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 Post subject: Running on one cylinder
PostPosted: Tue May 02, 2017 1:19 am 
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Joined: Tue Dec 03, 2013 12:12 am
Posts: 68
Location: DePere, WI USA
model: 750 Paso
year: 1988
1988 750 and its running on one cylinder. As its running I pulled off the front cylinder spark plug cap and it stays running. I stuck a plug in the cap and touched it to the frame looking for spark and nothing. Thought, OK, maybe a bad coil so I picked up a set of used ones on Ebay (that said they worked) thinking this was an easy fix but still nothing. Still only runs on one cylinder. Any way of checking if the coil is bad? I thought since the one cylinder runs fine of maybe trying that coil on the one thats not working to see if the coil itself is bad? Any thoughts on my issue?


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 Post subject: Re: Running on one cylinder
PostPosted: Tue May 02, 2017 4:08 am 
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Joined: Fri Nov 13, 2009 4:33 pm
Posts: 235
Location: San Francisco Bay, California USA
model: 750 Paso
year: 1987
Read the thread below yours a bit in this 750 Paso topics list called "Replacement Coils" from October of 2016 for some info and procedures which may help you find your electrical fault. The thread is a tad meandering and redundant, but it may prove useful to review. You will learn a few things valuable perhaps. Best of luck to you!


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 Post subject: Re: Running on one cylinder
PostPosted: Tue May 02, 2017 7:58 am 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5062
Location: southern Germany
model: 750 Paso
year: 1987
or the topic "Weber woes" just two below. Also have a look at the FAQ there`s info about the wiring mod and a picture showing how to check the coils.


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 Post subject: Re: Running on one cylinder
PostPosted: Thu May 11, 2017 12:47 am 
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Joined: Tue Dec 03, 2013 12:12 am
Posts: 68
Location: DePere, WI USA
model: 750 Paso
year: 1988
No carb issues, no coil issues (tested them) well actually no electric to the front cylinder, did the little black ignition things under the set and both are fine....stripped a bunch of wire cover to see if something was grounding out...nothing! I'm at a loss! I do have a full wire harness and thinking I'll switch it out???? If it doesn't run after doing that I'm pushing it off a bridge!


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 Post subject: Re: Running on one cylinder
PostPosted: Thu May 11, 2017 8:13 am 
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Joined: Wed Aug 28, 2013 12:34 am
Posts: 3
Location: New Zealand
model: 750 Sport
year: 1989
Not sure how you load tested the ignition units (under the seat next to your regulator). I struck a similar problem to you with a cylinder losing spark. The engine would start and idle fine but cut out under load (anything over 3000 rpm).

Have you tried swapping over the ignition units , and seeing if the problem transfers to the opposite cylinder?

Cheers,


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 Post subject: Re: Running on one cylinder
PostPosted: Thu May 11, 2017 9:22 am 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5062
Location: southern Germany
model: 750 Paso
year: 1987
Quote:
no coil issues (tested them) well actually no electric to the front cylinder, did the little black ignition things under the set and both are fine

:?: Can you give us some more info about what you exactly did? I`m not sure what "no electric to the front cylinder" or "did the little black ignition things" means. Is "no electric" no spark or no 12V at the coils ...?

I assume you measured the coils' resistance and they are ok.
Did you actually see if there is a spark?
Did you measure the voltage at the coils (orange wire)? If not do that and let us know what it is.
Also verify that the voltage arrives at the CDI units (same orange wire) and measure that the ground connection to the CDI modules is ok.

If all is good do as *MB suggested and swap parts. Begin with the spark plugs (which ones are you using?). If the problem does not transfer to the other cylinder swap the coils next then try again. At last swap the CDI units. Do this one step at a time so you can eliminate part after part as the potential issue.

If the problem remains with the same cylinder and all tests before were positive the issue is before the CDI units. Then it`s either the wiring to the pick-ups or a pick-up. If that was ok you`d have to do a compression test.


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 Post subject: Re: Running on one cylinder
PostPosted: Fri May 12, 2017 1:33 am 
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Joined: Tue Dec 03, 2013 12:12 am
Posts: 68
Location: DePere, WI USA
model: 750 Paso
year: 1988
paso750 wrote:
Quote:
no coil issues (tested them) well actually no electric to the front cylinder, did the little black ignition things under the set and both are fine

:?: Can you give us some more info about what you exactly did? I`m not sure what "no electric to the front cylinder" or "did the little black ignition things" means. Is "no electric" no spark or no 12V at the coils ...?

I assume you measured the coils' resistance and they are ok.
Did you actually see if there is a spark?
Did you measure the voltage at the coils (orange wire)? If not do that and let us know what it is.
Also verify that the voltage arrives at the CDI units (same orange wire) and measure that the ground connection to the CDI modules is ok.

If all is good do as *MB suggested and swap parts. Begin with the spark plugs (which ones are you using?). If the problem does not transfer to the other cylinder swap the coils next then try again. At last swap the CDI units. Do this one step at a time so you can eliminate part after part as the potential issue.

If the problem remains with the same cylinder and all tests before were positive the issue is before the CDI units. Then it`s either the wiring to the pick-ups or a pick-up. If that was ok you`d have to do a compression test.


Not sure how to measure the coils resistance? What I did is pulled the plugs to see which one had spark (the rear one) so I put the rear coil on the cylinder (front) that didn't have spark (thinking it was the coil) and nothing. So I thought maybe the CDI (black boxes in the back) might be bad so I switched them thinking that might be it and still nothing? So I started unplugging and replugging all the clips thinking its maybe some corrosion in one of them and still nothing.....hope this helps....kind of generic...lol

How do you measure the resistance?


