Just picked up a 99 4x4 400 Scrambler.....goes great except from just under half to full throttle it bogs...Can anyone point me in the general direction for what the factory jetting specs should be? I'm right at sea level, so any advice on which way to go is appreciated..

Also, at idle the clutch rattles like crazy, but the instant the rpms go up it quiets down. I gotta pull the cover off to have a look-see, but was wondering what your thoughts may be.

And finally, what's the best way to modify the airbox? Drill a few holes in the metal cover but on the outsides of the filter?

Thanks a bunch!! And any advice on things to look out for is appreciated!!

 

220-230 main jet, but depending on elevation, 200 should clean up your "fat" jetting from Poo Poo. Make sure the air filter is clean. If it were me, rebuild the carb, that way you know what you got

 

I had the similar problem on my 2000 400 4x4. I was told to go to a 260 main with all the mods i have from aaen. It took me a while to realize it was running to rich on full throttel. I droped it to a 250 still no power really. I droped it to a 240 and it woke it right up. Front end comes up now. I live at about 500 above sea level and i still think i might drop to a 230 if i go up north. also i drilled holes in the metal cover also on the top side of the cover. It restricts you when going through deep puddles.

 

Well if I looked right I believe the main jet said 2.5

Anyway, I cleaned the carb, then found the plug cap kept popping off the plug and thought that was it but a new one changed nothing.

Also, the battery is completey dead, but I dunno if that would affect anything or not...

I'm gonna go pull out the filter and see what happens....That'll narrow down a carb or electrical problem, so long as it goes like hell

Thanks!!

 

OK That was easy....

Removed air filter and almost went over backwards....put air filter back in but left off the outer metal lid and same bog....

I just cleaned the filter and it wasn't too too bad....But I gotta let it dry out and see if that does anything..

Do the boots collapse on these like the 4-stroke utes? I revved it but couldn't see a whole lot happening.

 

Now do I wanna go full tilt and kill the ignition and let off the throttle at the same time to check the plug?

Thanks!

 

for a plug chop yes you do. If you know your needing to change jetting get a few new spare plugs and start with a new one when plug chopping.

 

Well I'll be damned, but a new airfilter fixed the problem. I also added a few holes to the airbox and ended up rasing the needle one notch.

And it had a 210 main jet, which I thought was odd being smaller than factory. Although I am in Maine at sea level and the fourwheeler originally come from Oregan....weird.