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Discussion Starter · #1 ·
Hello I have a 71 cb175, given to me by my father, I've turned it into a cafe bikes. I've done a lot of work to it over the years, I'm pretty familiar with fixing it.

About a year ago I was sitting at a light and a gas leak caught fire right beneath me and the whole bike was toast. Surprisingly, the tank was still in good condition and the motor ran. I completely rebuilt it for the second time and it was running fine.

2 weeks ago I rode it home, parked it and went inside. Next day it wouldn't start, would only run on one cylinder and only when I was full throttle. Got frustrated then left it. Now it wont start at I'll.

It wasn't getting spark on the right side for some reason, so got a new condenser, got a new ignition coil, got a new battery. Still nothing. Spark is great on both sides now. I've set the points gap, the timing with the points plate, I even rewired the points plate wire with new insulation and everything. I've tried rigorously cleaning the carbs, and all the wiring 5 times. Battery is reading 12v. I am able to attempt to kick start/pop the clutch. It's not seized. Popping the clutch is the closest I can get it to start.

Another strange thing is the starter WILL NOT turn. Tried jumping the solenoid, pair of plyers just gets red hot, tried jumping my car battery directly to the starter wire same thing.

A friend told me a story about running his 240sx with no alternator and it frying the battery

I thought maybe possibly it's because after the fire I had to rewire the stator wires or magneto whatever it's called. And since I suck at soldering I thought maybe one of my solders broke and killed the battery from running without any kind of generator. I mean that battery was toast it would almost instantly drop to 0 volts and I have no clue what else could have caused it. I just put a brand new battery in it and I'm not seeing any kind of shorts and it's holding voltage fine. so I'm really at a loss here.

I'm seriously about to just sell this thing it is driving me insane to the point I'm losing sleep over it. Any advice would be a god send right now.

And yes I have air filters I was just trying to shoot the air compressor or carb cleaner in the carbs. And had them off. It should run without them either way.
 

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Sounds like youmught have more than one problem but, "I thought maybe one of my solders broke and killed the battery from running without any kind of generator. I mean that battery was toast it would almost instantly drop to 0 volts and I have no clue what else could have caused it." Sounds like you have a dead short in the electrical system - maybe in your rewound generator? Before connecting the battery it would be a good idea to check that you have an 'open circuit' between the battery terminals with ignition switched off.
 

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Discussion Starter · #3 ·
Sounds like youmught have more than one problem but, "I thought maybe one of my solders broke and killed the battery from running without any kind of generator. I mean that battery was toast it would almost instantly drop to 0 volts and I have no clue what else could have caused it." Sounds like you have a dead short in the electrical system - maybe in your rewound generator? Before connecting the battery it would be a good idea to check that you have an 'open circuit' between the battery terminals with ignition switched off.
The generator isn't rewound, just the wire insulation melted in the fire on the outside of the case so I just had to put new wires, the stator wires haven't been touched. What do you mean by an open circuit with the ignition turned off?
 

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Take the wiring harness out of the equation. Disconnect the coils from the harness and Just run the bike from a good battery. you don’t need the charging system to run the engine.
 

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Discussion Starter · #5 ·
Take the wiring harness out of the equation. Disconnect the coils from the harness and Just run the bike from a good battery. you don’t need the charging system to run the engine.
Sure, tried that, doesn't work. Unplugged the generator from harness still nothing
 

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I am going to back up what middletons said but a little different. Run a jumper from the + on the battery to the + side of the coil. By pass everything else. !2 volt at battery, 12 volt at + side of coil,12 volt at points . Points set, timing set, plugs firing? Try to kick start. No start pull the plugs and see if they are wet. Report back.

Bill H
 

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Discussion Starter · #7 ·
I am going to back up what middletons said but a little different. Run a jumper from the + on the battery to the + side of the coil. By pass everything else. !2 volt at battery, 12 volt at + side of coil,12 volt at points . Points set, timing set, plugs firing? Try to kick start. No start pull the plugs and see if they are wet. Report back.

Bill H
Plugs not wet. Tried this. They're a little black, but they still spark a solid white purple spark.
Points set with feeler, timing set with continuity tester
 

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Discussion Starter · #8 ·
I am going to back up what middletons said but a little different. Run a jumper from the + on the battery to the + side of the coil. By pass everything else. !2 volt at battery, 12 volt at + side of coil,12 volt at points . Points set, timing set, plugs firing? Try to kick start. No start pull the plugs and see if they are wet. Report back.

Bill H
When you say 12 volt at points where do you recommend I clamp it, right on the wire that goes to the points? Not really a good spot to do that other than that that I can think
 

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You can use your OHM meter to check it ,ground the meter and just touch the + to where the wire connects from the coil .Then connect the OHM meter to both sides of the points and use a finger to open and close the points . Points closed you should get a reading. Points open should read 0. If plugs are firing and you try to start it but no go. pull the plugs and they are dry seems to me you not getting any fuel. I rebuilt a CA 160 that had been in a fire. Basically the same motor. For the ing system I ran the red wire from the battery to the ing switch. Black wire from switch to horn . From horn to coil ,from coil to brake switch. Of course you have your points from the coil. This was from an original switch that had 4 positions. If using an after market switch you will have to work that out.
Thats the ing system . Battery to coil to points .and the plugs firing. In time and points set I would start looking at a fuel problem. Hows the compression? The motor runs from the battery and all the stator does is help with the lights and charge the battery. With a fully charged battery the motor should run fine till you run the battery down. As you said you have good solid spark and its in time I think I would start looking at the fuel delivery.

