Curvy fuel tap?

[garynortheast]

Bike started ok this afternoon, ran for a short while and then revs dropped away and it ran first on one cylinder and then not at all. I suspected water had got in somewhere so took the airbox off - all dry. Took the rear plug out - No sign of water and a decent spark. Thought I'd check to see if fuel was getting through. Removed the carb end of the the fuel feed hose to the front carb and petrol gushed out of the hose - frantic 2 minutes stuggling to get it back on! Removed the petrol tap hose from the frame mounted fuel pump and fuel gushed out again.
I was under the impression that fuel should not pass down that fuel line unless there is a vacuum to operate the diaphragm in the fuel tap? Not quite sure what is going on here, does anyone have any suggestions please?

[garynortheast]

In addition....surely fuel shouldn't be passing through the fuel pump either without a vacuum to operate the diaphragm?

[andrewsmith]

Originally Posted by garynortheast

In addition....surely fuel shouldn't be passing through the fuel pump either without a vacuum to operate the diaphragm?

It shouldn't

You'll have residual in the lines and the tap but it isn't much

[garynortheast]

Well it's gushing through when I take the pipe off the carb. Lost about quarter of a gallon on the garage floor while I was struggling to put the pipe back on!

I'm starting to think there may be two issues here.
1. Fuel tap diaphragm (may have been not working for some time, difficult to say as I've not had to remove the fuel lines before)
2. I'm wondering if I have water in the fuel tank and, more to the point, now in the float bowls.
Fuel is reaching the carbs, I know that because it peed out when I took the feed pipe off. It just may not be making it into the engine because the carbs could be full of water.
First job tomorrow is to undo the float bowl drain screws.

[garynortheast]

Problem sorted. It was caused primarily by the float bowls being full of water probably due to me lobbing buckets of water over the bike when I washed it the other day. It may possibly be down to the fuel filler drain hose being kinked or blocked although a quick check didn't show it to be so. I'll have a better look when I get a few minutes to myself.

This does leave the secondary issue of the vacuum switched fuel tap not doing its job. I've ordered a fuel tap repair kit from Wemoto so I can sort that out when it arrives.

I'm still interested to know whether anyone thinks it should be possible for fuel to flow through the vacuum fuel pump without the engine running as that is what it appears to be doing at the moment. I shall take another look at it once the tap is refurbished. I've found a couple of places selling pattern part fuel pumps for rather less than the oem parts if the pump is shot.

[Taipan]

Worth checking the drain pipe hasn't rusted through inside the tank as its not unheard of for them to do so.

[mister c]

Originally Posted by Taipan

Worth checking the drain pipe hasn't rusted through inside the tank as its not unheard of for them to do so.

I agree. Had a similar problem TWICE, but it was just that the breather was blocked, real pain in the butt.

Wrote about it http://forums.sv650.org/showthread.php?t=111512 Here
& http://forums.sv650.org/showthread.php?t=115724 Here.

It's easy to fix though

As for the fuel tap. If it is disconnected, then you should only have the residue that's left in the pipes, it shouldn't leak at all

[garynortheast]

Thanks chaps. I'll check the drain pipe over the weekend.

Got the bike ready to go into town to do a couple of errands earlier, it started and ran fine so I took it off the paddock stand and left it running on the sidestand. Got my riding kit on and went to pull away and the engine went onto one cylinder and then died! I suddenly twigged that there was just enough water left in the tank that when the bike was leant over on the stand it drained across to the left side of the tank where the fuel pickup is ! I tipped the bike over the other way, thumbed the starter and it fired up on one cylinder. Coaxed the revs up and slowly the other cylinder kicked back in. I held it at around 5000 - 6000rpm for a while and it ran fine although I could hear intermittant missing where the water was passing through. Rode it into town fairly briskly(!) and by the time I got there it seems the last of the water in the tank had gone. It ran impeccably on the way home.
I am starting to wonder if I just had a tankful of water contaminated fuel from the last fill up.