Bulbs blowing at high revs!!!

[caferacer]

Hey guys, I'm having a spot of bother... again

My bike has recently developed a fault which is causing all lights to blow when the engine is revved up.

To be honest it's a right PITA as it's got it's MOT coming up in a week!

I've replaced the battery. The voltage across it sits nicely at 12V at idle and goes up to about 15V max when I rev the engine. I did get it up to 18V at one point but for some reason can't recreate that so it may have been a blip in my reading skills...

I've replaced the Reg/Rec just in case with a brand new one and I've chased all the earthing back to make sure it's all got good connections.

But the problem is not solved.

It's still blowing all the lights (including in the dials - how the flip do I replace these!?!?!)

The only thing I can find is a 'ballast resistor' under the fuel tank with cracked ceramics and the spring exposed... I can't find a replacement for this anywhere so have covered it in tape to make sure it's not shorting. I believe that would only be connected to the headlight anyway?

WHAT AM I MISSING HERE GUYS!!! PLEASE HELP!!!!

If it helps it's a HONDA CB 125 RS.

Thanks

[Nobby the Bastard]

I'd be looking at an earth if I was having this problem on so many bulbs and the rectifyer/regulator replaced.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[paddlesat16]

You need to get yourself a haynes manual/workshop manual and look up the charging system for this bike. Blowing bulbs means its getting way too much juice and your reg/rec isn't sorting his out. The ballast resistor has probably something to do with restricting the amount of volts in the system as well.

Get yourself a meter and check your battery isn't cooking off as well.

Regards
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I once saw a bloke shagging a donkey.... in Saudi arabia. Theory Test Passed 26/10/09 Mod 1 Passed 26/4/10, Mod 2 Passed 7/6/10 Current Bikes Suzuki GSX1400 K5, Aprillia Pegaso 650, Suzuki DR350T.

[caferacer]

Unfortunately, there isn't a haynes manual for my bike (it's special).

I know the charging system, the magna coil charges the battery on one circuit (only at high revs) and it also powers the headlamp (through the regulator) - thus the ballast resistor to protect it from peaks in power particularly when changing between low and high beam.

I do have a multimeter (see original post) but the readings I'm getting vary every time I start the bike up. So I'm now thinking it must be a dodgy earth to the magna coils.

Make sense?

[doggone]

The only time I've had repeated bulb blowing it was a bad earth connection, the wire had almost frayed through.
This also ties in with your freak high reading, that's what it's doing when you go over a bump or something.

[mudcow007]

on my CG i went through a spate of bulbs popping, i changed reg/ rect checked wiring, battery etc

i changed the bulbs i was putting in to a better make (osram?) an they are now fine

[caferacer]

Ok, I found the earth wire from the alternator had a bullet connection that was only part way pushed together, I guess that could be it?

The indicators seem to be coming on without blowing now !!!

Haven't dared try the headlight yet - expensive bulbs.

Now I have a new problem - indicators aren't flashing, they are just staying on constantly.

Have I blown my relay? Or is it more likely to be another dodgy connection?

Thanks for the support guys - MOT is on Friday.

[caferacer]

Thursday today - problem still not fixed...

I thought it might be low voltage on the indicators stopping them from blinking as I've come across that problem before but the voltage is sitting steady at 12V.

Also I've just realised that both indicators come on at the same time with the switch in both positions.

In my head this either means the flasher unit is busted and directing current to both circuits or I have completely ballsed up my wiring in the headlamp somehow!

Please someone tell me the relays do this when they break!?

[Robby]

I assume this is the 125 version of the CB250RS, so it's from around 1980.

Electrics - clean the earths. A 30 year old steel frame will develop plenty of rust and crud at the earth connections, this will cause all manner of cocking around. You want to get the connections back to bright, clean metal on both sides and then give them a thin smear of vaseline or copper grease to reduce further corrosion.

Indicator relay - if it's the same as the 250RS indicator relay, then it's an old electromechanical switch with a bitmetallic strip inside. Looks like a metal cylinder about 2 inches long and 1.5 inches diameter. Water gets into them and causes rusty water to clog things up, you can carefully uncrimp the top and strip and clean it. Even in good condition they need a good power supply, so cleaning the earths also helps here.
I could never persuade modern indicator relay to work with a 250RS, they used to get hot and die in about 20 mins.

[caferacer]

[Robby]

Did you definitely clean all of the earths? There are a lot of them scattered around. I think the front indicators earth through the frame, so you need to make sure they have good clean nuts and bolts.

I also ran an additional earth from the battery negative to the frame - 30 year old wiring loom that had seen some "modifications" in the past wasn't great, and relied on a fairly narrow gauge earth back to the battery. RSD models with the electric start have an additional chunky earth strap from the battery to the frame.

If the ballast resistor is knackered you should replace it. It may be the same part as used on the CG, or similar, so you could try wiring in a CG one if CB ones are unavailable/expensive.

[bikenut]

you could always run a new dedicated earth wire from the frame up to the headlamp area, the earth will be the thickest wire as it is the "return" and carries all the load from the front electric stuff.........

do any on the electrics play up when turning the handlebars from lock to lock, suggesting a make and break contact in the wires due to fatique......?
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nuts about bikes