CRF 250 PROJECT

Brian Degulis · Posted: Fri Dec 14, 2012 12:15 pm Post subject:

The problem with the OEM Bike silencer was that it's just to loud. What I have on there now is very quiet. If I'm not losing power or just need to tune for it the only reason to change anything would be weight and I'm not sure a change would be worth it.

Brian

Brian Degulis · Posted: Mon Dec 17, 2012 4:29 pm Post subject:

So how do you tune/jet for the pipe. If it's running strong and the plug reads good what else should I be looking for?

Brian

Chris Reinhardt · Posted: Mon Dec 17, 2012 5:21 pm Post subject:

Brian Degulis · Posted: Tue Dec 18, 2012 5:40 am Post subject:

The street bike silencers like for the CRF250X have a small diameter output tube and will create some back pressure. I'm quiet now without excessive back pressure. What is the problem with a long pipe and how do you tune for it?

Brian

Chris Reinhardt · Posted: Tue Dec 18, 2012 5:50 am Post subject:

Brian Degulis · Posted: Tue Dec 18, 2012 9:14 am Post subject:

I guess what I'm asking is besides losing a little weight what is the advantage to a shorter pipe? After either is properly tuned is there a net power gain with a shorter system?

Brian

Chris Reinhardt · Posted: Tue Dec 18, 2012 9:54 am Post subject:

The CRF250 in stock form is a pretty highly tuned motor that operates at a high RPM and a fairly narrow power band. Going far off from the stock dimension could only decrease performance... If I was going to do anything, I would shorten the head pipe by a couple of inches, maybe increase the diameter of it. That should give you a little more up on top at the cost of the bottom which you'll never use.

I would guess from looking at your pictures, you probably at least 2x the length of the stock pipe....

If you don't plan on competing against anyone, what's the point, but just trying to help you out....

CR
_________________
East Coast Super Kart Series
"This is how we roll!"
www.eastcoastsuperkart.webs.com

CR2 Motorsports
"Home of Cobalt Superkarts"
www.CR2MotorSports.webs.com

Brian Degulis · Posted: Tue Dec 18, 2012 10:06 am Post subject:

That's what I'm looking for (the why) There is no class for these around here but still I want to get the most out of it. I think I could eliminate the lower silencer and the pipe running to it and use just the upper silencer direct. That's a 2" silencer and the stock silencer is 1 3/4". That upper silencer seemed to have the biggest effect for reducing noise. With that I would be around OEM lengh.

Brian

Chris Reinhardt · Posted: Tue Dec 18, 2012 10:11 am Post subject:

This isn't brain surgery here.... You have at least 24" of pipe you don't need with the current config.

Come off the head pipe with an elbow as you have it, directly into a muffler, done.

CR
_________________
East Coast Super Kart Series
"This is how we roll!"
www.eastcoastsuperkart.webs.com

CR2 Motorsports
"Home of Cobalt Superkarts"
www.CR2MotorSports.webs.com

Brian Degulis · Posted: Tue Dec 18, 2012 7:34 pm Post subject:

I got it. You explained it very well 2 posts up. I now understand the down side of a long pipe. That's the info I was looking for.

Brian

paul rees · Joined: 06 May 2007 Posts: 264

This what i run

Brian Degulis · Posted: Wed Dec 19, 2012 3:57 pm Post subject:

Nice!!! What is it and how loud is it? I switched to a single muffler and got flagged today for being to loud.

Brian

paul rees · Joined: 06 May 2007 Posts: 264

As you can see this is a Dirt Oval Kart . Uas rules state OPEN EXH . I did build pipe to bolt on a Super Trap though

Brian Degulis · Posted: Thu Dec 20, 2012 1:10 pm Post subject:

Well I've got the exhaust squared away with one oval sliencer it's quiet enough and it doesn't seem to be reducing power. The kart runs great but I'm dumping fuel into the catch can from the carb overflow tube. I tried setting the float level but when I get it low enough to stop dumping I'm staving for fuel on the corners. I've got the round Mikini pump with the normal Y and return. I do have a very short hard pulse line.

I tried drilling out the reurn line fitting in the tank and that along with float level helped but it's still dumping.

Brian

Michael Taksa · Posted: Thu Dec 20, 2012 1:13 pm Post subject:

Try "magic can". Or any three prong fuel filter from NAPA for under $5. Bottom to carb, top from tank, side closer to top is return to tank.