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Message started by Boule’tard on 01/07/10 at 19:17:33

Title: Fix your gas cap leak
Post by Boule’tard on 01/07/10 at 19:17:33

Please note the consensus, after much trial and error:

The Honda and Suzuki gaskets are about the same thickness. Replacing with the Honda gasket can fix it temporarily, just by virtue of being a fresh gasket, but probably not much better than a new stock gasket.

Rotating or flipping the stock gasket fixes the leak on some caps, but again, probably not for good. I imagine it will eventually pack down and get loose again.

The spud washer is thicker than stock, but not always made of a gas-resistant rubber, so you have to treat it with gasket dressing to be sure it won't swell or dissolve on you.

The best options seem to do that (use a spud washer and treat it) or shim up the Honda or Suzuki gasket somehow.

It is not necessary to roll your own gasket. If you go with the Honda gasket, the part number is 17631-253-010.

http://i33.photobucket.com/albums/d64/tjfisher28/76fca98e.jpg

645A565943585542300 wrote:

..so far so good on the fix no issues as of now and I don't see any in the near further

Thanks Tjfisher for the tip. [smiley=beer.gif]

If you'd still like to make your own gasket, read on..
=====================
Yes folks, this is how it's done. A little trick critically acclaimed as "one of the best and simplest mods available" :D And it really is simple, so simple even I can do it.. and you guys have seen me screw up stuff so simple a monkey could do better.

The hardest part is sourcing the gasket. Luckily I have a plumbing shop nearby, one of those warehouses where only the old codgers who work there can find anything. They let me wander aimlessly around with my cracked, too-thin stock gasket in hand until I found a suitable replacement. It turns out that replacement is called a 3/4" spud washer. Why it's called 3/4" I don't know. There is nothing 3/4" about it. These are the gaskets that fit onto "spuds" which in plumbing parlance are the fittings that connect wall-mounted toilet tanks (or urinals) to the water supply.

I THINK (but don't know for sure, will edit later) that this washer (http://www.azpartsmaster.com/Products/Spud-Washer---1-to-1-14-x-34-Urinal__9191.aspx) is it. NOTE: The gaskets are only 79 cents but they are charging $8.45 to ship(!) At that rate, you might want to do a small batch of gaskets, order a dozen or so stuffed into the same box. We need a guinea pig to order one and let us know if it's the correct dimensions. Or if someone can find someplace that does not require you to buy 100 of them packed in $8.45 worth of whale lard from China, let us know.

So once you have the right spud washer, it should look about like this one:
http://i48.tinypic.com/e9cej5.jpg

Verify the dimensions. The outer diameter looks about 2 1/8"
http://i49.tinypic.com/dc3p05.jpg

The inner diameter is roughly 1 3/16"
http://i47.tinypic.com/j5xw8y.jpg

And the thickness of the disc part of the gasket is about 5/32"
http://i48.tinypic.com/2zz01sy.jpg

Take a sharp new x-acto blade and slice off the flange, holding the blade flat against the "washer" part.
http://i48.tinypic.com/2m9obs.jpg

At this point the gasket is probably good enough to install, and if you don't feel like buffing it down perfectly flat.. don't.
http://i45.tinypic.com/dw2ct5.jpg

But noOoOOooo, Mr. Brilliant must have it PERFECT! Yes, the gasket nazi suffers for his gaskets, risking life and fingernail.. ::) Well anyway, just keep the gasket moving and your fingers clear, and this takes almost no time at all.
http://i48.tinypic.com/2mg5o9h.jpg

They really do look good, fresh off the sander. Rinse all the little rubber crumbs off the gasket so they don't end up in your tank.
http://i46.tinypic.com/5jwdmv.jpg

Ok, so time to install this thing and start enjoying gas-free pants. Take out your gas cap and remove the two screws that hold the lock cylinder cover on. Onion not required (it will reek enough to your wife's dismay as-is).
http://i45.tinypic.com/nlztpt.jpg

Remove that little bezel, pry out the old gasket, and replace it with your new SUPERGASKET :D Note how the six nubs around the inside of the cap squeeze the gasket tight against the lock cylinder and plumps it up. The rubber is fully bound from three sides and ready to put sufficient pressure against the tank, and not leak a drop. :)
http://i48.tinypic.com/28ro7lg.jpg

That's it.. put the bezel and black cover back on with the two screws, and go fill up your bike knowing the cap will seal like it's supposed to.

