What is expected battery charging voltage at idle and cruise

[cm08]

Hello all,
Finally got my fj1100 - 1984 which I picked up last September inspected and declared roadworthy.  I have installed a new battery and upgraded to the new voltage regulator. 

I have noticed that the charging voltage at cruise can rise up to 14.4 volts as expected.  At idle (1000 rpm) voltage drops gradually down to 11.8 volts which discharges battery. Headlight and tailight is on at all times (law requirement). When driving in city traffic this low voltage is an big problem as restarting can be affected.

Is this low voltage normal on fj's of this era? What charge voltage are you folks normally seeing at idle with headlight on? If this is not normal any thoughts?

Thanks for your comments and help

[ribbert]

cm08 (Name?) If the voltage rises to 14.4 just above idle that is pretty spot on. I don't have a figure at idle, but it is common for everything to go dull (headlight etc) at idle.

If it is 11.8 at idle and immediately rises with revs I wouldn't worry about it.

Are you speculating about or experiencing difficult starting after riding through traffic?

It is common for a tired starter motor not to want to crank immediately after turning off when hot and needs a few mins to cool down.

The symptoms of this are very similar to the battery not having enough oomph to crank it over.

I wouldn't think what you are describing would be enough to discharge the battery.

Noel

[FJmonkey]

If you are having trouble starting with a hot engine try cracking the throttle open about 1/8 when cranking. It really helped my 86' before I put UNIs and Supertraps on. She breathes real well now and does not need the throttle open to start hot.

[cm08]

Gentlemen,
Thanks for your responses. Yes sorry for being rude. Name is Costa and am from Montreal. Just back from overseas 8 year assignment in Europe where I enjoyed riding my triumph sprint.  Really loved that bike.  A friend gave me his fj which was collecting dust for the last 15 years, as he was moving out west and clearing out the garage.

Spent the winter getting her up to spec for inspection. Replaced lots of bits, removed the yamaha flasher/cutoff relay and rewired to add in 2 standard relays and a flasher ($11.00 total), new voltage regulator based on advice from this forum, new battery,cleaned carbs,valves adjusted, welded back bracket for left amber reflector, added rear reflector,repaired Cowlings which were cracked and missing tabs, new brake disc's and pads,added givi topcase, Etc,etc. All the basics I guess.  Spent lots of time reading this Site for direction and insight.

Back to low voltage at idle, yes it cranked very slow after riding for a while in city traffic with low voltage. Engine was hot though. I noted rpm was closer to 900 so just increased the idle by 100 rpm to about 1000 and it increased the charge voltage to 12.2 volts. An improvement. I am basing this on a voltmeter I have installed on the left side fairing so there may be some slight error in the reading. What is for sure is that it improved and that it rises quickly when I blip the throttle.

Thanks again
Costa

[ribbert]

If the range is 12.2 -14.4v you're looking good.

The slow cranking when hot is common and can be fixed with a starter motor freshen up.

I lived with this for a couple of years. It is surprising how seldom you want to restart the bike as soon as you have turned it off, unless you stall it of course.

A few minutes rest will normally see it spring back to life.

Noel

[movenon]

cm08 (Name?) If the voltage rises to 14.4 just above idle that is pretty spot on. I don't have a figure at idle, but it is common for everything to go dull (headlight etc) at idle.

If it is 11.8 at idle and immediately rises with revs I wouldn't worry about it.

Are you speculating about or experiencing difficult starting after riding through traffic?

It is common for a tired starter motor not to want to crank immediately after turning off when hot and needs a few mins to cool down.

The symptoms of this are very similar to the battery not having enough oomph to crank it over.

I wouldn't think what you are describing would be enough to discharge the battery.

Noel

+1   Had just that problem.
First just weak but started OK, then later had to crack the throttle open, then last it would not work when heat soaked....
Upgraded to a 4 brush starter (91-93 FJ ?). Now no problem. Starts like a bike should.. Cold or hot.  
George

[cm08]

Following the advice re starter being potential problem when engine warm, I decided to check brushes. Brushes are double the min length limit so ok. Commutator was dirty so I sanded it clean and also cleaned gaps between Commutator segments. Will see if it makes any difference next warm start in city traffic (after low charging at idle).

Also while doing this found the alternator mounting bolt broken. Managed to drill and the extract it. The other remaining bolt was still there but the head was stripped and had to use extractor to remove. Replaced both bolts with M8x30mm flanged bolts from auto shop. 12mm head instead of 10mm. Searching for info found that I am not alone and this was/is an problem with 2 bolt alternators.  I hope the bolts I used are tougher than the originals.

Costa

[movenon]

Following the advice re starter being potential problem when engine warm, I decided to check brushes. Brushes are double the min length limit so OK. Commutator was dirty so I sanded it clean and also cleaned gaps between Commutator segments. Will see if it makes any difference next warm start in city traffic (after low charging at idle).

Also while doing this found the alternator mounting bolt broken. Managed to drill and the extract it. The other remaining bolt was still there but the head was stripped and had to use extractor to remove. Replaced both bolts with M8x30mm flanged bolts from auto shop. 12mm head instead of 10mm. Searching for info found that I am not alone and this was/is an problem with 2 bolt alternators.  I hope the bolts I used are tougher than the originals.

Costa

I did the same with my old starter. It got a little better but then started to heat soak and hard to start. Took it apart again and with very close inspection I could see where the motor was hitting the field lamination's. It doesn't take much to slow it down. The bearings were bad. They are not easy to replace without a small internal bearing puller. And when you are done buying a "kit" you are close to just getting a new starter from RPM or e bay and you can upgrade to boot.

Good catch and repair on the alt bolt. All those small bolts only need 5 -7.2 lbs of TQ in general. Quiet a few owners have snapped those by putting to much TQ on them. You are lucky to get it out. That go's for the clutch slave, sprocket cover, clutch cover ect.. As you found out. The bolts are OK, it's the over TQ that breaks them or in some cases strips out the threads in the AL case..
George

[movenon]

Following the advice re starter being potential problem when engine warm, I decided to check brushes. Brushes are double the min length limit so ok. Commutator was dirty so I sanded it clean and also cleaned gaps between Commutator segments. Will see if it makes any difference next warm start in city traffic (after low charging at idle).

Also while doing this found the alternator mounting bolt broken. Managed to drill and the extract it. The other remaining bolt was still there but the head was stripped and had to use extractor to remove. Replaced both bolts with M8x30mm flanged bolts from auto shop. 12mm head instead of 10mm. Searching for info found that I am not alone and this was/is an problem with 2 bolt alternators.  I hope the bolts I used are tougher than the originals.

Costa

PM me, I might has some info that will help you troubleshoot. 
George