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i should have specified, the starter is going. Did a compression test, and am using a starterfluid. Should be very strange that it suddenly does not start again. I do suspect a weak spark as i need to hold my sparkplug quite a bit away from the bike to get a good spark. How can this be so of a...

I just started my CB again. Rectifier/regulator was toast. Changed it out along with the battery and had a great ride. now i am in the process of changing the front tire, took it out and suddenly the bike does not start again. The spark is there although you need to have it a couple of inches...

i think i found a problem. The charging is not commecing. When idle the battery is 12,6V and staying there.I found this link: https://www.cb750c.com/publicdocs/charging_system/genesound_charging_system.html And you need to check the regulator by bypassing it. As when your key is on it should...

but the battery is just brandnew, is it possible that it charges with too little of amperage and that i need to check the alternator going to the battery?

Hey all! I finally got a new battery for my cb750c. One with a digital display that lets me know when the battery is getting low by beeping or flashing the display. I just put it in my bike and went for a ride. I started a couple of times and went on the ride. When i came back( with lights and...

Does the sound go away with the clutch pressed in? Maybe it can also be the chain that connects the crank with the gearbox. It makes a rattly kind of sound on my CB

Not to hate but did you check compression? Mine goes way harder with a good starter and battery. This is more like no compression is even existing. Did you check the basics? Compression, spark and are your plugs getting wet or smelling like gas? What happened, did the bike hydrolock or...

About a month later, tried to drive it everyday: Bike starts up better, no more choke and such needed. Bike is sort of waking up, the idle jumped from a steady 1,5k rpm to 2k, i suspect that it has something to do with the fact that the exhaust valves are getting clean, and therefore i need to...

okay so i changed the plug to iridium and the bike finally revs like it should, still a somewhat hard start but i am thinking that the bike needs some tweaking on the carb end again(i turned the 1 and 4 cyl a bit more closed then 2 and 3). Compression has been tested and 1 and 4 are still a bit...

good luck and keep us posted, really eager to know what your issue is.

when you pull the carbs apart consider getting some rebuild kits for them, makes the job easier and also ensures that your carbs are back to spec(air cut off valves tend to be a bit stiff with a bike this old). I didn't do mine but checked them when they cleaned my carbs.

You may also need to check the cdi boxes under your seat, if they are the black type they tend to crack and leak and cause a weak spark.

The rubber can dry out indeed, but when u still have a leaky petcock about 3 days from initial startup you may need to replace the bastard, i use cmsnl.com(a great partstore) for used or new stock parts. Ships fast and is reliable. never use cheap petcocks, they tend to leak when in off and...

thats why i always fill up with 98 or more, we rarely have ethanol free gas here in the netherlands, i find it a bit unpleasing that 98 is also 5% ethanol. I always go to fuel stations that claim that their 98 is ethanol free. will make the bike much happier. I also put in some lead replacer...

Thanks for the advice, but the carbs have been rebuild with rubber orings that make the choke sometimes hard to close, shall i lube the orings with a bit of oil or smth to make the choke close all the way and make it a bit smoother. Will do a compression test and also a syncing when the engine...

So basicly i synced the carbs, idle is getting much better, when i cruise around 80 kph the idle jumps up from 1250 to around 2-2,5k but when i slow down it falls back down. Also the sputtering is clearing up(maybe the carbon that is getting blasted from cyl 1 and 4), compression is getting...

Shimmed the bastard within specs, and the idle is fine. I can get it to idle roughly to about 500 rpm and then it wants to huddle and fails to maintain it. I resynced the carbs when the valves were bad so that could be a thing. Still does not want to get past 7/8 k rpm, maybe because it floods...

Hey Guys, I finally got around and started the valve clearance job. But here comes a vague situation. I got a micrometer and also a feeler gauge. When i measure the feeler gauge with the micrometer it gets to the appropriate measurement( so 0,05mm is 0,05mm+-0,01mm) I started measuring my...

Yes but the filter is leaking from the airbox to the carb boots. I sprayed starter fluid there and it ramped up, i am going to seal that, check the valves and then take it for a last spin when the valves are at around 0.005" or between 0,10 and 0,15 mm in and ex. We will post an update when i...

@Amc49, I did detect some leakage from the boots that go from the airbox to the carbs, could these be the culprit along with maybe the valves? I haven't found the time to check them though but will get to it soon!

I will check the valves out because they could maybe need new clearances. Will get back on that and the results! The compression gauge is checked yearly(is from motorcycle shop) they checked them when the bike was hot though. Dont know if that gauge is right. Thanks for the help and i will...

Thanks amc49! I checked the compression and they were all around 170-175 psi. The lowest was 167 psi with throttle full open and a couple of starting turns. How do i get the slides to open better? I cleaned them and checked them on how smooth they are. I do suspect that the rings in the...

Hey guys i have a cb750c from 81 which has the dohc and when i ride it it sputter from 7k upwards. When i give it full throttle it cant get higher then 7k but when i turn down the throttle it again starts increasing beyond 7k. I cleaned the carbs and checked the spark plugs. Can you guys point...