Help starting a diabolical bike!

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I have a an original Rita Lucas Electronic ignition on a 79 Triumph T140E .Never had a problem. That MkII carb is a good carb.It'll run that bike just fine.
 
I had a similar problem mnay years ago when I fitted a single Mikuni carb to my 850. It was a first kicker when warm but a beast when cold. Long story short I suffered through a complicated ritual of choke on and off, part throttle, etc. until one day I changed the carbon thread plug wires for some stainless steel ones from a speed shop and the by product of this was a first kick bike hot or cold.
 
triumph2 said:
I had a similar problem mnay years ago when I fitted a single Mikuni carb to my 850. It was a first kicker when warm but a beast when cold. Long story short I suffered through a complicated ritual of choke on and off, part throttle, etc. until one day I changed the carbon thread plug wires for some stainless steel ones from a speed shop and the by product of this was a first kick bike hot or cold.
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intersting! I have no idea how old the plug wires are.
 
Nielsen said:
Nater Potater:I cetainly didn't notice anything looking like jets on it because, as I say, the bottom of #40 is mostly covered by that rubber gasket.
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Oh, my bad! You're absolutely correct; #40 is the cold start plunger. The piece I should have tagged is #28/Cold Start Jet. First the hair, then the eyes...
Here's a better diagram with a bonus; a parts list! http://www.clubmanracing.com/amalmk2.php It's located in the float bowl. It's the equivalent of an idle jet for the enrichment system, and we all know how bad they run if the idle jet plugs!

Nathan
 
I use Mk2 Amals with the lever operated enrichers. With the enrichers on and the throttles closed the bike will start every time. If I take the enrichers off when the motor is first running, I usually get the spit-back through the carbs which indicates lean-ness. I suggest that if the motor does not start easily when cold, and behave as mine does, you probably have a blockage or too small jet somewhere.
As far as float levels are concerned, there is a measurement to be made to check that the height is correct. I have no idea what it should be. I only ever check the floats by shaking and listening to them to see if they have fuel in them and are likely to sink. If the jetting is too rich or there is flooding, the motor should always start, it will simply be sluggish
 
Thanks very much for all this. It is wonderful to have a world of helping experts. I'm off the radar for a few days, but will report back. Forums are a wonderful thing--especially to those of us new to the subject!
 
Here's an update and a real head scratcher..... Checked the cold start jet (listed as a # 50, which the Amal site says is correct), and the pilot jet (#25). Both were spotless, as was the rest of the carb. I was completely puzzled until I started methodically going through the whole carb system. What I discovered was that the former owner--who was a professional motorcycle mechanic--had neatly tapped the air inlet for the cold start system, and threaded a grub screw into it. Thus the entire cold start system was inoperable, regardless of the placement of the cold start lever. The former owner was a clever guy and did some interesting and very sympathetic upgrades to my bike. He was no dummy. My question then is: why did he do this? Is this perhaps an old racers' trick or something? Anyone have any ideas.....?

The second issue I discovered is that the float level is quite a bit off from what it should be according to the Amal stuff I've read. The float is certainly not parallel with the top of the bowl when it has the small pressure put on it.

The photos show how the former owner had closed off the cold air inlet--and he must have had a reason, but what was it.....? Haven't yet reassemble anything. Hoping to hear from some of you first.
Help starting a diabolical bike!
[/URLHelp starting a diabolical bike!
 
Possibly because he couldn't get the choke to stay shut?

It certainly comes under the category of 'choke circuit obstruction'!
All you can do is try the carb on the bike with the screw removed - it'll either work great, or inform you of why he did it.... :roll:

Has anyone else got cable operated chokes on their MkII carbs?
I'm suspicious that the return spring may not be strong enough to overcome the friction of the cable - I never had a problem with the carb-mounted levers personally.

I'd see how the choke performs (with/without cable attached) before interfering any more with the float, but there's a possibility that the issue may linked.

Good luck!
 
Somebody has stolen the ticklers off my Mk2 Amals, I was wondering why it wouldn't rev over 7000 RPM.
 
Nielsen said:
Here's an update and a real head scratcher..... Checked the cold start jet (listed as a # 50, which the Amal site says is correct), and the pilot jet (#25). Both were spotless, as was the rest of the carb. I was completely puzzled until I started methodically going through the whole carb system. What I discovered was that the former owner--who was a professional motorcycle mechanic--had neatly tapped the air inlet for the cold start system, and threaded a grub screw into it. Thus the entire cold start system was inoperable, regardless of the placement of the cold start lever. The former owner was a clever guy and did some interesting and very sympathetic upgrades to my bike. He was no dummy. My question then is: why did he do this? Is this perhaps an old racers' trick or something? Anyone have any ideas.....?

