Electrical problem that I can't figure out

Hi guys, 

I have a problem that I can't figure out. I have a 2002 VFR that has 72,000 miles now. I had the whole engine replaced at 65,000 miles because I bought manual CCTs and I overtightened them and resulted with the Cam Chains snapping. So I replaced the engine with a 2004 VFR engine that only had 15,000 miles. Everything was great. But today, my battery died on me. Its my daily ride, so I cant seem to figure out what is going on. 

Things that you guys might think are problems had been changed already when I replaced the engine. I changed the stator, rectifier, VFRness, and battery.

1. Things that happen to me on a daily basis. I live in San Francisco, and I have to ride in the city everyday. After riding for about 20 minutes in stop and go traffic, the horn would get weaker and weaker to the point of not having sound. Mind you, the engine temp is always around 200-210F when I ride in the city. 

2. Another thing that happens is the engine cutting out when I blip the throttle. That happens when I have the clutch pulled in and blipped to shift from 2nd to 1st. 

Anyway, its confusing for me because I have the parts that could've caused the electrical problems replaced already.

Any input will be helpful to me. Thank you.

Check your connectors (see threads in electrical section of the forum) and the main relay housing next to the battery.

Thank you Auspanglish. I will check and will post back here once its done.

The parts you replaced may not have been bad--and the new ones could have been.  The way forward is to start testing (which would be easier if you still had the old parts), first the battery, then the reg/rec and stator, and the wiring and connections.  The symptoms you have related suggest that the battery is not being charged, so that is either due to the battery being bad or the charging "system" not charging it.  I always test the battery first to eliminate it as a cause.

Ciao,

Hey JZH, I tested the battery this morning and it wasn't charging at all while I had it at 4000 RPM. No movement in voltage. It stayed at 12.5v with the engine running. This battery is 6 months old, and the R/R is the new Mosfet RR with Fins to dissipate heat.

Actually, just to make it clear, the bike idles with 12.4v and with the revs at 4000rpm, it moves to 12.53v.

Your list of replacement parts didn't include the starter relay. Failure of the relay can leave no connection from rectifier/regulator to battery.

Your first step should be to test every stage of the charging system, including the condition of all the connectors.

1. check all three phases of the stator - engine off, engine at idle, and engine at ~5K rpm

2. check the output of the rectifier/regulator both at the starter relay and at the battery positive

Do not replace any parts until you have determined the source of the problem.

Thank you Lorne, I will check it out today and update you guys tomorrow. 

Hey guys, I found out the problem. It turned out to be a bad rectifier. I was really surprised because I replaced my rectifier 5 months ago and it wasnt a cheap part. It was a Rick's motorsport rectifier.

Has anyone used that brand before?

I found out the problem. It was a bad rectifier, and it was bad because the  wires got oxidized and making it less conductive. Thanks for all the help.

There you go.  It sounds like the reg/rec was bad, but for the record, you test a battery by charging it fully using an appropriate charger--and then testing its voltage a few hours after taking it off the charger.  It should read over 12.6v (for an older battery) or over 12.8v (for a newer one).  You can also "load test" it, using a special battery tester, but the tester needs to be appropriate for the particular motorcycle battery you're testing (I have to enter a code into mine to tell it the battery is a YTX12BS, for example).

Ciao,

Thanks JZH.