Didn't most of us plug this hose when we perfomed the smog removal mod? So maybe this mod is beneficial because it actually allows air to move rather than stop it??

 

actually mst of us should have drilled the airbox out where this hose goes...if we did our mods correctly

 

You're thinking of the one on the front of the engine near the exhaust port. This hose is toward the back of the engine below the carb and feeds into the airbox.

 

Well, I went out and re-jetted the carb with a 128 and it's so smooth right up to redline now. I'm very happy.

I might have been a bit stoked on the results, remember, I have been riding the stock bike we use at the school I teach at. The first time I've been on my KLX recently was right after doing the mod.

Man, when you get off a stock KLX250S and get on mine with all the mods in it, the difference is almost scary! The stock KLX will not spin the rear tire like the modified one. I was on a clay road - had just rained, so it was not loose. I was riding down the road, slowed down and whacked the throttle. The rear tire just started spinning like in right now! I kept it all the way to redline, then shifted and the rear tire kept spinning almost through half of 2nd. What a difference with the stock, unmodified bike.

I am really impressed with the mods after riding the stock bike so much!

 

I'm hoping to make it to the Tour de Pisgah in October, Marty and you'll be welcome to try out mine w/the 300cc kit. I think it's running pretty great now but maybe by then I'll have the new pumper carb and I'm anxious to see the effects of that. I've got an honest to god engine crank case vent on order and I'll be bypassing the airbox completely - no need sending that nasty engine stuff back up into the carb, IMO. This will increase the vent from 3/8" to 5/8" and was actually suggested by Jerry Leighton of Four Stroke Works where I've ordered my pumper carb. He is formerly of Stroker, the KLX300 gurus. I'll decide at that point whether I'll do your PCV mod or not. Chances are I will since I can think of no disadvantages to it and the logic behind it seems sound enough to me.

 

Brian,

I'll be looking forward to it.

I was planning on bringing a couple of bikes - the KLX and KLR.

However, since I won't have as much time up there as I want, it's going to be a Strom-Slabber weekend. I'll head out Friday morning at "O-Dark-Thirty" and ride the Strom up. Stay Friday and Saturday nights, then head south on Sunday about noon. New job, little time off.

 

Yeah, I googled the location and it looks like a 6 hour trip for me by interstate. Too far to ride my KLX I think so I'll be working on figuring how to get it there. I'll probably leave real early also on Friday.

 

I installed the mod using a Napa 2-9281 (Fits a 1970 Ponitac GTO), I used electrical tape on the ends to adjust the fit, secured it with 2 hose clamps, and painted it black so it would not stand out. I used the "hot drill bit" method outlined in a previous post and it worked as advertised. Just wanted to point out a couple of observations before you install the mod:

1.) The exit point in the air box is in front of the backfire screen, any debris from the drilling will be sucked into the carb if not removed and this requires removing the screen. The hot drill bit did not leave any debris when I did it.

2.) The PCV valve MAY act as a check valve in the WRONG direction should you ever lay your bike over far enough for the oil to run out of the crankcase. The oil will run into the airbox but may be trapped there because the valve seals in this direction and any oil that gets into the air box has a straight shot into your carb. You will have to remove the filter to really determine if you have a problem after a crash. The valve will hopefully restrict the amount of oil that is able to run out in the event of a crash.

Does anyone know if the gearbox is designed to prevent the oil from running out?

 

I know the airbox has a drain hole on the bottom, very close to the inlet for the crankcase breather.

 

So this is just a normal PCV valve, right? Is there anything special about that specific model that makes it better than another model, or is it just because this has an in-line hose connection, rather than some models that fit into a grommet in the valve cover? (Am I dating myself with that question?)

Also, is it truely dependent on gravity to ensure the 1-way valve action, or is there a spring inside (which would probably be better for our purposes)?

If there's nothing special about this particular model, and there are other models that have a form factor that's better suited to our bikes (e.g.: right-angle hose connection, same size hose connection on both sides, allows horizontal positioning, etc.), does anybody see any problems with trying a different PVC valve model? (Man, I'd hate to see this mod suffer the same part number / availability issues as the 13 tooth sprocket mod!!!)

Mike