I have a 2005 Eton Viper 90R that is stock. The only change I made is I installed a pod filter on the atv. Now I am having problems with the jetting. The atv accelerates fine up to about half throttle then it wants to die. I changed the main jet from a 85 to an 90 but it only helped slightly. Then I tried adjusting the needle in every position posible but it didn't help. Does anyone have any ideas how the carb should be set up?

 

Way too lean. You'll need about a 120-150 and more than likely you'r carbs float bowl is gonna run out of gas about 30 feet out and it will die. I hate to tell you this but I'd put the stock filter back on.

 

motokx250,

Fastestdad is correct. If your engine starts to bog or cut out when going above 1/2 throttle, its running way too lean. Stop driving it above 1/4 throttle. If the spark plug is white, has white specs or your engine smells hot, stop driving it. Check your spark plug now!!! If too lean (which it sounds like it is), it will burn a hole in the piston when driving above 1/4 throttle. Or, it will over heat the rings and score the cylider walls.

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Here's a couple of options to consider:

If into racing &/or extreme trail riding, replace the stock 18mm carb with a 20mm carb. Many racers love the 20mm carb because of its low end and high RPM range. Some folks do run larger mm carbs but the 20mm carb has the best overall range - for the 90cc 2 stoke engine. When you upgrade to the larger carb, install a new matching mm intake. Then install the upgraded air filter system with proper outer wear. While doing this, many install a single throttle cable (and remove the OI system) and install a NEW cable that fits the new carb size. If wondering, WRH Racing at http://www.wrhracing.net/carb_kits (and other performance shops) offer a Carb Upgrade bundled kit. All parts are matched and proven to work together.

If into trail riding that has small amounts of water and huge performance gain isn't a concern, leave the factory carb and factory air box "as is" and silicone the heck out of it. If dustry trails, oil down its internal air filer material. If wondering, I use Bel-Ray Foam filter on my son's '03 Pred-90 factory air box filter material. This special oil helps trap the dust - that enters into its snorkel pipe. Here's the trick with the factory air box. Replace or cut the factory air box snokel so its much shorter. Say, only 5" long. Take a small rubber hose and slide it over the shortened snorkel pipe. The end of this larger diameter rubber pipe can be routed under the front hood area, or make it longer to reach mid way - under the gas tank area. This longer hose keeps it away from sucking dusty air from the left front wheel area. The longer the hose, less Main Jet size number needs to be used. If wondering, this is the method I used on our '03 Pred-90 factory air box. We had to upgrade from an 82.5 main to a 87.5 Summer and 90 Winter Main jet. In colder air or lower altitude, use are larger main jet size. For a picture of our modifed factory air box, surf: http://community.webshots.com/photo/...52910875iCaQAK

The other method is to leave the factory carb as is. Install the foam filter under the front hood and install a flex hose from the carb to the front hood area. Jetting will need to be done. The size of Main Jet increase depends on the wind drag within the flex hose, the length of flex hose and how much outerware is installed on the foam filter. Some folks install foam filter outerware and also install an old oiled down sock. When the sock gets dirty, they remove it, throw it away and install the other oiled down sock. Jetting will need to be done. If going above 90 Main jet size of 90 (if I remember correctly), the carb's Main jet inner hole and carb's float needle will have to be drilled out. One needs to use special size drill bits for this trick. Therefore, Fastestdad is correct in this area too. For a nice picture of this customization, surf: http://community.webshots.com/photo/...52910875vbjDzv

NOTE: Folks often use different flavors of the above options. Use the best option based on your unique riding needs and/or performance gain wants. When it comes to this area, there's no perfect answer. Although, each method will obtain more performance gain compared to the other. Regardless of the option you do use, ensure the end results is a dark brown to light black spark plug color in every throttle range.


Hope these options help.....

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I appreciate the info you guys gave me. I didn't realize it was going to be such a drastic change to put a pod filter on. 98% of the time the quad is being rode in the desert with dry conditions so I wasn't worried about water. I just wanted to install the pod filter because I don't like the stock filter and it looks restrictive. Now I know that it has to be restrictive for the carb to work right. I'm going to experiment with adding two old socks over the pod filter to make it more restrictive. From there I'll try some different jetting and If this fails I'll go back to the old filter.