I'm going to add a screen-type spark arrestor end-cap to my ktm 250xc(to be compliant here in SoCal). Would this make the bike run richer becuase it's more choked up-or not enough to require any change? Can I expect to see much in the way of performance change?
Screen type spark arrestors are extra maintenance compared to the turbo/cone style ones. If you are running a bit rich or do a lot of low speed riding, you will need to inspect and clean that screen from time to time, to keep it from getting clogged up. If it clogs up enough, you will see a marked drop in overall performance for sure.
I added a spark arrestor screen to a leo vince silencer on new to me wr250. On a really long, low speed single track section, off the pipe, it got clogged and I didn't know it. The rest of that dual sport ride I had zero top end power and lots of dripping at silencer to pipe connection. The screen was about 3/4 clogged with carbon. Since then, I bought an fmf with integral sa and bike runs great, lots of top end and no drooling.
Oh yeah, I didn't adjust jetting but cleaned it out. Also had partially clogged pilot. I read some threads about clogged sa screens. Some guys just jam a screwdriver through them to make a hole so it breathes more freely. Then, replace it afterwards.
when I ran a screen type, it was just part of my maintenance program, pull the screen and torch it with the blow torch when it looked to getting overly dirty and always before a race.