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 Post subject: Re: Running on one cylinder
PostPosted: Fri May 12, 2017 3:15 am 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
Posts: 1528
Location: Newzealand
model: 906 Paso
year: 1990
You really need a multi meter , which with you can measure volts and resistance. A budget one can be had for the price of Feed of Macca's ( a really good one could cost a grand ) . If you have changed over ( from one cylinder to the other ) both the coils and the black boxes and the fault stays with the front cylinder its pretty safe to assume that its either there is no power to the coil or the pick up is duff..........both of which you need a multi meter to confirm
http://www.ebay.com/itm/Digital-Voltmet ... SwHnFVkYPk

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 Post subject: Re: Running on one cylinder
PostPosted: Fri May 12, 2017 9:31 am 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5062
Location: southern Germany
model: 750 Paso
year: 1987
Quote:
Not sure how to measure the coils resistance?

There's a picture in the FAQs.

You have the wrong approach and are skipping things.
Did you swap the spark plugs or replace them with new ones?

Quote:
so I put the rear coil on the cylinder (front) that didn't have spark (thinking it was the coil) and nothing

ok, but did the rear cylinder still fire? If so you can assume the front coil being basically ok.

Swapping parts only makes sense if you make sure that they all have 12V. You have to check that first!
$10 for a multimeter is money well spent. That´ll do the job.


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 Post subject: Re: Running on one cylinder
PostPosted: Fri May 12, 2017 6:27 pm 
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Joined: Tue Dec 03, 2013 12:12 am
Posts: 68
Location: DePere, WI USA
model: 750 Paso
year: 1988
paso750 wrote:
Quote:
Not sure how to measure the coils resistance?

There's a picture in the FAQs.

You have the wrong approach and are skipping things.
Did you swap the spark plugs or replace them with new ones?

Quote:
so I put the rear coil on the cylinder (front) that didn't have spark (thinking it was the coil) and nothing

ok, but did the rear cylinder still fire? If so you can assume the front coil being basically ok.

Swapping parts only makes sense if you make sure that they all have 12V. You have to check that first!
$10 for a multimeter is money well spent. That´ll do the job.




1.) yes replaced the plugs
2.) yes, rear cylinder did fire


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 Post subject: Re: Running on one cylinder
PostPosted: Fri May 12, 2017 6:30 pm 
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Joined: Tue Dec 03, 2013 12:12 am
Posts: 68
Location: DePere, WI USA
model: 750 Paso
year: 1988
Mc tool wrote:
You really need a multi meter , which with you can measure volts and resistance. A budget one can be had for the price of Feed of Macca's ( a really good one could cost a grand ) . If you have changed over ( from one cylinder to the other ) both the coils and the black boxes and the fault stays with the front cylinder its pretty safe to assume that its either there is no power to the coil or the pick up is duff..........both of which you need a multi meter to confirm
http://www.ebay.com/itm/Digital-Voltmet ... SwHnFVkYPk



Ok - have one. Where do I start? DCV ACV DCA? which one do I use and what number do I need to turn the dial too? Also - where do I read it from? I'll try the wires first then wire?


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 Post subject: Re: Running on one cylinder
PostPosted: Fri May 12, 2017 10:08 pm 
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paso grand pooh-bah
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Joined: Wed Dec 05, 2007 12:35 am
Posts: 1528
Location: Newzealand
model: 906 Paso
year: 1990
Dude , I don't want to sound derisive or smart arsed but teaching someone how to use a multi meter , ohm's law and basic electrical theory over the internet is a recipe for disaster , Do you have anyone there who could show you how ? work mate , buddy ? Even a budget meter will come with instructions but they assume that you have a working knowledge of electricity . Your not likely to damage anything ( maybe the meter itself ) but I imagine it could get #ucking frustrating real quick if you don't understand what its trying to tell you, and your likely to be chasing your tail . If you want ( last resort :D ) I will try and go thru this with you but Id rather do it via email simply because its way easier to post pix of whats going on ..... and there would be a few, so if you want PM me and we can go from there :)

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 Post subject: Re: Running on one cylinder
PostPosted: Sat May 13, 2017 8:51 am 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5062
Location: southern Germany
model: 750 Paso
year: 1987
While Hamish will explain you the details I will only mention one or two things.
If you have the meter plug the black probe to its COM connection and the red probe the connection that`s named mA/V/Ω.
Set the scale to DCV (or V= which is the same) and 200V. Switch the bikes ignition ON. Hold the black probe to a blank piece of steel that`s connected to the frame for instance the bolts of the coil mounting bracket. (Of course you can also hold it to the battery`s negative pole). There's an orange wire connecting to a spade connector on each coil. Touch the spade connector (w/o pulling the orange wire off) with the red probe. Read the voltage the meter shows. Done. You should try measuring the voltage of a small battery first just as an excercise.

Measuring resistance is fairly easy, too. If you want to check the coils disconnect the battery (!) then pull the ignition wire off the spark plug and disconnect the wires connected to the coils' spade connectors.
Set your meter to the Ω ohms scale and 200Ω. Then connect one probe to one spade connector and the other to the second. Read the primary resistance of the coil. Repeat with the second coil.
Then set the meter to 20KΩ connect one probe to a spade connector and the second probe to the spark plug connector of the ignition wire. Read the secondary resistance of the coil. That' s it.
Disconnecting the battery is a safety measure. You don`t want to try measuring resistance if there`s power on whatever you`re trying to measure.


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