99 yz400f

8 replies to this topic
  • mespey08

Posted August 05, 2011 - 10:43 AM


Hello Everyone, I am new to this forum and got to say I already like it more than any Forum I have joined before.. Alot of information.
So I just picked up a 99 yz400f. I changed the oil it was pretty black. I changed the oil filter and air filter as well. I changed the fuel line, and lines around the carb too. The 1/8th lines. Not sure what exactly they are. What else should I check or change? The radiator is full of fluid in it as well. But does look murky should I change it? and if so how?..
Also, there is a long black line that goes down the left side of the bike that does not look good. Can I like reroute this line to the airbox?
And can someone send me a link where to purchase some cool graphics for this bike at. I have some on it but just the sides not on the tank or anywhere else.

Thanks a head of time for the replies.

  • Stinger1133

Posted August 05, 2011 - 02:25 PM


Welcome to the forum. The 1/8th inch lines coming from the carb are overflow lines. The radiator fluid is good to change atleast once a season in my opinion. As far as the long black line on the left side of the motor, Where is it coming from ? Ebay has quite a few graphics kits available for it also. Post some pics of the bike if you can so we can see your new toy. :eek:

  • grayracer513

Posted August 05, 2011 - 03:22 PM


The small hoses on the carb are vents except for the one at the bottom of the float bowl. That one is the overflow and drain hose.

The 12mm black hose of the left side of the frame that comes from the cam cover is the crankcase vent tube. It's fine where it is as long as you remember not to submerge it in water or very fine dirt when you shut down or restart the engine. If you route to the air box, you'll need to install a filter on it, since doing so will shorten the hose excessively.

  • Stinger1133

Posted August 05, 2011 - 03:31 PM


Hey Gray, I am curious where is a good place to route that hose anyway ? I am also new to the 4 stroke bike world. Mine goes down right in front of the engine by the oil hoses. I trail ride alot and sometimes water crossings are deep. Not submerged motor deep but atleast shifter deep sometimes.

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  • hende

Posted August 05, 2011 - 03:38 PM


I have got 2 diffrent graphics kits off fleabay and both did not fit my 400 right but with triming i got them to fit the rad shrouds where the worst..

  • grayracer513

Posted August 05, 2011 - 03:47 PM


There's a posting in Common Threads about that. IMO, the easiest and most functional way to modify the stock setup is to install a T fitting near the top, wit the T oriented so that the existing downward leg of the hose still exists as is. The stem of the T would then be routed back to the air box with a simple breather filter on the end to prevent the fine dust at that point from getting into the engine.

This will allow exhausted oil to run down and out without intervention, but any effort to suck water or whatever else up the hose would be spoiled by the air drawn in through the air box leg.

The ultimate setup would, in my view, have a check valve in the T, allowing air out only through the lower hose, and in only through the upper. Then the upper could be tapped into the air boot and draw only filtered air.

  • Stinger1133

Posted August 05, 2011 - 04:58 PM


I read the common threads post but I actually like the way you just posted better. I will do it this weekend. Thanks alot Gray.

  • mespey08

Posted August 05, 2011 - 07:37 PM


So I changed my oil. I know the bike calls for 1.7q after an oil change if you replace the oil filter which I did.. Can someone please tell me how much 1.7 quarts is exactly. I know on the side of the yamahlube quart bottles it shows like q and numbers going down. Where should I stop at putting the second quart in at? If you get what I'm asking... Thanks.

  • grayracer513

Posted August 06, 2011 - 06:21 AM


A quart = 32 ounces

32 x .7 = 22.4

Take the second quart and pour 22 ounces into the emptied first quart, then dump that into the tank. Start it, run for a minute, check the level.

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