advice on removing tank off a CB400sf (with pic)

[ausdrifter]

hey all,

Spring maintenance time and Ive just spent the day buying up on all sorts of junk to throw at the CB400SF in the coming weeks when the weather warms up.

The main difference this time around is Im going to change the sparkplugs. Heres where the trouble starts. last time I tried to take the tank off it was unplanned, I was stupidly un-prepared (had about 8L in the tank... yeah, I know) and i ended up spilling fuel a fair bit, denting the tank and scratching up the plastic. So in the interests of doing it right, Im after a little help.

1, How does the tank and petcock (?) system work? I heard that it might be something to do with a vacum, like once you start the bike it draws fuel into the carb. Though would it be gravity fed? whats going on?

2, If i unplug the fuel hoses attached to the tank will fuel leak out uncontrolably?

3, Do i have the turn the switch to anything specific (on, off,res) or doesnt it matter?

4, any more info or tips on how to take this off succesfully. I have a pic attached tho i doubt how helpful it is. There appeas to be 2 hoses attached, one to each side of the petcock assmbly.

Thanks, im still kinda nervous about taking this off after the disaster of last time, esp the fuel leaking thing, so any help is much appreciated.

[slowB]

turn the gas to off at the petcock and run the bike for a min or two and then pull the gas pipe off you might get a small amount off gas come out( one or two drops)and then pull
the two small pipes off but remember where they go and make sure you put them back in the right place or your bike will not run when you go to restart

I had mine off about 4 hours ago

[Fastbike]

If you want to head over to my place i will show you and help do the work..

[Dana]

It's always easier with one person holding up an empty tank and another competent person taking off the lines.

I use one of these to get as much out as possible and then try propping the tank with some wood underneath so I can get my hands in to disconnect lines.



I spray a dab of silicone grease on my finger and rub it on the petcock nipples for easier penetration of the hoses. Makes getting hoses on and off a cinch, but might not be worth spening Y1000 on a tiny bottle you may never use again (actually I use it quite often around the garage).

Good luck!

Dana

[Jav]

hey all,
1, How does the tank and petcock (?) system work? I heard that it might be something to do with a vacum, like once you start the bike it draws fuel into the carb. Though would it be gravity fed? whats going on?.

Turn it to off and disconnect the lines. Some fuel, as mentioned will leak from the pipe but not much. If there are two pipes connected to the petcock then one is vacuum and the other fuel. Usually that means that
without vacuum fuel cannot flow ( safety mechanism ). You can test it.

hey all,
2, If i unplug the fuel hoses attached to the tank will fuel leak out uncontrolably?.

Not if the petcock is turned to OFF or the petcock uses a vacuum mechanism, as mentioned

hey all,
3, Do i have the turn the switch to anything specific (on, off,res) or doesnt it matter??.

Off

hey all,
4, any more info or tips on how to take this off succesfully. I have a pic attached tho i doubt how helpful it is. There appeas to be 2 hoses attached, one to each side of the petcock assmbly.

Ok, two hoses means one is vacuum, so just label them so you know which one to put where or else your engine will get no fuel when you put it all back together.
One piece of advice is to take many pictures during disassembly as they will help you work out where thing go on reassembly.
Also, usually you will need to lift the tank to get to the hoses, or maybe not, but if you do, it pays to have some rags around to put between the tank and
the chassis or engine to prevent scratching.

Don't over tighten the plugs. Tighten them as much as you can by hand ( with socket and straight extension but no ratchet ) and then tighten them 1/4 to 1/2 a turn with the ratchet.

[ausdrifter]

thanks everyone, that should pretty much clear it up. Ill be sure to go for a nice long ride first though to empty the tank as much as possible.

Also, fastbike thanks for the offer, I appreciate it for sure, but I think I'll give it a go here first.

[ausdrifter]

just as a follow up, i took off the tank today and it al went well and surprisingly easy. I got almost no fuel spillage at all too, so that was a pleasent bonus. I first pumped out as much fuel as i could and transfered it into my scooter tank, then I unplugged/took off the fuel then vacume hose going into the petcock, next i took off the overful hose located at the rear underside of the tank, then unhooked the electrical plug on the opposite side of the tank. then it was just a matter of picking the tank up and placing it cafefully ont he ground on a bit of cardboard. the plugs themselves were worn but didnt seem excessivly so. The crankcase breather? bit of foam had pretty much disintergraated and some bugs had died in it, so i scooped that out and replaces it with just a thin bit of cotton towel. Annoying the previous owner tightened the sparkies in mega tight, so i was just happy to get them out withing damaging anything. So put it all together, went for a little test and maybe its my imagination, but combines with the other fluid changes and thes and that ive been doing these past few days it all seems just a little faster/more responsive and louder than before, so pretty happy with the result.