Charging system not working- and- should this affect the fan? (92 VFR750F)

Hey everyone,

I recently picked up a 1992 VFR750F in mint condition. On my first ride the bike quit on me, and we found the regulator/rectifier fried.
So after replacing the R/R with a heavier duty part from the states, and re-charging the battery, the bike starts fine, HOWEVER- the charging system is not going (multi-meter to battery shows 12 volts when it's running, so it's not getting charged).

AND, the frame tends to get quite hot, and the radiator fan doesn't kick in.
We're troubleshooting this now, and would appreciate some direction.

Does the fan not run unless it's really hot? Is a hot frame normal? Is this somehow related to the charging system not going?

I can see some great threads on here regarding the charging system, ( like http://vfrworld.com/forums/1st-2nd-generation-1983-1989/34842-problems-charging-system-help.html ) but what I'm wondering is how the cooling fan (or lack of) ties into all this.

Cheers,
Jordan

 

Check FAN FUSE under the right front cover under dah brake massa cylinder. Could be a blown fuse, I had one once.
Your charging system aint doing its yab. You gota be at 13.5 to 14 something at 3500 RPM or about, its in the book you know (0ld Man-you-all)manual.
Maybe your stator is bad, or your r/r is bad. These bikes run hot as fuck btw, I wouldnt wana rest my dick on any part of my bike after a ride. Damn thing is a heat sink!

 

My 4th gen was showing around 12.5volts at idle...but when you bring the revs up it goes to the 14ish volts it should.

Hot frame is pretty normal in warm weather conditions. Fan doesn't come on until the bike is quite hot (but not overheating)

 

Thanks- and yes, we have checked the fuse in the fuse box, they all appear fine!
Despite that, I'm positive it remained at 12 volts when revving, but we'll double check that as well.

Sounds like running hot is normal? How high should the temperature gauge get in normal running operation? (mind you I'm in New Zealand with 20 degree celsius, 68 fahrenheit)

Cheers,
Jordan

 

Get urself a laser point thermometer Kiwi! Its fun to point it at the tarmac or your dashboard on your car so you can figure out if you can fry an egg also works nice to figure out temps on your radiator and cylinders. :smile:

Kidding aside, me thinks that the fan comes on at about 198 Farenheit or so. btw when I lived up north my fan would rarely come on and I rode in 30 F to 50 F during the winter months. Now I am spoiled and freeze if it gets into the 60s ; )

 

I've owned two 3rd Gen VFR's and they both ran very hot (including frame) and the fan will only come on when the temp reaches a certain point above 200 degrees. After speaking to numerous other 3rd Gen owners I've concluded that this is normal for these bikes. As far as the charging goes I would start by pulling your right mid panel and checking the plug that connects the 3 yellow stator wires to the main harness. Both my bikes and several bikes belonging to friends of mine suffered from charging issues because these plastic connectors were getting burned/melted because the wiring used was inadequate. In addition to this you should obviously check the plastic connector that plugs into the R/R itself. If the wiring and connectors look OK on both connectors you'll need to check the stator itself.

With the bike off unplug the connector between the stator and reg/rec unit. With your multimeter on Ohms, touch the positive meter lead to one of the yellow stator wires and the other lead to ground. There should be infinite resistance or no continuity showing. Repeat the test for each of the yellow wires and ground.

Next check for continuity between each of the stator wires. With your meter still set to Ohms, check resistance between wires 1 and 2, wires 1 and 3, and wires 2 and 3. There should be @ 0.2~0.5ohms of resistance between each set of leads.

For the last test you should switch the multimeter to AC voltage and then start the bike to check the AC voltage between each set of yellow wires. Again start with wires 1 and 2 and then move on to wires 1 and 3, then 2 and 3. While the bike is running and under slight load you should get somewhere @ 20-60 volts range between each set of yellow wires. If not then you stator is probably going bad.

Rollin

 

Another nice place to check is right next to your battery. Thats where the starter relay resides, they do like to get hot btw. Mine melted, so I had to solder new spade connectors on the end with the shrink tubing. Nice thing about doing away with the plug is that you can actually see the condition of the connections.

Replaced my stator 5 years ago, R/R went bad recently, (melted and left a black blob of shate on my frame :sad used carb cleaner for that shate.

Rollin - How many miles you got on ur Gen 3 bike?

 

not to beat a dead horse or anything, but this subject does tend to come up a LOT on this forum. a few years ago i had the same problem with my 2nd gen and went batshit crazy researching root causes and fixes for the charging system specific issues with these bikes. i ended up doing a bigass write-up on the whole deal, and it may end up helping you through this one. here's the thread below:

http://vfrworld.com/forums/mechanics-garage/17895-charging-system-upgrade-explained.html

 

I currently have 12k miles on my bike. My previous 3rd Gen had 42k on it when my brother in law totaled it. I wanted another 3rd Gen and was lucky enough to find another one locally with only 7k miles for $2000. It was almost perfect cosmetically but was not running due to be stored incorrectly for a couple years. After replacing all the fluids and cleaning the carbs she looked and ran as good as new. People can't believe how old it is.

Rollin

 

Ok, I've heard back from my mechanic- sounds like there was actually a loose wire stopping the alternator from charging properly- AND, sounds like the radiator is damaged or for some reason- maybe only cooling 15% as well as it should. I'll see it on Tuesday, and having the "motorcycle doctor" check it over the next day. Cheers for the advice guys!