Title: Re: Fix your gas cap leak
Post by Digger on 01/10/10 at 19:54:33

Boule,

How does the rubber in that gasket stand up to gasoline? Is there any swelling?

TIA!

Title: Re: Fix your gas cap leak
Post by Boule’tard on 01/11/10 at 06:34:56

143937373522500 wrote:

Boule,

How does the rubber in that gasket stand up to gasoline? Is there any swelling?

TIA!

There's no swelling. The last picture actually shows the gasket I made several months ago. It now takes slightly less pressure to close the cap, because the rubber eventually bedded into the filler neck.

I don't know how the gasket will stand up to gasoline in the long term. But I DO know that the stock gasket was cracked when I bought the bike (4 years old) and the new one is still perfectly pliable. The only sign of use is the impression from the tank.

Title: Re: Fix your gas cap leak
Post by Digger on 01/11/10 at 20:42:12

A good sign. If the rubber was incompatible w/ gasoline, I think it would have swelled fairly quickly.

Good tip!

Title: Re: Fix your gas cap leak
Post by kimchris1 on 03/02/10 at 18:02:57

Boule, one quick questoin. The 6 lil nubs that hold the gasket down. Do they have to be pryed open or does the gasket just slip in under neath them?

Thank you for this info and I don't need it yet like Piglett, if I do I know where to find it.. :)

Title: Re: Fix your gas cap leak
Post by John_D on 03/03/10 at 01:59:17

50525658534952480A3B0 wrote:

Haven't really looked at mine, but if that piece is cast rather than stamped, for cripes sake, don't try bending them; they'll snap right off! :( If the rubber's halfway bendy, a person should be able to wiggle them out and back in without doing anything to the tabs, maybe? :-?

Title: Re: Fix your gas cap leak
Post by Boule’tard on 03/03/10 at 14:28:55

4C4E4A444F554E5416270 wrote:

..The 6 lil nubs that hold the gasket down. Do they have to be pryed open or does the gasket just slip in under neath them?

The nubs hold the gasket inward toward the lock cylinder, not so much "down." There is no need to deform them to get the gasket in, just compress the gasket slightly so it fits between the nubs and cylinder.

Title: Re: Fix your gas cap leak
Post by Boule’tard on 03/23/11 at 19:16:19

I'm glad you guys are finding this info useful. If you have any trouble finding the spud washers, send me a message and I'll pick up a half dozen or so from that plumbing shop. I also have an idea for version 2.0, which is to sort of "grease" the washer with Permatex gasket dressing. That would seal the pores of the rubber and make the cap glide on and off really nice.

Title: Re: Fix your gas cap leak
Post by splash07 on 03/25/11 at 07:28:03

I just got http://www.azpartsmaster.com/Products/Spud-Washer---1-to-1-14-x-34-Urinal__9191.aspx and darn if they did'nt charge $8.45 for S+H. A bit redic if you ask me. When she comes in I will post a report.

Title: Re: Fix your gas cap leak
Post by Boule’tard on 03/25/11 at 07:36:05

Those bastards. I am going to edit the 1st post to include a warning about their shipping charge. Thanks for the heads-up, and we will be curious to see if the rubber from that one plays nice with the gas vapors.

Title: Re: Fix your gas cap leak
Post by youzguyz on 04/07/11 at 16:07:12

I went to Home Depot, and everyone thought a spud washer was some kind of a kitchen appliance for potatoes.

Went to a plumbing supply house, and found out why.
A spud connection is used on urinals. Home Depot doesn't sell a lot of urinals..
The only spud washer the supply house had was as part of the connector.
Hmmm.. look around some. A lavatory drain washer is also the size as specified by Boule’tard. The only difference is that is has a dome lip that needs cut off instead of a straight lip.

So, if you don't have a plumbing supply house in your area, try a Home Depot or Lowes, and look for a lavatory drain washer. BUT, make sure you measure!! As it is possible to have different sizes of those.

P.S. The "3/4" part of the "3/4 spud washer" refers to the size of urinal supply line. Now you know.

Title: Re: Fix your gas cap leak
Post by Boule’tard on 04/16/11 at 19:39:05

737878717D727369681C0 wrote:

I am not sure one of those would stand up to gas.

