Headlight High beam

My high beam keeps burning out.

I put in a new bulb and about 1/2 mile down the road the high beam quit working. The low beam continues to work. This has happened two times in a row.

What to check?

How / Where to check for a short?


Re: Headlight High beam

What kind of ped? check out how big the bumps your hitting are... thet is usually my problem. I got a tractor light hooked up to my Honda Express right now.

Re: Headlight High beam

my moped is a Tomos Sprint 2003. New this year.

I didn't hit any bumbs.

Can a tractor light be hooked up to a Tomos? You know a tomos doesn't have a battery, so...?

Re: Headlight High beam

if you have any modifications you could be revving out too high and blowing the bulb. put a voltage regulator on it.

Re: Headlight High beam

I installed a Airsal 65cc piston on my Tomos Sprint. The headlight worked fine for 3 weeks. Then out of no where the high beam blew. THe new bulb blew the high beam in less than a mile of riding. I did upgrade to the 35watt bulb instead of the 25watt stock bulb.

What could be wrong with the wiring?

Could a short cause this ?

What else to check or do?


Re: Headlight High beam

Why does revving out too high only cause the High beam to blow out and not the low beam?

This never happened for the first 1,500 miles after I put on a new Airsal 70cc engine.

Could it be due to something else?

Will this voltage regulator work on a Tomos Sprint 2003?


Thanks for your reply.

Re: Headlight High beam

John Joedicke /

Yes it will work, put in line to headlight. More speed, more revs, more vibration ,more volts generated = blown bulbs. First one filiment then eventually the other. Tomos are a pain to change the bulbs because of that ugly square headlite setup.

Re: Headlight High beam

The low beam element on my bike is protected by a fat, wire wound, high wattage resistor. This resistor thing is mounted near the fork.

This resistor limits how much current can flow through the low beam element. Low beam is protected.

But the high beam element is not protected (which is why it is burns bright) and must absorb whatever voltage is coming from the lighting coil. At high RPM this voltage can be as high as 28 volts.

A brand new bulb, with it's new thick element might withstand this high voltage but elements get thin with age.

Another thing to remember is that all the other bulbs on that circuit that are connected also absorb some of the current.. Bulbs act like resistors.

(Several bulbs on one circuit will burn dull. A single bulb on that same circuit will be very bright or may even burn out.)

So, if your tail light is burnt out it is not sharing the load, the high beam element alone will be force to withstand the entire load and may fry. So make sure all bulbs are connected and are working.

The electrical system works fine when the bike and all the parts and bulbs are brand new and everything is connected and working..

Re: Headlight High beam

Thanks Joew, great explanation.

Now I know why my high beam blew out.

I don't have a speedo bulb working and my high beam indicator light sometimes goes off and I have to jiggle the wires around to get it back on. That is when my high beam went out.

I just don't know how to go about fixing electrical problems;

replace the wiring? I don't want to do that. This is a new Tomos Sprint. The Speedo light never did work and now the high beam indicator light has a short or something?

Again, thanks for your knowledge.

>I may just add on a voltage regulator, or ride w/ a low beam only. Although I find it more dangerous not to ride with a high beam in the day and not being able to flick the light from high to low to high to low so cars can see you when necessary.

Re: Headlight High beam

Electrical is no fun but we all have to deal with it. Most stuff can be diagnosed visually, like corroded connections or broken wires. A few tools are needed.. wire stripers and soldering iron.. and learning how to use a multimeter is a time saver and a necessity imo.

I have an old bike and got tired of messing with the expensive original headlight replacements..

So i installed a single 12 Volt, 25 watt halogen bulb (Home Depot .. $4) inside the headlight. Something like this:


This job involved prying off the sealed beam lamp lens, un-soldering the original bulb in the back, silicone the new halogen in the hole.. silver soldering the wires to the new bulb.

At least i now have a cheap replaceable bulb that will not burn out and i still have my original sealed beam headlight and adjustment screws.. The "low" beam is enough for me since it makes me legal and, anyway, i avoid riding at night.

Re: Headlight High beam

Is there a way to hook up resistors in place of where there should be bulbs? Or some other way?

I don't want the high beam indicator light to come.

