Waking a VFR700F - Fuel questions...

So a buddy of mine had this '86 VFR700F languishing in the cellar and he wanted to get it going... Great.

Old gas, brittle fuel lines, weak clamps, plugged up fuel filter, all that changed out. Checked for spark, I did not check compression.

With a new battery I cranked her up for a bit and no joy so I pulled the fuel line off just ahead of the pump and there is only a trickle. Emptied the tank and pulled the fuel tap off to ensure that the internal piping was not partially blocked and reassembled. This fuel tap is that recessed little number set into the left side of the tank. Not a bad set up really. Three O-Rings under the valve itself, no leaking.

Does the pump need to actually suck from the tank or is the gravity feed from the tank enough to fill the pump and push the fuel to the carbs...?

As an added oddity, the pump relay clicks when I hit the go button but I do not know if it should or not...?

Thoughts...?

Thanks,
Rob

 

Inside your tank are two convoluted pipes that feed the fuel tap that could be clogged. I have drained gas by gravity and it should be more than a trickle. I saw a picture where someone cut open a tank, and it showed these long tubes. I gave up trying to clean a badly rusted & gummed tank and bought a used one.

 

It should click, so no worries there. First, make sure that the fuel flows freely from the tank with the petcock open. When half full or better, the fuel will flow to the pump on it's own. It really starts doing its job when the tank is half full or less. Suggest a clear filter (if you haven't put one on already) to see the fuel flowing. That tank probably has sediment and all kinds of whatnot in it if the bike has been sitting for a long time, leading to the petcock being clogged.

 

I did put a clear in-line filter in place of the metal canister type just to prove that I had flow, the intent was to swap it back out after I got it running although I am not sure that I need to.

Since pulling the fuel tap off and blowing compressed air though the openings, I have not re-fueled and tried it, I will tonight... Mother's day and all that , ya know...

I am actually tempted to hang an auxiliary tank to fuel it for starting but I need to be assured that the flow problem is cleared up as well.

 

Ok, I'll take the fuel tap back off and root around with wire to see if I can clear the openings... just in time too as I was going to refuel it and give it a spin.

When I had the tap off I blew compressed air through the openings and found it odd that from the "OFF" position hole, air would come out of the pipe at the bottom of the tank but not from the other positions... WTH...? ? ?

I'll get after it tonight then.

Thanks,
Rob

 

Found some good pictures, be careful pushing wires through, could damage screens:

 

In my humble opinion, it's much better to have the clear filter than the OEM type. For obvious reasons.

Those tubes in the tank are pretty ridiculous in the way that they're routed. You're gonna hate pushing wire through there. Also, the pickup tubes have made-on metal screens on them where they suck up the fuel, so have fun with that. Mine were a real bitch. The bike I have came with the same kind of backstory.

 

Beat me to it, damn. Looks like the innards of a VF tank. Those are a bit different from the way that the VFR lines are routed, but you get the "picture." See what I did there?

 

Holy old WTAF...? And I had such respect for Mr. Honda too...!

Geezus...

So there is no way to know that you have cleared the debris... I guess I will poke at it gently and flush the tank. Wow, this is gonna suck...

Ok, riddle me this: If remove the fuel tap and push compressed air through each hole I should be able to tell, to some degree whether the air is getting through the tube vs just dead-ending at the suspected blockage... No..?

And how does one explain the fact that when air is applied to the "OFF" position hole that I have air coming out, quite strongly of the outlet (the tube that exits the tank)...?

I will pay closer attention this evening when I'm fartin' around with it... Wow.

Great photos BTW...


Thanks,
Rob

 

Remove the low fuel sensor from the bottom of the tank. The ring gasket is pretty robust, so it's most likely reusable. You can see the screen filters that way. One for the "ON" line and one for the "RES" line. I can't seem to remember what happened when I blew air through the lines, honestly. It's been about two years. You seem savvy though, bet you'll figure it out.

 

Answer to your riddle, there is no "off" hole, you have normal "On" pipe hole (which picks up gas to a higher level), a "Reserve" pipe hole (which picks up gas at a lower level) and then gas is routed to the exit pipe through the third hole. Find a large type syringe (or baster) in the kitchen department and try feeding gas back through each pipe, all three should flow about the same. If one or more feel restricted, try some lacquer thinner. You haven't indicated if it was rusty in side.

 

I pulled the low sensor plate off and the screens are very clean and shiny... shocking. The tank is not at all rusty.

So, I used a tie wrap to use as a Roto-Rooter to get to the screen, I could feel the probe at the reserve side pipe poking the screen. I could not reach the On side pipe but I am pretty confident that it is clear as well. No gunk came back after pushing and twisting the tie wrap through the hole.
Then blew some air through the tubes to move any debris but I did not see any...
I'll go gas it up and have a peek at the flow...

Thanks all,
Rob

 

Sounds like you should have delivery then. To prime it quicker, I loosened the bowl drain screw on one of the carbs, allowing the fuel to displace air already in the line and get to the carbs. Also a good idea to hook up a battery box or jumper cables while you let it prime up. The pump will stop clicking when the bowls and line are full, but it can take a minute and drain a weak battery quickly.

 

Well I put the tank back on 'cause I screwed up the aux tank while trying to fix it... lol long story and not worth it. :crazy:

When I put the fuel in the tank, initially the tap was Off, when I turned it to Res I thought I would see fuel flowing but no. Odd, put more fuel in and cranked the starter and fuel started to flow, still not what I expected though.

I let it crank for a bit following the suggestion to open one of the bowl drains... low and behold, the tone of the cranking changed to that "I wanna start" sound and away she went...! Closed the drain and let it run for a bit looking for leaks.. sure enough the left/front carb bowl seems to have a bowl gasket leak... I think. While watching though I went over the right side and with a long screwdriver tightened the drain screw slightly, still was not the issue.

So anyway, even though it runs well enough, revs really nicely on choke and half choke and even off choke until it started to get punky, I am going to pull the carbs off to clean the primary jets. I can get it to idle nd then turn up a little but it really has that plugged up low speed jets feel.

I was hoping against all hope to Not pull the carbs but hey, you know that the jets are plugged up... Maybe a dose of Seafoam or so other "Cleaner" might do it but I doubt it.

I had forgotten just how cool the growl of that engine was... Sweet.

Thanks again for the assist,
Rob

 

I have heard (but have no personal experience of) that carb gaskets tend to shrink when there's no fuel around, and magically swell back up and stop leaking if you give them a chance with some fuel around.

I've been playing with my ST1100 carbs for the last few weeks (also unused for nearly 10 years) so I know where you are headed with this. Good luck with the resurrection.

 

⬆️⬆️⬆️This is true. If you let the fuel sit in that bowl overnight, the gasket SHOULD swell up and be 100%. If she runs and revs you might get away with some B12 or Seafoam. You're right though, best to tear down and do it right. Happy to be of service and happier that she runs! It's nice to know there'll be another one stalking the streets again.

 

Thanks again guys... I'll think about the Seafoam, I would love to see (hear) that clear up the issue but if the carbs are not too much of a PITA to pull and clean, I will prolly do that..

I'll start a new Carb Thread with questions when I figure out what I gonna do.

Best,
Rob