1999 yz400 questions


7 replies to this topic
  • bhsballer76

Posted November 04, 2007 - 01:59 PM

#1

So i bought a 99yz400 a few weeks back and i have a few questions. First is that i nocticed that the exhaust has a prettty large dent from the rear tire hitting it. Also after i took it out the first time i noticed that there were tire marks on the exhuast. The first time out was mostly whoops and trail type riding. So i am wondering why my tire it hitting my exhuast and what can i do to fix it. btw im 6'2 and about 230. Also, the clymers manual says the bike needs 95 or higher octane. Is this neccesary? what do you guys run in your bikes as far as fuel goes?

  • USED YZ426F

Posted November 04, 2007 - 03:02 PM

#2

Not sure about the tire problem. Can you post some pics of the dent?
As far as the fuel, I run premium (93 octane) in my '00 426 and it has no problems. I wouldn't run anything below 91 as these engines are pretty high compression and performance. Running the cheap gas is just asking for problems IMO.

  • jbrooks26

Posted November 04, 2007 - 03:58 PM

#3

The tire rubbing the exhaust is most likely due to a bent subframe. You may be able to straighten it since the 99's have a steel subframe, looking down the fender from the rear, you will be able to see the bend. Pretty common actually. Hope this helps.

Josh

  • grayracer513

Posted November 04, 2007 - 05:30 PM

#4

So i bought a 99yz400 a few weeks back and i have a few questions. First is that i nocticed that the exhaust has a prettty large dent from the rear tire hitting it. Also after i took it out the first time i noticed that there were tire marks on the exhuast. The first time out was mostly whoops and trail type riding. So i am wondering why my tire it hitting my exhuast and what can i do to fix it. btw im 6'2 and about 230. Also, the clymers manual says the bike needs 95 or higher octane. Is this neccesary? what do you guys run in your bikes as far as fuel goes?

If the bike has a stock muffler on it, that dent was put in the muffler when it was made to provide clearance for the rear caliper. The tire conflict could be due to a bent subframe, bent muffler bracket, or an oversized rear tire.

There are two (3 actually) kinds of octane ratings, research, motor, and the average of the two, which is what you see on US gas pumps. The octane requirement is for 95 research octane, which is about equal to 87-88 motor octane, or 91 by the US averaging method (R+M/2). US pump premium rated at 91 or higher meets this requirement.

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  • 426 NOOB

Posted November 04, 2007 - 08:14 PM

#5

For gas, I run Cheveron premium and NOS octane booster. This usually puts me at about 98-100 octane. Hasnt pinged yet

  • grayracer513

Posted November 05, 2007 - 08:51 AM

#6

The octane booster is totally unnecessary.

  • bhsballer76

Posted November 05, 2007 - 12:23 PM

#7

thanks for the help, but what size tire should be on my bike? Also, will a bent subframe be a major issue in the future? I want to get everything right b/c i plan on taking it out this friday.

  • grayracer513

Posted November 05, 2007 - 02:02 PM

#8

The standard tire size is 110/90x19. Bent subframes are not big deal, really, if they aren't off by much, and for that matter, neither is a tire that rubs the muffler.





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