Fuel Leak. Help!

3 replies to this topic
  • bfox55

Posted May 15, 2007 - 10:39 AM


I have a slow fuel leak on my 99 YZ400F coming from the base of the fuel cock where it mounts to the tank. Originally, I repaired it during a day of riding with liquid gasket, that held for the rest of the day which was all I expected. The second time I repaired it with liquid gasket that was made to withstand fuel. That lasted about a week. So I decided to go to the yamaha dealership and get the actual gasket. I cleaned everything off and put it together. It didn't leak at all during the first ride over a week ago, but has just now started leaking again. Did I do something wrong? Is there a sealant I should be using in conjunction with the O-ring? Thanks in advance for the help.


  • grayracer513

Posted May 15, 2007 - 02:26 PM


I haven't seen it with a stock tank, but every once in a while you see one like this where the surface onto which the petcock seals is no longer flat enough for the O-ring to compress adequately. In that case, I have taken a large flat file (medium single cut is the best) and worked the area down a little until it was closer to flat again.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • fritzelman

Posted May 15, 2007 - 03:04 PM


I had this same problem sometime back, but all I did was replace that gasket and all was well. You might try a new O-ring and see if that might help. You might want to check the little spring that holds the valve to the casing. I'm not sure how your exact bike is setup, but my 02 426 had a little round bent medal washer that acted like a spring to keep tension between the valve and the casing. Just an idea.

  • Ga426owner

Posted May 15, 2007 - 04:02 PM


It happened on my 03 - tried to replace oring and worn parts, still leaked. Then I got smart and priced entire petcock assembly.....15.00. It was a no brainer and no more leaks

Related Content


Is it worth it? (Cam and High compression piston) by macgi77

Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies

YZ450F 03 Sparks driving me crazy by SirAttard

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F

Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies

Need help by Goforaride

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  68 replies

100 hrs on 2014 yz450f, shim valves or replace them? by ttr230rider6

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  79 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.