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Gen 4 leaking gas when running. Does not leak when shut off.


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I finally fired up the gen 4 I bought a few years ago today.  I noticed it was from the left side, coming down over the water pump drain bolt. Maybe I should put it on the center stand to see what where it leaks then?

 

I smelled the fluid and it is gas and not coolant.  Any ideas about what it could be?  The carbs were rebuilt 5 years ago so I am wondering if it could be a fuel line or something.

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Probably a sticky float so it doesn't close properly when the bowl fills up. There's no vacuum when it's not running so it doesn't pull more fuel. At least that's how I understand it. I've got a similar problem on my wife's CBR600 that I trued to revive last week after years of sitting. I haven't gotten around to it yet but been watching YT videos. This is a good one: 

 

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I agree that the most likely culprit will be a float valve, but could also be a loose floatbowl drain screw, or an o-ring between the carbs, or as you say a fuel line.

 

For the float valves, these are easily accessed once the carb bowl is removed, the float hinge pin is slid out and the float valve piston will lift out with the float. Look very closely at the rubber cone tip on the float valve, replace if it has a ridge or lip, otherwise just clean well, and do the same to the seat in mates to. Chances are you might just have a little grit that is stopping it sealing, and that would suggest time for a new fuel filter as well. Give the float bowls a thorough clean, and if you feel enthusiastic, clean the jets.

 

Be really careful with the floatbowl screws, very easy to round these out without care. If you have them JIS screwdrivers are the best way to avoid chewing them out.

 

If you do have to remove the carbs, I'd suggest you invest in some new inlet rubbers as the old ones go hard, sometime crack and the act of removal/refitting can apparently crack them leading to air leaks and poor running. They're not expensive and will definitely also make refitting the carbs easier, especially if you add a little silicone lube to the process. 

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New, fresh carb boots are SOOOO nice. I smear a light layer of petroleum jelly to make the on and off easier.

 

They were rebuilt 5 years ago, but have the carbs been sitting with gas in them for that time? I always assume that if a carbed bike sits for a year, I'll need to pop the carbs off and clean the jets out.

 

Fuel only leaks when the bike is on because the 4th gen have a fuel pump. No power, no fuel pumping.

 

I would pop the carbs off and give them a once over just to make sure everything is good in there. To check the carbs, I was holding them in the same position they would be if they were on the bike, and hand pouring fuel in the line. Easy to check if there is a major leak without having to get them back on the engine. If it still leaks, give the bowls a tap to make sure it's not a stuck float. If it still leaks then you might have a leak by the float needle.

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I've had luck cleaning the inside, mating surface of the float needle with blue magic and a q tip. Makes it all shiny and smooth.

Sent from my SCH-I545 using Tapatalk

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41 minutes ago, mk2davis said:

I've had luck cleaning the inside, mating surface of the float needle with blue magic and a q tip. Makes it all shiny and smooth.

Sent from my SCH-I545 using Tapatalk
 

Image result

Awesome, I must try that!

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Quote

 

Thanks for all of the replies.  I have been driving the bike every year since I bought it and the longest it has sat in storage is about 8 months, with fuel stabilizer.  I hope it is a simple fix, since I had to cancel my front tire change appointment yesterday and they are out two weeks during summer bookings.

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All my VFRs get used routinely, but over the winter one of them sat for about 3 months.  

When I started it, it leaked fuel.  So I parked it.  A week later I started it, and no problems.

Haven't had a leak since.

Sometimes the o-rings can shrink, and then expand again, without actually being compromised.

Thats the only thing I can think of.

Maybe start it up again and see if it it still leaking, maybe you'll get lucky.

 

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On ‎6‎/‎22‎/‎2017 at 10:18 PM, otmaximus said:

All my VFRs get used routinely, but over the winter one of them sat for about 3 months.  

When I started it, it leaked fuel.  So I parked it.  A week later I started it, and no problems.

Haven't had a leak since.

Sometimes the o-rings can shrink, and then expand again, without actually being compromised.

Thats the only thing I can think of.

Maybe start it up again and see if it it still leaking, maybe you'll get lucky.

 

I took your advice and it worked!  I just started it ten minutes ago and zero leaks.  I am relieved since I was dreading not being able to drive the vfr this year and only get to ride my twins and inline 4's.   Nothing beats the sound of a v4 or a sport bike twin on long rides.

 

I am not going to mark this thread as solved since it may start leaking again and if I does I will revisit my old thread.

 

Thanks to all that replied. It is good to see so many wanting to keep the gen 4 and 3 on the road.

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Maybe I should try the same thing with my wife's CBR 600. I tried pulling the carbs today but they've been in place for 28 years and don't want to move.

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On 6/24/2017 at 6:49 PM, squidzilla said:

I took your advice and it worked!  I just started it ten minutes ago and zero leaks.  I am relieved since I was dreading not being able to drive the vfr this year and only get to ride my twins and inline 4's.   Nothing beats the sound of a v4 or a sport bike twin on long rides.

 

I am not going to mark this thread as solved since it may start leaking again and if I does I will revisit my old thread.

 

Thanks to all that replied. It is good to see so many wanting to keep the gen 4 and 3 on the road.

if it happens again, my vote is on the orings that are on the fuel supply hard lines. I've had this happen on my friend's Magna a couple years ago.

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