79’ CT90 front light headaches

[GabrielVilla009]

Hi all,

First post here! I’ve been having an issue with my newly acquired CT90, that I’ve searched an answer for, but I just keep coming up short.

The bike is having an electrical issue with the front lights. The speedometer bulbs were blow, but the blinker and front light(s) were perfectly fine. The tail light works just fine, but there are no back tail lights. I fixed the front brake switch, and horn. I’ve taken the electrics in the front apart, cleaned them, and rewired. Still no lights. There doesn’t appear to be a ground issue, the battery is new, and the fuse is not blown. Because the horn works, the back is getting power, I’m a little lost.

I’ve never seen the front lights on the bike in action, and have yet to blow the head light, or tail lights while testing. The wire harness and all harnesses in the handles still have their wrap, and don’t appear to be shorting in any area from a cut. Are there places I’m forgetting to check that could be causing this issue? Or is this a possible issue that could be coming from elsewhere that may manifest into something larger? Or will replacing the speedometer bulbs create a full circuit in the front allowing for the other lights to work?

Thank you ahead of time for any helpful comments!

Best,
Gabriel

 

[b52bombardier1]

Run a temporary wire ground to each trouble place to eliminate a ground problem. Get a good multimeter set to DC volts and use it to backtrack within the harness to find where you lose your six volts of DC. What is the engine running DC volts number at the battery?

Hold old is your rectifier? Still using the orange finned selenium rectifier? I'd replace it with a modern silicon device.

Rick

 

[GabrielVilla009]

Run a temporary wire ground to each trouble place to eliminate a ground problem. Get a good multimeter set to DC volts and use it to backtrack within the harness to find where you lose your six volts of DC. What is the engine running DC volts number at the battery?

Hold old is your rectifier? Still using the orange finned selenium rectifier? I'd replace it with a modern silicon device.

Rick

Thanks for the info!

This is embarrassing to admit. I haven't given the bike an in depth look into in about a week and a half. I've taken it out riding a bit since then. Owned the bike for two weeks now. The battery was brand new when I got the bike, and now seems to be missing a quarter of its acid. The rectifier appears to be older, but is not orange.

I'm assuming the rectifier is faulty, leading to the battery getting drained, and not allowing the front lights to draw enough power to engage. The horn and back brake light must not draw as much power which is why they're working. I've also had issues recently where the bike likes to stall when in high gear, if I can even get it to move out of it. I've read the bike needs the battery to be full and kicking out the 6v for the bike to operate properly.

Is there a rectifier, and battery you'd recommend? Once I replace those parts, and the speedometer bulbs, I'll see if I still don't get power, and use your grounding technique, after that!

Thanks for your time,
Gabriel

 

[b52bombardier1]

Hello Gabriel,

Try this for a rectifier:

https://www.digikey.com/en/products/detail/genesic-semiconductor/GBPC2506T/3927928

Its rated at 600 volts peak inverse and 25 amps which is over-the-top PLENTY for the electrical system. Even with flipping the high beam low beam switch at 6000 RPM on our bikes which rocks and quakes the electrical system won't lay a glove on this silicon semiconductor.

If Radio Shack was still around, I'd send you after their 276-1185 part number - almost the same, but only 400 volts peak inverse.

Let me know when you need instructions on hooking it up.

Rick

 

[GabrielVilla009]

Hello Gabriel,

Try this for a rectifier:

https://www.digikey.com/en/products/detail/genesic-semiconductor/GBPC2506T/3927928

Its rated at 600 volts peak inverse and 25 amps which is over-the-top PLENTY for the electrical system. Even with flipping the high beam low beam switch at 6000 RPM on our bikes which rocks and quakes the electrical system won't lay a glove on this silicon semiconductor.

If Radio Shack was still around, I'd send you after their 276-1185 part number - almost the same, but only 400 volts peak inverse.

Let me know when you need instructions on hooking it up.

Rick

Hey there,

Super! Thank you so much! Order placed. I'll fill the battery as well prior to install.

Fingers crossed.

