Commando just won’t start

Have you taken the carbs off and had a careful look at them?
I was having a strange problem where my bike was really running badly. I chased all sorts of things until I eventually noticed that one of the spray tubes had dropped down onto the jet holder.
Unless you are really careful, you can easily miss something that you are not expecting to see.
 
Given the facts presented it must be April 1st. ;)

If you have spark and know your ignition switch is good and the timing is good. Squirting fuel into the carburetors past the slides should have fired the engine up for a few strokes, or backfired. Do you have Amals on this engine or a Mikuni? An old Mikuni with a dried up choke is a bear to start. Amals are usually tickle and go unless way out of sync or you have water in the float bowls.

My apologies for not being able to be very serious. There are enough serious guys on this site to make up for me though. lol
 
Schwany said:
Given the facts presented it must be April 1st. ;)

If you have spark and know your ignition switch is good and the timing is good. Squirting fuel into the carburetors past the slides should have fired the engine up for a few strokes, or backfired. Do you have Amals on this engine or a Mikuni? An old Mikuni with a dried up choke is a bear to start. Amals are usually tickle and go unless way out of sync or you have water in the float bowls.

My apologies for not being able to be very serious. There are enough serious guys on this site to make up for me though. lol
Click to expand...
New premier carb sonic cleaned twice,Float height correct, and ensured all channels clear.
 
With a single carb the manifold could be leaking air, check all the fixings including the hidden centre fixings.
 
is the Boyer wired correctly? the black/white and black/yellow wires aren't swapped anywhere. That would make the ignition look like it's working, but the timing will be way off.
 
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Dave Harvey, you said the bike broke down and sounded terrible before it stopped.

And now you talk about it being difficult to start.

You’ve skipped a lot in the logical sequence of events there sir !

Why did it break down ?

What was the source of the ‘sounded rough’ ?

What remedial action was taken to fix the cause of the breakdown and the rough sound ?
 
Last edited:
Take the rocker covers off.
Turn the engine over, do all 4 valves open and close?
With left inlet valve fully open check for clearance on right inlet valve
Check the same on left exhaust, right inlet and right exhaust valves
 
Dave Harvey said:
New premier carb sonic cleaned twice,Float height correct, and ensured all channels clear.
Click to expand...
So in theory fuel should not be an issue and you should not have had to squirt fuel into the engine. Spark or timing it must be. And I think you know that.

As a couple of guys have mentioned you must be skipping a troubleshooting step somewhere. I did not want to bring up the noise thing because I was under the impression you were kicking the engine over and it would not start. If it were busted mechanical parts like timing chain, rod, wrist pin, dropped valve, you probably wouldn't be able to kick it over without the engine making a terrible noise and or locking up. But that is just one of many scenarios and guesses.

Could be a weird intermittent short between the alternator and your regulator rectifier killing the spark when kicking, or the list goes on.
 
Your dog is lost. He went down a road. You are at the crossroads thinking, "Which road do I go down?" Is there a simple test to tell me which road it is? Is there a test to tell me which road it ISN'T? Since, in a binary question knowing either answer answers the other question too given there is only one dog and two roads.....

My "crossroads" diagnosis tool is a squirt bottle with a 90 degree straw with fuel in it. It bypasses the entire fuel delivery system. I remove the air filter, lift the throttle bodies and give a squirt into each open carb mouth. I turn the key on and give a kick....

If the bike goes, "pop pop pop and dies, I go down the fuel delivery road looking for my lost dog.

If the bike does not fire at all, I go down the ignition problem road for my pup.

As was said previously, you should also pull the valve covers and make sure they are going up and down correctly (maybe you snapped the timing chain or something like that)
 
I had a similar thing happen a couple of years ago (and posted about it on this forum) After two different mechanics went crazy trying to figure out what the problem was, the problem was traced to the spring holding the kill switch settling and shorting out the ignition. Suggest you wire a temporary bypass to the kill switch and see if that fixes the problem
 
I had a recent issue that sounds very similar. New rebuild engine would start and ride fine, but it felt like the bike hit a wall around 4500rpm, almost like a rev limiter. Chased fuel system for a while before I noticed I never fully tightened the ring terminal on the negative side of the battery. You could also try running a parallel ground and power wire straight from the battery to the ei/coil/head to see if you have a short or broken wire somewhere.
 
If you have compression spark and fuel, the motor will usually fire. However I once took my Seeley 850 to Winton, and I could not get a peep out of it until I changed the spark plugs.
 
Schwany said:
Given the facts presented it must be April 1st. ;)

If you have spark and know your ignition switch is good and the timing is good. Squirting fuel into the carburetors past the slides should have fired the engine up for a few strokes, or backfired. Do you have Amals on this engine or a Mikuni? An old Mikuni with a dried up choke is a bear to start. Amals are usually tickle and go unless way out of sync or you have water in the float bowls.

My apologies for not being able to be very serious. There are enough serious guys on this site to make up for me though. lol
Click to expand...
Well I took your advice but the fuel was getting through. My friend said try a squirt of brake cleaner and it fired up for a couple of seconds. I thought problem is not electric. Thought why won’t it run on the petrol as I filled up with premium so it should be good. I drained the carbs and set up a temporary supply of fresh fuel and I’m glad to say It now runs fine just got to get a strobe for the ignition and will be goo to go . All my work because of bad fuel from the garage .
I would like to thank everyone who gave me good advice. A Big Thank You
 
Was the rotor loose on first check ? Or the stator ? Did it start acting up while being ridden ? When shimming out the rotor spline with a pazon I found I could get the timing completely wrong "180%" out ? However if it was all tight I'd be looking at carb or coils. Good luck. Roy. 🤞🤞🍺
 
Dave Harvey said:
Well I took your advice but the fuel was getting through. My friend said try a squirt of brake cleaner and it fired up for a couple of seconds. I thought problem is not electric. Thought why won’t it run on the petrol as I filled up with premium so it should be good. I drained the carbs and set up a temporary supply of fresh fuel and I’m glad to say It now runs fine just got to get a strobe for the ignition and will be goo to go . All my work because of bad fuel from the garage .
I would like to thank everyone who gave me good advice. A Big Thank You
Click to expand...
There you have it something simple. 👍

Been there with bad fuel from a remote gas station that has really old nearly empty tanks. Makes for a jerky ride home.
 
o0norton0o said:
Your dog is lost. He went down a road. You are at the crossroads thinking, "Which road do I go down?" Is there a simple test to tell me which road it is? Is there a test to tell me which road it ISN'T? Since, in a binary question knowing either answer answers the other question too given there is only one dog and two roads.....

My "crossroads" diagnosis tool is a squirt bottle with a 90 degree straw with fuel in it. It bypasses the entire fuel delivery system. I remove the air filter, lift the throttle bodies and give a squirt into each open carb mouth. I turn the key on and give a kick....

If the bike goes, "pop pop pop and dies, I go down the fuel delivery road looking for my lost dog.

If the bike does not fire at all, I go down the ignition problem road for my pup.

As was said previously, you should also pull the valve covers and make sure they are going up and down correctly (maybe you snapped the timing chain or something like that)
Click to expand...
If you leave an old T-Shirt that you haven't washed lately off to the side of the crossroads and leave it overnight, the dog will be laying on your T-Shirt in the morning. Fact not fiction. Has nothing to do with fuel and everything to do with dogs. Of course if you spend most of your time mistreating the dog, I'm not sure if that would work.
 
Did the "gas" have a funny smell or appearance to it? Did you ask the place you brought it from if others had bad experiences with it the "fuel"? Did it have water in it?
 

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