2004 fuel leak

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Well-Known Member
Sep 29, 2021
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British Columbia
Hi guys,

My 2004 has been in storage, off the road for a few months now (all winterized, etc.). Went to start it the other day and noticed moisture on top of the rear exhaust pipes (was there while bike was sitting), above the swing arm, just after the pipes cross over. Upon further inspection, I believe the leak is coming from the fuel meter sender unit / gasket area at the bottom of the tank (great design Yamaha, thank you!). Checked inside of the tank, there is a small amount of debris, but cant see any rusting or major issues there (outside of tank looks good as well), so don't believe this is a carb overflowing problem (fuel filter was changed earlier this year as well). I can't see a way to get at the sending unit with the tank still in the bike...any thoughts on what to check or try for, or do I just need to remove the tank to do this repair? If so, should I look to refurb the tank and replace the sending unit at the same time?

Thanks in advance

If you have an OEM exhaust, it's going to be much easier to drop that and to reach the fuel level sender. Tank stays. I have a 4/1 and can easily reach the phillips screws.

VMax fuel sender switch.png
Good thought fire-medic. I have stock exhaust still, I'll take a closer look and see if that method will work best for this. Thanks
I just removed the sender on my bike yesterday, it was easy to do but I don't have a std exhaust.
it's a rubber oring seal, so if leaking probable needs replacing.
Hoo-hah, sure they are! But I think anyone knows that the phillips and JIS are pretty-much terms describing a steel right-handed threaded helical Archimedes tool with cross-head, for use in securing two objects in proximal relation to one another, using sufficient torque to prevent loosening of said objects during work and heat/cool cycles. ;)
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I only mentioned it as small screws (add the brake and clutch reservoir cap screws to the list) that are likely to have some corrosion are easily chewed up using the wrong tool.

Sure Phillips and pozi drive screwdrivers work, I've done that, but your best chance is to use JIS and press very hard, maybe tap the screwdriver with a hammer to prevent it slipping put of the screw head. A drop or 2 of penetrating oil oughta help.

Nuts and bolts were invented in medieval times, each one made by hand and matching so on disassembly, both needed to be kept together.

As you can imagine this adds time so during the industrial revolution a Scotsman, whose name escapes me, devised a thread standard so that any bolt will fit any nut (of the same size).
Other than the OEM toolkits bikes come with, I've never purchased a JIS screwdriver. I have clutch-head screwdrivers, used upon Detroit vehicles in the 1950's. I have multiple sets of screwdriver tips, including ones for security screws.

Years ago, I bought a couple dozen tapered flathead SS screws for the Japanese clutch and brake reservoirs, which I use to replace those OEM which become too-knackered to count upon to easily loosen. I've even used hex-head screws for replacement of the OEM's, and never had an issue with leakage. I suppose if you were doing a track day, where you were repeatedly hammering the brakes, you might get some seepage past a hex head screw, as the brake fluid heated-up.

There is a story about Samuel Colt standardizing tolerances so he could assemble pistols more-quickly, because of interchangeable parts.

Along the same line, Cadillac once brought several cars to the NY Auto Show (1903) and in a public display, workers disassembled the multiple cars into piles of identical parts, and then reassembled the cars. They started up and ran, without drama showing that interchangeability was beneficial. The brand gained a lot of respect for that.

The same display was later done in London UK. It won for Cadillac the Dewar Trophy (1908) so recall that, and offer a toast, next time you tipple a fine Scotch.

If you read the second link's article, you will see that attributed to Cadillac is the first use of Phillips screws in automobile production.
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I had the same issue, also found out the sender will not clear exhaust. What I did was remove the rear tire and liner for access, unplugged the sender harness and dropped the sender down. cleaned the old groove of corrosion and fitted the new o-ring around the sender body and reinstalled. (BWY that little o-ring cost me $14.00 at local dealer:oops:)
Joseph Whitworth was the 1st to have a standardized screw thread adopted as a national standard 1841. He was born in Stockport (Manchester) England.
Mass production of identical parts was 1st achieved in the manufacture of ships blocks (block & tackle) in England in the late 18th cent & into the early 19th.
Eli Terry (Conn USA) Pioneered the mass production of clock movements from c.1800 making 20,000 brass clocks annually by 1840.
Springfeild Armoury developed parts interchangablity & mass production to more robust engineering (muskets & rifles) c. 1850. Sam Colt borrowed from them. Henry Ford borrowed from Colt's (or Springfield - can't remember which) production line assembly methods but was the 1st to have a moving assembly line.

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