That concern was raised on page 1 by Digger. The rubber I used held up fine to the gas vapors and splashing. I realize that some guys may be cutting their gaskets from spud washers not as gas-resistant, or may want to fill their tanks chock full so that the gas is in contact with the gasket a significant amount of time. For those reasons I recommend putting gasket dressing on the gasket before installation. If I do another batch, they will have it. This stuff (http://www.permatex.com/products/automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Hylomar_Universal_Blue_Racing_Formula_Gasket_Dressing_Flange_Sealant.htm) is what I'd use.. I got it from Autozone.

Title: Re: Fix your gas cap leak
Post by arteacher on 05/12/11 at 05:13:34

Finally found a spud washer. None of the plumbing supply stores in London had one, or a lavatory washer the right size. I had to buy the whole spud assembly to get the washer ($8) at Rona. Did the mod works great.

Title: Re: Fix your gas cap leak
Post by arteacher on 05/14/11 at 06:15:58

373C3C353936372D2C580 wrote:

The gasket went punky after a day and leaked brown tar onto the top of the tank. Guess it wasn't gas proof after all.
Next I will try to add 1/16 gasket material on top of the old gasket, glued together with liquid gasket stuff. I think the real problem is that the sealing lip on the tank had rusted and did not make a good seal. I plan to clean it up with emery cloth as well.
Any ideas as to how to avoid getting abrasive material in the tank would be greatly appreciated.

Title: Re: Fix your gas cap leak
Post by arteacher on 05/22/11 at 08:26:07

Well I did it. Taped off the tank and flattened the contact area, and put the 1/16 thick piece on top of the old gasket. Worked a charm! I have to push down a bit on the cap to get the clips to engage, but no more leaky leaky. :)

Title: Re: Fix your gas cap leak
Post by built2last66 on 06/13/11 at 14:18:06

I just picked up a 3/4 spud gasket today, paid $3.15 total from a local plumbing store. I can't wait to try this.

Title: Re: Fix your gas cap leak
Post by arteacher on 06/15/11 at 13:42:52

575C5C555956574D4C380 wrote:

Update: I can fill the tank to half way up the neck now and it hasn't leaked a drop, no matter how far I lean it. :)

Title: Re: Fix your gas cap leak
Post by lg_fry on 06/25/11 at 12:39:00

@Boule'tard
have you had any problems with the gasket being too good of a seal, creating a vacuum as you ride and eventually starving the engine for gas til you pop the cap again?

I only ask because I'm trying to find one locally and you seem to have had the most success with your sized gasket.

Title: Re: Fix your gas cap leak
Post by Boule’tard on 06/26/11 at 11:16:52

292437222023373C450 wrote:

have you had any problems with the gasket being too good of a seal, creating a vacuum as you ride and eventually starving the engine for gas til you pop the cap again?

The vent does not depend on air passing by the gasket. There is a pinhole somewhere else in the lock cylinder that bypasses the gasket. There will not be a vent problem unless the pinhole gets clogged.

Title: Re: Fix your gas cap leak
Post by arteacher on 06/26/11 at 12:23:05

There is a valve in the cap behind the lock cylinder with a ball in it. If you tip the bike over the ball rolls down to plug the vent. It stops gas from pouring out but it will still drip, or maybe I didn't lean it quite far enough when I put it down last week, or possibly the ball is spring loaded and my spring has rusted away. I think it vents through the key hole, as I can't see anyplace else for it to vent.

Title: Re: Fix your gas cap leak
Post by CBH on 07/07/11 at 16:40:53

I fixed mine a much easier way. I happened to have a sediment bowl cork gasket that I just placed underneath the gas caps original rubber gasket. It snugged it right up and I couldn't get it to leak afterwards.

Title: Re: Fix your gas cap leak
Post by built2last66 on 07/07/11 at 21:53:53

I ended up taking off my 3/4th spud washer that had no treatment on it because it eventually started leaking after 2 weeks, and some weird brown odorless stuff starting dripping down the tank. Since I have had the original washer back on I haven't had any leaks, it seems it may have just needed to be rotated.

I tried to fit the 3/4th spud gasket under the original washer for a super tight seal, but I couldn't get the cap to lock on the tank. I'm going try a sediment bowl cork gasket though. Thanks!

