Hi

My VFR 40 will start, run and rev without misfire, after 5 minutes it will run on 1 or 2 cylinders and will not respond to throttle. To add to the excitement the temperature gauge will shoot up to its stop. While all this is going on the actual water temperature is normal. The bike has been de restricted using on of Rick Oliver’s plug in resistors.
I have checked the ignition wiring for damage and checked all earths.
The wiring from the ignition pulse generators the ICU has been checked for resistance and is 2 ohms.
Both The pulse generators are within spec at 405 ohms
The wiring to both ignition coils has been checked for damage and the cable resistance measured at 2 – 3 ohms
All connectors have been cleaned are all ok
The primary ignition coils resistance is 2.8 ohms and the secondary resistance has been checked with and without plug caps and are within spec.
Fuel is new and flow freely from tank to carbs. Carbs have been cleaned and the jets cleaned using the ultrasonic method
Spark plugs are new and have been interchanged on each cylinder.
I’m starting to suspect the ICU are there any tests I can do to this sealed unit?
All other systems are working fine.
Any suggestion and ideas will be greatly received
I’m now doing a little roof maintenance please respond before I jump off.
Regards John

When you say "checked all earths", that includes the loom chassis connection on the left side in front of the ignition coil. Does battery voltage remains below 15.5 volts and above 14.5 volts when engine over 5000rpm.

Good Morning

Thanks for your reply. Yes I have checked the main earth which is ok. You raise a interesting question re voltage. Before this latest drama I noticed with the lights off at tickover I have 12.8 volts. At tickover with the lights on at full beam the temperature gauge starts to rise towards the stop and the voltage drops to 11.1 volts, as I increase the engine speed the temperature gauge returns to normal. So it seems that the rise in temperature reading is caused by a voltage drop of 1.7 volts can this be true?
Regards John

12.8 volts at idle no lights and 11.1 volts with lights on says that the battery is not being charged. Does the engine crank well? Voltages are measured where, at the battery? The ignition system would be unhappy with low battery volts.

Yes the engine grank's well. I'm measuring the voltage at the battery. I have noticed the 3 yellow cables from the Alternator are very small in diameter I'll change them as there must be a high resistance them being so small, i'm also going to change the HT cables as they are very stiff and my be braking down under load. Thanks for your interest and advice, keep it coming.

Regards John

What battery voltage do you measure at 5000rpm. You need at least 14.5 volts to charge the battery any less indicates an alternator, rect/reg or wiring problem.

Ok I'll let you know how I get on. Thanks.

I

Hi

I found a high resistance earth joint in the wiring loom, this i remade with solder, have added a extra earth from the ICU to the chassie .The bike now runs perfectly . Thanks for your help.

Regards John

Aldershot wrote:Hi

I found a high resistance earth joint in the wiring loom, this i remade with solder, have added a extra earth from the ICU to the chassie .The bike now runs perfectly . Thanks for your help.

Regards John

Ah you fixed it.

I was going to say.. the only way the temperature gauge will jump to hot is from a bad earth.. the temp gauge earth is in the wirign loom not the main earth so clean that up and start from there.

glad you have it fixed now.