A misfire cause?

classic Classic list List threaded Threaded
5 messages Options
Reply | Threaded
Open this post in threaded view
|  
Report Content as Inappropriate

A misfire cause?

Sali Rostami
 Misfire problems have been the subject of many threads. The usually suspects are caburation and timing/point adjustment. But, I'd like to add another possible cause.

 Let's look to see what  causes the spark to jump across the plug's gap. Okay, we know that it's the collapse of the magnetic field about the primary winding that induces a high enough voltage in the coil's secondary that enables the spark to discharge across the plug.

 The collapse of a coil's magnetic field occurs when we interrupt the flow of current. In a classic coil and battery ignition such as that found in our RE's, the contact breaker points accomplish that interruption hopefully at the right moment. The points are caused to interrupt the flow of current by opening the connection to ground. But wait, could we also cause an interruption by opening the positive or battery side if the coil's connection? The answer is YES!

 My contention is that an inadvertent interruption of current flow TO the coil is going to fire the plug. A poor/intermittant connection to the positive terminal of the coil or at any point along that portion of the ignition circuit may cause this problem.

 What do you think?


  Al in Philadelphia  

Reply | Threaded
Open this post in threaded view
|  
Report Content as Inappropriate

Re: A misfire cause?

laxt57
Hi Al
Well, maybe.
But a poor or intermittent connection?would not "fire the plug"
It would prevent it from firing.
It would need to be a clean and fast open, not? resistive.
Thanks
Jeri


-----Original Message-----
From: Al <[hidden email]>
To: [hidden email]
Sent: Fri, 12 Jun 2009 5:52 am
Subject: [Enfield] A misfire cause?








Misfire problems have been the subject of many threads. The usually suspects are caburation and timing/point adjustment. But, I'd like to add another possible cause.

Let's look to see what causes the spark to jump across the plug's gap. Okay, we know that it's the collapse of the magnetic field about the primary winding that induces a high enough voltage in the coil's secondary that enables the spark to discharge across the plug.

The collapse of a coil's magnetic field occurs when we interrupt the flow of current. In a classic coil and battery ignition such as that found in our RE's, the contact breaker points accomplish that interruption hopefully at the right moment. The points are caused to interrupt the flow of current by opening the connection to ground. But wait, could we also cause an interruption by opening the positive or battery side if the coil's connection? The answer is YES!

My contention is that an inadvertent interruption of current flow TO the coil is going to fire the plug. A poor/intermittant connection to the positive terminal of the coil or at any point along that portion of the ignition circuit may cause this problem.

What do you think?

Al in Philadelphia








[Non-text portions of this message have been removed]

Reply | Threaded
Open this post in threaded view
|  
Report Content as Inappropriate

Re: A misfire cause?

Sali Rostami
In reply to this post by Sali Rostami
 Jeri an intermittant/interrupted connection on the plus-side of the coil  certainly would cause the plug to fire as the magnetic field would collapse just as it  would if the negative  side(breaker point side) were interrupted.

   Al

--- On Fri, 6/12/09, [hidden email] <[hidden email]> wrote:


From: [hidden email] <[hidden email]>
Subject: Re: [Enfield] A misfire cause?
To: [hidden email]
Date: Friday, June 12, 2009, 9:53 AM








Hi Al
Well, maybe.
But a poor or intermittent connection?would not "fire the plug"
It would prevent it from firing.
It would need to be a clean and fast open, not? resistive.
Thanks
Jeri

-----Original Message-----
From: Al <k3eax@yahoo. com>
To: royalenfield@ yahoogroups. com
Sent: Fri, 12 Jun 2009 5:52 am
Subject: [Enfield] A misfire cause?

Misfire problems have been the subject of many threads. The usually suspects are caburation and timing/point adjustment. But, I'd like to add another possible cause.

Let's look to see what causes the spark to jump across the plug's gap. Okay, we know that it's the collapse of the magnetic field about the primary winding that induces a high enough voltage in the coil's secondary that enables the spark to discharge across the plug.

The collapse of a coil's magnetic field occurs when we interrupt the flow of current. In a classic coil and battery ignition such as that found in our RE's, the contact breaker points accomplish that interruption hopefully at the right moment. The points are caused to interrupt the flow of current by opening the connection to ground. But wait, could we also cause an interruption by opening the positive or battery side if the coil's connection? The answer is YES!

My contention is that an inadvertent interruption of current flow TO the coil is going to fire the plug. A poor/intermittant connection to the positive terminal of the coil or at any point along that portion of the ignition circuit may cause this problem.

What do you think?

