Poor running - another reason - SV650.org

04-05-06, 05:31 PM

Just spent some time sorting out a poor running problem on my SV.

Symptoms are;

1. Intermittent reduction of power.
2. When loss of power occurs, no tacho reading (i.e. drops to 0 rpm), and recovers when power returns
3. Excessive fuel smell when stopped.
4. Eventually only reduce power was available.

Wasn't the usual problem - water in the front cylinder's spark plug well.

The fault was that the earth lead had disconnected from the HT coil.
Obviously the intermittent part was when the lead was working itself loose, and permament reduction was when it finally fell off.

You learn something new every day.

A.

12-05-06, 06:06 PM

Doesn't the tacho get it's reading from one of the coils?

Sid Squid · 13-05-06, 01:26 AM

Yes.

And no.

The tacho takes a connecfrom a coil negative, in essence it counts the pulses that the coil receives from the ignition unit, thus knowing the engine speed.

However, to say that it's connected to the coil is misleading, if you were to pull the wires off the coil the tacho would still be connected to the wiring as the physical wire junction is in the loom, not an extra connection to the coil itself. Therefore pulling the relevant wire off the coil would stop the cylinder in question firing, but the tacho would still fiunction.

14-05-06, 04:34 PM

Had a simlar problem on mine just after getting it, spent ages faffing about, bleeding fuel from the carbs (thought I had water in the fuel) etc. In the end it was a loose connector to one of the coils, quick fix, but required a garage to spot it forme (as i had given up).

Always worth a look if your SV has some intermittant problem (and the weather is dry).

04-05-06, 05:31 PM	#1
Topaz Guest Posts: n/a	Poor running - another reason Just spent some time sorting out a poor running problem on my SV. Symptoms are; 1. Intermittent reduction of power. 2. When loss of power occurs, no tacho reading (i.e. drops to 0 rpm), and recovers when power returns 3. Excessive fuel smell when stopped. 4. Eventually only reduce power was available. Wasn't the usual problem - water in the front cylinder's spark plug well. The fault was that the earth lead had disconnected from the HT coil. Obviously the intermittent part was when the lead was working itself loose, and permament reduction was when it finally fell off. You learn something new every day. A.

13-05-06, 01:26 AM	#3
Sid Squid No, I don't lend tools. Mega Poster Join Date: Jul 2003 Location: Skunk Works, Nth London Posts: 8,680	Yes. And no. The tacho takes a connecfrom a coil negative, in essence it counts the pulses that the coil receives from the ignition unit, thus knowing the engine speed. However, to say that it's connected to the coil is misleading, if you were to pull the wires off the coil the tacho would still be connected to the wiring as the physical wire junction is in the loom, not an extra connection to the coil itself. Therefore pulling the relevant wire off the coil would stop the cylinder in question firing, but the tacho would still fiunction. __________________ If an SV650 has a flat tyre in the forest and no-one is there to blow it up, how long will it be 'til someone posts that the reg/rec is duff and the world will end unless a CBR unit is fitted? A little bit of knowledge = a dangerous thing. "a deathless anthem of nuclear-strength romantic angst"

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12-05-06, 06:06 PM	#2
Razor Guest Posts: n/a	Doesn't the tacho get it's reading from one of the coils?

14-05-06, 04:34 PM	#4
Tim in Belgium Guest Posts: n/a	Had a simlar problem on mine just after getting it, spent ages faffing about, bleeding fuel from the carbs (thought I had water in the fuel) etc. In the end it was a loose connector to one of the coils, quick fix, but required a garage to spot it forme (as i had given up). Always worth a look if your SV has some intermittant problem (and the weather is dry).