old skool bike electrical issue

[hmmmnz]

well, you'd think this cb250 was complecated,
im not getting a spark,
before you say check your plugs or something daft, ill explain what ive done so far,

new plugs, been tested in another bike so are ok,
i have tested the coil resistances on the primary windings, both are with in acceptable limits,
secondary windings are 26kohm and 24kohm so are fairly good as well,

i am getting power from the main switch to both coils and continuity from the coils to the breakers
i have replaced the condensor that links the 2 coil in the hope that was the cause (i didnt have a capacior test on my meter)

the breakers are opening correctly and the points are clean,
im all out ideas, its a very basic electrical system and im still not getting a spark,
what am i missing???
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[Kickstart]

Faulty kill switch? Works by earthing the coils out, so it it sticks you will still get power to the coils, points open, etc, but a continuous earth with no interuption to discharge the coils.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Blau Zedong]

In my experience on bike with active igntion (points, coil and 12V battery),the kill switch and ignition switch work by cutting 12V to the coils (brown wire on Yamahas, not sure on Honda). Making and breaking the earth to the igntion is a CDI practice.
____________________
18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

[hmmmnz]

yep thats the way it works on the cb,
so, still no further ahead,
i just dont get it,
fucken frustrating. grrrrrrarhhhhh
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[stinkwheel]

[hmmmnz]

just sanded the points, power getting through them as i turn the bike over by hand,

i measured the secondry resistance through the ht leads and caps and came up with the correct results, so im assuming the leads are sweet,

replaced the condensor today its well earthed
frame is clean under the coils,

this is he most frustrating problem, i just don't get it, according to all my tests, it should be sparking,
ill try again tonight in the dark, and see if i can spy a mini electrical storm
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[theshmoo]

Its got no timing pick up then, just points?
____________________
CBR 1100 blackbird.

[hmmmnz]

yep just points, she's old skool shmoo

the wiring goes like this

as you can see, it doesn't get any simpler.
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[stinkwheel]

You got an electronic version of the circuit diagram I could have a look at? Honda do the same thing several different ways on their older CBs depending on the year.

Many of them even self-excite which would make it pretty simple to rig up a temporary ignition setup to check the componants and eliminate switches, wiring etc. It would also let me check if the stator coils could be an issue.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[stinkwheel]

Never saw your wee diagram there.

Have you tried disconnecting the end of the yellow or blue wire from the points and flicking it against the engine to see if it throws a spark? I don't trust old points.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[finpos]

If you are getting no spark from either side, I'd be looking for a common point of failure, and I'm eyeing up the condensor with great suspicion. Make sure it's got a good earth - if it's just bolted to something, clean the mating surfaces.

Edit - oh you said you did that In which case, check you have continuity back to battery -ve from the side of the points that the wires don't go to, and also from the cylinder head. i.e. check your engine has continuity to earth at all the right bits.

finpos.

[hmmmnz]

ill go and have another play and get back with results
attached is a colour diagram of the g5
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[hmmmnz]

ok had a play, getting desired results all around,
and managed to get a spark on the plug when i shorted the earth on the breakers to a seperate earth and not the termanals on the points them selves.
weird considering when i put a meter across its defentially making and braking the contact,
shame the points i got delivered today, were for a k4 and not a g5. god damn ebay
cheers for all your help guys, you are all pillars of society
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[theshmoo]

Glad things are getting better, cant be many folk left that can set points lol.
____________________
CBR 1100 blackbird.

[finpos]

If there's any resistance at all on the earth side of the points it'll kill the spark stone dead. There may be a hard-to-find frame to engine grounding strap which was never re-fitted after an engine change or may just have rotted and dropped off. If it's gone, the engine ends up getting earthed through stuff like the throttle cable, which isn't great at doing that job!

CDI - stands for "Best Invention Ever". Sort of.

f.

[stinkwheel]

[Blau Zedong]

CDI is heavier too. Points are OK if you keep an eye on them.
____________________
18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

[stinkwheel]

Oh aye. A bit off topic but I knew there was something that made people really dislike the G5 superdream. I just checked an old issue of Used Motorcycle Guide to find out why.

They were one of those bikes built in the era when Honda thought it would be perfectly ok to run the cam straight on top of the alloy cylinder head without any form of bushing or bearing. They were wrong. Sitting a rapidly rotating piece of hardened steel on a lump of alloy and hoping nothing will wear out is somewhere the other side of wishful thinking.

People used to get someone to machine the head and cam to take roller bearings which increases longevity somewhat. If you are very lucky, there may still be odd people out there who still know how to do this.

So, if you get it up and running and intend to ride it any distance, my advice would be to either get the conversion done or sell it to someone who wants to trailer it round shows and buy something else.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[hmmmnz]

Its alive:up:
fantastic
i pulled apart the other points and made them fit the g5's base, got a spark connected every thing up, turned on the gas gave her a couple of kicks and she roared into life, can't beat the sound of a parallel twin
wicked,
now all she needs is a wee carb balance and she'll be as good as new
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[finpos]

Well done!

Points are a pain in the arse. Give me the extra weight and lower MTBF any day

f.

[Blau Zedong]

The CB250G5 is disliked for being slower and cruder than the K models that preceeded it, and having bizarre traits such as running like crap if you even breathed on the points cover. The cam thing is endemic to most Honda's of that era, a combination of lack of oil changes and not keeping the internal filters clean. The XL trial bikes suffer really badly, I've seen two XL185's where you could lift the end of the cam a good 2mm .

In decent nick the G5 is probably a quite pleasant bike.
____________________
18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

[hmmmnz]

my biggest problems with it so far have been the cam chain slide breaking, and tappet coming loose, snapping 2 rocker arms, and wrecking the cam sprocket and chain,
lol, other than that and all the electrical gremelins its reliable
aha i swear
no play in the cam, but i did think it was weird when i took the top off it, when i saw the cam just sitting there
____________________
the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[stinkwheel]

UMG also says the rectifier leads are a weak point when trying to track down those "Why the bloody hell wont the battery charge!" gremlins.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[hmmmnz]

[stinkwheel]

Used Motorcycle Guide. It's a magazine (no longer in print) that was compiled from articles submitted by the readers on their bikes which had a 'bike buyers guide' at the back. The buyers guide had a short speil on each bike listing the spec., pros and cons of each model. They were notoriously blunt with their descriptions and didn't beat about the bush.

For example. They wrote the folowing about the CD185:

"The CD185 is a machine that will smoke rattle and bang its way into history as a motorcycle worth forgetting. In the unlikely event you should find one still running, do the decent thing and throw a match in the tank."
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.