I found a good deal on the KDX 200 on craigslist and picked it up. I was considering pulling the motor for another hybrid and then parting out the rest of the bike. The bike had several performance upgrades, mainly an AirStriker carb and a VForce3. I decided to pull those two items, replace them with my factory pieces and then sell the bike.
After removing the carb, I took it apart to clean it up. This is the carb completely disassembled.
After installing the VForce3 and the AirStriker, I went for several rides and the conditions were very, very dusty. After the 1st ride, I cleaned the air filter and greased the rim. During lunch on my 2nd dusty ride, I went to swap main jets and found a lot of dirt in the bottom of the float bowl cap. Once I got the bike home and cleaned it up, I removed the air box from the bike and was expecting to find a lot of dirt/dust inside the air boot. To my surprise it was clean.
Spending some time doing Google searches led me to some posts of CRF 250 owners complaining of something similar. They tracked the problem down to dirt being sucked in through the vent hoses.
Sure enough, that is how dirt got into my carb and engine.
This is what a q-tip looked like after going in one of the lines:
And this is what a container looked like after I flushed all the vent lines (the AirStriker has 4) with carb cleaner:
There are some specialty filters you can buy, but they are pretty expensive. A cheaper route was using some model airplane fuel filters. These are rebuildable and come with a fine wire screen. I replaced the screen with some air filter foam.
I went on a few more rides and didn’t see any dirt in the vent lines between the carb and the filters. I opened some of the filters up and verified that dirt was still trying to be sucked up, but was being trapped.
I was pleased that I had stopped dirt getting in, but I wasn’t happy about having to use those filters. For kicks, I put the factory reed valve back in the bike and I cleaned out the foam pieces in all four filters. After several more dusty rides, I opened up the filters and didn’t see any dirt.
The VForce3 was in good shape, all the reeds were flat and weren’t frayed. Instead of taking a chance on buying a set of reeds for the V-Force, I found a set of 607 Boyesen reeds on eBay for a good price.
I had an extra #5 slide that I sent to RB Designs and had it machined to a #7. The #6 slide from the AirStriker is on the left, the new #7 is on the right.
It doesn’t look like a big difference, but it really cleaned up the off idle performance.