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VFR800F 8th Gen Fuel Tank Vacuum Problems


Skids

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On 9 October 2017 at 7:56 AM, NZCam said:

I get a little bit of suction noise when opening my petrol filler cap, but not so much that I've ever struggled to open it. How much is normal; a little or none?

Hi Cam.

There is a small one way valve in the fuel cap that is lightly spring loaded. It should keep the tank in positive pressure but when venting is needed a small amount of suction is going to be required to overcome the small spring tension on the valve. Pretty sure that's how it works!

Cheers.

Post Edit - Close inspection of the fuel cap shows independent Pressure and Vacuum relief vents. The Vacuum has the valve, yet the two vents end up at the same point being the breather hose! So you could end up with slight tank vacuum because of the valve, but next to no positive pressure.

 

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11 hours ago, fink said:

Shouldn’t have any suction noise at all.

Agreed.  I've never had any suction noises on mine and I'd be worried if I had.  I know the 2 chaps Skids mentioned in this post and neither are getting much joy from Honda and at over £700 for a new tank I wouldn't want to fork out for a new one :(

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2 hours ago, StubyDoo said:

Agreed.  I've never had any suction noises on mine and I'd be worried if I had.  I know the 2 chaps Skids mentioned in this post and neither are getting much joy from Honda and at over £700 for a new tank I wouldn't want to fork out for a new one :(

 

 

Agreed.   However my origin question was never answered in fact a Whole host of questions left unanswered .

 Did this start to happen after the sat nav was installed & who was last to lift the tank?

If it was a member of staff at the dealer then I would have said the dealer would have been responsible for the replacement.   How long was it like this before the owners noticed there was something wrong?   As the owners are happy to let someone else ask the questions rather than participate themselves???????????????

 

  I noticed on my first fill up  and looked into and resolved problem myself after the third ( initially I thought it was unusually hot weather) no tank deformation with mine.

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I'm not sure the gentlemen in question are aware of this site but I have pointed them to this thread as did Skids.  I know one of the chaps did fit a sat nav and I did ask him if he lifted the tank to which he replied no, he only took the black trim off.  He knows the original owner and both are adamant the tank hadn't been lifted by themselves.

 

I changed my air filter a couple of weeks back and the breather hose is well stuck and became detached from the tank.  I had to pull it up to reattach it as there is no slack on it so I'm grateful for this thread as I could have easily caused the same issues and I'll be uber careful in the future!

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If the indentation was caused by a vacuum then save the £700 because it's pretty easy to get those dents blown out and the tank refinished 

 

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2 hours ago, Thumbs said:

If the indentation was caused by a vacuum then save the £700 because it's pretty easy to get those dents blown out and the tank refinished 

 

I was wondering if that was possible.  Is it just a case of sealing it and pumping air in?

 

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Finally... Thanks Skids. I'm already a member but couldn't recall my site name so I've been trolling along trying combinations of emails, passwords, eventually just gave up and started afresh...

 

Mine is one of the "Collapsing Tank" VFR 800F's. It's been a long saga but I have temporarily  cured it in a way by removing the carbon Canister system and simply running a vent to atmosphere.

 

It's also, somehow, made it much better on fuel. It's just done circa 260 miles before the fuel light came on, I don't hang about on my journeys, but keeping it below Vtec has just given me that figure. That's a journey to and from work (Hayling Island to the Science Museum in London) back to work a 2nd day and approx half way back again. Can't knock that because I usually cruise at just about fast enough to collect speeding tickets. So it's about 7 miles of twisties off an Island, about 50 miles of very smooth dual carraigeway mostly national limit, and about another 12 of London Traffic filtering to Exhibition Road more or less.

