Cb450 new coil. Weak spark!

joevirus563

joevirus563

Coast to Coast
Hi guys.

I've been working on my cb450 project for quite a while. And now I can get it to start and when I do... I can't make it idle more than a few second. I took my sparkplugs out (iridium) and they do spark but a little weak for my taste. Any idea or advice? I coil cable ignition system plus are all new...

Thanks!
 
That sounds more like a fuel problem. You could try charging the battery fully first and see if that makes any difference and then I'd turn attention to the carbs
 
teazer said:
That sounds more like a fuel problem. You could try charging the battery fully first and see if that makes any difference a then I'd turn attention to the carbs
Click to expand...
Carbs are fine. Fuel is fine. I have a small tiny spark. How big is it supposed to be?
 
Big enough to ignite the gas in the combustion chamber.

If you say the ignition is new, then it's most likely good. The motor starts, right? Then you are getting decent spark at idle. If it wont stay running, then either your battery is junk or the carbs aren't supplying enough gas/air to sustain the engines rpm at idle.
 
Big Rich said:
Big enough to ignite the gas in the combustion chamber.

If you say the ignition is new, then it's most likely good. The motor starts, right? Then you are getting decent spark at idle. If it wont stay running, then either your battery is junk or the carbs aren't supplying enough gas/air to sustain the engines rpm at idle.
Click to expand...

Sometime its start... sometime now... i've been pumping it since 3 days now... not starting.

Batterie new... and full
Spark new
Electronic Ignition
Gaz in the tank.
Carb new VM32.

The thing is I can't ajust the carb because the ignition timing is not spot on... and I can't set the Ignition timing because I can't start the bike... :S... I'm screwed now :)
 
Don't set your timing with the engine running. You just set your gap on your points then adjust it by turning the Crank to the timing mark and seeing if your timing light is turned on. Turn your points plate untill the light comes on. try doing a google search for a online repair manual for these bikes. If you need more detailed information just ask.
 
whataulooknat said:
Don't set your timing with the engine running. You just set your gap on your points then adjust it by turning the Crank to the timing mark and seeing if your timing light is turned on. Turn your points plate untill the light comes on. try doing a google search for a online repair manual for these bikes. If you need more detailed information just ask.
Click to expand...

Dyna-s ignition... so no point.
 
The ignition still needs to be set when the engine isn't running.

Ignore the size of the spark, what color is it?
 
Sonreir said:
The ignition still needs to be set when the engine isn't running.

Ignore the size of the spark, what color is it?
Click to expand...

I know... but to fine tune it the engine MUST run so I can use the timing light...

I'll check the color of the spark... almost no spark so... pretty weak.
 
Your problem doesn't sound like a "fine tuning" issue. It sounds like a "seriously out of spec" issue.
 
Get some standard plugs to set it up.
The iridium are resistor plugs, are you using resistor plug caps with them?
What resistance caps? (5 or 10 K/ohm?)
Your not using carbon 'performance' leads? (they also have specific resistance per foot)
What jetting is in the VM32?
It's probably too rich as NO ONE supplies them correctly 'out of the box'
 
Sounds like fuel to me. What happens when you adjust the idle screw? Did you rejet your carbs? Post video if you can.
 
see the thing is on these cb450's you can't see the timing mark while its running all you do is with the engine not running but the key turned on connect a 12volt light bulb to metal strip coming off of the point and to the engine for ground. then After setting your gap correctly turn the engine so the timing mark is lined up and turn your points plate untill the bulb comes on. The light will light up without the engine running as long as the key is on.

*Edit did not see the Dyna S ignition Comment*

Still try the timing light with it not running but the key on see if it still works that way
 
Timing can be set statically at the stock F and LF marks or with a running motor to see that it advances to the fully advanced marks. You can also check full advance timing statically. It is not necessary to run the motor to do that. In fact we rarely use a timing light on race bikes. There are very few "must" issues here. Lots of "should" or easiest to" or "recommended" but few obligatory items.

So you have a Dyna S on the cam end. To check timing at full advance, turn the motor to fully advanced position and tun on the ignition (plugs out and lying on the head) Grab the rotor and advance it and see where it sparks. Spark should be fat and blue. Adjust as required.

If the spark is weak, check your plug leads and caps and all the wiring and especially the switches for corrosion.

Instead of using a plug, go to your local auto parts store and get an ignition tester. they cost like $5 and are just an adjustable gap. use that in place of the plug. You put one end in the plug cap and clip the other side on the head fins. It should easily jump 1/4" or more in air. You can hear it as easily as see it.

Or just check that it sparks at the F/LF marks at around 5-10 degrees BTDC.

But it still sounds like a fuel problem. Are the bowls full of fuel and are the carbs new or "pre-loved"? How are they jetted? and who set them up?
 
Re: Cb450 new coil. Weak spark!

What??? Iridium need resistor? I first time I hear that... I I should use normal plugs then..? I btw I think that my engine ground is the problem... I have none... I only grounded by the rectifire.

Sent from my Nexus One
 
Re: Cb450 new coil. Weak spark!

I set them and they are new. The jetting should be fine now... I was rich a little before? I think my problem is the engine ground... I I have none. Only grounded by the rectifire

Sent from my Nexus One
 
The 'R' in the plug grade means it has a built in resistor
I was just wondering if you fitted NGK plug caps (which are also resistor, usually 5K/ohm) then fitted 'racing' plug wires (often resistor as well)
Your not using 30+ yr old plug caps?
The engine should ground fine through the mounting bolts, if you remembered to clean the paint off at least one of the mounting points?
 
crazypj said:
The 'R' in the plug grade means it has a built in resistor
I was just wondering if you fitted NGK plug caps (which are also resistor, usually 5K/ohm) then fitted 'racing' plug wires (often resistor as well)
Your not using 30+ yr old plug caps?
The engine should ground fine through the mounting bolts, if you remembered to clean the paint off at least one of the mounting points?
Click to expand...

Nop I use Dyna HT.

Ok back to begining... i've check and I was wrong... I DONT HAVE SPARK!

I checked with spark plug and its not it... I changed the coil for the old one... still no spark. Ground is good to the engine.

So back to basic... what does a CB450 needs to be plugged in so it have sparks?

1- Spark plug check
2- Ground check
3- Battery check
4- Coil check
5- Dyna-s or point check

What else?

6- Kill switch?
7- Headlight?
8- Rectifire or voltage regulator?

Let me know if you can help me I'm kind of desperate...
 
Get yourself a wiring diagram and start from the plugs and work your way back. You do need a kill switch (or at least power to the coils).
 
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