919 Gas Tank Replacement - Wrist Twisters
 
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post #1 of 11 Old 09-10-2012, 03:21 PM Thread Starter
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919 Gas Tank Replacement

So I finally got sick of looking at the rashed tank on my bike, and had a mechanic install the replacement tank that's been sitting on my shelf for a couple years.

Everything seems to run great, BUT the first time I ran it for any distance (150 miles), I get it home, I go to the gas station to refill it, and the gas cap fights me. MAJOR suction. Like it has no venting at all.

1) I see pictures on eBay of replacement OEM gas caps, and they all have this little rubber thing wrapped around one of the real screwposts in the gas cap assembly. The exploded parts diagram tells me this might be the breather seal. Sounds like a thing to have, right? Well, I don't have one of them.

2) If I was missing something that acts as a valve for the tank, that only opens up when the suction is high enough, wouldn't it be venting all the time without one?

3) The bike's a CA one. That is, it has an evap canister. I don't know if the replacement tank is CA or not. Do the CA bikes vent differently?

4) If I buy an aftermarket gas cap assembly, will it be vented?

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post #2 of 11 Old 09-10-2012, 03:28 PM
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Keep an eye on this issue, some peoples tanks have imploded without the proper venting.

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post #3 of 11 Old 09-10-2012, 03:32 PM
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Yes, CA tanks vent differently - they have an evaporative emissions canister that the tank vents into. Some people 'convert' CA tanks into regular ones by closing off the vent line.

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post #4 of 11 Old 09-10-2012, 03:36 PM Thread Starter
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Does that mean that my CA gas cap wouldn't have that breather? And furthermore, that buying that little hunk of rubber wouldn't do me any good?

I was concerned with an imploding tank. Also, if it's fighting that much suction, I have to assume the condition would burn out a fuel pump pretty quickly.

As it is, I can burp the tank every 20 miles, no big deal, but it's a dumb thing to have to do.

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post #5 of 11 Old 09-10-2012, 03:50 PM
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Quote:
Originally Posted by starman View Post
Does that mean that my CA gas cap wouldn't have that breather? And furthermore, that buying that little hunk of rubber wouldn't do me any good?

I was concerned with an imploding tank. Also, if it's fighting that much suction, I have to assume the condition would burn out a fuel pump pretty quickly.

As it is, I can burp the tank every 20 miles, no big deal, but it's a dumb thing to have to do.
Yeah, you'd better watch it. More so if you burp it in hot conditions and ride extended lengths when it's cold out. The vacuum pressure (ie, lack of pressure) would be more.

Check under the tank for any pinched lines.

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post #6 of 11 Old 09-10-2012, 03:58 PM
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If you can't fix it, now you have an excuse for an aftermarket gas cap!

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post #7 of 11 Old 09-10-2012, 04:27 PM Thread Starter
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I'm happy to get an aftermarket cap if it'll do the job.

Do the aftermarket caps have breather valves on them? I'm told the "breather seal" on the OEM (presumably non-CA) cap assembly is pretty much a piece of rubber with a slit in it that stays closed unless the suction gets high enough.

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post #8 of 11 Old 09-10-2012, 05:13 PM
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Quote:
Originally Posted by starman
I'm happy to get an aftermarket cap if it'll do the job.

Do the aftermarket caps have breather valves on them? I'm told the "breather seal" on the OEM (presumably non-CA) cap assembly is pretty much a piece of rubber with a slit in it that stays closed unless the suction gets high enough.
I had a twist off from ebay...it did have just a seal and I believe just a hole drilled for a breather. I could hear it hissing slightly after letting my bike sit for awhile during a hot day. The anodized wore off in a couple weeks. I really liked the twist off factor though, no biggy being my bike is always in my view.

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post #9 of 11 Old 09-10-2012, 05:42 PM
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according to the parts fiche there is a difference as far as part numbers between tank and gas cap on the CA vs non CA model.

THAT SAID.

the stock gas cap regardless of ca or non ca NEVER vented. There is, however, a vent tube in the tank, where it went to open air on the non CA models, and to the evap canister inlet on the CA models.

There are two tubes that go to the top near the gas cap of the tank on the underside.
1. the overflow tube, easily seen by opening the gas cap and looking on the out side of the fill hole to the tank on the left... try it pour a lil fuel down that tube it should pour out by the right side peg.

2. the vent tube. like stated this is a vent that is open on the INSIDE of the tank to vent gasses. it is easily pinched. if it is pinched it will not allow the vapors to expand or contract and or not allow for the change in volume of fuel in the tank.

If your bike is equipped with an evap canister its easy (even easier without evap canister) to test of the tube is pinched.

Simply pull the tub off the evap canister (its the round thing in front of the rear tire on the bottom of the swing arm) on the throttle side (right side as you sit on the bike). there are two tubes comming off the evap canister. the one in the middle is the tank vent. Pull that off the canister, Open the gas cap, and you should be able to blow air through the tube freely.

While your this far... do yourself a favor and remove the evap canister completely, including canister, all tubing for the purge valve, purge valve itself, and cap the vacuum line off at the throttle boddies, leave the vent tube hanging by the right peg with the overflow for tank and coolant.

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post #10 of 11 Old 09-10-2012, 11:25 PM Thread Starter
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Thanks! I'll do that this weekend.

It's looking like I should've swapped out the tank myself, but I didn't trust my own skills. Looks like I shouldn't have trusted this mechanic's Honda knowledge, either. I called him yesterday, and he suggested that maybe it was normal for there to be major vacuum in the tank. Um... no.

But now I might have to lift the tank up to see if there's a pinched hose (I doubt I'd have to drain the tank to do that), and I still don't know how that "breather seal" thing actually works. I might just not have the right cap, so as a backup I grabbed one of the eBay vented aftermarket caps.

No key, but I don't think that can matter much. I'm hoping that "roving gasoline thief" hasn't been a profitable profession since the early 70's.

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post #11 of 11 Old 09-10-2012, 11:57 PM
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Roving gasoline thief is currently a popular profession, given the current price of fuel. They're more direct now, too - they've taken to spiking the bottom of a car tank and letting all the fuel drain out.

I got hit by some who used the older siphon technique and loaded up their car with it. I am not sure what they thought they would accomplish because their car was a gasoline fueled model and the truck they siphoned fuel out of was a diesel. They were caught not terribly far away after a neighbor phoned it in.

More worrisome to me are the kids pulling pranks - apparently some of them watched Mythbusters and they are running around pouring bleach in gas tanks.

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