pcaso
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Post by pcaso on Jan 17, 2022 10:28:49 GMT
I don't know if anyone can help? 2 questions here.. why wont the starter work off the button and why wont the engine fire. I have recently purchased a partly restored CB250N 1981. The starter wont work from the button. When I press the starter button the neutral light dims to show its doing something. The only way I can turn the engine over is to arc the starter solenoid. The head lights work and don't dim very much when the starter button is pressed...my thinking of a dead short? Even arcing the solenoid the engine turns slower than I would have expected - I might need to check oil level - too much oil? I have replaced the CDI unit and there is a good spark. There is a smell of fuel from the spark plug when removed. When I remove one spark plug and arc the solenoid i do get a backfire through the exhaust. Is this a sign of not enough air? Any advice would be greatly received. Pete
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Post by na44superdream on Jan 17, 2022 11:30:30 GMT
If the frame has been powder coated or even repainted the first thing I would check is that the main earth point on the right side upper engine bolt is making good electrical connectivity. I had a that on my CB400NC (worked initially and went downhill as only a small contact area and corrosion had started), took the top bolt out and replaced it with A4 stainless, I buffed back the powder coat with a bremel, fitted two additional copper crush washers against the frame.
The solenoid may be stuck, (can take them apart maybe as a last resort), but a couple of taps with a pin hammer may free the mechanism.
The red fuse box connector under the left side panel is clean and good connection? (it does sound to be ok as every thing else is lighting up)
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pcaso
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Post by pcaso on Jan 17, 2022 13:20:40 GMT
Thank you for the tips...I will give it a go. Many thanks
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pcaso
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Post by pcaso on Jan 18, 2022 9:20:21 GMT
Ive been going through the wiring and can see there's a clutch switch fitted. Does the clutch need to be depressed to activate the starter?
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Post by aryan57 on Jan 18, 2022 12:54:30 GMT
If the bike is in gear, then the starter will not operate unless the clutch lever is pulled in. This is a safety device. If the neutral light is glowing and you can opush the bike backwards or forwards, then the starter should operate. Sounds like you could have a short somewhere in the starter circuit.
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ian
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Post by ian on Jan 18, 2022 22:00:22 GMT
If the starter motor turns when you short the terminals on the solenoid, the circuit the circuit from there to the motor is working. you can check the circuit from the button to the solenoid with a multimeter or bulb between the yellow/red wire & ground, there should be 12v across here when you press the starter button. If there is, the contacts in the solenoid are probably corroded. Had this on my 250NB. You can dismantle the solenoid to clean the contacts up. If you don't get 12v when you press the button, it sounds like there's a problem in that part of the circuit, so you'll need to check it out with the multimeter. There's a colour wiring diagram in the 'manuals' section, which makes following the wiring much easier. As to the issue getting it to fire up, it's worth checking the battery voltage & the compression, then the carbs. There's some pictures of a dismantled solenoid here - honda-superdream.co.uk/thread/12916/today?page=16
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pcaso
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Post by pcaso on Jan 19, 2022 4:08:09 GMT
Thanks guys for the info. I did remove the solenoid and put the 2 wires directly on to 12v and got a nice click. So think solenoid is ok? When all connected back together, I tried pressing the start button and measuring voltage on Y/R. It measured 11.3. checked battery and that's still at 12.6. so I guess I can rule the button out? I tried continuaty through all the earth wires and Y/R but only found a broken wire in head light, an earth wire. so soldered that but didn't resolve issue. The wiring is flakey and on inspection there are a few old fixes on the loom. Just wondering whether to cut losses any get a new loom? I saw a guy advertising on eBay new replica looms for £265. More than I'd like but would be a fresh starting point. Any comments would be appreciated. I'm completely baffled.
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pcaso
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Post by pcaso on Jan 19, 2022 4:10:41 GMT
I need to add that I can't understand the voltage drop, which is why I checked the earth's and Y/R
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Post by roger7 on Jan 19, 2022 11:30:27 GMT
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Post by roger7 on Jan 19, 2022 11:31:03 GMT
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Post by Dennismenace on Jan 19, 2022 19:22:14 GMT
If I recall correctly, there is a link to the neutral switch that prevents the starter working if the bike is in gear UNLESS the clutch is pulled in. So, is the neutral light on i.e. is the bike in neutral before you attempt to start it? You should check that the neutral switch at the gearbox end is working and connected. If the loom is badly butchered it could well be worth replacing to avoid other problems in future. Dennis
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pcaso
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Post by pcaso on Jan 19, 2022 21:03:16 GMT
Hi Dennis The neutral light is on. I have tried pulling clutch in too. I'm getting voltage down to solenoid yellow red when I push start button but there is a voltage drop of about a volt. I need to double check battery voltage when I press starter to see if the batter voltage drops there too. Ie if there is a drain on the system. It's a new battery. But the loom has seen better days.
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ian
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Post by ian on Jan 19, 2022 21:51:21 GMT
If I'm understanding it correctly, your getting 12v at the solenoid when you press the starter button and you can hear the solenoid 'click' though the starter motor doesn't spin but if you short out the 2 screw terminals on the solenoid, the starter motor does spin. If that's the case, it's definitely worth pulling the solenoid apart & cleaning the contacts as that suggests the solenoid plunger is moving but the contact bar isn't properly connecting across the screw terminals. I've only ever come across this twice on a bike: my son's Kymco Pulsar 15 years ago, and my 250NB recently. In both cases, cleaning up the contact bar in the solenoid fixed the problem. The yellow/red wire on the solenoid supplies 12v to the solenoid coil via the ignition switch & starter button. The other wire for the solenoid coil is the green/red wire which supplies the 0v for the coil provided either the clutch or neutral switch is closed. if they are both open, ie not in neutral and clutch lever not pulled in, there is no 0v so no circuit & no starter.
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pcaso
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Post by pcaso on Jan 19, 2022 22:23:10 GMT
I will give that a go and strip solenoid. Thanks for the idea
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Post by earlystock on Jan 20, 2022 13:46:47 GMT
The solenoids are cheap (as long as you dont buy OE) and plentiful, might just be worth replacing it
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