I have a problem riding my 400ex slow... Anything between 0 and 10 MPH it bogs and skips badly.. once the engine speed is up and Im moving it rips the front wheels off the ground, its a beast... and takes throttle and such with out a problem.. also It idles great....no wandering speeds or stalling....
I wonder if its my cam... It has a web cam 9i grind in it right now,
the other mods are a, .040 overbore with a hi-comp piston, k&n filter in the stock airbox(uncut) and a pro-circuit head pipe with the stock muffler (the pro-circuit can was too loud, so I took it off) I put in a 160 jet (148 is stock, it had a 190 in it!) that didn't solve it so I started playing with the needle positions...then I took the carb apart and cleaned it and set everything back to factory spec. I checked the cam timing, and The last thing I have to check is possibly the valve lash is too tight and hanging a valve open bleeding off cyl. pressure.... but after all I have done low speed performance still sucks...any ideas?

 

Next time you're out pulling slow wheelies, shut it off and pull the plug. The spark plug can be the window to whats going on inside your engine. If you have a manual, it'll help you in properly reading your plug. But long story short... by reading the plug will help you determine if the bike is running lean, rich, or hot.

I would also check the fuel lines and the floater in the bottom of your carb. Make sure the lines are clear and that the floater moves up and down freely. Good luck.

-Drew

 

How good was the accelerator pump working? sounds like it may be starving for fuel until it is able to run on the main jet.

 

change your blinker fluid, my girlfreind told me too a while back and ever since then nothing but good whoolies, then they got even better when i turned my choke off!

sorry brah got no idea

 

the worst part is that its so mind numbing... I have checked every thing.. and I know how to set up a carb.. I'm a mechanical engineer with a specialty in automotive powertrain design..I know my way around an engine.. I'm going to check the valve lash and check for vacum leaks again ...but i was hopping there was somthing dumb I was missing.... and I did check the plug, it was running a little rich...but that suprises me with the colder denser air and the mods with stock jetting..I would think it would go lean...and the acc pump is working well.. I did check that ...

 

What happens if you ease into the trottle at low rpm? still stall

 

yea, it still stumbles, I tried pumping the throttle a bit at low speed to see if that helped, it didn't make a diffrence...

 

Weird I got no idea try selling it on ebay???

 

no, I might just try putting in the stock cam though...

 

sURE YOU CLEANED THE CARB GOOD ??

SURE THAT THERE WASN'T SOME BAD GAS LEFT IN THERE OVER A SEASON OR SO ?

soory caps ??

when did this start happening ?

overflow tube is clean ?
fouled plugs ?? they are picky about good plugs !

does it all the time even after warmed up good ??

 

maybe an ignition problem? doesn't take long to get out a meter and ohm out your ignition just to know for sure.

 

put a for sale sign on it
when it's sold go buy a kfx or a ltz

Problem fixed

J/K

 

its maddning.. but in other news I picked up an un -modded 400ex las night for my G/f to ride... its like new with 90% tread on the orig. tires so I know there is a low speed prob now..hers is smooth at really low speeds..

 

http://www.webcamshafts.com/honda-atv.html

I have the 9i race cam(third cam down on the 400ex) .. that could be the problem with low end power..