Starting problems and petcock leaking cb400 SF project big 1

[mykel49]

Hi,I'm a newbee and here this is my first post. I have just bought a cb 400 super four project big 1jap import. It is an N registered bike here in uk, with very little miles. It has sat without starting for at least two years. I charged battery fully and tried to start however nothing happened, not even a click. The headlight did however light up and engine did not turn over. I'm new to bikes so do not have any idea other than thinking maybe starter not working, or serious ignition issue.

So what am I doing wrong, I had both centre and side stand up, neutral, and pulled in clutch lever in case this was the problem.

UPDATE :

I managed to solve the initial problem. the battery was fine once charged fully and is holding charge. The issue was not the battery but the kill switch, I sprayed some WD 40 lubricating spray and it now turns over really well, but still didn't start. So I took out the plugs which were back, Cleaned them and re-gapped them, and sprayed lots of WD 40 down before putting plugs back in. I also put into top gear and manually moved back and forward incase engine seized. I also put some clean fuel in, check air filter which looked ok, and then tried to start her.

Still did not start, and then I noticed fuel dripping from the fuel valve/Petcock valve when attempting to start, so I stripped it down but rubbers were fine, and sucked on the vacuum pipe and it sounded like it was operating, by a quiet click from inside. So I reinstalled it but fuel still dripping when trying to start. It looks like maybe the fuel is being restricted somewhere after the valve but before the carbs and the back pressure is forcing fuel out of the petcock valve, or there is no vacuum being created from the vacuum pipe. I have not even attempted to remove carbs or clean them as i do not know where to start.

HELP FROM ANYONE WOULD BE GREATLY APPRECIATED !!!!!!

[Superjack44]

Do not touch the carbs just yet.
Find out exactly where the fuel is leaking from , the fuel pipe is fitted on the back of the petrol tap.
The vacuum pipe comes from No 1 cylinder and is fitted to the side of the petrol tap.
To determine if fuel is getting into the carbs there is a small grub screw on the bottom of the No 1 carb crack this open to see if fuel comes out.
To see if you have a spark remove the spark plug cap from No 1 cylinder fit a spare plug to it and place the plug body onto the cylinder head ignition on make sure the kill switch is in the run position and turn the engine over you should see a spark.
Its all I have time for just now but I will be back got to go out there is a pint with my name on it.

[mykel49]

Thanks Superjack44 for your speedy response, and enjoy your pint!

This is a pic of the petcock, the petrol is coming from the small pipe right in the middle of the pic when trying to start, and not the vacuum pipe or the main fuel pipe, but the small one you see in the pic (hope I have attached pic properly). I also must add that there does not seem to be a filter inside the petcock or between petrol tank and petcock so I reckon any shit can get through to the carbs.

[mykel49]

Ok so check out the colour of the petrol removed from the bottom of the carbs. So Im guessing this could be a major reason for failure to start. So what should I do now? Should I keep trying to start and emptying carbs until clean fuel gets through.


This is a pic of the petcock, the petrol is coming from the small pipe right in the middle of the pic when trying to start, and not the vacuum pipe or the main fuel pipe, but the small one you see in the pic (hope I have attached pic properly). I also must add that there does not seem to be a filter inside the petcock or between petrol tank and petcock so I reckon any shit can get through to the carbs.

[mykel49]

Could someone tell me the best plugs to get for this bike.

[cb400joe90]

Mykel49 That looks like coolant in the tub?????

I use NGK CR8EH-9 spark plugs which are fine.

[bureklton]

Congrats on the new bike mykel49. As other members have suggested, for the time being, leave the carbs alone and make sure they are getting fuel is the first place. A good way to test if your petcock is working is to disconnect it from the carbs and place the fuel line in a small tub. Remove the vacuum line and suck on it with your mouth. If everything is working fuel should start flowing into your tub and you can confirm the petcock is not the problem.

I would agree with cb400joe90 that the fluid you have looks more like coolant than petrol. If this did come from your carb float bowls (generic version shown below and the drain screw pointed at with an arrow).
then I would suggest draining each of the carbs and refilling them with clean fuel. Other members might correct me on this but that would be my approach. .

Also, as Superjack44 has said make sure you are getting a spark by the method he outline. Touch the electrode of the plug against metal and turn the bike over with the kill switch in the run position. In decent light (no direct sun light or anything silly) you should be able to see a bright thick blue spark everythime that cylinder fires. As for the correct plugs, cb400joe90 is right again, CR8EH-9 is what I use and they are what is suggested by Honda or CR9EH-9 for extended high speed riding.

Sorry about the wall of text, but CB400 SF are way more fun than work.

[mykel49]

Hi guys thanks for your advice, much appreciated.

The fluid is definately the the fuel from all four carbs, I drained each one with the drain screws that you show in pic and collected in the cap of a spray can which is the only thing I could get into spaces. Like I said, bike been lying at least a couple of years. The coolant I currently have is bright blue and not anything like this colour. I think the petrol has definately gone off!!!!

Do I need to fill the carbs manually, or if petcock working correctly will they just fill when I turn the engine over??

[bureklton]

That's unusual, (hopefully its not green diesel ). It could be, as it was sitting for so long, that the previous owner added a fuel stabilizer or something to that effect. Either way, whatever the stuff is, I think you were right to drain it. With the carbs drain you now have two options to fill them, turn the bike over or suck on the vacuum tube, both methods will work.

BEFORE doing this however make sure your plugs are sparking and fuel can flow through your petcock using the methods in my last post

[mykel49]

Hi thanks again, I don't think the previous owner would have added a fuel stabilizer as she did not have very much knowledge of bikes ( like myself lol ). Anyway, I tried as suggested and sucked on vacuum pipe when valve open and fuel flowed through the fuel line, however, still have a leak in petcock, so I have ordered a cheapo petcock with new tank strainer ( which I found when removed petcock that it was up inside tank) from Chinese Ebayer, which I hope will solve issue, it was cheaper than just buying the just internal seals and spring from wemoto.

I will try out the spark at the weekend, as I want to a-ensure all traces of petrol have evaporated from engine prior to spark test, just incase lol .