temperature was very hot and dry.
Please keep us posted as to how your recent tune holds. Could easily have been the pilot jet cleaning or the setting. Or a combination of both. Either way, would love to know how you get along with it. I've got a 66 Atlas, and live close to you, so always good to compare notes.

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Can I just point out to you that the 1 ½ turns out of the air /pilot screw is not written in stone-every engine, indeed every cylinder, is different and no two cylinders requires the exact same setting on the air jet ajusting screw.
For the benefit of you all, I have found that if you are a home mechanic use a Gunson’s Colortune (outside on a dark night) to fine tune the carb mixture, you will also find a slightly better acceleration from standstill and low throttle off/on throttle response if only slightly out by even 1/16 turn.
Also that most muticylinder bikes from the far east have an idle adjusting knob of some sort, the variation in barometer pressure and air humidity can sometimes play hell with the tickover. :shock:

Bernhard said:

[

Can I just point out to you that the 1 ½ turns out of the air /pilot screw is not written in stone-every engine, indeed every cylinder, is different and no two cylinders requires the exact same setting on the air jet ajusting screw.

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Yes. That's why it's adjustable!

For the benefit of you all, I have found that if you are a home mechanic use a Gunson’s Colortune (outside on a dark night) to fine tune the carb mixture, you will also find a slightly better acceleration from standstill and low throttle off/on throttle response if only slightly out by even 1/16 turn.
:

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Not so sure that there's any real benefit to using the Colortune. It's fun though.

Triton Thrasher said:

Not so sure that there's any real benefit to using the Colortune.

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Yes - the times I've seen one of those colortunes used, on a perfectly running engine it must be said, it indicated that the tuning was not correct....

A pair of vacuum gauges - on a Commando at least - is a far more useful weapon. ?

Triton Thrasher said:

Bernhard said:

[
Can I just point out to you that the 1 ½ turns out of the air /pilot screw is not written in stone-every engine, indeed every cylinder, is different and no two cylinders requires the exact same setting on the air jet ajusting screw.

Click to expand...

Yes. That's why it's adjustable!

For the benefit of you all, I have found that if you are a home mechanic use a Gunson’s Colortune (outside on a dark night) to fine tune the carb mixture, you will also find a slightly better acceleration from standstill and low throttle off/on throttle response if only slightly out by even 1/16 turn.
:

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Not so sure that there's any real benefit to using the Colortune. It's fun though.

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If you can get 100% right-then there is no need for it-but if you are even 1/16 of a turn or indeed 1/32 of a turn out, then it’s out.
So, the blue flame principle means absolutely nothing to you :?:
I take it you are not a chemist or a heating engineer , or ever used a Colortune at all:?:

Bernhard said:

I take it you are not a chemist or a heating engineer , or ever used a Colortune at all:?:

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I have seen a colortune used.
And would best describe it as 'in-exact science'.
It was sooo far out, on a perfectly running engine, that I would consider it near useless.
To get a perfect blue flame, it would need to be lean as blazes. (?)

Maybe the fuel chemistry has more to do with it than makes it useful ?

Rohan said:

Bernhard said:

I take it you are not a chemist or a heating engineer , or ever used a Colortune at all:?:

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I have seen a colortune used.
And would best describe it as 'in-exact science'.
It was sooo far out, on a perfectly running engine, that I would consider it near useless.
To get a perfect blue flame, it would need to be lean as blazes. (?)

Maybe the fuel chemistry has more to do with it than makes it useful ?

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Only you Rohan would give a reply like this on the forum :!:
If you mean just the one engine, there could be 101 different reasons why the Colortune appeared not to work, the engine could have carb, engine, and ignition issues if it was an old one.
Or, what do I know! -The person using the Colortune was colour blind :!:
Any 10 year old child, who could get a Bunsen burner right, could operate and get the Colortune spark plug right.

http://www.gunson.co.uk/items/pdf/Produ ... _Chart.pdf

The lesson here:

Dozens of threads are started each year on dozens of internet forums by people who's classic motorcycles don't run, and the reason usually turns out to be that they just have not read and gone through the most basic tuning texts or tuning check lists.

And that is the "magic wand" that they are looking for, taking the time to learn the basics and think for themselves.

Someone a thousand miles away is never going to be able to do what you can do by reading over the original owner's manual for your bike and seeing what it says the bike needs to be on square one.

A few years ago this kid was bugging me to help him with his Honda cb450 twin which he had bought for a few hundred bucks so he could participate in the latest cafe racer fashion trend. He was a lot more interested in how the bike looked and that it ran so he could get it parked out on main street somewhere and pose than he was in learning how it worked and how to work on it.
He had the original owner's manul for the Honda which I looked through and saw was absolutely stunning in it's information and explanations of the bike and what it needed as far as tuning and maintenance. I stressed to him that all he had to do was start on page one of the bikes manual and do what it said, everything was in there laid out very simply. This advice he did not take, instead he took the bike to a shop and had them sort it out.

A long time ago I was talking to an old Triumph dealer who agreed with me that if you are going to ride an old British bike, then you are either going to spend an hour on maintenance for every two hours you ride it, or you are going to have to be wealthy enough to pay someone else to do it.

There are all sorts of businessmen chomping at the bit to get into your wallet to do what you don't want to learn to do yourself, and in most cases what they want to do for you is as easy as falling off a log as they are not particularly smart, just particularly greedy. Do yourself a favor and become your own mechanic, in almost every case you will be better than those who will not do it unless you pay them.