Also does the speedometer light have to be grounded to work? Can I test it while it is outside of the speedo and only connected to the female connector?


My low beam blew tonight and I had to ride home in the dark.

Re: Headlight High beam

The wire in a bulb has a certain amount of resistance. Try to push electricity through the wire (this electric pressure is 'voltage') and it 'resists' the flow of electricity and gets so hot that it glows brightly.

Lets say you push 6 volts through a bulb and it shines. Now increase the voltage (pressure) to 12 volts. The bulb burns out. Why exactly did it burn out? It burned because the wire inside had too much resistance to survive with all that extra pressure (12 volts instead of 6 volts) and the wire got too hot and melted.

You could solve the problem by delivering ONLY 6 volts.. Or you could use a bulb that had less resistance. A wire with less resistance would be bigger in diameter (or shorter).. thicker.. easier for electricity to flow through it.

A 12 volt bulb is such a bulb. It has thicker wire inside which has less resistance. It will not burn out under 12 volts of pressure.


So, instead of replacing bulbs with resistors in your circuit (which should work, keeping your bulbs alive but only by wasting lots of energy as heat instead of light) just use a higher voltage bulb than what you now use.

The downside is using higher voltage bulbs might have negative effects like dim light at low engine RPM. Even if you pick a high wattage-higher voltage bulb it may always be dim. And the bulb might draw too much electricity for your system, causing some other parts of the lighting system to not illuminate brightly or work properly.

It's always a royal pain in the ass to track down and fix these annoying electrical things. Whatever works is OK, but the best way to handle it is get your system back to the way it was when new.

As to testing bulbs:

All circuits must be complete. a circuit.. a circle.. Current must be able to travel from the battery (or generator) positive pole, through the device and to the battery negative pole (and internally through the battery itself back to the positive pole.). So you cannot test a bulb unless the circuit is complete. The metal frame of the bike can and often does act like the 'negative ground' wire. So, attach both a 'hot' and 'ground' wire to a bulb that is disconnected from the bike to test it.

A easier test is to connect the bulb to a multimeter set to "Resitance" or "Ohms" or "Continuity" and see if it's broken or not.

(it's late and im tired.. if someone sees an error here please feel free to say so.)

Re: Headlight High beam

Joew ,

You are right on the money, these mopeds use a negitive ground, yes your light bulb has to be grounded to light. I was having the same problems as you, and simply switched to a 12volt $2 walmart bulb that fit, I havent had any problems since.

Re: Headlight High beam

My Tomos Sprint 2003 moped requires a 12 Volt light.

Can I go up to 24 volts in order to stop my bulb from burning out?

ps> even when I bought this moped brand new the speedo light never worked. When I took it back to the dealer; Heeters, they didn't fix it.

They just charged me $45 to change the oil and told me to "get a running start" to make it up a hill. They said that in regards to my questioning them about my engine having soft seized on two occasions.

I finally just ordered an Airsal 65cc engine from Ike; and yes my piston had two smear marks on it.

Re: Headlight High beam

I'm running a 24volt Halogen at the moment..

OK, so the Dealer has his head up his ass. I wouldn't want them "fixing" my bike.

But you say that speedo light never worked.. It's just a couple wires and a bulb. If it never worked and you are burning headlamps the problem is probably nearby.. Could be as simple as a couple bulbs wired in series instead of in parallel or the opposite.. Someone at the factory had a hangover and missed it.

One thing i always do is get the complete service manuals to any new vehicles i acquire... electrical diagrams, vacuum diagrams.. the whole works. It doesn't take much learning to know more about your own vehicle than a dealer does.

Re: Headlight High beam

ooops.. hit the Post button too quick.

I was saying. I’m running a 24volt Halogen at the moment.. I meant to say

Im running a 12volt , 25 watt halogen at the moment. These halogens can burn very hot without burning out. The halogen gas and quartz envelope preserves the hot element.

Sure you can try going up to 24 volt bulbs.. You can experiment with anything without much danger beyond burning the bulb. All you care is you have enough light to see where you are going and people can see you and you don't burn bulbs all the time.

Re: Headlight High beam

Jeff Strahle /

yea your voltage reg. could be bad it just happened to my friend where it kept blowing the lights out

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