Hi all, my first post

Bought an Fy 2 weeks ago and bike broke down on the way home turned out to be a vacumm prob but got it sorted. Whilst sorting that out discovered headlight dimming when revving so got the multimeter out changed rectifier for a new one, took more readings and discovered the stator nacked too replaced with 2nd hand one, i also put in a new battery while i was at it.
Readings from the battery fully charged 13.4v
When I start the bike 14.5v
As the bike heats up to normal operating temp the revs dip and the voltage at the battery gradually starts to fall until it gets to about 12.5v and then the bike cuts out!
The bike can still be started with the starter and when revved starts to put about 12.8 volts in but when left to idle it cuts out again.
I've also noticed when the bike is idling im getting a faint flicker in all the lights and if i put the indicators on i get like an occasional double flash from them.
I've taken the tank and dash off and checked all the connectors i can find but although the one at the main fuse was a bit green inside the rest looked fine.
Im totally stumped someone please help

 

To start what model F4? The 99-2000 models still sported carbs vs fuel-injection,
if I understand correctly. From your mention of vacum leak, I'm assuming you're carbed.
Correct me if I'm wrong.

From your description, the charging sounds right. I don't think it's electrical that's
causing your problems. It sounds like the carbs need to be sync'd and idle adjustment,
to me.

What is your idle set for? It should be about 11-12 hundred. If it's set too low,
that might be the issue.

On the chance that I'm off base, here's a couple of comprehensive diagnostics
for the charging/electrical systems...

Charging System Diagnostics - Rectifier/Regulator Upgrade - Triumph Forum: Triumph Rat Motorcycle Forums

https://cbrforum.com/forum/f2-tech-9...-solved-27739/

For a pretty good, general diagnostic chart on engines in general, check this one out...

Four-Stroke Motorcycle Troubleshooting Guide | CYCLEPEDIA - Repair Manuals Online - ATV Motorcycle Scooter UTV

Hope my comments and these links get you started.

Good luck, Ern

P.s. Welcome to the forums and kudos on doing your own wrenching. ;-)

 

^ Good info from Ern. Except for the F4, idle should be set 1300-1500 depending on climate.

 

I would also look at the battery. Check all the connections. Also I would charge the battery then check it with a load meter. If you do not have one auto zone will check it for free. Sounds to me like it is charging good but not holding a good charge? You could have a bad cell, you never know, batterys are funny, espicially small ones, good luck

 

Thanks for the info guys
Bike is the carb model and battery is brand new and was charged overnight
Im gonna keep checking but it doing my head in!