After 1st ride I have a few ???

Joined
Jan 25, 2001
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#1
Hello,
today was my first ride on my new bike. A 1999 yz400f. I was riding a KDX 200 and then bought this beast. Today was my first time on a 4 stroke and I loved it. Anyway's I just have a few questions about my bike.

First, did the 99 have cooling problems or is it cause it was around 107 here today when i was riding. I came in from about a 20 minute run and I could here the water bubbling in the radiator. I had heard that the YZF's had cooling problems but I thought it was only the 98's? Also are there any signs I should look for that tell me the bike has overheated. Also what should I do when this occurs.

Secondly, The guy before me put in a 185 jet and it is way too rich. Do 4 strokes always hesitate when you are coming out of a corner and you pin it really fast or is that because it is running rich. The shops tell me about a 175 - 178 would be the right jetting for around here . Does this sound right? I am in Phoenix AZ and I have a FMF power core IV on it.

Thanks Alot
 

CRGuy

Posts Too Much
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Nov 14, 2000
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#2
Any rich bike will Bog out of a corner when coming on the throttle hard. A way to tell if it overheated would be if you ran it slow or if you can smell a burning or crisping coming out the exuast if it's extra crispy then you have a nice Burnt piston. Check the spark plug it would probaly melt if it was real hot! 107 that's crazy! I would lean the jetting out but the richer the better for hot weather. The cooler fuel will cool the Piston and crown and allow then engine to run cooler but when you give it less fuel ( leaning it out ) then it will run hotter but only by a degree or two. Leaning the bike out will save some fuel depending how far you lean it out. The KTM's in the paris dakar rally were lean so they could run on a tank of gas to each stop.
 
Joined
Jan 25, 2001
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#3
Thanks. Can anyone tell me if a 185 main jet is too rich or should i keep it in here for the summer? I would rather have it too rich than anything. Also is the FMF power core IV a good silencer for the 99. And in 99 did they have colling problems?
Thanks
 
Joined
Dec 18, 2000
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#4
KDX,

Before you start messing with the jetting, you need to figure out what is going on. Have you pulled the plug, to check for color? These bikes are very sensitive to jetting changes in all throttle positions.

For the overheating......if water did not "overflow" from the radiator and you did not hear the motor ping (detonate), you should be fine. Water does bubble in the radiator but, so long as it stays in the radiator, your ok.

Use the email address in my profile and let's see if we can help you figure out your jetting.

vetwfo'er