I have a 1998 Scrambler 400 "stock". I did a plug check & it was "BLACK".. I"m wondering if this machine is jetted rich from factory so the motor will have a good break in?? has anyone else had this problem with stock jetting on this machine? if so what changes did you make [drop one on the main etc..] I live in Wisconsin. Thanks alot for any help you guy's are great!!

 

Yes they are jetted rich from the factory to work in all kinds of elevations and conditions. They still run really well with them being this way. Is yours running poorly?

 

No, I wouldn"t say it's runing poorly. But you know how it is with a 2-stroke if the plug is black your allways thinking I can get this thing to run BETTER![img]i/expressions/face-icon-small-smile.gif[/img]

 

Do you know what jet is in it now? I had a 240 in mine. When I put the Boyesen Rad valve in I actually had to jet it down to a 210. I wouldn't suggest you doing that though. Look adn see what you have and then change the plug and do a plug run with the new plug and see what you get. If it turns out to be dark brown or black then I would say that it is rich. Then you could go down to the next jet down. And do another plug check. Just be carefull when doing so. I know everyone wants the most power out of their bikes but with two strokes you just gotta be carefull cause you can burn one up real quick. But I'm sure you already know that.[img]i/expressions/face-icon-small-smile.gif[/img]

 

My manual say's that the stock main is "230" The carb has never been touched so I would asume that is what is in it. What about adjusting the needle one notch [lean] or would just droping one size on the main be all I need to do? Thanks again!!!
PS: What in the word is the best way to get at the carb to change the main ?? I can hardly see the dam thing!!

 

Try a new plug first. Sometimes when you ride at slower speeds the plug tends to be wet and have a darker color. I wouldn't do any changes until you change the plug then check the color at wide open throttle. The way to do this is to have the engine already warmed up with an old plug then change out the old one and put in preferably a slightly used plug that has some color already(not mandatory just recommended) then run the bike at wide open throttle for about a 1/2 mile or so then kill it while you have it still penned then let the bike come to a stop then take the plug out and see what color you have on the plug. You need to have a medium to light brown color. If it's a really dark brown or black color then you are rich and then can jet accordingly. I wouldn't want to just say "put in this jet" cause I might do you a disservice and something could happen to your bike and I would feel really bad because all bikes are different and that's why it's so important to do the plug checks before you just put in a smaller jet. You may know all of this already but just thought I'd throw it out there anyway. Good luck with it and if you need any more help just let us know.

 

be sure the air filter is new or brand clean before droping the main,
then if it still look black drop one at time,stock is 230 main,
the most restriction come from the airbox doing richer mixture through
the carb,or drop a k&n air filter in the box,that will easier to lean out
and gain some more output.

 

They already told you good info. I have seen a 230 and a 240 in stock machines. 240 in a 97 and 230 in a 99, and 01. It may be your oil as well. The cheap stuff works fine but smokes a little more/blackens plugs some more. Maybe oil?

 

I agree with the Duneman.

Also...
If it runs fine and is a little rich and if you ride in cold weather or in the winter there in Wisconsin you might want to leave it so you dont need to rejet between seasons or risk blowing it.

Jim

 

I raised my friends up a clip on the needle from factory he says it runs alot better just my 2 cents