Banjo1974CB450K7
Veteran Member
Sounds like an excellent plan. Will do!Just run a backbone ground wire from the headlight bucket back to taillight. Branch it off to the battery negative and the rec/reg.
Sounds like an excellent plan. Will do!Just run a backbone ground wire from the headlight bucket back to taillight. Branch it off to the battery negative and the rec/reg.
That's what I've always understood it to be, though our thinking is generally that the + terminal provides the output.Just for grins, my intro to power electrics professor taught that electron flow is from (-) to (+).
They weren't wrong! Watch lightning in super slow motion and the electron flow is visible, but damn does that make what is already a confusing system just that much more difficult. I've always wondered how many of these bikes get scrapped due to electrical issues that are misdiagnosed as engine/carb/etc.Just for grins, my intro to power electrics professor taught that electron flow is from (-) to (+).
And now you know why I say you can never have too many ground connections.Just for grins, my intro to power electrics professor taught that electron flow is from (-) to (+).

I put new plugs in it, set the gap in 'em to .030 if I recall correctly. The old plugs looked a bit lean but not too bad when I took em out. I would need to check the new ones I put in to give you a current answer though.How do the plugs look after a ride? Also what kind of plugs are you running?
I should expand now, I just had the most exhausting ride on it. It was a long ride, at first the bike seemed to run really well and if I didn't hit the throttle too hard it was running really well. Then progressively it ran worse and worse, even after I parked it for a while it didn't want to idle anymore, and when I limped it home it was basically consistently getting fuel and running on the right side but the left side would be cut out completely and then as you hit certain throttle spots it would start kicking in too making the bike lurch with the sudden power increase. To me it reminds me of when a carburetor slide is catching and I believe I had to do a fair bit of sanding on that side's carb to make it run smoothly.I put new plugs in it, set the gap in 'em to .030 if I recall correctly. The old plugs looked a bit lean but not too bad when I took em out. I would need to check the new ones I put in to give you a current answer though.
After putting some more miles on it, it really is running the best it ever has now. Unless you really gun it and move fast for a long time it won't bog down or go lean or whatever is happening when it starts seeming fuel starved. You could almost fool yourself into thinking it's completely fine if you never pushed it throttle wise.
It also seems to sort of want to die if I gun the throttle with it in neutral.
Some of this I can shed some light on, some of it I will definitely follow up on the bike with.This one’s going to take a pretty methodical approach, but the first thing I’d rule out is trouble with the fuel supply - sounds like the bike had been sitting a while which means you could have tank rust, varnish, contaminates of some sort, etc that running a bunch of fuel through has shaken loose.
I’d go top down on fuel first, then ignition.
With the modified intake and exhaust you’re going to have some challenges regardless, but that’s usually idle performance and flat spots (likely a contributing factor to your WOT lag as well).
Check petcock screen and that you’ve got clean flow through both ports. Float heights and jets being clean and proper (was it rejetted after the intake/exhaust modifications?)
I’d really rule out that slide being bad as well. That thing should slide and spin like butter - and really shouldn’t need sanding - maybe a steel wool polish but sanding is rather aggressive.
Less likely but also possible is that the left coil is failing. Sometimes that takes them a bit of heat to start exhibiting real issues. Try flipping the coil leads and see if the issue changes sides.
Roger that, I'm still hunting for those issues and will carry on.Lots of possibilities here. Adding to Pete's suggestions, keep an eye out for an intermittent connection or grounding issue somewhere in the ignition wiring, i.e., points, leads, coils, caps, plugs, power, etc.
The idle issue was more than likely directly related to running on one side only.
It's easy enough to check the fuel level in these carbs. Just shut off the petcock, pull over, and drop a bowl to see where it's at. Too much fuel can cause a cylinder to drop out (bog) as easily as too little fuel.
You mentioned slightly lean plugs, so I am less likely to suspect fouling, but this should be ruled out also.
Was there any indication that the motor was getting too hot? Poor fuel flow can cause a lean condition and overheat the motor. An overheated motor will not run well.
Makes th coil even more of a possible culprit unless you’ve got non-resistor caps. Definitely try the coil swap and see if the problem moves side to side. If that coil is getting close to outer limit on spec the additional 5K ohm of the BR plug can give you some weird spark issues.Oh, EzPete I forgot to reply to you and say I'm running the NGK BR8ES at .030.
If you remove the airboxes and have the bike running on the center stand, try giving it throttle to see how the vacuum pistons behave. If one is rising and the other not, then maybe you need to replace that questionable vacuum piston. Which carb model do you have?I appreciate it. This makes me more confident that it's the carb slide I need to go to next.


