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Hard starting after installing mikuni pumper carb

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Hi everyone this is my first post but I have been reading this forum for a while now.  The most useful info on the web.  I just bought an 04 xr400R and I couldn't be happier.  When I got it, it was running wierd and took several kicks to get it running.  I started reading a lot on here and figured rather then buying a rebuild kit, I'll just buy a mikuni pumper for the power increase and ease of starting.  I ordered from xr's only and had to email them because I never got the package.  They told me carbs were on back order, so I went a head and pulled the stock carb apart.  I cleaned everything several times and set the float height dead on.  Wow I couldn't beleieve it the bike starts first kick weather its hot or cold and even if you dump it.  Most of the time it will stay running when you dump it.  Now thats why I bought a honda, cause they're reliable and user friendly.  Anyways, I e-mail xr's only to tell them they can keep they're carb, I'll sacrifice the power increase for a bike that runs this great!  Two day's later they send me an e-mail back saying they just sent out the carb.  I pondered for weeks weather to put it on or send it back, and I figured just put it on, I've heard lots of good things about the Mikuni.  Now my bike starts like crap! It will start in 2 to 4 kicks with the choke/start circuit on, but takes probably 10 or more kicks to start when its hot.  The pilot screw runs best at 1 to 1.5 turns out.  I saw lots of threads on here similar to this one, but none that said its hard to start hot.  Anyone have any advice before I put the old carb back on?  Other then starting, it runs pretty good.  I don't feel like it idles as smooth as the old carb, but when you pin the throttle, you can't keep the front wheel down!

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That's what I'm worried about with a pumper carb, I have an 03 x4 and it's awesome of course, but it WOULD be nice once in awhile to get better power up hills and to conquer the wheelie! It sucks that now your bike starts hard, I don't know what would cause that other than a loss of fuel, pinch, leak?? Hope you figure it out.....but, all in all would you recommend the new carb on your bike? If you were to get the hard start issue worked out, are you just kind of happy or really happy?

Thanks, cheers!

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It's tuning, not a flaw.  I'm in the same boat with mine and need to swap pilot jets and adjust the screw, just haven't had time to mess with it and it runs good enough.

To me: it's $200 mod nice (buying used)

Not $400 mod nice.   (buying new)

If that makes sense. Everyones dollar amount of what is "reasonable"  is different. I do quite a few myself. It's very noticable, but it's the not liked you added cc's.   ;)

If you are happy with the bike as is, it's not a "must do" like tuning the suspension is.  

Edited by MindBlower

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I agree its worth 200 bucks.  probably not 400 unless you have money burning a hole in your pocket. 

 

So you think I need to swap pilot jets?  Thats what I was thinking but wasn't sure what size to go to.  weather to go up or down in size.  And do I have to swap the main jet also if I change the pilot jet?  I'll have to check what additional sizes they sent me, maybe I can use those.

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They usually set them up with 15 pilot and 130 main. Only if the rest of your bike is 100% stock would I suggest leaning it out.

How are you starting it? The mik is a little different technique. I would cycle the kicker slow, looking for TDC. Then pull in CR handle so you can bump it past there as little as possible. Then give the throttle 1 quick twist to approx. 3/4 open, close it and now leave it closed then give it a good solid kick.

Make sure fuel screw is around 1.5 2 turns out, pump timing is set to come on as late as possible (bottom out screw), you don't have any air leaks and the pump spray nozzle sends gas stream right at your needle.

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This is what I was pointed to when I posted about my poor idling.  Very nice.    http://www.zodiac.nl/instructions/234862.pdf

With snorkel pulled, Uni filter, and free flowing exhaust it was reommended that I needed to go up on the pilot jet size, so I bought 1 and 2 sizes up  but haven't messed with yet. 

Edited by MindBlower

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First off I really appreciate the help guys.  I am new to this and sounds like I might be starting it wrong.  Like I said after going through the stock carb it started first kick everytime no matter what.  I'll tell ya I was close to throwing my bike off a cliff today when I was in the middle of the woods kicking it 50 plus times because of the "upgraded" carb.  I have the pilot screw set about 1.5 turns out but I had the pump set to come on immediately.  Sounds like thats something I should change.  I thought I read somewhere to set it up like that.  Also I havn't checked the spray nozzle.  You can spin it with pliers, right?  I never checked the float height either which is what I was thinking the problem might be.  I know anything will run poorly if the float height is off.

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Pump needs to come on as late as possible, definitely change that. Bottom that screw out on the spring. 1.5 turns out is a good starting point on fuels screw. Search on here for the XR starting drill. Makes life much more enjoyable. The 2 main points for you will be to always kick from the hard spot in the stroke (TDC) and to not give any gas when kicking. Give it 1 quick squirt of gas just before you kick then do not do it again even if you have to kick 2 or 3 more times. Good luck!  :thumbsup:

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I trust MI400 and know that it must be my  mis-tune but giving any gas to mine before or during kicking is asking to kick it 10 more times.  JUST like it was with the stocker.  LOL

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First off I really appreciate the help guys.  I am new to this and sounds like I might be starting it wrong.  Like I said after going through the stock carb it started first kick everytime no matter what.  I'll tell ya I was close to throwing my bike off a cliff today when I was in the middle of the woods kicking it 50 plus times because of the "upgraded" carb.  I have the pilot screw set about 1.5 turns out but I had the pump set to come on immediately.  Sounds like thats something I should change.  I thought I read somewhere to set it up like that.  Also I havn't checked the spray nozzle.  You can spin it with pliers, right?  I never checked the float height either which is what I was thinking the problem might be.  I know anything will run poorly if the float height is off.

Yep.  Knowing I have a perfectly setup stocker that starts 1st or 2nd kick setting in a box makes it a bit annoying. I just haven't been in that situation or I'd have probably swapped it back and sold the pumper. As is, haven't ridden it much, so it hasn't annoyed me. Much.   ;)

And the increased response makes it seem worth ironing out. 

I'll get around to it now that we're talking about it!  LOL

 

Mine is popping on decel unless the screw is almost 3 turns out, which I'm told means I need a bigger pilot jet.  (it's all greek to me) 

Edited by MindBlower

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I should add that was intended for for cold starting, I would give it 1 quick twist before I kicked then that was it. Warm starting, no gas at any time. Most important part is kicking from the right place of the stroke.

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Mine is popping on decel unless the screw is almost 3 turns out, which I'm told means I need a bigger pilot jet.  (it's all greek to me) 

 

There's nothing wrong with three turns out if you like the way it runs.  

 

I went from there to a larger pilot with one turn out and will probably switch back to the smaller pilot and raise the needle one notch.  

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There's nothing wrong with three turns out if you like the way it runs.  

 

I went from there to a larger pilot with one turn out and will probably switch back to the smaller pilot and raise the needle one notch.  

Interesting. It runs fine once warm, just doesn't start as easy as the stocker cold or warm. And idle is a tad iffy. 

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