Bill H
 

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Discussion Starter · #10 ·
You can use your OHM meter to check it ,ground the meter and just touch the + to where the wire connects from the coil .Then connect the OHM meter to both sides of the points and use a finger to open and close the points . Points closed you should get a reading. Points open should read 0. If plugs are firing and you try to start it but no go. pull the plugs and they are dry seems to me you not getting any fuel. I rebuilt a CA 160 that had been in a fire. Basically the same motor. For the ing system I ran the red wire from the battery to the ing switch. Black wire from switch to horn . From horn to coil ,from coil to brake switch. Of course you have your points from the coil. This was from an original switch that had 4 positions. If using an after market switch you will have to work that out.
Thats the ing system . Battery to coil to points .and the plugs firing. In time and points set I would start looking at a fuel problem. Hows the compression? The motor runs from the battery and all the stator does is help with the lights and charge the battery. With a fully charged battery the motor should run fine till you run the battery down. As you said you have good solid spark and its in time I think I would start looking at the fuel delivery.

Bill H
I just fully disassembled the carbs and cleaned and put back together last night.i agree it seems like fuel problem. Check fuel lines and petcock all working good. Fuel in the bowls. Jet's clear. I'm going to make a video and post it cuz this is just unbelievable. I'm not sure on compression. But like I said, it ran fine when I parked it
 

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Reread your post and am just as confused as you are. If the ing is good , the carbs are right and you try to start it with the choke on and the plugs are dry. You might try the compression for some reason you are not pulling air/fuel mixture into the motor. Did you try spraying starter fluid into the carbs?

Bill H
 

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I also have a cb175, although my bike was not damaged in a fire, I had some similar issues. The bike would not start, and if it did, it wouldn’t idle. If I cleaned or changed the plugs, I could usually get it to start again, but still it would not idle. I do have a modern reg/rec combo and I’ve done the yellow wire charging mod. I also tried everything. I had been through the carbs and timing numerous times, replaced the condenser, was damn near ready to replace the coil. One thing I learned was, if you do an adjustment properly and you still have a problem, doing that adjustment again is a waste of time. In my case, I ended up figuring out that I had a bad battery. Perhaps it’s possible that your new battery is bad. I found out mine was bad because my boss has a professional battery tester and I brought it to work one day, we tested it and it was bad. Mind you I was also reading 12v and my lights and horn all worked, all indications that my battery was fine. I went and bought an AGM battery, a smart charger and a low voltage alarm. Even a new battery can be bad, even if it’s reading proper voltage. Once I put the new battery in, it runs and idles just fine.
 

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I also have a cb175, although my bike was not damaged in a fire, I had some similar issues. The bike would not start, and if it did, it wouldn’t idle. If I cleaned or changed the plugs, I could usually get it to start again, but still it would not idle. I do have a modern reg/rec combo and I’ve done the yellow wire charging mod. I also tried everything. I had been through the carbs and timing numerous times, replaced the condenser, was damn near ready to replace the coil. One thing I learned was, if you do an adjustment properly and you still have a problem, doing that adjustment again is a waste of time. In my case, I ended up figuring out that I had a bad battery. Perhaps it’s possible that your new battery is bad. I found out mine was bad because my boss has a professional battery tester and I brought it to work one day, we tested it and it was bad. Mind you I was also reading 12v and my lights and horn all worked, all indications that my battery was fine. I went and bought an AGM battery, a smart charger and a low voltage alarm. Even a new battery can be bad, even if it’s reading proper voltage. Once I put the new battery in, it runs and idles just fine.
So you had the Voltage but no Amperage, is that right?
As for a New battery being bad, I went through that too - twice in about 3 months.
The 3rd battery finally worked - almost 3 years now!
I Hate small batteries!
 

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Same exact same thing happened to my 72 CL175 (the non-starter thing, I never had a fire).

I was pulling my hair out and racking my brain for months trying to figure it out.

I went through many of the same tests you are to try to figure it out, and honestly don’t know what I did do finally get it to start turning over again.

Sorry I’m not more help, but wanted to clarify that it may not be related to the fire.
 

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If this happened to me, I would remove the starter and take it to the bench. There i would try it on an 12v source. If it spins fast and free, then I would troubleshoot the wiring. If it did not turn, I would rebuild or replace the starter. Old motorcycle wiring harnesses are pretty dodgy just being 40-50 years old. After a fire, it would be even more of a concern and I would replace it. I have replaced wiring harnesses two times on two separate rebuilds, and it solves a multitude of issues.
 

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If this happened to me, I would remove the starter and take it to the bench. There i would try it on an 12v source. If it spins fast and free, then I would troubleshoot the wiring. If it did not turn, I would rebuild or replace the starter. Old motorcycle wiring harnesses are pretty dodgy just being 40-50 years old. After a fire, it would be even more of a concern and I would replace it. I have replaced wiring harnesses two times on two separate rebuilds, and it solves a multitude of issues.
No disrespect, seems kind of like a wholesale approach. If the starter is bad, it’s bad. True, I’ll give you that. But there’s still the kickstart. My starter clutch is bad, but my kickstart works fine so I haven’t bothered with it. Yes, I agree they are 50 year old bikes. But I feel like if it doesn’t start with electric or kick, it might be the wiring or it might be something else. After my experience, I’d be testing the battery first before anything else, then working my way forward and going to the starter last.
 
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