Best,
Gabriel

 

[-Nate]

Gabriel ;

#1 : WELCOME ! .
You'll soon learn many helpful things about this fine little motocycle but for now :
The reason the rectifier is so important / critical is : there's no voltage regulator on these old Honda's, the BATTERY serves as the regulator and modern Chinese made wet batteries don't do a good job so the acid boils out and then the bulbs begin to blow .
First and foremost buy a new battery, for trouble free operation you should get a sealed, "AGM" typ of battery, there are many out there, I'm sure the proper size / part # is on this site else ASK or do some research .
Secondly, your '79 has a potted epoxy rectifier and sadly they age out so yes, you're needs replacing and as Rick mentions, they're cheaper to buy the upgraded typ .
If you're handy with tools and a soldering iron I highly suggest you work closely with Rick here .
If you're not familiar with soldering etc. go to : https://www.parduebrothers.com/cub/makeyourownrectifierforthecuborpassport.pdf as this man (Jon) has been making top quality rectifiers that are simple plug and play for years now . tell him Nate sent you, he can be trusted .

The taillight bulb sits in a rubber isolated socket, the better to protect it from vibrations .

The part # for the correct 6 volt bulb is : # 1154 very few partshaus' carry them these days, your Honda Motocycle dealer will have it in stock although they may say they don't, ask them to look it up and check as they use different P/N's . theirs will be a top quality made in Japan part, better lasting than the average Chinesium ones .

Most often, once you've tested the taillight bulb to ascertain it's okay, the problem is the taillight socket proper has a poor ground, the rubber isolator has a tiny thin ground wire that often looses contact at one of it's ends .

If you're not sure how to test the taillight's ground path ASK, we'll walk you through it, not difficult .

You're going to need to learn some basic maintenance things if you want this to be a reliable easy starting Motocycle, we'll walk you through that too, most of the necessary tools are not expen$ive but getting the *exact* as described ones is important as much of this fine machine has delicate fasteners that are easy to damage / strip / ruin when using the wrong basic tools (screw drivers, sockets, wrenches and so on) .

Once you've done the basic maintenance you'll fine this to be a sturdy bike that you can abuse the heck out of (but please don't) for decades to come .

Remember : NEVER HESITATE TO ASK ! .

 

[GabrielVilla009]

Gabriel ;

#1 : WELCOME ! .
You'll soon learn many helpful things about this fine little motocycle but for now :
The reason the rectifier is so important / critical is : there's no voltage regulator on these old Honda's, the BATTERY serves as the regulator and modern Chinese made wet batteries don't do a good job so the acid boils out and then the bulbs begin to blow .
First and foremost buy a new battery, for trouble free operation you should get a sealed, "AGM" typ of battery, there are many out there, I'm sure the proper size / part # is on this site else ASK or do some research .
Secondly, your '79 has a potted epoxy rectifier and sadly they age out so yes, you're needs replacing and as Rick mentions, they're cheaper to buy the upgraded typ .
If you're handy with tools and a soldering iron I highly suggest you work closely with Rick here .
If you're not familiar with soldering etc. go to : https://www.parduebrothers.com/cub/makeyourownrectifierforthecuborpassport.pdf as this man (Jon) has been making top quality rectifiers that are simple plug and play for years now . tell him Nate sent you, he can be trusted .

The taillight bulb sits in a rubber isolated socket, the better to protect it from vibrations .

The part # for the correct 6 volt bulb is : # 1154 very few partshaus' carry them these days, your Honda Motocycle dealer will have it in stock although they may say they don't, ask them to look it up and check as they use different P/N's . theirs will be a top quality made in Japan part, better lasting than the average Chinesium ones .

Most often, once you've tested the taillight bulb to ascertain it's okay, the problem is the taillight socket proper has a poor ground, the rubber isolator has a tiny thin ground wire that often looses contact at one of it's ends .

If you're not sure how to test the taillight's ground path ASK, we'll walk you through it, not difficult .

You're going to need to learn some basic maintenance things if you want this to be a reliable easy starting Motocycle, we'll walk you through that too, most of the necessary tools are not expen$ive but getting the *exact* as described ones is important as much of this fine machine has delicate fasteners that are easy to damage / strip / ruin when using the wrong basic tools (screw drivers, sockets, wrenches and so on) .