 

So: I bought the bike as a two year old, just had it's 8,000 service and found that as I was commuting and doing circa 150 miles a day, the suction on the tank was steadily getting worse. It has reached the stage where the tank is now creased and damaged, it's been to a Honda Dealer who thought they had found the problem but they didn't. They thought they found a kink in the breather pipe that runs to the carbon canister, but it continued to build vacuum when commuting. The previous owner told me he'd never noticed a problem so it's a bit of a mystery.

 

I and a friend lifted the tank whilst it was "holding vacuum" at both ends at the same time and the tank started to expand again as air started to get in, yes it does have a Tomtom but I routed the cables along the cable clip route and never lifted the tank. I re-routed the breather pipe and put a piece of plastic inside it to stop it collapsing but it still carried on shrinking...

 

I have tried all the usual issues, I can easily "blow" into the tank, when the cap is in place, it's only when the carbon system is connected, it seems, that I have the problem. So for now it's running a proper bodgy tank vent until I get time to strip it down. Which will be pretty soon, it's just clicked oveer 16,000 miles so the tank has to come off anyway to do a valve check. I think the Video that Skids loaded was of mine with the tank popping back out. That was after a 75 mile run. Yes it has Satnag installed, but it did this before I got around to fitting that.

 

I've had all kinds of theories, over filling the tank (the handbook, which I read for once, says never to fill over the plate in the tank. I tend to do this occasionally though, it's not the easiest tell tale to spot) the valve that releases the contents of the carbon canister sticking open, the little spring loaded valve in the cap, I've tried most all of them. The separate vent works though. I plugged the carbon connection with an M6 bolt, as you do... Whist I was sorting the vent, there was a noise like a very quiet escape of intestinal gasses every so often until I plugged the connection, so there's a lot for me to look at.

 

When I took it to the Honda Dealer for them to have a look.... Well they sent it back with the tank top hat washers upside down and when I spotted that they had also put copper ease all over the studs. The tank was wobbling all over the place, I think they literally didn't have a clue but told me they had found a kinked hose. It isn't nice dipping into a corner gripping the tank with your knees and having it feel like it's coming off.... This was Crescent Honda in Southampton. Not impressed... The tank is permanently creased, but I've managed to "inflate it" back to roughly the right shape. But it needs a new one now. There are creases on the sides and under where the Airbox area is shaped to clear the plastic box, it's actually bad enough that paint is coming off the tank now.

 

 

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On 9 October 2017 at 11:14 AM, fink said:

Shouldn’t have any suction noise at all.

Hi Fink.

Wonder if NZCam is experiencing a positive pressure, vapours expelling from the tank when cap is opened. I get this often, just back from a ride today, bike in the sunshine, opened the filler cap and had positive whoosh of vapours from the tank, it's relatively slight though. Info - No Carbon Canister on the Australian version.

Think we might hear of many a sad story of tank deformation due to a pinched breather hose after the first tank raising. The problem is the first 12inches of small hose from the tank.  BE AWARE!

Cheers.

Grum.

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3 hours ago, Sparticus said:

Whist I was sorting the vent, there was a noise like a very quiet escape of intestinal gasses every so often until I plugged the connection, so there's a lot for me to look at.

Hi Sparticus.

It sounds like you have diagnosed a faulty Carbon Cannister. Got the same gastric bubbling sound the other day whist I had my breather tube disconnected investigating this issue. Suspect it was the tank venting and the valve in the fuel cap bobbing.

Real shame about the quality of workmanship you received at the Honda dealership - Bloody disgraceful. Don't know wether you could claim warranty on your tank caused by faulty Carbon Canister, I'd sure be pushing for it. Good Luck.

Cheers.

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4 hours ago, Grum said:

The problem is the first 12inches...

 

That what Mrs Skids always says.

 

Usually every 3rd Friday. :goofy:

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There's one thing that's missing. If you shake a petrol can full of petrol for a while if it's plastic, it would tend to expand somewhat. Tin ones do as well if left in the sun.
By definition. If the "Breather" is kinked stopping the air getting in, wouldn't it also stop the fuel vapour expanding in the tank from venting? Wouldn't the the tank have had pressure popping the cap off on a hot day, after having the heat of the day, and possibly the Sun play on the tank all day?
Well mine still had suction.

