rev limiter or jetting problem on xr4? plz help


Mar 19, 2001
Hi, I've got a california model '01 xr4. I just installed a xrs' only pumper carb, 14 tooth front sprocket, an white bros pro meg pipe. K&N filter an removed the snorkel. Xrs' sent me the carb with a 130 main and 17.5 pilot. My bike maybe has 15 hours on it. It pulls like crazy until I peg the throttle, then sputters. Am I hitting the rev limiter or do I have another problem? I checked the valves and they are fine.


Mar 16, 2001
Sorry, I don't have an answer for your problem, but I was wondering how you like the mods you did. I have the same carb and pipe on the way in the mail for my 98 XR400, and have already done the snorkel/filter change. Other than your current problem, which I hope is minor and temporary, what is your opinion of the carb and pipe?

Thanks, and good luck!


Aug 22, 2000
Have you tried a smaller mainjet? It may just be too rich.

XR's only should have info on jetting for different situations, although it's impossible to know how "brand X" carb will work with "brand y" exhaust system. The carb may be jetted to go with a bore kit, or some other mod and may be too rich.

If it's popping thru the pipe it's probably rich (or hitting said rev limiter), if it's coughing thru the carb, it's a lean condition.



Feb 24, 2001
i have had similar problems on my dr and it was the carb. take your carb apart and carefully inspect and clean it. if that don't help check you plug. you can usually tell what your problem is if it is a carb prob by looking at the plug. If it is really brown or tan and burnt looking=lean, if it is black and carbon looking=rich. nice deep brown and electrode is good, than it is electrical. other than that i dunno.

90 dr250
94 ktm 125


Feb 12, 2001
Hey xr owners!
Sorry, I know this is a bit off topic,BUT...
If you haven't already done so, pull the header pipe off and look just inside the inlet ends of the pipe.(I'm sure this info's been posted here before, i saw it on another site a while back) If the welds inside yours are anything like mine, you will be truly amazed at what you are looking at.Mine were so big and sloppy that they reduced the inside diameter by almost HALF! After grinding most of them down(almost 2 hrs with a dremel) the bike runs MUCH better on top. I added a muffler at the same time, so I can't say just how much it helped, but I would bet it helped AT LEAST as much as the new pipe. Anyway, sorry if I'm repeating old news, but WOW. I don't see how any of these bikes can run right with garbage like that in the pipe, no matter how much money is spent on hop ups.

'97 cr250
'00 xr400
'00 Buell x-1


Jun 12, 2000
Sounds like your main jet's not right. Try flicking the choke to the half position. If that inhibits some of the sputtering, go with a larger main; if it makes it worse, go the other way. BTW, if you haven't called xrsonly with these symptoms, do that first. One other goof I've made on K&Ns is to oil before the guaze was dry. I discovered a damp K&N oiled restricts airflow significantly.

[This message has been edited by mtngoat (edited 03-28-2001).]

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