Title: Re: Fix your gas cap leak
Post by built2last66 on 07/17/11 at 08:55:55

Ok, so for anyone still having problems with leaks after trying all of these fixes, it seems that simply moving my gasket around gave it a great new seal, I've only had 1 minor leak so far but I did over fill it.. but the leak was just a few drops.

Title: Re: Fix your gas cap leak
Post by Tjfisher on 08/07/11 at 15:56:52

Ok so I finally started riding the bike last and now I have started slow fixing the minor stuff ( cap head leak / head retouque ( in process ) ). Also working on the gas cap fix got a Honda factory gasket that works perfectly and I'll report back in the next week or so when I get back on the road

http://i33.photobucket.com/albums/d64/tjfisher28/76fca98e.jpg

http://i33.photobucket.com/albums/d64/tjfisher28/eeb1f849.jpg

http://i33.photobucket.com/albums/d64/tjfisher28/4ad36677.jpg

http://i33.photobucket.com/albums/d64/tjfisher28/7a641b60.jpg

Title: Re: Fix your gas cap leak
Post by Boule’tard on 08/07/11 at 17:29:20

Awesome, I hope that works. Apparently there's a lot of variation in the rubber, and therefore suitability of spud gaskets for this application.. if TJFisher's turns out good I'll edit the original post to include the Honda part number and TJFisher's feedback. Great find! [smiley=dankk2.gif]

Title: Re: Fix your gas cap leak
Post by EJID on 08/09/11 at 12:08:07

27302C293177292436317373450 wrote:

I'm about to order one of these.. if it doesn't work by itself I'm gonna double the original and this one up..

I doubled up the original and a different rubber washer that fit just last night. Took a mild amount of pressure to close the cap and it felt like it fit very snug.

Fast forward to my ride to work this morning and I thought I ran out of gas (90+ miles on the tank so it seamed about time, but reserve wouldn't let me start it either) Pop the cap back off and slosh it back and forth to see if there was any left & I could see it in the bottom. Switched it to prime, put the cap back on and it fired right up. Since I was just about out of gas anyway I stopped and topped it off and put the petcock back in the ON position.

Lunchtime ride home was just fine, but on the way back it acted like it was running out of gas. Died on me and I pulled off the road. Thought it might be the new gasket and listened close when I opened the cap, sure enough you could hear the air go into the tank when I popped the seal. Put the cap back on and it fired right up so I could be on my way. I guess when I get home today I will take out the 2nd gasket and try again.

Title: Re: Fix your gas cap leak
Post by arteacher on 08/09/11 at 16:24:05

The cap has a breather in it that can get dirty and clog up. Soak it overnight in carb cleaner, blow it out with compressed air, and it should work again. - unless you have a california bike with the charcoal canister, then I'm lost. :-?

Title: Re: Fix your gas cap leak
Post by EJID on 08/10/11 at 14:13:28

3A313138343B3A2021550 wrote:

I've had that cap apart 6 or 8 times trying different things and this last time I did take some compressed air and blew it through the vent-no problem at all. Just going to be more careful and fill it a little less.

Title: Re: Fix your gas cap leak
Post by CBH on 08/10/11 at 17:26:32

I found that Honda gasket on eBay.
http://cgi.ebay.com/ebaymotors/Honda-Gas-Cap-Seal-Gasket-50-65-70-90-110-160-200-_W0QQcmdZViewItemQQitemZ320733186382#vi-content

Title: Re: Fix your gas cap leak
Post by EJID on 08/25/11 at 14:53:58

I received this gasket from this exact link on Tuesday. (Excellent seller, very quick shipping) Replaced it on Wednesday night and had to gas up at lunch today. It seemed like it was a tighter seal than the others I had tried so I had high expectations. Maybe too high...I filled it really full up the neck then put the cap on. Rocked the bike side to side some and none came out. Rode the 1/2 mile back to work and no spills, I was happy :) About an hour later I had to leave to run an errand. When I tilted the bike back upright gas poured out the cap all over the tank :-[ The heat of the sun had heated the tank so much that it must have caused the gas to expand or something :( Guess I'm just going to have to learn to fill it less.

Title: Re: Fix your gas cap leak
Post by built2last66 on 09/10/11 at 21:13:02

Ok, update time. It's been a few weeks now since I've had the Honda gasket.. I still get the same leak problem just not everytime, and I have weird crap dripping out of the tank hole after the bikes been in the sun.. I'm gonna try to double up the original gasket and the Honda one for tighter pressure and make sure the gas cap vent isn't clogged.