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1 hour ago, Skids said:

 

That what Mrs Skids always says.

 

Usually every 3rd Friday. :goofy:

 

:beer:

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6 hours ago, Grum said:

Hi Sparticus.

It sounds like you have diagnosed a faulty Carbon Cannister. Got the same gastric bubbling sound the other day whist I had my breather tube disconnected investigating this issue. Suspect it was the tank venting and the valve in the fuel cap bobbing.

Real shame about the quality of workmanship you received at the Honda dealership - Bloody disgraceful. Don't know wether you could claim warranty on your tank caused by faulty Carbon Canister, I'd sure be pushing for it. Good Luck.

 

 

WP_20171003_18_50_19_Rich.jpg

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Cheers. I think the noise was coming from the Carbon connection. The tank "vent" I put in is simply a plastic piece of hose from my Vacuum gauges, I cut the hose from the canister so it was open to atmosphere, pretty sure that this is where the noise was coming from. I could be wrong, my daughter picked up the noise before I did, having 60 year old ears means I don't always hear stuff as well. But once she pointed it out, it was plain as day. Oh. And I'm still missing the Linked Brakes my Vtec has.

WP_20171003_18_50_01_Pro.jpg

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Hi all ! I've been lurking here for a while but this post prompted me to join.

Just to add to the Discussion. My bike is just reaching 10k so it hasn't had its 10k service yet. I use it every day to commute. .My problem only started about 3 weeks ago. I went to fill it up and I thought the Fuel Cap Lock was "Jammed with Gunk "or something. I managed to get it open after a struggle and lots of Pushing Down.

When I got home, I opened it and it worked fine. So I put some Silicone down the lock. Checked the key, and tested it again. Everything fine.

I run the Bike from Full to Virtually Empty...Next Refueling, I have the same Problem...And Again.

After reading this Post, I dismantled the Fuel cap Valve and lubed it. I blew down the vent tube and it doesn't seem to be blocked....Right now the bike is Empty and I just went out and tested it. It

opened fine with that "Gasping" sound but it has always had that Sound.

Thanks for the great Info lads.

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16 minutes ago, Sparticus said:

Did I just read that right? The Aussie version doesn't have the carbon canister system?

That's correct, no Carbon Canister. The breather goes directly from the tank via the small and large hose to the underneath of the bike, the forward hose of the three.

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Why not just replace the small and very thin vacuum hose with a armed fuel hose that do not bend that easy?

I'm gonna do that. It will just be a matter of time before you forget to check the hose after a dealer service.

 

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17 hours ago, Grum said:

Hi Sparticus.

It sounds like you have diagnosed a faulty Carbon Cannister. Got the same gastric bubbling sound the other day whist I had my breather tube disconnected investigating this issue. Suspect it was the tank venting and the valve in the fuel cap bobbing.

Real shame about the quality of workmanship you received at the Honda dealership - Bloody disgraceful. Don't know wether you could claim warranty on your tank caused by faulty Carbon Canister, I'd sure be pushing for it. Good Luck.

Cheers.

 

 

Only usa bikes have the carbon cannister.

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Hi All.

Some more general info regards the Filler Cap.

I was unaware that the two vents in the cap are independent! The left one provides Pressure Relief while the Right provides Vacuum Relief (via the slightly spring loaded valve). Yet both of these vents end up at the same point being the breather hose! ------ WHY? Stuffed if I know.:blush:

 

The bottom line from this is, provided your breather isn't blocked you should only ever have very slight vacuum (due to valve spring tension) and virtually no positive pressure.

( Ignoring all the Evap Canister plumbing stuff, its not on the Aussie version. )

Cheers.

Grum.

 

P1010028.JPG

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