Gas cap blues....
- Thread starter Onespeed
- Start date
The gasket on my 2011 300 shrank and would leak gas. I replaced it with a gas cap gasket of a kx65 with and extra vent hole drilled in it. Keeps the gas from leaking.
Onespeed
New member
Could you explain the "extra hole"
GMP
Active member
My take is this:
The cap has a rather large check ball system built in, always did. Retainer cap has three holes. They used to have a full rubber gasket that covered these holes, and the gasket had smaller holes. Problem was the rubber would shrink and harden, blocking these tiny vent holes. Now with just the ring gasket, this is not an issue, but there is a lot more opportunity for fuel to escape. The check ball works if the bike is down but splashing allows a path through.
Solution (with a warning):
I added a small alloy shorty vent hose cap, with its own check valve, because I run a Scotts damper anyway and another hose gets in the way. Has worked very will for years on my '07 and on my '12 since new. Sunday was first harescramble of the year. It was freezing and snowing at my house Sat night with my bike loaded in my truck for a 4AM departure. It was just as cold Sun AM. Well, bike starts up and dies on the way to the line. Thought it might be plug as it was really cold. Pushed bike back to truck and changed plug, bike starts, go to line. Bike dies on line warming up.
Will not start until many rows are gone, I finally get off with the C200s.
Runs OK and dies in the woods a few min later, but its cleaned out now. Open gas cap and air rushes in. Little vent hose cap/valve is frozen closed, blocking vent! Bang it on the bars a few times, check it and now good. Bike starts right up and runs awesome.
So, this is a decent solution just check that its open before a race especially if its freezing.
The cap has a rather large check ball system built in, always did. Retainer cap has three holes. They used to have a full rubber gasket that covered these holes, and the gasket had smaller holes. Problem was the rubber would shrink and harden, blocking these tiny vent holes. Now with just the ring gasket, this is not an issue, but there is a lot more opportunity for fuel to escape. The check ball works if the bike is down but splashing allows a path through.
Solution (with a warning):
I added a small alloy shorty vent hose cap, with its own check valve, because I run a Scotts damper anyway and another hose gets in the way. Has worked very will for years on my '07 and on my '12 since new. Sunday was first harescramble of the year. It was freezing and snowing at my house Sat night with my bike loaded in my truck for a 4AM departure. It was just as cold Sun AM. Well, bike starts up and dies on the way to the line. Thought it might be plug as it was really cold. Pushed bike back to truck and changed plug, bike starts, go to line. Bike dies on line warming up.
Will not start until many rows are gone, I finally get off with the C200s. Runs OK and dies in the woods a few min later, but its cleaned out now. Open gas cap and air rushes in. Little vent hose cap/valve is frozen closed, blocking vent! Bang it on the bars a few times, check it and now good. Bike starts right up and runs awesome. So, this is a decent solution just check that its open before a race especially if its freezing.
Jakobi
Super Moderator
Seal on 2 caps leaked on my 2010 (same as 2011). I ended up first trying to make my own seal out of some rubber purchased from the rubber store. Didn't work so well. I don't think it liked the fuel even though I told them thats what I'd be using it for. In the end I just decided to run no seal. The cap seals against the tank better than any of the stock seals have so win there. I think I have a brand new cap in storage too which I purchased some time back. Can't confirm if the 2012/13s use the same cap as earlier models or same threads though.
So my first suggestion, pull the seal out and try it without.
So my first suggestion, pull the seal out and try it without.
Jakobi
Super Moderator
Does the 2012 model still vent into the frame? I do get some splash and overflow out of the hose like you said. Its only ever when the tank is filled right up from what I have noticed. I still use the original hose but just have it resting next to the damper so any overflow goes straight on the frame. It doesn't seem to do it much as theres never a mess to clean up there I figure. When the seal on the cap was leaking if felt like it lost heaps more fuel and what it did lose would make a big miss everywhere.
Onespeed
New member
Im running a shorty right now....it looks like its the seal. I have to play with it. Going to try putting a new longer tube on and run it down the hole. If the total mess on the tank goes away I know the problem. I have a really strong feeling its leaking around the threads of tank...so Ill try ditching the gasket and see how I fare.
andoman
New member
Im running a shorty right now....it looks like its the seal. I have to play with it. Going to try putting a new longer tube on and run it down the hole. If the total mess on the tank goes away I know the problem. I have a really strong feeling its leaking around the threads of tank...so Ill try ditching the gasket and see how I fare.
Mine leaks: The top of the neck has imperfections that allow fuel by the the gasket. Trueing the top of the neck helped, but it ends up uncovering more voids in the plastic, so its not a sure fix.
The best result I have had is to run two gaskets: one under the cap for the top of the neck and one on the outside of the base of the neck that seals the lip of the cap.
GMP
Active member
The '12 tanks are different vendor. Quality is fine except for the swelling issue. Take it off and hold it upside down with some fuel and the vent line pinched off, that should tell you if you have a gasket problem. I'll bet it's the check ball.
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Sent from my iPad using Tapatalk HD
bowhunter007
New member
Had a look at Onespeed's tank, this evening. I hate saying this, But GasGas really dropped the ball on his tank. It appears that the plastic was contaminated during the molding process. Another downer...The plastic is so weak, around the filler neck...I'm sure that just the right impact would tear off the cap, and pull out a big chunk of tank. It would be an easy way to empty the tank, quickly, though a less than desireable method. I see a new tank in someone's future. The big question...who gets to eat the cost. I'll gladly take the bike off your hands, for the outrageous price of a new tankNo wonder its leaking.....
GMP
Active member
Absolutely go to your dealer, you should have no problem getting a new '13 tank. Clay has been great with dealer/customer support like this. The '13 tank is supposedly from a different vendor, with ethanol compatible plastic so it will not swell.
Ever fix ski bases with a PTex candle? For now, drain and dry the tank to remove all traces of gas. Light a PTex and drip a layer on that cap seal surface. Dress flat with a fine file and fine paper. I never had to do it but it should work. It works on the old tanks for fixing stripped out shroud screw holes.
Sent from my iPad using Tapatalk HD
Ever fix ski bases with a PTex candle? For now, drain and dry the tank to remove all traces of gas. Light a PTex and drip a layer on that cap seal surface. Dress flat with a fine file and fine paper. I never had to do it but it should work. It works on the old tanks for fixing stripped out shroud screw holes.
Sent from my iPad using Tapatalk HD
swazi_matt
Active member
I have managed to solve my shrinking gas cap issue. it used to work fine until recently when it obviously shrunk smaller than the tank. I tried it without the check valve and found that with the typ of riding i do the fuel was sloshing through the vent hose and all over the frame (i did not have it going into the frame)
So what i have done is to purchase a sheet of 1mm viton rubber, a compass cutter (http://www.amazon.com/X-acto-Precision-Compass-Cutter-compass/dp/B000KNNJ2I) off ebay. cut the outer diameter to fit the cap and the inner one is small enough to hold the original check valve/seal in place so now no fuel leaking through the cap and the check valve is working as it should
So what i have done is to purchase a sheet of 1mm viton rubber, a compass cutter (http://www.amazon.com/X-acto-Precision-Compass-Cutter-compass/dp/B000KNNJ2I) off ebay. cut the outer diameter to fit the cap and the inner one is small enough to hold the original check valve/seal in place so now no fuel leaking through the cap and the check valve is working as it should
