Mikuni Pumper Carb XR 400

Hi guy's

Anybody use a mikuni pumper carb from XR's only on here. I bought one for my XR 400 and have had nothing but problems? It leaks bad, it idles irratically, the the throttle sticks, and it won't start for anything? By chance I bought another bike to back door mine in street legal and it had the same carb and it is a POS too. I did my homework and was sure it was the right thing to buy, but man what a waste of money?? Anyone else have the same experience

Sorry you've had such a time with it.

I can't say I've had trouble with mine. Sure, in the beginning I had a heck of a time starting it sometimes. Over a period of time experimenting, I found that most of the no noes for starting with the stock carb don't apply for the Mikuni. The starting routine we've all become accustomed to with the stock carb doesn't always work well with the Mikuni.

I too wish the XRs Only would lengthen their bell housing adapters by a 1/4" or so. They're too dam short and that causes difficulty centering the carb between the boots so that there's actually enough clamping surface inside the boots on each end to make a stable and leak free mounting. The first time I got mine installed and mounted stable and leak free, I marked a line on the rear bell housing adapter as a reference point from then on.

As for the throttle cables, just have to make sure you're using the ones in the kit from XRs Only and that you have them routed and rigged properly. If you can operate the throttle valve pulley by hand with out it sticking, then it's not the carb that's causing the hang up.

I have the Mikuni Pumper on my 01 xr400.. not sure if it came from XRsonly, since it came with my bike.. but, it is most likely from XRsonly. (assumption)

I have nothing but good things to say about it... well at first, something was up with it. (forgot what the symptoms were).. but, cleaned it out and it's been running like a champ.

Just today it started on the 4th kick(no choke) after sitting for a little less than 4 weeks. The gas is about 6 months old. :busted:

it's a night and day difference from the stock carb I had on my 98 xr400.. I remember it took 40 kicks after sitting for like 2 months

I guess YMMV, but, I'd suggest you rebuild/clean it and start from "scratch".

I doubt the throttle sticking has anything to do with the carb.. disconnect the cables and operate the "thingy"(where the cables attach on carb) by hand and see how fast it snaps back shut.

Every issue you are having, sounds the opposite of how mines been working out for me.

I love mine. I did have problems with the cables sticking, when first installed. I had to lubricate them and they've been fine since.

The only problem I had,was 12.5 pilot jet had to go up to 25 pilot,and change the adjust every thing on carb. For starting works great,runs great.Send me pm and I will help you with carb.

I don't know, I just have that kinda luck usually, I didn't have trouble with the rubber boots tho?? Go figure? I wouldn't buy another one, but oh well. Thank's for the replies.

My mikuni pumper carb work well on my Xr. Only needed one kick to start it most of the time, the most 2-3. Nv have to use choke at all.

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