Smog block off

What a huge difference. The throttle responce is insane compared to what it was like. It honestly feels like it has more power. I would recomend this to anyone that has not done it. It feels like a new bike. Now it is time for a pipe. Which one is the best. I don't want it to loud.

install the DynaJet kit, and drill your carb. slide as directed in the instructions, for an even more significant boost ... personally, I run the stock muffler setup ... after studying every pipe test and dyno results, I find it ridiculous to spend $300+ to gain one horsepower, and if 3 pounds difference matters, I'll skip lunch ... the dirtbike muffler business is the biggest ripoff I have ever witnessed ... enjoy your pig

did you put on the smog block off by itself and it made a huge difference? or did you do the whole uncorking?

What is the smog block off?

I had it done for me. Just jet and took the smog off. What is the dynajet kit?

The smog block off kit is exactly that. You can buy it from xr's only and Baja designs. It makes the bike run like it is supposed to.

The smog block-off itself doesn't add any power, but it does relieve the popping on decel, and the occaisional very-low-rpm stall.

For the XR650L the baja designs/dyno-jet kit is not needed, and on some bikes doesn't work worth a damn. In my opinion, the kit is a rip-off and your money is much better spent elsewhere. Yes, some people use the kit and it seems to work OK. Some of those 'kit' people have done the mods with the keihin jets and have found it to be much better than the kit- myself included.

There is, however, a cheap absolutely-guaranteed recipe to wake the beast up. There are several converts on this board, and on other baords where I've been spreading this recipe.


You drill the off-center holes in the slide to 5/32 of an inch. There are 3 holes, one in the middle for the needle and 2 off to the side- drill the 2 not in the center.

THE NEEDLE: When you pull the slide, the needle is held into the bottom of the slide by a little yellow widget that you press down on and turn a little with a screwdriver or an 8mm socket. When you remove that, the needle comes right out. Notice that the needle sits in a small recessed section, a little well. Find a small washer that meets the following


1) is about 20-30 thousands of an inch thick.

2) fits fairly snugly over the needle at the thickest part at the top.

3) has the same outside diameter as the top of the needle.

You just put the needle through the washer like you would a washer on a bolt so that the needle will be raised up out of the slide by the thickness of the washer. Some have found washers like this in a kit at radio shack. I found one that I had to make a little smaller on the outside diameter in my "supplies".

If you do this, remove the snorkel, and grind off the tab on the bowl that keeps you from spinning the low-speed mixture screw around, and put in a good air filter, you'll wonder how you managed to ride the bike without these mods. If the mixture screw is out more than 2-3/4 turns, you need to go up on the pilot jet.

The suggestion to replace the screws on the carb with allen heads is an excellent one as well. I replaced the 4 bowl screws, the 4 screws in the top, and the 2 that hold on the throttle cover.

The slide gets raised when vacuum is applied at the bottom of the slide, and the holes are how the air leaves the area above the slide. Hence, the bigger the holes the faster the air can leave.

I'm running stock exhaust, K&N filter, and run a 55 pilot and 158 main (both keihin jets from Baja Designs), and this setup is rich enough to run with the baffle out. Note that there is a 55S short pilot jet, and the 55 regular pilot jet will work but you have to trim the slosh baffle in the bowl a little, as it can move a little and partially cover the pilot jet.


Now it is time for a pipe. Which one is the best. I don't want it to loud.

For tunability and noise concerns, get a pipe that uses a disc system like the Trapp IDS2 QS. I run this one with (7) discs (Uni-air filter, carb jetted, slide drilled & needle shimmed) and it works excellent. Not too loud and good low end pull. Plus it weighs about (5) pounds less than the stock anchor.

I got my bike used with the smog still on.

It has a T4 Pipe, airbox mod & has been re-jetted.

Would the smog block-off make a big difference in HP or throttle response?


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