Really sick of worrying when I fill up... plus I'm sure the people on the other side of the pump get sick of me saying "oh nuts, oh nuts.." and running toward them for the napkin dispenser. :-[

Title: Re: Fix your gas cap leak
Post by arteacher on 09/25/11 at 14:43:24

Honda gasket didn't work for me at all- leaked worse than the original.

Title: Re: Fix your gas cap leak
Post by arteacher on 09/25/11 at 15:26:16

What I did was cut the hole in the Honda gasket a little bigger and used it as packing behind the stock gasket. The cap fits tightly now with a little bit downward pressure till the pins click. The gas tank is nearly full and I sloshed the gas around and tipped the bike to the left till the peg touched and no leaky.
Time will tell.
If this doesn't work I'm all out of ideas.

Title: Re: Fix your gas cap leak
Post by Arizuno on 09/30/11 at 11:07:33

Same problem, and I no longer have the original gasket. I'm wondering if if one, two or more "washers" cut from an empty plastic oil can could be used between the new gasket and the cap to shim the gasket for a tighter fit. Would the plastic hold up to gasoline?

Title: Re: Fix your gas cap leak
Post by Boule’tard on 09/30/11 at 11:10:54

Dammit.. is the Honda gasket not as thick as the original gasket?

Title: Re: Fix your gas cap leak
Post by built2last66 on 09/30/11 at 12:00:33

Its about the same thickness and works as good as the stock one ::)

I just need to find something a bit thinner to stick under the stock gasket or the honda one and I believe my pants will be unleaded free..

Title: Re: Fix your gas cap leak
Post by verslagen1 on 09/30/11 at 12:40:02

77445F4C435859360 wrote:

Oil can plastic should hold up to gas.

Title: Re: Fix your gas cap leak
Post by built2last66 on 10/11/11 at 09:51:22

Ok, my gas cap leak is fixed. What I did was use the Honda gasket for awhile, then I cut the middle of it out leaving only the outer edge where it contacted the fuel tank. I put this cut out ring behind my original gas cap gasket just for a little bit of added pressure and it works without any problems such as not being able to close the lock and it comes right off.

Now that my gas doesn't leak, apparently my breather hole in my gas cap is clogged or something, because at around 60mph+ my bike thinks it's it out of gas.. so I'm in the process of trying to clean the gas cap or either just switch up to a Raptor 660 petcock.. but let me tell you, I'm 100% sure every time now that no gas is gonna come spraying out, and no more crap dripping down my tank in the hot sun :D

Also, at 60mph+ I figured out that you could flip the petcock from reserve to normal every once in a while and you wouldn't "run out of gas" on an almost full tank..

Title: Re: Fix your gas cap leak
Post by AlphaBarney on 10/14/11 at 14:44:21

I'm getting the same problem with the Honda gasket. Replaced the stock one, which was cracked and very stiff, with the Honda replacement. The replacement doesn't seem like it's making a tight enough seal with the tank as it's very pliable. Filled up today for the first time after the switch and cap leaked when i rocked it side to side.
Want to shim the gasket to provide a better seal. Stock washer is shot, so I was wondering if I could use this:
http://www.drillspot.com/products/1327956/Thrust_Washer_AS3047_Thrust_Washer?s=1
as a shim behind the new Honda gasket. Anybody ever try this? For $2 I'm probably gonna give it a try.

Title: Re: Fix your gas cap leak
Post by verslagen1 on 10/14/11 at 15:12:06

Can't say whether it will work or not, but be carefull arizuno did this with a homemade washer and jammed his cap on.

would much rather see this done with the correct material thickness anyway. One issue you'll have is the steel washer won't seal.

Title: Re: Fix your gas cap leak
Post by AlphaBarney on 10/15/11 at 13:55:07

Versy,
What I intended to do was use this behind the Honda gasket to give that gasket a little extra push against the tank. Hopefully that would give a better seal, not sure.

As for getting the plug stuck, after fooling around with the lock while I had it apart, I found that any extra thickness added to the gasket moves the pins that are fitted into the plastic housing away from the lock core that pulls them in. Thinking that may be what happened to Arizuno, didn't he say he doubled up the gaskets? I'm hoping that 1mm doesn't make much of a difference with the lock, but I'll update once I get it installed.

