Bought a car yesterday that's running a busa engine and noticed a problem with poor running when the headlights are on.

Had charging issues with an R1 motor previously so I've done some basic troubleshooting tonught.

Battery reads 12.4 when engine off
With engine running at idle reads around 13.1.
If I turn the headlights on I see late not much change in voltage.
The but that's confusing me is that if I increase the revs the voltage goes down to low 12s regardless of lights on/off.

when trying to drive the car with lights on it's like a bucking bronco, almost feels like intermittently running on 3cyls back to 4 then 3. Or constantly on/off ignition breifly.

I've ran a diode test on the rectifier and get the same reading across all yellow wires...

And now I'm out of ideas!

Anyone else have any suggestions?

Thanks,

Bri

Sounds like a bad rectifier to me.

Try swap it out. It's one of the things I would always keep a spare of.

From what I understand you can use ones from loads of bikes.

No idea which sorry. I only know zzr1400 and cbr 900 engines.

ECU's have compensation for voltage changes, it sounds like yours is not operating correctly I am afraid or as above its leaping around so much it cannot stabilise itself.

Bang on another rectifier, one with big cooling fins!

[Edited on 20/4/18 by mark chandler]

Thanks, I'll give it a try, I had it down as a suspect since they are so common to fail and I had it happen on an R1 motor, although with different symptoms.

Check all your wiring too,mine on the R1 melted the wiring around the multiplug joining the stator to loom.

Mosfet regulators are the ones to go for to upgrade.

Also location on a BEC is important, if it's not getting much air passing over the regulator relocate it to somewhere it will

[Edited on 21/4/18 by CosKev3]

Let us all know when you have sorted it. We hear about a lot of issues here but sometimes never hear what it was and if it was easy to solve. Good luck.

Will do, picking up another rectifier today and will see how it is.

It's mounted quite far forward in the car behind the rad so i would presume it gets good airflow through there, what surprises me about the suzuki rectifiers is that they don't have much of a heat sink to them, compared with the one from my 5VY R1 engine its tiny.

Quick update, test fitted the new rectifier last night and instantly had 14.2v at the batter with the engine running. So i'm sure this will have sorted the problem.

Just gotta get the car out for a run at some point and see if it's fixed the poor running which i'm pretty sure it will have.

Thanks,

Bri

Is your rectifier mounted to a decent heat-sink surface and have good airflow around/past it?
Poor cooling is a common cause of rectifier failure.

I'd say so yeah, it's on an aluminium mount hanging off the front triangular section of the chassis behind the rad. I'd presume there's enough airflow thru the rad to this area behind to cool it.

I'd suggest behind the rad isn't ideal as you'll be passing hot air over it.

Just a final update on this one in case anyone is ever searching in future.

I think i found the rectifier issue by chance when troubleshooting the running problem, but when test driving the car yesterday it was still like a bucking bronco down the road.

The issue appears to be with the power commander, i bypassed this and ran with just the standard ECU and the issue has gone away. I know the issue isn't with the PC map itself since i plugged the laptop in and zero'd the map and it still run's terrible. So i'm going to put the issue down to some bad wiring or the power commaner itself going bad.

Thanks,

Bri

Check the PC has a good earth. If it does check the earth lead/terminal is OK. It's not unknown for those to break.