Does anyone out there know where I can get some detailed information about jetting my Scrambler400? I would really like to do the work myself and get to learn a lot about both my machines at the same time.

Are there any articles available? Kind of like what Mike Chero wrote about pipes and clutch kits on another site. Before reading that I had no idea how a pipe worked in detail. As the saying goes "we learn something every day"

Any help would be appreciated. Even if someone has to write a dissertation here on ATV Connection. That would be great!

 

Xplor,

++Try www.off-road.com in the atv sections. They also allow you to look through all their old mags. as well.

++The june 2000 atv sport mag has an article on "becoming a carb. guru"

++I have heard that AAEN has a book on carb's and making adjustments.

These are just off the top of my head, but worth a shot.

Erin

 

Thanks a million Quadbuster!

 

RCR Racing

 

Xplor -

Go to atv connection's front page and click on tech connection. Then click on advanced search, and search that way. You can select "carburation" and "all quads." You will find at least a 100 questions asked and answered about jetting. You will learn more than you'll ever need to know!

ogre

 

Xplor,

I'm new to 2-strokes, but have recently learned something about jetting. When changing air filter system or exhaust system, you need to change the main jet. The correct way to do this is to buy a range of jets around the stock size. i.e. if your stock jet is a 210(stock on my Xplorer 400), and you're going with a high-performance pipe, buy 220, 230, 240, 250, and 260 main jets. Put the 260 in with the pipe change, and run the bike. Keep in mind that the main jet only comes into play from 3/4 to wide open throttle (WOT). The main jet is the only one I have information on for now. Pick a long straight to open the bike up all the way. If the bike "blubbers" at WOT, go down one jet size (go to the 250) and check again. Let me back up a little to tell where the main jet is located: For my Xplorer 400, I had to remove the air box, and loosen the clamp at the front of the carb to access it. Once you have the air box removed and front clamp loosened, you can pull the carb out(leave the throttle cable and vent lines intact, as you don't need to take them off. Remove the 17mm bolt from the bottom of the carb(when reinstalling, you need not overtighten this, since it is an o-ring seal, only needing to be snugged to seal. Overtightening can strip the aluminum threads in the bottom of the carb). Once you have removed this nut, look into the bottom of the carb, and that brass piece with the hole in the bottom is the main jet. Remove it and replace with another size. Use a 6mm socket on the end of a nut driver. Don't overtighten the main jet. Just a snug fit will do.
All right, back to jetting: Keep going down one size on the main jet until the bike no longer "blubbers" at WOT. Don't go down any further, as engine damage could occur.
I installed a Boyesen Rad valve, and it required going down on the main jet from the stock 210. The rad valve change is the only modification that I know of that requires a smaller main jet. Pipes and air filters that flow more air always require a larger jet. I hope this helps you.
BTW, using genuine Mikuni jets will run you about $5 each, while using aftermarket jets could run as little as $1 each. Your choice, as I don't know any downsides to running aftermarket jets.

Later,

Waylan

 

Tomorrow I am probably going to take the Scrambler to the shop to check the jetting and clutching, until I learn to do it myself. I tried yesterday and noticed that my plug is all black...is that rich? Can this harm my motor or just kill performance in certain power ranges?
By the way, this dealer is downtown and has no wide open areas to test out the WOT....Just how do they accomplish this in the shop? The wheels jacked up I suppose?!