Title: Re: Fix your gas cap leak
Post by verslagen1 on 10/15/11 at 14:28:07

Just wanted to make sure you knew what happened and to double check before you find you can't get it off.

Also, why spend two bucks when the fix is in your trash can.

Title: Re: Fix your gas cap leak
Post by AlphaBarney on 10/23/11 at 13:29:50

Okay, so I did what Art and Built did -- cut the ID of the stock gasket a little bigger and fit it behind the new Honda gasket. Takes a bit of pressure to click the cap down fully now. Filled up today and rocked her side to side...no leak!! Not even a little. Hoping it holds up, but this seems to be a good fix for now. Didn't bog on the ride at all today either so I'm thinking my vent is clear, too. Good Times!!

Title: Re: Fix your gas cap leak
Post by built2last66 on 10/26/11 at 07:14:53

I had the screws under the gas cap too tight, cutting off circulation.. my "empty tank" vac problem is fixed now.

Title: Re: Fix your gas cap leak
Post by arteacher on 10/26/11 at 09:21:13

Those screws are supposed to be tight, otherwise they come loose and you have to go fishing.

Title: Re: Fix your gas cap leak
Post by Eicas on 05/21/12 at 09:20:40

Just noticed a little leakage from mine after last fill up. Honda part on order. Thanks for the info.

Title: Re: Fix your gas cap leak
Post by Ben aka ubergeek on 05/21/12 at 09:27:23

I fixed mine by flipping the original gasket over. No leaks. I do not push it up into the gas cap. I just flipped it and put the cover back on. Now I have to press harder on the gas cap to get it to latch in.

Title: Re: Fix your gas cap leak
Post by Boule’tard on 05/21/12 at 11:36:11

So.. to recap (huh huh) :D

The Honda and Suzuki gaskets are about the same thickness. Replacing with the Honda gasket can fix it temporarily, just by virtue of being a fresh gasket, but probably not much better than a new stock gasket.

Rotating or flipping the stock gasket fixes the leak on some caps, but again, probably not for good. I imagine it will eventually pack down and get loose again.

The spud washer is thicker than stock, but not always made of a gas-resistant rubber, so you have to treat it with gasket dressing to be sure it won't swell or dissolve on you.

The best options seem to do that (use a spud washer and treat it) or shim up the Honda or Suzuki gasket somehow.

Title: Re: Fix your gas cap leak
Post by arteacher on 05/21/12 at 17:33:11

And don't forget to smooth the seat (remove the rust) that the gasket contacts, if needed.

Title: Re: Fix your gas cap leak
Post by NegroniMoto on 10/24/14 at 20:23:27

I tried to use the Honda gasket fix, but the gasket deformed two days after. I order an OEM gas cap and now is fixed.

Title: Re: Fix your gas cap leak
Post by batman on 05/15/16 at 18:04:01

I just joined the club about2 weeks ago but have been riding my 95 since new ,I had the cap leak about 3 years back and found that the side of a gallon milk jug to be a perfect shim. I cut a piece just slighty smaller than the gasket and turned the gasket over placing the shim behind it .You'll notice when the gas cap goes on/off that it tight again and there is no leaks, the only cost being your time .(I took out the two screws to place my shim under the edge of the locks plastic cover)

Title: Re: Fix your gas cap leak
Post by lhaas on 08/28/17 at 15:26:46

Just wanted to add in case it could help someone. I was having the leaking gas cap problem and added a shim as suggested but the leak continued. Since the plastic cap that houses the catches sits on top of the rubber ring I am not sure how a shim behind it makes it seal tighter other than just adding bulk.
I sanded the bottom of the cap where it contacts the gasket with sandpaper on a flat surface which makes the catch closer to the gasket for a tighter seal. It worked well and did not interfere with the operation of the catches.

Title: Re: Fix your gas cap leak
Post by stewmills on 08/30/17 at 09:42:46

I recently solved my problem by a similar approach to the OP, but not one I have seen noted before. I added a strip of medium density closed cell foam behind the rubber gasket between the gasket and the cap. It made the pressure of the gasket against the top of the tank a bit tight, but I just push down on the cap when installing it so it goes down far enough to let the two catches engage, then release. Haven't had a leak since (knock on wood).

Here is an image where you can see the foam strip under the gasket.