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VFR800F 8th Gen Fuel Tank Vacuum Problems


Skids

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Have any 8th Gen owners had any problems with a vacuum forming in the fuel tank, or have any of you heard of one?

 

I have 2 friends here in the UK who have both had issues, to the extent that the tank has deformed and the paint has cracked. Both bikes are out of warranty and Honda seem to be avoiding any liability, though one of my friends has had a £200 goodwill gesture paid (replacement tank is over £700).

 

Honda still have not ascertained the cause but one of my friends is actively investigating why a vacuum should be building up.

 

There is a Youtube video here showing the tank moving as the vacuum is released - 

 

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I asking about ;) , if not first must check them , or better disconnect from the bottom of the tank

than must see :

When you apply pressure , max0,2 psi !!! on both petcock under(with open fuel tap) they must free flow

If not , try to set them free

 

(do not have to add , or may yes : this operations are just for people with a bit of knowledge otherwise workshops are the answer)

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Hi Skids.
I've had the high vacuum issue with my tank once, the vacuum was so strong I thought I was going to break my key in trying to open the filler cap.
You will either have a pinched breather hose  (one of the three hoses that ends up at the bottom of your bike) ,OR as I did, a suspected jammed small one way valve thats inside your filler cap. The valve allows for positive pressure to build in your tank but never negative (unless its jammed).
Have a very good look for a pinched tank vent hose, this can easily happen after raising and lowering the tank from the maintenance position. Failing that, remove your filler cap from the tank, there are 5 allen head screws, open your filler cap and you will see only 3 of these screws hold the filler cap in position just remove these 3 the other 2 are dummies. With the filler cap removed undo the centre Phillips head screw to access the one way valve and spring, give the valve and seat a squirt of WD40 then reassemble. While the filler cap is removed have a good look at the vent line for any obstructions, you should also be able to freely blow air through the tank vent hole and feel the air exiting from one of the bottom three hoses under your bike. Its an easy thing to do, I've had no further reoccurrence of the problem since doing this almost 2 years ago.

Cheers.

Grum
 

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Breather hoses pinched.  Did it start to happen after the twat nav was installed.  Did on mine, lift the tank and give breathers some more slack.

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21 minutes ago, fink said:

Breather hoses pinched.  Did it start to happen after the twat nav was installed.  Did on mine, lift the tank and give breathers some more slack.

 

Says he's checked those.

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1 hour ago, Skids said:

 

Says he's checked those.

 

When did this start to happen? Was it after the sat nav install? 

 

Why noy get them to join the forum? 

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I've linked to Grum's post so they can find this place. It's up to them if they want to join.

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7 hours ago, Skids said:

I've linked to Grum's post so they can find this place. It's up to them if they want to join.

Hi Skids.

Further to my posting above. This is the method I used to confirm my Breather Hose was not blocked. Simply holding this hose to the breather coupling and blowing I was able to feel air exiting from the other end of the breather hose underneath the bike. Hope this helps.

Cheers

Grum.

 

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Very well timed post ....just had my 16,000 mile service done, went to fill up and when I opened the tank there was a loud sucking noise .... I guess it's back to Fowlers to sort 

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11 hours ago, Thumbs said:

Very well timed post ....just had my 16,000 mile service done, went to fill up and when I opened the tank there was a loud sucking noise .... I guess it's back to Fowlers to sort 

 

Are you guys getting your tanks blown regularly to help release the built up vacuum pressure?  I believe the owner's manual recommends this service be done at least twice a month in order to ensure proper performance :tongue:

 

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I got a new tank on mine. My tank got vacuum dents and was totally out of shape because the breather hose was bend. 

The breather hose was bend where it attach to the tank. 

 

If tank has been rised for service, it is ekstreamly important to check that the breather hose is not bend. It bend very easy.

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Well it's sorted after wasting a morning taking it to Fowlers, next time I'm checking the vent line after they have the tank off 

 

Thanks to Skids for raising the matter and kudos to Grum for solution and how to check the line 

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Hi All.

After hearing the bad news that this issue could destroy your tank!!!

Decided to have a very close look at this problem and think I have discovered why this is happening, and, as reported, this is a SERIOUS situation the vacuum created can be so strong it can seriously DAMAGE your tank!!!!

 

It seems there are a few people that have had this happen after any servicing has been done around the airbox (air filter replacement etc.) requiring the tank to be extended in maintenance position. 

 

When the tank is placed in the Maintenance position the small breather hose is pulled up by a few inches through a whole lot of clutter. The problem is, when the tank is lowered back to normal position the hose doesn't naturally go back from where it came and bunches up and gets crushed and kinked against all the other clutter so close to the breather inlet to the tank. See attached photos.

 

The solution is to simply pull at the small to large hose coupling area to take up the slack while lowering the tank. (see photos).

You should always be able to blow air from either end and feel air being expelled at the opposite end (fuel cap open of course).

 

Hope this helps.

Cheers.

Grum.

Post Edit - Some clarification here, there is a difference in being able to Blow air through the breather hose (positive pressure) than able to Suck air through it (negative pressure). A kinked partially blocked hose will allow blowing air to flow, However suction could further help to collapse the hose causing a complete blockage.

 

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Thanks again Grum ....

 

This should be the first 8th gen sticky

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Good write up there Grum.   

 

  Should also maybe include the signs that it occurring. ie Difficulty in trying to open the fuel cap followed by a hissing sound as the pressure is released, as well as the aforementioned tank deformation in some cases.

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Just some pictures what vacuum can do to your tank. 

Pictures show the marks on the breather hose where it was bend.

And the dent and deform tank.

The dealer replaced my tank under warranty.

 

Your tank will for sure deform and get dents before first fillup if vacuum hose is bend, the fuel pump will do the job.

As Grum already tells, first thing to check after service is the vacuum hose, it's very important.

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Hey All, Thanks for the heads up and follow up info!  Quick question (sorry if it's been answered already, I didn't see/remember it) - at what point (how much fuel used) will the tank start visibly deforming?  I like topping off as often as possible - I think the most I've used before refueling is about a little more than half tank (fuel gauge reads under half full)...  

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24 minutes ago, Samuelx said:

Hey All, Thanks for the heads up and follow up info!  Quick question (sorry if it's been answered already, I didn't see/remember it) - at what point (how much fuel used) will the tank start visibly deforming?  I like topping off as often as possible - I think the most I've used before refueling is about a little more than half tank (fuel gauge reads under half full)...  

Don't know. I did not notice when i happend. But the dents will come on each lower side of the tank and will be identical. You can see it on my picture just above the black plastic. 

Also the black plastic attached to the tank will fit very bad if the tank has vacuum damage. It will fit even worse when the tank is under vacuum.

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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?

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