Runs bad on one cylinder

[Larrymace]

Hi. My bike runs bad on one cylinder on low revs (up to 1/4 gas). I have removed the carburettor bridge and cleaned it in ultrasonic bath. Also all nozzles. The carb. bridge is also synchronized. I have mounted new spark plugs. Could it be a bad ignition coil or bad connection in one of the ignition cables? Does the bike have the same behaviour as a clogged idle nozzle when there is a problem with an ignition coil or cable? I have a feeling that the problem shows more when the engine is warm.

[Bub]

...

Hallo Larrymace,

Have you checked the ignition wires? Maybe there ist the mistake!


Gruß vom BuB

[Larrymace]

I will install a new (used) ignition coil with new cables within a couple of days. I was just posting the question to find out if it was a common problem for our bikes.

[Lederclaus]

If something is wrong with a coil, it´s much likely that both cylinders have problems. (1and 4 i.e 2 and 3)
Check the connection between plugcap and cable. Should be tight fitting when cap is turned c.w
If not, cut appr. 1/4 " off the line and try again.

Check plugcap for resistance (shold be around 10 kilo ohms) . If it is far over (say 200 k ohm or 10 M ohm) try to clean it inside .
You can open it from the bottom side. Take a well fitting screwdriver and undo the brass-fitting with the slot. Careful to not breaking the plastic housing. It´s mounted with threat-lock. Take out the resistor and the little spring and clean everything with a steel brush. There is a 50% chance your plug cap is doing well after that.

A new plug cap is very expensive due blatand profiteering aims of Suzuki. (like 50 € each)

Once having the coil in your hand you could check the connections. Ohm-meter between pin 4 and pin 4 (to say between the two high tension lines). Should read something in kilo-ohm region) Now wiggle at the lines close to the coil and have an eye on the meter.

Check low tension lines. Between them it should read 2 ohms or so.

good luck!

[Larrymace]

Thanks for the reply. If I have a bad connection i.e. plugcap/Cable, why does it only show on low revs?

[Lederclaus]

There are several reasons for that. Maybe it´s a clogged jet as well. But you write that everything has been cleaned and balanced.

One reason could be that something in the ignition circuit is starting to become weak. It´s very difficult to make a diagnosis without the bike.