Bandit 250 Fuel Lines

[shidoran]

Hi Guys I'm rebuilding a GSF250P (1992 GJ74A) which I got in pieces for next to nothing...

The one thing I don't have is any fuel lines, nor do I understand how to hook them to the carby. I know it's a vacuum fuel tap but it looks like there are at least four connections to the carby so I'm assuming t pieces are are required somewhere in there... Can anyone assist? Attached is the exploded diagram (closest I could find).

I'm assuming the lines underneath are fuel drain lines too?

I'm not completely new to mechanics but this is the first time putting a bike together so please bear with me... I am running off the 400 workshop manual and it's slightly different (and doesn't have enough detail in some areas) but at least I have a point of reference.

[ventYl]

B4 seems to have little bit different lining, but i think that:
* thin hoses pt no 34 & co are fuel drain lines, i've personally never seen them connected.
* hoses pt no 13 & 14 could be gasoline fumes lines back to fuel tank (B4 only has one with all four carbs bridged together). these are connected to pipe on bottom of fuel tank and usually are too short to connect with tank lifted up.
* hoses pt no 12 & co could be fuel intake lines (B4 has only one again). additionally image seems to be wrong because one of them is connected to different place on left pair of carbs than other one. this is connected to fuel tap.
* vacuum for fuel tap is taken from first carb's (leftmost in direction of drive) rubber intake adaptor.

[shidoran]

Thanks for the help,

Forgive the hella noob question but what do you mean by "B4"? You keep referencing it and I am not sure what you mean 

Yeh it doesn't look like any of the drain lines were connected, given there seems to be a consistent build up over the years under the carbies on the points that these would have connected to.

The fuel tap is actually slightly different to what is in the explosion diagram (see photo) so I'm wondering if I need a special "screw in" piece to connect to it?

You can see by the carby photo the four hose connection points. Would the two larger ones connect together via a T piece then go into the fuel tap vaccum line point? And the same deal for the fuel line? I guess I need to figure out which one "sucks", according to the 400 manual (see attached) it looks like the larger one is the fuel line and the smaller one the vacuum line. But on my carby the larger inlets are located at the high point, hence my confusion.

You can also see by the 400 manual the carby exploded diagram is slightly different. I wonder which one is better to use?

I suppose the worse that can happen if I get it wrong is that the bike won't start... but I'd prefer not to do this via trial and error as I'm testing for a number of other things when I kick her over and don't want to compound my troubleshooting lol   

[ventYl]

B4 = bandit 400, sorry :)

this fuel tap looks like it is missing one hose connection pipe. you may try to glue or pressure-fit something inside. fuel tap is from fragile material so i wouldn't risk rupture by screwing something in. but other than that is looks like stock fuel tap. pipe directing downwards (when mounted) should be for vacuum, pipe directed to the front should deliver fuel (at least pipes on my fuel tap are organized in this way).

The two larger upper hose connection points on carbs are for fuel fumes recirculation back to fuel tank. You should connect them by T-piece and connect to free hose connection point on bottom of fuel tank. There's no vacuum. These lines are connected to upper wall of float bowl with atmospheric pressure inside.

Two smaller lower hose connection points are for fuel delivery line. There will be probably another T-piece and this will be connected to fuel tap.

Try to find small hose connection point on rubber piece which sits between carbs and cylinder heads. (At least) One of them should have it (Mikuni carbs on B4 have vacuum line this way). If not, there will be connection point on carb but only in place behind throttle flap (towards engine) in order to provide vacuum for fuel tap while cranking (Keihin carbs on Bandit 600 have vacuum line this way).

There may be rubber-blinded hose connection point on top plastic cap. This won't be vacuum delivery line, it's for carb ballancing and it should be left blinded under normal conditions.

[shidoran]

Thanks for the help.

I suspected as much regarding the fuel tap, I'll have to think about how I can fix it or try and source another.

When you say free hose connection on bottom of fuel tank, you're talking about the connection point in the attached photo? It's smaller than the lines coming from the carbys? (the carbys are definitely Mikuni)

I get what you're saying, but what then is the point that the carbys connect to the fuel tap for the vacuum line? If the larger hose connections aren't the vacuum line but are fume vent lines, surely there must be another connection somewhere? I know what you said about the vacuum line for cranking but this isn't the only one is it?

[ventYl]

AFAIK, there are replacement 3rd party fuel taps available due to low reliability of vacuum mechanism of original fuel taps.

Yes it looks like the one we are talking about.

Later today, i plan to go to do some job on my B4. i'll make a photo of vacuum line connection for you, hopefully B250 has similar connection.

[shidoran]

That would be awesome thanks. I'd want to know how all the hoses connect to the carbies if possible. 