I did find some NGK 0K caps on eBay from Latvia - whether or not they’re real remains to be seen but they work.Wow I had no idea the can of worms that the non resistor vs resistor caps and plugs would open up. I'm sort of shocked but not shocked that those guys in Houston collective sells resistor plugs and doesn't warn about the need for non resistor caps with them. Where do you guys get non resistor caps? Have you done the conversion yourselves?
Were those 120° or 90°?I did find some NGK 0K caps on eBay from Latvia - whether or not they’re real remains to be seen but they work.
120’s VB-F…Were those 120° or 90°?
Be cautious buying B8ES now, there were a lot of Chinese fakes out there right after the non-resistor B8ES were discontinued.Oh and of course I'll order some non resistor spark plugs from one of your guys' sources after I move in and can use my new address! And probably do the resistor removal mod on the caps ADs post explains so nicely.
Many Thanks for the informationThe R stands for resistor and if you use resistor plugs you need to make sure you are using non resistor caps otherwise there is too much resistance and you have poor spark. The resistance for one or the other should be 5 thousand ohms and the other should be close to zero. Also be aware that there is problem with counterfeit NGK plugs being sold. I ordered some from a reputable source when I first started my build and when I got ready to use them had issues and when I checked with an ohm meter they all checked bad with very high resistance, 20K ohms and more, and should have been zero as I was using resistor caps. I am currently using Denso 4030 W24ES-U spark plugs with good results with resistor caps.
That's great to hear about the 500T advancer! And the synch looks good to me by eye as far as watching how far both inner bits of the carb's move when I slowly open the throttle they seem pretty well matched up no slack in either line and they both are relatively similar as far as how far they are adjusted (I've noticed when the cable gets hung up on the frame one will have to be adjusted to far to compensate).I've run the 500T advancer on my CB450 without any issues and mapped out the advance curve for the particular used unit I have. It fell within the ranges indicated in the factory service manual.
It never hurts to verify your timing dynamically. If it's not advancing far enough at high rpm it might cause stuttering.
If your float height is high, one or both bowls may be running dry. Throttle cable synch plays into this also. If they are out of whack, the side that's working harder could exhaust the fuel in the bowl. Both of these fuel level ideas are consistent with the idea that you can let off the throttle momentarily and then go again after the form delivery catches up. Show petcock flow is another possibility
I ignored the float height when I was first learning my way around my carburetors, but it's super easy to check the float height and it is important to have it right. You can substitute a ruler or pair of calipers where I have the float gauge or make a fixed gauge for 20mm and use that.The float bowls are sort of an unkown quantity on these carbs. They look fine but I never submerged them to test them or really measured the bowl properly just eyeballed the bend in the tabs to make sure it looked normal at a glance. I haven't seen any leaking out the overflow tubes at least.

Yeah, I'll do this next. Already did it for my other bike, I will do it next for this one, It's not that much effort besides waiting for the gas and gasket to dry out before putting the bowl back on perfectly.I ignored the float height when I was first learning my way around my carburetors, but it's super easy to check the float height and it is important to have it right. You can substitute a ruler or pair of calipers where I have the float gauge or make a fixed gauge for 20mm and use that.
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Eyes are notoriously fallible. Sync using the wire method.That's great to hear about the 500T advancer! And the synch looks good to me by eye as far as watching how far both inner bits of the carb's move when I slowly open the throttle they seem pretty well matched up no slack in either line and they both are relatively similar as far as how far they are adjusted (I've noticed when the cable gets hung up on the frame one will have to be adjusted to far to compensate).