Fuel Cap Leak Overflow

Hi from Canada,

I just did my first ride of the year on my GRiSO. Had a blast until I got home and had the fuel treatment that had been used for winter storage overflow through the fuel cap. Check out the mess below. Nothing like this has happened before. I had noticed over the years some squealing in the tank and figured there was some over pressurization but didn't think much of it. Today I noticed some leakage as the bike was stopped and the tank had more fuel but later in the day when it was low was when it really came out. I've worked on Japanese bikes but have hardly gotten my hands dirty on my GRiSO. Any advice on where to start looking? Thank you and happy riding!

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There should be two drains under the filler cap - one is for water ingress around the cap, the other is for overflow of fuel. looks like the fuel treatment and the agitation caused by riding are a dynamic mix. Maybe next time, drain the tank instead of fuel treatment.

These drains are easy to clean, though you will have to remove the tank. These have been known to get blocked with normal crud (as distinct from abnormal crud). I have had to drill my nipple out where the drain hose attached. I used a very small drill < 0.5 mm in dia.

And don't push it in to far or you will hole the tank!

The hoses from both drains run a very tight curve in front of the frame tube before dropping down - easy to fold them and block them on re-assembly

Hi Folks,
I stick a bit of white vinegar down the drain hole whenever I remember to & it does the trick.

Over lockdown it clogged up again... I couldn't face taking the tank off in the cold. I stuck a drinking straw down the hole & gave it some puff & that worked fine. The straw was an exact fit & can be pushed in about 2" or thereabouts so is now my new "go to" solution.

Had the tank off last week, though..... new clutch switch!!!

Cheers to everyone.....

Thank you all! I really appreciate it. I just found out what that fluid was, it wasn't fuel stabilizer. It was gearbox oil that got into the fuel/engine line. In checking the gearbox level after having some shifting issues a ton of fuel/gearbox oil came out, just as through the fuel cap. I'll put up another post with pictures to find out how this could ever happen. Last year a dealer re-threaded the gearbox drain plug. Could they have somehow drilled too far and caused this? What a mess.