Once you've done the basic maintenance you'll fine this to be a sturdy bike that you can abuse the heck out of (but please don't) for decades to come .

Remember : NEVER HESITATE TO ASK ! .

Hey there,

I’ve read this probably 10 time throughout today. The information is invaluable, just In this reply. I was worried at first my post would come off poorly, so thank you and Rick. You two have given me more ambition when it comes to really dialing the bike in! Much appreciated!!

I really only have two questions from your post. That may help others in the future. I’d purchase a AGM battery in a heart beat, but am worried about the positive wire having a fuse and two inputs. Is this something that can be soldiered to another wire and corrected? I don’t see why not, but the price and wait for a battery, can be a little worrying!

I have a little mechanical experience, I’ve been making my cars run since I was a kid (bikes seem a little more refined honestly), I can soldier, and have a basic understanding of electrical. With all that, your comment about the tail light did throw me a little. Is there a possibility that there’s a short back there causing the front to not operate? I’m extremely interested in learning as to why that’d be! It’d honestly be incredible to me that the electrical system is so tight, that a small ground would cause such a huge issue!

Lastly, in regards to the rectifier, can an old rectifier cause this issue? Even watching in depth videos, it seems as though this component is wayyyy more important on our bikes. Almost like an alternator on a car.

Thanks again for the awesome comment,
Gabriel

P.S. she’s mainly been In the dirt riding some hard trails since I got her, I promise I’ll start to take it easier… until I upgrade the suspension

 

[-Nate]

Yes ;

There are TWO positive wires to the battery, one has a stripe on it and MUST NEVER BE FUSED ! .

It is the direct charging output, why it must not be fused .

It sounds to me like you're about to have a lot of fun and learn things you can use to help others or make $ if you're so inclined .

I don't always have internet access so sometimes my replies come after a few days, I'll never ignore you, not to worry .

 

[joel1234567]

Did you ever test to see that the headlight was blown? Seems reasonable that if speedo and tail lights are blown then headlight is also blown. You posted "I’ve never seen the front lights on the bike in action, and have yet to blow the head light, or tail lights while testing" but what does that actually mean? If the headlight was already blown then you wouldnt blow it again while testing. Put a continuity meter on it and test. If continuity is good check for voltage on the wires to the light. In my experience no amount of battery or voltage or rectifier or anything else will light a blown bulb.

Personally i wouldnt run a sealed battery on a ct90 unless you enjoy a potentially small explosive device directly under a gas tank which is directly under your ass while riding but hey, different folks different strokes.

 

[OLD CT]

Or just run a voltmeter, as finicky as the 90's sound. If you get low on volts you are pushing it. Seems like a great idea to me. That would allow monitoring the voltage at all times while riding it. Now he won't blow up or have to push it 10 miles back home. Crisis averted. Lol!

 

[Uglyox]

Gabriel ;

#1 : WELCOME ! .
You'll soon learn many helpful things about this fine little motocycle but for now :
The reason the rectifier is so important / critical is : there's no voltage regulator on these old Honda's, the BATTERY serves as the regulator and modern Chinese made wet batteries don't do a good job so the acid boils out and then the bulbs begin to blow .
First and foremost buy a new battery, for trouble free operation you should get a sealed, "AGM" typ of battery, there are many out there, I'm sure the proper size / part # is on this site else ASK or do some research .
Secondly, your '79 has a potted epoxy rectifier and sadly they age out so yes, you're needs replacing and as Rick mentions, they're cheaper to buy the upgraded typ .
If you're handy with tools and a soldering iron I highly suggest you work closely with Rick here .
If you're not familiar with soldering etc. go to : https://www.parduebrothers.com/cub/makeyourownrectifierforthecuborpassport.pdf as this man (Jon) has been making top quality rectifiers that are simple plug and play for years now . tell him Nate sent you, he can be trusted .

The taillight bulb sits in a rubber isolated socket, the better to protect it from vibrations .

