Can you take the end cap off of a Stock 400EX silencer. Will this do any damage. Will you gain or loose power. I've seen some people at the races with out then on. Is there anything else you can do to a Stock 400EX to gain more power?

 

My Buddy ran with his off for a long time and it did not damage anything. He said he felt a little boost. Want more power? Get a full exhaust or silencer, jet kit, aftermarket air filter, and a big bore kit if you really want to get crazy with it [img]i/expressions/face-icon-small-smile.gif[/img].

 

How much did those Tinner's air scoops cost?

 

They were $38.00 + $7.85 shipping. I am very pleased with them. They are extremely solid...no dissapointments. I have been riding really hard and they have not moved and/or had any problems with them. Here is the article on exriders.com Tinner's Air Scoops Jim (Tinner) is great to do buisness with. He sent them out right away and had great email support. His email address is Tinner's email.

 

Heres what I did on my EX:
After removing the silencer from the quad go ahead and remove the 3 8mm bolts and pull the spark arrestor.
Towards the front of the silencer you will see some spot welds that the factory made. Using a 14in chopsaw, cut the silencer in half just in FRONT(meaning towards the front of the quad) of those spot welds. It helps to scratch or centerpunch 2 marks on either side to help re-align the halves later.
Using a Dremel or a small cut off wheel, cut the pipe off as far down into the "cone" or "funnel looking piece" as you can When you look into the cone shaped piece you'll see the part that needs to be cut off.
Next, using a drill bit in the large variety(13/16,15/16/or 1") drill three holes in the inside canister from the back as if you were looking into the silencer from the back. Your bit should be long enough to reach in and drill the holes . The metal is not thick. Do try and line up the new holes w/ the tubing that runs thru the inside canister.
Next put the spark arrestor in the chopsaw and cut it off at the metal band. You can save the wire mesh if needed and braze it back on the end cap.
Using a wire feed, weld the two halves back together and grind the weld smooth w/ a flexible grinding wheel. Paint w/ high heat black and put it back on. Mine took me abou 1.5 hrs. start to finish. You'll also want to grind down the welds in the header. Pull the header off and look into the tubing. You'll see that the welds in the header choke down the I.D. of the tubing. Use a stone and grind them down to the same size as the tubing Add a uni-filter, cut the front part of the snorkle off(under the tank) to open up the hole bigger, add 6 uni 1" vents to the airbox and go to a 152 main and you'll be happily impressed. Total cost of around $35.00.
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SDuncan, That is pretty impressive. Do you have any pics you can attach to see what that looks like?

 

It looks completely stock with the exception of the end of the silencer. The large chrome piece is still there but the "pea shooter" looking part in the center is gone. If you weld it back together correctly and grind it smooth its hard to tell its been touched. Since I ride mainly dunes, I haven't brazed the metal mesh screen back on yet. Its just open. As you know, in some parts of the country, park rangers sometimes check for spark arrestors. Sometimes they just stick a rod or a piece of wood in the end of the silencer to see if it bottoms on the metal screen which is the spark arrestor. If you braze the metal mesh screen back to the end piece then you could pass this test. I don't think it would hurt the flow either. Just something for the woods riders to consider.
As for the header welds, if you feel around just inside the header where it bolts to the head then you'll feel the factory welds and how they decrease the flow and ID of the header in that one spot. Grind them flush and you'll be suprised how much extra material was there. I have had ZERO problems with any cracks from doing this. I haven't heard of anyone else having any issues with it either.
No kidding, I ran within half a bike length next to an EX with a Sparks X6, advanced keyway, Uni-Filter, Sparks jetting,CDI box, identical gearing(15/40) Sand Skate 2 paddles and riders of equal skill and weight. It was a friend of mine so we even swithched quads with the same result. Needless to say, he was rather pi$$ed about the whole deal.