Al in Philadelphia

[Non-text portions of this message have been removed]

















     

[Non-text portions of this message have been removed]

Reply | Threaded
Open this post in threaded view
|  
Report Content as Inappropriate

Re: A misfire cause?

laxt57
Hi Al
It would be a timing thing(how fast it opened)
and how resistive it was(poor connection)
If it opened like a set of points and was not resistive
then--------yes.
Thanks
Jeri


-----Original Message-----
From: Al <[hidden email]>
To: [hidden email]
Sent: Fri, 12 Jun 2009 9:47 am
Subject: Re: [Enfield] A misfire cause?








?Jeri an intermittant/interrupted connection on the plus-side of the coil? certainly would cause the plug to fire as the magnetic field would collapse just as it? would if the?negative? side(breaker point side)?were interrupted.

?? Al

--- On Fri, 6/12/09, [hidden email] <[hidden email]> wrote:

From: [hidden email] <[hidden email]>
Subject: Re: [Enfield] A misfire cause?
To: [hidden email]
Date: Friday, June 12, 2009, 9:53 AM

Hi Al
Well, maybe.
But a poor or intermittent connection?would not "fire the plug"
It would prevent it from firing.
It would need to be a clean and fast open, not? resistive.
Thanks
Jeri

-----Original Message-----
From: Al <k3eax@yahoo. com>
To: royalenfield@ yahoogroups. com
Sent: Fri, 12 Jun 2009 5:52 am
Subject: [Enfield] A misfire cause?

Misfire problems have been the subject of many threads. The usually suspects are caburation and timing/point adjustment. But, I'd like to add another possible cause.

Let's look to see what causes the spark to jump across the plug's gap. Okay, we know that it's the collapse of the magnetic field about the primary winding that induces a high enough voltage in the coil's secondary that enables the spark to discharge across the plug.

The collapse of a coil's magnetic field occurs when we interrupt the flow of current. In a classic coil and battery ignition such as that found in our RE's, the contact breaker points accomplish that interruption hopefully at the right moment. The points are caused to interrupt the flow of current by opening the connection to ground. But wait, could we also cause an interruption by opening the positive or battery side if the coil's connection? The answer is YES!

My contention is that an inadvertent interruption of current flow TO the coil is going to fire the plug. A poor/intermittant connection to the positive terminal of the coil or at any point along that portion of the ignition circuit may cause this problem.

What do you think?

Al in Philadelphia

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]








[Non-text portions of this message have been removed]

Reply | Threaded
Open this post in threaded view
|  
Report Content as Inappropriate

Re: A misfire cause?

Romy_M80
This post has NOT been accepted by the mailing list yet.
In reply to this post by Sali Rostami
Hi everyone. I was hoping I could get some advice on a problem i've been having on my Enfield bullet 500 Cast iron bike which is a 1997 model.

I purchased this bike a couple of weeks ago second hand. When i initially started riding I noticed a slight miss in the idle and there was also a miss when riding on throttle. It felt like the fuel wasn't reaching the cylinder or the bike was about to run out of fuel. But this was not the case as the tank had enough fuel in it. The problem was quite severe during cold start and got a bit better after the engine warmed up but not completely. So started my attempts to get the problem rectified :

1. I had my mechanic change the oil, clean the carburetor, set the ignition timing etc. But this did not solve the problem.

2. I replaced the spark plug as I felt the spark on the plug in the bike was weak when i did a spark test by myself. This also did not solve the problem.

3. I checked the battery and filled it with water as the level was a bit low. Did not solve the problem.

4. My next attempt was to tune the bike's carburetor once it was warm. I followed the standard tuning procedure of closing the air/fuel mixture screw completely to make the mixture lean, while opening up the throttle stop screw so that the bike idles much higher than normal and then slowly turning out the mixture screw to which increased the revs even higher and then reducing the idle speed back to normal. This also did not solve the problem. In fact while doing this, the bike started to cut off while the revs increased while i was opening out the mixture screw. Fortunately the engine didn't stop running.

Finally before I could try anything else, the bike completely stalled on my ride back home. The way it stalled was, the bike still had the miss in the beat, only it felt more now after my attempt with the carb. After 3-4 kms, the bike stalled with sudden jerks and i realised the instrument cluster lights started to dim and finally the bike came to a halt. I could smell something burning and it felt like it was coming from the battery. the box containing the battery felt hot to the touch. I tried turning on the ignition but nothing was working.

Now i'm not sure if the unsteady idle and riding was due to the battery/electrical problem or it was completely different problem and the electricals gave up coincidentally around the same time?

Any advice would be useful. I've uploaded a video of the bike idling on youtube. here is the link. This was after i had started it in the morning.

https://www.youtube.com/watch?v=pubU4nEIgCI&feature=youtu.be
Loading...