The part # for the correct 6 volt bulb is : # 1154 very few partshaus' carry them these days, your Honda Motocycle dealer will have it in stock although they may say they don't, ask them to look it up and check as they use different P/N's . theirs will be a top quality made in Japan part, better lasting than the average Chinesium ones .

Most often, once you've tested the taillight bulb to ascertain it's okay, the problem is the taillight socket proper has a poor ground, the rubber isolator has a tiny thin ground wire that often looses contact at one of it's ends .

If you're not sure how to test the taillight's ground path ASK, we'll walk you through it, not difficult .

You're going to need to learn some basic maintenance things if you want this to be a reliable easy starting Motocycle, we'll walk you through that too, most of the necessary tools are not expen$ive but getting the *exact* as described ones is important as much of this fine machine has delicate fasteners that are easy to damage / strip / ruin when using the wrong basic tools (screw drivers, sockets, wrenches and so on) .

Once you've done the basic maintenance you'll fine this to be a sturdy bike that you can abuse the heck out of (but please don't) for decades to come .

Remember : NEVER HESITATE TO ASK ! .

Hello! I’m John, I’ve been posting to assist me in rebuilding a ct110. 6 v . I have the lil beast running like a top now, but can’t convince the front light to work. Sad, but true, the light worked before I dismantled it, and now I can’t locate a hot wire in the birds nest to attach to. I know there should be a bl wire from ignition switch that provides 6v, but with the switch on, I only see one bl with a white stripe and it’s not accessible unles I unplug it from a connector, and it’s mot hot either. What is available is a yellow wire uncommitted in the nest along; it’s not hot either when I turn switch on. I’ve included a photo for clarification. If that’s possible. Oh, I hooded up the light to a battery and it worked.

 

[-Nate]

IIRC (possible) the headlight is run directly from the alternator and uses the single white wire .

It's critical to get the correct wiring diagram for your year CT110 as they changed slightly a few times, the battery is still the voltage regulator and needs to be in good shape, one that won't hold 6VDC for 24 hours is going to spike the alternator and blow the headlight seal beam .

My son's '79 CT90 had a tiny chafed spot in the main harness' black (fused, ignition) wire inside the frame, it'd touch every once in a while and cause the alternator to spike and low the headlight then the fuse .

He gave up on it and it took me quite a while to discover the little bitty bare spot, fixed it and never any more issues .

He soured on the bike, I still have it .

In general you need to make the engine run well enough to maintain a steady idle then set it on the center stand and open the headlight then use a TEST LAMP to see which wires/connectors have power, even at idle the headlight feed will light up our test lamp very brightly .

BE CAUTIOUS using a meter to test ! . IIRC the CT110's headlight runs off a separate AC coil in the alternator .

You can always try the Pardue brothers, they know more about this than anyone else .

 

[Uglyox]

Thank you! I have been fumbling about with a multi meter that is not working; I ordered an 8 buck test lamp this morning. I will follow your steps when the test lamp appears.

 

[-Nate]

Okay ;

I hope you didn't get a cheapo test light, here's what it should look like : https://www.homedepot.com/p/Calterm...GjtyNJcVC3n0FItTDJplaF46_dqGhTbadWRYv_KZz9Xic this is a box of SIX making them very reasonable at $14 each, I'm sure if you copy the brand and part & you'll find them even cheaper else where .

The main thing is : NO COIL CORD ! a coiled cord on a test light will cause you no end of troubles because it will always be trying to pull the ground clip off .

There are thousands of lamps that look like this, the better quality ones will have a matt finish of the cord ~ shiny cord means low quality .

The up to 24 volts means it won't blow the bulb out every time you find the correct alternator wire .

The XT90 & 110's alternators easily produce 20 VOLTS AC so whatever you do, NEVER, EVER mindlessly rev. the engine trying to make it charge ! this can blow the coils in the stator (!$$!! BAD!!) .

Even at the slow ,600 RPM tickover the correct wire will light up the tester bright white .

I'm sure others here will chime in, don't forget to spend some time on the Pardue Brother's site, they're 100% honest and don't sell junk .

Kee[ us posted please, I may be off line a few days but will always respond eventually .