I have a 97 900ss ie cafe racer it runs great except....when it is run a vacumm is created in the fuel tank, i know theres supposed to be some sort of breather to equalise, this is obviously defective or missing, could anyone explain or point me in the direction of what i am looking for to correct this issue? Also...the breather at the left hand rear of the crankcase has a piece of rubber tubing attached and nothing else therefore oil mist vents to open air near the rear tyre, any advice on how to improve or rectify this please? lastly, in the long run this is a project, i want to create something akin to this: Can i junk the airbox and replace with cone type filters? theres lots of discussion on other forums about stacks and intake tracks, technical advice on this too please. thanks in advance Firesorter
The breather for the tank is usually a one way valve either in the fuel cap or in the recess around it, normally it's a ball with a very weak spring below it. if there is a small hole in the cap or recess you could try poking the hole gently with a paper clip or something to see if it's stuck closed. With The crankcase vent you can either fit a filter kit, or put the vent pipe into a small plastic bottle and cable tie it to the frame or refit the vent pipe into the airbox but I guess there's a reason why it's not there already. Good luck, great looking bike by the way, Kev
Thanks for the steer it would appear the filler cap has a breather route, this gas a rubber figure 8 shaped restrictor this is only one way that us vent excess pressure from the tank, i could remove this however this would allow a constant free flow of fumes from the tank.
If your going to re do the tank: Mocal In Tank Breather Valve - Allows Fuel Tank To Breathe-Motorsport/Motorcycle | eBay
For the crank case vent I would go back and fit it back in. It has reasons to be there. Does not have to be like the original but something. Make a custom one if you have to where there is a bit of tube, expansion chamber with grids inside so oil can not slush about (if it gets there) and exit rather then going to airbox has a crank case filter that will catch oil. If you fit filter directly to crank case it will stop most of oil mist but depending how much you get might need frequent replacing. Yes you can get rid of air box. It will change characteristics of engine so remap would be handy. A rule of thumb is by doing that you sacrifice low/mid range torque for bit more top end BHP. It does look sweet.
Nah, nah, nah....I'll answer this on Sunday.......unless the OP can find the breather pipe which is somewhere under his fuel filler cap and runs downwards.....
Hmm mm no breather pipe attached to filler cap just a wee hole in the black plastic that vents out wards ( see above post) interested to see what you can come up with
The tank breathes through the filler cap which has a ball and a tiny spring inside it. The filler cap itself vents to a rubber grommet at the rear of the filler which the cap seals against when it is closed. This lead to a rubber tube inside the tank which connects it to a spigot at the bottom of the tank. There is another for the filler cap drain. Both of these are joined with a Y connector to a rubber tube that exits under the engine. Check that the tube isn't kinked and that the route through the tank isn't blocked below the rubber grommet.
Thanks Derek..........You beat me to it............I was too plastered last night to go looking for the right page in the Parts Manual. The device that Exige mentions is only OK if a suitable location on the tank can be made to make a hole, plus nearly all, if not all the breather valves on the market have to be mounted so they are upright........which isn't easy on a bike......they let air into the tank and they let pressure out, but unfortunately they do not stop fuel from coming out when it is sloshing about....... .........the breather valve on the carbed models allows pressure out, but not fuel unless the bike has the tank brimmed and it's on a paddock stand, when after a short while fuel finds it's way past the seal in the valve. The genuine OEM valve for the carbed model will set you back £50 as near as dammit (it doubled in price in one year).
"nah nah nah" in the style of alexei sayle in the young ones, yep, pissed! okay guys tanks for the help so far i now have a clear understanding of the route and have taken the cap apart checked hoses etc, no apparent blockage, i now have another minor problem, how do i get the ring around the cap ( part 6 ) in the above diagram back into the tank, bugger wont go back in fully and seat.
I will be using these or similar on my project bikes as there is no facility for a cap based breather and the original KR had similar
how do you get it back together ...........with difficulty had to apply lots of pressure to hold in place while refitting grub screws got the wife to help lol in the summer when direct sunlight on tank pressure build up vents from the breather and sounds like a small cow mooing :Hilarious:
In the summer when it gets hot the workshop I leave the bike filler cap unlocked so it can breathe easier than it can through the valve (but not when I'm using the bike, of course). It seems that the SS IE has more issues than the carbed SS has with collapsed tanks owing to blocked breathers........
You will have to mount it right on the top of the tank so it is vertical, with the outlet horizontal........ ...here, save yourself a few quid...... Mocal Fuel Tank Vent Valves | Motosport Roll Over Fuel Shut Off Valves | Horizontal | Rallynuts Ltd Newton Fuel Filler Vent Valve from Merlin Motorsport
Plenty grease around the filler opening helps but the filler cap often needs a new o-ring before it will go back in.The o-ring absorbs fuel and swells so that no way will it go back together. I'm currently about to struggle with a carby one :Arghh:
Yeh, it goes front left of the tank but comes off vertical like the one in the second link - better price too
got the cap refitted, lubed ring, vaseline etc i also put it in freezer to contract, then i looked on ducati ms where i read " make sure the black seal sits out in the rim", doh so i repositioned it and it slipped in a treat, bike is back together and i cant find a blockage or kink, i think the figure 8 rubber in the cap is the culprit.
I have tried both on my SS as a cheaper subsititute for the OEM one, but I found that fuel could get out in small amounts while it was sloshing around, but correctly sealed if I upended a full tank.......seems they need the weight of fuel against the valve to close it off in the event of a spill. Used similar ones on our outfit tank (flat topped affair) and they worked fine, because we had the foam filler in the tank.
