1996 XR400 Carb swap to 1998 XR 400 Carb

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#1
Hi guys, this is my first post here. I have a 1996 XR400R and would like to swap my stock carb to a 1998 XR400 carb. Will I get a cleaner and smoother running motor? Are there any problems or will it just bolt on? Any help would be appreciated.
 
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#2
It might run a little better. It should bolt right on. I wouldn't do it unless it was free or very cheap. You can get the same needle in the '96 carb as the '98 and it should then be the same carb.
 

mtngoat

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#3
If the 98 carb's been sitting around for a while, you may introduce other annoying problems. Also, the 98 carb is jetted a lot leaner and if you have typical airbox/exhaust mods, it will probably be too lean. The 98 carb has the A16A dual taper needle (if it's a 49 states/non-CA model), which is desireable. I wouldn't do this swap as a short-cut to setting up your stock carb properly. If the 98 carb is free, you might cannibalize some of the parts though.

There's lots of XR jetting info here. Just search for it.

Here's a link that explains the component differences between the carbs and offers set-up guidance:
http://john.rushworth.com/Motorcycle_Co_UK_archive/xr4faq/
 
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#4
Thanks for your replies. I bought the used carb for $32.00. I will clean it thoroughly then bolt it on or should I just change out the needle and slide and install in my carb?:cool:
 

mtngoat

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#5
I'd change out needle and slide on your 96 carb and then tackle the jetting. Write down your main/slo jet sizes and post with all mods on your XR4, with your typical riding altitude and temp.

BTW, the link above also has correction factors for jetting.
 
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#6
I live in the panhandle of Texas at 4,000 ft. elevation. The stock carb has 160 main and the stock pilot jet with the needle in the middle or stock position. We ride in the mountains of New Mexico during the summer at between 8,000 and 10,000 ft elevation. I was having rings put in the 96 and decided this would be a good time to "upgrade" my carburator since all that I had read says the 1998 carbs and up were better than the 1996. Mine is certainly fat in the mid-range at the higher altitudes, so I was going to have to lean out the needle anyway. These carbs are so hard to get on and off that I don't want to have to mess with the needle anymore, so I think that the 1998 carb with the needle in the next to the top would hopefully fix the problem. Do you think I would be better off to just take the needle and slide from the 1998 carb and insert it into my 1996 carb? Thanks for all of your help.
 
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#7
Hello,
I don't think it really matters if you swap the whole carb, or just change the guts. You can swing the rear subframe up and expose the shock, and pull the carb from the right side of the shock. It is still a pain but is possible.
I have a 96 also, I put on an XR's Only competition exhaust and a UNI filter with the snorkel removed from the airbox. Xr's Only recommended 160/60 jets, down from 162/62 stock (I'm at sea level) and she responded well. It will still bog if you whack open the throttle from idle, but througout the rest of the rpm range she pulls crisp and clean. I'm also considering the dual tapered needle and slide, however, I hear that no matter what you do to the stock carb, it still bites. In the long run, I think I'm gonna try a Mikuni pumper carb. Supposedly, it's like night and day the difference it makes. Good luck and keep on thumping.
 
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#8
I can remember a fix for the early 400's Something about cutting a short length of fuel hose and fitting it over the main jet. I'm not sure exactly what they did to fix it in '97.
 
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#9
I don't recall the fuel hose over the main jet advice, but there were a number of things recommended by Honda's Bruce Ogilvie in a Cycle News article from Oct. '97.
The jetting he suggested (#158 main, #60 pilot) is for bikes with the baffle still in the exhaust.
The A16A needle (part #16012-NKK-000) that came stock on the '97's was a necessary change for '96's. As was limiting the travel on the floats to 19mm instead of the stock 25mm.
The '97's also had stiffer clutch springs.
With a K&N filter and Thumper insert, I run a #155 main jet with good results.
The Cycle News article is no longer achieved, please contact me if you need more information.

DAVE
 
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#10
Snaggle,
I have a 96 XR 400, Xr's Only Exhaust, Uni filter, and Pumper Carb. The bike is night and day difference from the stock set-up. I put all these accesories on at once, so I don't know how much difference the pumper carb makes by itself. It doesn't scream like a 250 2-stroke, but it's a great woods bike with good throttle response. I don't think you would be disapointed with the pumper carb, although it's pricey. Xr's only pre-jets the carb for the area of the country you will be riding and also sends some extra jets so you can fine tune if needed. Mine was jetted spot on when I got it.
 
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#11
Is the '96 and '98 carbs identical with the exception of the needle and slide and of course different size main and pilot jets? If so, maybe I should just put the needle and slide from the '98 into my '96 carburator. Anyone have any thoughts about this? Thanks so much for all of your replies, I certainly appreciate it.:)
 

mtngoat

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#12
There are some other minor differences explained in the above link. I'd swap in the slide and needle. I run the dual taper in the middle position for 7-9000' riding and it works fine. Based on your starting altitude and assuming hotter temps and typical mods (open airbox and exhaust), the correction factors would put you in the 155m and 55p "starting" range (the correction tables can be linked from the above link). This errs a little on the rich side (based on above assumptions), but you should be alert to lean symptoms nonetheless. Give it a try and post back. Changing main/slo jets is pretty easy making further tuning simple and worthwhile.