72 CB450 starting problem

W

wtskm

Active Member
Hey guys,

So being a newb to older bikes I had forgotten the check list to follow when starting my 72 cb450, and guess what ? I killed the battery. So, after an overnight re-charge things were well for about 2 weeks, fired up no problem a little picky in the morning but nothing out of the ordinary. Fast forward 2 days ago, it ran perfect all day it was like a dream 1 second on the electric start and it fired.

Now, all it wants to do is cranck and not fire, toasted the battery once again ( no worries it was a 3 year old Walmart special and I wanted to replace it).
So, fresh battery and all it does is crank, the gas is getting there but no fire.

I should have grabbed a set of plugs while getting the battery but it never occured to me that it would be something other than lack of juice.

What do you think my process of elimintion should be. Plugs for sure, I'm thinking it might be the coil.
 
How do you know the gas is getting there? Wet plugs? Just making sure.

Make sure the plugs are clean (or new) and do a visual check for spark. If they are getting wet with gas then all will be left is compression. Assuming the valves and timing are all in spec?

When you got the new battery, was it charged properly?
 
It was charged properly, tons of juice compared to the old battery that came out.
I'm just smelling gas and pretty sure I floaded it one or 2 times trying to get it to start, I will do a visual for sure later today. I should have grabbed a set or 2 of plugs when I grabbed the battery. Is there any way to clean them ? I'll pick-up a new set for sure.

When I had the bike saftied the guy that checked it out said it ran beautiful, as it did on the way in to work on Friday.
If it were compression, would that not be a gradual thing and not something out of the blue ?
 
Ok, both plugs are dry fouled so they gotta go. I get spark on the right side only, nothing on the left.
 
Compession can go both ways - gradually or suddenly. But i dont think that's your problem.

There's some debate about cleaning plugs, but for testing / tuning purposes i think clean ones work. To be on the safe side get some new ones anyway.

No spark at the one plug? Try a new plug first, then check for spark at the points.
 
Will do, actually picking up 2 sets of plugs ( I should have done that when I grabbed the battery)

Thanks !!!!!!!
 
As Rich stated, check you points gap and timing. Then see if you have proper spark. Visually inspect the points contact surface to check if they are burnt or just worn out. A new set of points and condensers are pretty affordable and can make a huge difference. Good luck.
 
It could be almost anything, but a good place to start is getting the electrics in order. Clean and set the points and replace the plugs. Insert new plugs into the HT leads/plug caps. Rotate the motor slowly so that one or both points are closed. Turn on the ignition and flick the points open with a plastic rod of some sort - or a finger nail.

As the points open, there should be a nice blue spark from the plug. Repeat for the other one.

If one side is really poor, try removing the plug caps and place the HT (plug) leads on the head and flick the points again. If they now spark bright and blue, the problem was in the cap or the plug.

If still a poor spark, clean the points again and clean every connection in the ignition circuit. Clean out the Kill switch by spraying it full of WD40 and work it on-of a few times.

Could also be a partially broken lead somewhere in the system.
 
Points are pretty much brand new ( 3 weeks old and about 45 miles on them). And when it was running earlier it was smooth as silk so I can't imagine the points being an issue. With the old plugs the right side has a good spark the left nothing. I should have swapped plugs as a process of elimintion.

The one thing i did notice is that were the plugs connect to the leads the top of the plug has the threads exposed and that's what the wires are connected to, no top or plug cap just threads on both plugs and they seem to connect very well.
Back when I used to work on my Honda Civic the NGK's I used came with 2 different cap sizes one longer than the other for different app's, I find it odd that my plugs do not have a cap on the top at all, but maybe that's the way ????
 
wtskm said:
Points are pretty much brand new ( 3 weeks old and about 45 miles on them). And when it was running earlier it was smooth as silk so I can't imagine the points being an issue. With the old plugs the right side has a good spark the left nothing. I should have swapped plugs as a process of elimintion.

The one thing i did notice is that were the plugs connect to the leads the top of the plug has the threads exposed and that's what the wires are connected to, no top or plug cap just threads on both plugs and they seem to connect very well.
Back when I used to work on my Honda Civic the NGK's I used came with 2 different cap sizes one longer than the other for different app's, I find it odd that my plugs do not have a cap on the top at all, but maybe that's the way ????
Click to expand...

That's how they're suppose to be. No problem there.
 
Yeah, I just did a quick internet search. The wires look pretty good also, no cracks.

This oughta be fun.
 
There are two styles of plug cap. One fits over the threads on top of the plug and the other fits over the ferule which would screw onto those threads. As long as yours are tright, they are Ok from that perspective.

No spark on the left and new points suggests crappy connections or a bad plug/cap.
 
So....fresh plugs and caps (why bother with the old caps).
I thought I would turn things around with the kick, and on the first one she FIRES and purrs!!!!!!!

Thanks guys for all your suggestions. I can't wait to start playing around with other things. Next, the points will be replaced in favour of a Dyna.
 
And guess what this morning ? No dice.
I only warmed it up yesterday, did not rain as it was pouring here.

I don't get it, since I've had the bike i have never been able to start it using the kick always used electric.
New plugs and caps, half a kick and it starts and runs great.
Now's it miss behaving again less than 24 hrs later! WTF !
 
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