Yosh suggests two 1 3/4 holes and no snorkle. Where do you guys drill your holes (there's a joke there somewhere I know) in/ on the airbox. Any other suggestions if I'm removing the snorkle, such as the breather tube, what to do?
TIA

 

You might want to check a previous article in DW magazine(I forget which month), it says they lost or gained very little with holes but saw 3hp gain with removing the lid & going much bigger on the mains, just food for thought!

 

Check out page 134 of the March 2002 issue of Dirt Wheels. This is the article that Chimmer was talking about. In this article, they took a stock Raptor, with a stock exhaust and tried various intake and jetting mods to see how responsive the Raptor was to intake modifications only. On a Dyno, the Yoshimura's air box and jetting recommendations increased horse power by .6 hp at 4,000 rpm and actually lowered horse power by .6 hp at 6,300 rpm were max horse power is made. They determined, and I agree, that this is not worth the effort. They next cut the back of the air box lid off, leaving only enough to hold the filter in place and went to 160/165 on the jetting and saw nearly 3 horse power increase from 5,000 to 6,300 rpm. That was with the stock exhaust in place. You should just do what most people are doing and go with a Pro Design filter system, and leave the air box lid off. That way, you know you are getting at least a 3 hp gain.

As far as the crank case breather is concerned, I went to Checker Auto Parts and bought a small Fram crank case breather, part #BA3812, and a 3/8 inch hose clamp. This filter will plug right into the crank case breather hose on your Raptor and fits nicely. I plugged it in with the hose clamp in place, tightened it down and then secured it to the radiator over flow line that runs right next to it. I just took a small zip tie and wrapped it around both of them. Looks pretty good in that position (facing down) and works like a champ. I was disappointed to see that there was dust in the breather hose when I removed the little elbow before I installed the Fram filter. I don't understand why Yamaha would design it so that in can ingest unfiltered air. I know that it blows air out of the crankcase, but like I said, to my surprise there was a coating of dust in the line. Hope this helps.

 

Thanks for the follow up feed back. I drilled 8 1" holes in the top and popped in these grommets with a filter in 'em.
I do have the proflow filter and flange already. What's the skinny on prefilters- do they restrict the airflow significantly?

 

bump