[ventYl]

Ok, I examined my B4 yesterday with following results:
* vacuum line for fuel tap is short thin hose from rubber carb adaptor as you can see on attached image
* fuel fumes are not recirculated back to fuel tank but that hose (double walled) goes under carbs down below rear brake fluid container where it is open ended
* that tiny hose connector on bottom of fuel tank apparently serves as connection point for coolant reservoir overflow hoses. Coolant reservoir is connected with filler / thermostat housing with narrow hose which has T-piece in the middle with third hose directed upwards right under connection point on fuel tank. Also the pipe on the bottom of fuel tank does not go directly into tank, but it ends under tank refill cover. It is probably in order that hot overflown coolant does not burn you directly, but it's held somewhere relatively safe.

(in attachment you can see part of top cover of carb, carb rubber adaptor and cylinder head. Black hose with pink/magenta stripe on it (going to upper right corner of picture) is vacuum hose for fuel tap)

[shidoran]

Thanks mate that's a great help. So if I read you correctly...

In the first photo, the one with the red circle that connects on the join between the carby and the engine is the vacuum hose?

In the second photo, the larger (red) holes are the fume vent hoses which is open ended to the floor somewhere. So where do the yellow and pink ones go?

And on the coolant line, just curious because my reservoir tank has a connection on either side. I know one side connects directly to the coolant cap next to the thermostat by going up over the top of the airbox. I'm assuming that is just overflow.

What about the other side of the reservoir tank? I get that there is a t piece, so one end connects to the reservoir tank, one of the other ends goes to the piece under the fuel tank, but what about the last connection? does that just go down to drain perhaps?

 

[ventYl]

Yes, red circled hose connection should be fuel tap vacuum. There's no other sane usage of that hose.

To be honest, i can only guess. All carbs I've seen yet had only two connections. One on top end (red) for fuel fumes and other on bottom end near needle valve (pink). I have no idea what is purpose of yellow hoses.

Despite that both your and mine carbs are Mikuni, they are different. But, I still have one theory about them. In the photo, you can see airbox side of B4 Mikuni carb with slide and slide holder both removed, so you can see throttle flap too which is normaly obscured by slide. You can see that upper part of intake manifold has thin "submanifold". This one is for supply of reference pressure for slider diaphragm. You can see, that manifolds of B250 carbs are missing this "submanifold". Therefore I think that:
* larger red holes are for reference pressure for slider diaphragm. You can test this theory by applying some slight air pressure to this hole (just blow there stronger) and one or both sliders of interconnected carbs should rise slightly. Look at the air box, if you can find some holes which may fit these one. Normally B4 air box contains only one hole for crankcase ventilation. You air box will either contain more than one hole, or there was T- or X- piece connecting red holes with air box with crankcase ventilation and air box throught connection piece.


* smaller yellow holes are fuel fumes hoses. You can test this too by blowing in there. If carbs are in normal upward position, you should feel some air leaking from pink bottom hole (some will also leak from other holes in carbs). If you position carbs upside down, no (or much much less) air should be leaking from pink hole

* smaller pink hole is for fuel intake. Test process is the opposite as for fuel fumes holes.

Distinction between fuel fume and intake is easy. Fumes naturally goes up, so upper of pair should be for fumes and latter should be for intake.

About that coolant line, to be honest, I didn't examine it so deeply. I just figured that I have T-piece on this overflow line and third hose looks like it is connected to bottom of fuel tank. I can look at this today if I be in garage and hopefully B4 has same piping like B250.

[shidoran]

That is awesome thanks so much 

When I blow through the pink hole, air comes out of the yellow ones. When I blow in the large red ones, air seems to flow out of the air box side cylinders. I think you're right that the larger red ones are the ventilation lines. I'm still a bit stumped by the yellow ones though...

I can see how the pink one is probably the fuel inlet. I found the below diagram that seems to back up what you're saying 

As for the airbox it has a crankcase connection on top, and a drain on the bottom, and four connections to each of the carby chambers. The rear side has one large hole with the air filter in it (internally) and the filter spout that extends external to the airbox.

Separate question - Thinking about replacing the HT leads, after trimming them back they're a bit short... what specs do I need to know for doing this? I can take the old HT lead in, but for all I know it's a certain brand, type, diameter, internal diameter or something...

[ventYl]

This diagram looks like Bandit 600 1996-2000 Keihin carbs.

AFAIK and also as far as i've seen, HT leads in this type / age of bikes are stock copper non-resistive leads. I've replaced two longer leads by leads from 1965 two-stroke Jawa and it works better than with original leads. I didn't see any specs for HT leads anywhere so I can't say more about it. Try to bring your original leads to your parts dealer and ask for HT leads of same diameter with copper wires inside.

[shidoran]

Yeh, the carbs look the most similar to mine in terms of structure (from what I could find).

I'll try to get some by the meter to replace them from somewhere.

Just a thought - any tips on removing a flywheel without a puller? or where I could source a puller from? The flywheel has a 12x1.5mm metric thread but most pullers available here are 10, 14, 16, 18mm.