The second issue I discovered is that the float level is quite a bit off from what it should be according to the Amal stuff I've read. The float is certainly not parallel with the top of the bowl when it has the small pressure put on it.

The photos show how the former owner had closed off the cold air inlet--and he must have had a reason, but what was it.....? Haven't yet reassemble anything. Hoping to hear from some of you first.
Help starting a diabolical bike!
[/URLHelp starting a diabolical bike!
Click to expand...


To clarify a few points made in recent posts:

Amal mk2 carbs do not have ticklers. It is impossible to try and fit them! Forget ticklers completely!
The cold start plunger has a rubber tip. This rubber tip seals off the FUEL supply when the cold start system is OFF. This is commonly damaged and allows excess fuel to leak into the carb system even when the cold start system is off. A new plunger cw factory fitted rubber is the only answer in this case, a leak here makes it impossible to correctly adjust the carb settings.
The air passage which was blocked off in your pictures IS indeed the cold start air intake. Air entering this circuit passes over the (opened) fuel intake and sucks fuel in via the Venturi principle, thus enabling the entire cold start system.
The fuel flow during this, is regulated by the cold start jet (which you have checked as ok).

So, in summary, the grub screw that you showed is clearly completely disabling the entire cold start system. With no tickler facility, you have zero cold start support. I have no idea why this would have been blocked off! Any correctly set carb MUST have cold start support, as by definition, it will be too weak when cold. Therefore, it is a no wonder you've had troubles.

The first next steps would therefore be, IMHO, to clean everything and re-assemble WITHOUT the offending grub screw, and try that. It is possible that some carb adjustments maybe required if previous adjustments have been made in the past to compensate for errors caused by cold start system leaks etc.
 
I think I'm getting closer and closer to a resolution--which all goes to prove that many heads are better than one! The little rubber tip on the cold start plunger, which you describe, is not in very good condition. Unfortunately my local Norton parts supplier is closed for the Easter holiday, but I have the part number and will get a new one (assuming he has one) Tuesday. I've now also adjusted the float level to its correct specs. Fingers crossed that next week I will have an easy-starting Commando.
 
Nielsen said:
Here's an update and a real head scratcher..... Checked the cold start jet (listed as a # 50, which the Amal site says is correct), and the pilot jet (#25). Both were spotless, as was the rest of the carb. I was completely puzzled until I started methodically going through the whole carb system. What I discovered was that the former owner--who was a professional motorcycle mechanic--had neatly tapped the air inlet for the cold start system, and threaded a grub screw into it. Thus the entire cold start system was inoperable, regardless of the placement of the cold start lever. The former owner was a clever guy and did some interesting and very sympathetic upgrades to my bike. He was no dummy. My question then is: why did he do this? Is this perhaps an old racers' trick or something? Anyone have any ideas.....?

The second issue I discovered is that the float level is quite a bit off from what it should be according to the Amal stuff I've read. The float is certainly not parallel with the top of the bowl when it has the small pressure put on it.

The photos show how the former owner had closed off the cold air inlet--and he must have had a reason, but what was it.....? Haven't yet reassemble anything. Hoping to hear from some of you first.
Sometimes people with mechanical/machinist skills are the most dangerous, if they don't also possess the analytical mind to go with it. :oops:
Click to expand...
Click to expand...
 
I think I've fixed the issue, and my suspicion is that the float level, which was way off, was actually the root of the former owner's trying to bypass the cold start system. I set the float level according to instructions, and the 'Commando' fired up without the cold start lever even engaged (it's a mild day today). I initially tried it with the cold lever 'on', cranked it half a dozen times. Nothing. Turned the lever 'off', and first crank it fired up. Took it for a run and it seems to run really strongly.

Before these fixes I had to have the air mixture screw turned way out. Now it isn't exactly 1.5 turns out (more like 3), but it responded to fettling as it really didn't before. That again suggests that the float level may have been the culprit. Agree?

Anyway, I'm sure I'll be back here with more issues as I learn about the bike. Meantime, thanks so much, everyone, for sharing your expertise. I couldn't have done it without you!
 
i have a mk11 amal fitted to my 74 but what confused me was why isnt yours rubber mounted to the inlet manifold
 
john robert bould said:
Good point! infact how is it fixed full stop?

phippsy said:
i have a mk11 amal fitted to my 74 but what confused me was why isnt yours rubber mounted to the inlet manifold
Click to expand...
Click to expand...

Wow, I didn't notice that until I opened the picture properly!

What IS going on there? How is the carb fitted?

It looks like its just 'stuffed in' to the manifold... but I assume there must be more to it than that...?

Do tell...
 
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