Strange problem...

i replaced my 83 vf750f battery today as the old one died. All was good riding home from the battery shop for about an hour...then my bike started to miss fire. I`ve worked out that when i have my headlight(or any other light) turned on the bike starts to miss fire. It seems that all the battery charge is being drained by the lights when i turn them on. The bike runs fine when the lights are off. Any ideas what the prob is?? Regulator/rectifier??
Thanks,
Dave

 

Dave:

I'd say my gut reaction is a regulator/ rectifier issue.

Do you know how to use a multimeter?

BZ

 

Yep. What BZ said. Check out your charging system.

 

yeah that what i figured. how do i check if the r/r is faulty?
thanks

 

Here's the cliff notes version:
You have three yellows, one red, and one black wire on your rr. Current should flow (using an ohm meter) from the black out the three yellows, but not in the opposite direction. Current should then flow from the three yellows out the red, but again, not in the opposite direction. You should have about 5-15 ohms resistance in the correct directions that I've described. When they fail, you will USUALLY have current flow where you shouldn't. I hope this helps you out. It's really easier than I make it sound. You should check your stator while you're at it. A Honda manual will have these checks in there if you can get your hands on one.

 

Also check your connections and make sure they're tight, along with the chassis ground.

 

It sounds to me like the new battery is bad or you got a bad connection when the batt was installed. I've had several 1st gen bikes and never had an R/R issue except for the plug going to it getting too hot and failing.
I'd check the connector going to the R/R and see if it has turned brown from heat. If it is brown, just use some crimp-on connectors and do away with the plug. But, I'd look closely at the batt installation job and the new batt itself before digging in too deep looking for other possible causes.

 

You should always check the charging system whenever a battery is replaced, since a bad regulator might well be the cause of the failed battery and will quickly cause another battery failure!!

 

thanks for all the great info guys will had a look at it on weekend.

 

ok well i`ve just had a look at the R/R and the connector that joins the 3 yellow wires coming out of r/r to 3 other wires is completely burnt out. my question is could that have happened from the old batt and should i joint the wires back together and see what happens...........or do i need to replace my r/r as it will do it again?
thanks,
dave

 

I would replace the r/r and then try again. I don't think your old battery caused the issue, I think the r/r probably caused your battery problem. The melt down is from the r/r sending too much voltage out, which will kill your battery and melt the harness.

 

That plug has always given trouble. Just join the wires back together with some crimp-on connectors, check voltage at the batt (should be 12-14v), then RIDE IT!! It seems that that plug gets a little old, the connection gets a little corrosion in it, then it gets hot and melts. I don't think you have a problem beyond the plug.

 

Eddie is correctomundo!

Join up the wires and don't worry about the v.r. ( for now) if you see about 14 volts across battery terminals with engine at about 4000 rpm.

 

will do. thanks again

 

Crimp on wires can cause the same issue. The design from Honda is bad. The standard fix it and forget it solution is to cut back the wires until you see good copper wire and then solder in replacement wire (same guage) replacing the wire you cut out along with the now removed connector. Heat shrink or liquid electrical tape the exposed wire connections.

Crimp on connectors or the stock connector allow very little copper-to-copper contact. There is a lot of voltage going thought that tiny surface area. If it gets corroded or a solid contact is not made, the wire encounters resistance, which heats up the wire - melts insulation and connectors.

Before soldering, be sure you have enough length for removal of parts if it becomes necessary.

 

does all this also apply to an 86 vfr700?

thanks

 

SURE does....

 

all sorted was just the connection that had burnt, re-joined the wires and all is good. thanks again