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Came across a strange occurrence today. After opening up my headlight. not sure what I could have done but my headlight now goes out when the front or rear brake switch is activated. (brake light does turn on) I've opened it back up and have disconnected everything not required for the...

Yeah I get that. But the bike should not be doing this anyways so i am trying to figure out the root cause. Ignition timing is set correctly and running a Dyna S ignition system

Could this maybe be considered normal for these bikes? I wasn't alive back in the late 70's to try one of these bikes out for any kind of reference. I've also thought about the accell pump timing thing as per the manual my gap is set correctly. Should you even have adjustable needles? I know...

Hey all, Looking for a little more advice on getting this bike running nicely. I Currently have the bike idling and accelerating fairly well. But what seems off is if I give it throttle just a little too quickly from lower Rpms the bike bogs down. I'm starting to think it's time to adjust the...

Maybe will try another set of floats and valves. 14.5 brings the fuel too high and it sits right at the overflow port

Hey Just got back into my years delayed K8 project I just rebuilt that carbs with the deluxe rebuild kit from 4into1, made sure all the floats were sitting at 14.5mm with the carbs on their side But when I do a clear tube test it appears my floats are set too low. Did i just get unlucky with...

Makes sense, Although should turning on high beams activate the rear running light? Currently it doesn't so I went back to the PO did for now. Although I would like to have this fixed properly. I also seem to have a strange issue of my guage lights activating and blinking with my signal lights...

Problem solved with the headlight

ahh no idea that was the case Thanks!

Deleted problem solved

Hey Everyone, I swapped out my wiring harness today for a new one from vintagecb750.com While doing this I noticed that there was an additional wire running from the rear brown connector all the way up to the headlight and plugged into the black that would normally power the signal buzzer (its...

Accel pump 100% works on all 4. I am able to squirt fuel right out the front of the carbs when I have it out of the bike. I have heard people have some luck with the older carbs without the Accel pump. If they raise the needle. Would that actually help or just cause other issues if I shimmed...

Ah my bad #35. Finally received new coils and now all 4 cylinders are working. So far this is the happiest i've seen the bike I had to adjust my mixture screws with the additional cylinder burning gas every stroke instead of every few. I was able to get reasonable throttle response out...

Ahh shoot my bad went back to size 35. Anyways went back to the 40. I cut the ends of the wire and recrimped, still had the same issue. so I swapped the ignition coils. And then the same issue appeared on 1 or 4 with the 1/4 spark plug wires attached. depending on which wire was attached. so...

Found something interesting today. I switched the ignition cables between #2 and #3 and now #3 is the one not firing correctly. these are brand new coils and cables. does it make sense something is up with the cable as the coil still fires one of them fine? There is spark from both. I will...

Is there a possibility of a bad pilot jet? I'm using #40 I purchased off cb750supply. I've probably cleaned these 12 times trying to figure out what's going on. I have them on my bench right now and air blows through all jets easily

Yes it will respond, Nothing wrong with the colortune it just made the issue more obvious I'm using Magna dual output coils with whatever wire they come with Dynatek ignition NGKD8EA plugs and boots The color tune works great on all other cylinders it just made it very obvious to me that #2...

Sorry, wrote things down wrong everything is around 135 psi +/-5 psi Even if I did have a pump that wasn't accurate if there was a compression issue on just #2 wouldn't it be getting a much different reading than the other 3?

Yes all cylinders were within 5 psi of spec

Yeah Ideally I would like to get to that point, But I need to figure out why cyl #2 isnt igniting consistently below 2000RPM first. I realized I've checked all valve spacing apart from #2 intake as I cant get it with a socket and a the crescent wrench seemed like it wanted to strip it. (17mm...

I'm still learning tons so by no means am I even close to an expert so I may have done a few things wrong. Originally the bike was barely running and had to idle at 2500 RPM. So every time I've tried a new potential fix for its many symptoms its seemed to get better and better. I believe I saw...

I will give it a try today with carb cleaner. brand new ignition system and coils so I'm assuming the spark is good (you can also easily see the spark through the colortune as it performed perfectly on the other cylinders especially #3 with the shared coil. Thanks THomas

Hey Everyone, Noticed a bit of an issue today. I was using a colortune system to adjust my mixture and I noticed that cylinder 2 was firing intermittently below 2000 RPM. You are able to see the spark but there is only ignition every few cycles. There wasn't any obvious signs of a vacuum leak...

Hey guys, Trying to get the bike tuned a little better, Right now from at Idle when I give a large throttle blip there is little response/ the bike almost dies. I cant be a bit more gradual and its ok. Same for once I'm at a bit higher RPM. Fuel accel pump is working. Currently only non...

Hey Everyone, I've Been working on my CB750 for a few months now and have found a pretty decent amount of help on the forums. Before the bike was barely running and wouldn't idle below 2000 rpm, Now its quite better but still a ways away from running well. I'm not a mechanic so don't be...

Just took the bike for a spin around my parking garage, didn't adjust the mixture screws yet Am I right in thinking I should be able to roll around on flat ground at idle with using only the clutch and no throttle? I have to rev up to around 3000 rpm to get moving. and then I can start to bring...

Ok awesome. I was going to try and see if i can get it a little better with the mixture screws. I reset them back to factory spec. But I found an extra half turn helped when the problems were worse. I've essentially taken them apart 4 times now. The 1st time was almost a complete rebuild they...

Ok, Checked over everything again, I found the valve that fills the accel pump was clogged so it would slowly refill. so now the pump spits out wayy more gas. Throttle still doesn't really want to work until around 2100 now but its getting better. I will check compression and sync them next so...

Thanks, Could you point me in the right direction of checking the fast idle? Can't find any info online about it. Maybe I'm searching the wrong thing

Just checked on #3 it was full of gas when I opened the bowl. The drain valve was just completely clogged