I was hoping someone could give me some advice on my carb.

Problem: over the winter, my 2001 sp 400 would not start. I put it in my garage, heated it up - it still wouldn't start (and yes, it had fuel). I finally sprayed starter fluid into the air intake and with full throttle, it started - however, it wouldn't stay running without pressure on the throttle. I cleaned the carb, checked the fuel filter, cleaned my K&N air filter, and adjusted the idle, and it would stay running, but when I would ride it for a while, the idle would rev up a bit...I adjust the idle down and it would run just fine, but when I start it again (cold), I have to adjust the idle back up to keep it running (can you say run on sentence?).

Any advice? New needle valve? Jets?

 

Have you ever had the valves adjusted on it? A tight intake valve can cause it to act like this.

 

When you say you cleaned it, do you mean that you took a apart and cleaned it, or just sprayed some cleaner in it? It sounds like your jets are dirty to me. Goto my gallery and there is a link for the Mikuni carb manual .pdf at the top of the page. Should have everything you need to know about your carb...

 

No, I haven't touched the valves.

 

This is a 400 I believe...
It doesn't have valves that would stick... 2-cycle

 

Redbullssg,

Cleaning for me was taking it off of the manifold and spraying it with carb cleaner. I'm pretty much mechanically retarted, but doesn't a 4-stroke have valves?

Thanks for the carb manual![img]i/expressions/face-icon-small-happy.gif[/img]

 

The 400 Sportsman does have valves and it is a 4 stroke. Check the throttle safety thing inside the throttle cover to make sure there is a gap between the connectors as well. I forget what they call this adjustment but it can loosen up and keep the quad from running right. Then I would check the valve adjustment. If you take off the timing chain inspection plate and valve cover you just ling up the motor to TDC by aligning the two horizontal lines on the cam shaft gear with the horizontal line of the case and then check the valve clearances with a feeler gage. The valve lash is supposed to be .006 on intake and exhaust. Just insert your feeler Gage and adjust the valves until there is a slight drag on the feeler gage.

Don't attemp this unless you think you can do it as engine damage can occur if you do it wrong.

 

Oh, I thought it was a sport 400, I will insert my foot again, god I keep doing this, LOL!!!

That manual is for the sport or scrambler 400, and I am not sure if it is the same as the others. It may be, you would have to compair. It is the same as the 500 I believe...

 

Actually it is a 425 named a 400 they are 4stroke

 

What I would do...if your having these problems....take the carb off...take out the pilot and main jet and clean them with some gunkout...clean the float bowl....then I would make sure you have a good clean air filter on it.....and also, if you had your quad sitting for a while...maybe the gas has some moisture in it..........I would drain the gas and put some fresh in (even though that right now would be a little expensive with these gas prices!) After that...see if she runs better..

quadracer