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Author Topic: Frustrating starting problem still happening  (Read 22948 times)
Keebs
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« Reply #75 on: July 10, 2019, 06:42:46 PM »

Hi all, been good reading this page about starting problems. My CB-1 either starts easily or not at all, even though the new battery spins the engine over rapidly. It doesn't always start on a bump either, but after it starts on the bump it then works perfectly for a period after that.

Looking at the separate wiring diagram for the ignition, I notice that the CDI is grounded through the side-stand switch when the stand is up i.e., in normal operation. My thought here is that the coils, which are permanently powered by the Bl/W lead, ground in the CDI (I don't think it gives them positive pulses,  I think it gives short periods of connection to ground). Therefore, since:
1) There is a route from the CDI to ground through the side-stand switch in normal mode, and
2) When the stand is up, there is no ground to the CDI and no spark
Therefore, I'm thinking the coils could ground through the CDI and side-stand switch, so a mucky / high resistance switch could mean low or no spark.

Wither could cause the problem, but just giving my view. I'll report back if I find anything conclusive. Cheers.
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a_morti
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« Reply #76 on: July 11, 2019, 01:23:09 AM »

Remove spark plugs, gap, clean with brass brush and solvent. Cut back 1/4" off spark plug wires.

These bikes don't start well on worn plugs. Replacing everything is expensive, the above often works at least enough to prove the theory.
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filterMan
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« Reply #77 on: July 11, 2019, 10:40:57 AM »

What a_morti said. It's always best to eliminate the simple things before splashing cash.

Also you could check your choke cable is operating correctly. Remove the tank and take a look where it connects to the carbs. Check it's travelling smoothly and the travel at the lever is the same as a full travel where it connects to the carbs.

My -1 won't start ever on less than full choke when cold.

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Keebs
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« Reply #78 on: July 12, 2019, 05:56:15 PM »

Cheers for the suggestions guys. In my case there's more to the story. I replaced the original HT leads with new leads & new NGK caps a couple of years back. The spark plugs are not that old but I could check the gap from a servicing perspective.

The thing is, when it wouldn't start, I could tell it wasn't even trying, at that point I tested #1 and #4 leads for a spark with an alternative plug held to ground on the engine, there was a really weak spark, suggesting low voltage to, or a bad ground from, the coil packs. I believe bumping it mechanically jolts some bad connection somewhere, hence it starts from the motor fine after that. When I repeated the spark plug test when the bike was starting OK, I couldn't hold the plug with a glove on as it was giving me a kick. So when in fault condition is is getting only a weak (or no spark) at at least 2 plugs. There being a spark suggests the CDI and crank position sensor were both working.

I don't relate the neutral switch to the spark as you get a spark in neutral and in gear. It only matters that you're in gear when you're starting the bike, in which case, if you've got the clutch in and the side-stand up, it will start, else it cuts the starter motor relay - not the spark from the CDI.

Regarding the side stand switch, for anyone's future reference:
a) It is a rotary switch bolted to the inside of the sidestand, not a plunger switch.
b) The tag which makes the switch rotate fits into a hole in the s/s, so there's no chance of it not moving or not returning, it's not possible.
c) There are actually 2 switches which are the inverse of each other, one provides a ground for the s/s light when it is down, the other provides a ground for the
    CDI unit when it is up.
d) You can remove the switch by unscrewing it from the inside of the s/s with an 8mm socket / spanner.
e) I found infinite resistance or 0.5 Ohm in the appropriate positions for each switch, with the plug disconnected under the tank.

Having played with the switch I think I've probably got another problem, or it'll just work now! (Please)

It has only ever completely failed to start twice, both times were in the past 5 days and after the bike had been on the s/s, which until fitting a gate to my yard recently, I never previously used.

Always something to challenge you on these older but lovable bikes! Will report back if I get any more useful information.

Cheers
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