Major Sudden Sputter

I just got a full dr.d exhaust system off ebay and bolted it on my 05 wr450. Got it all buttoned up and went for a 20 minute ride on the railroad tracks. I came back and checked the plug to see how lean I really was. It was a kinda white so I went down three needle clips (all the way to the bottom) and reassembled. Went out down the driveway and could barely ride the thing! It had a HUGE sputter all the way till like half throttle that wasnt there before, then shot out like a bat out of hell.

Then I came back went back up two clips on the needle and I felt very little difference. It still does the same thing. Am I not putting something back in? It ran okay the first time, then even now with only going one clip lower than what it was it still runs horrible. It almost runs better with the choke on, but pops like crazy. HELP!!

Was it running fine before? Have you recently put on a new gas cap or vent hose? What you are describing sounds a lot like when I put an IMS tank on my YZ with a new cap. After a few rides, my bike started doing the same thing. I found out that the IMS cap was never drilled for ventilation. I was experiencing major vapor lock.

Just a thought......... :excuseme:

I dont think its that. I just went back to what it was, and went out for a test doing the same loop at the tracks. It ran like crap, unless I was about 8-9 thousand rpms. Then it screamed! I think this is a result of just way too much gas. I thought about the vapor lock too, but thats not the problem.

I am begining to wonder if it is my valves too, judging by the fact that it is getting a bit tougher to start and wont idle, but it runs so good after 8 grand...

Take off your exhaust and bolt it back on properly.

Be sure to line up the header on the outlet gasket evenly, hold it in place and tighten bolt and nut evenly!!!

People just throw them on their bike, not paying attention to allignment. :excuseme:

You will be amazed at how a little exhaust leak can create havoc.

Your first mistake was looking at the spark plug to determine the mixture. Since the lead was removed from gasoline, spark plugs are almost unreadable, and nearly always look white.

Then, you raised the needle an enormous amount, and got the results you should have; the bike ran hugely rich at part throttle, and stuttered badly.

Return the needle to it's original position. The only jetting changes Dr.D recommends for that system is to move the needle on an '03/'05 YZ450 DOWN one to the 3rd position. You went the other way.

When jetting, You change the main first, then the pilot, THEN trim the needle height. Go by how it runs, not by the plug.

I dont think I have an exhaust leak, its almost like my acv is stuck open, causing it to be rich on the bottom.

Alright everybody, I am a retard. When I first pulled the plug I must have hit the tip on something because there was very little plug gap. I also took matty's advice and threw in a new copper crush gasket for header to valve head joint. Just went out to ride and it was WAY BETTER! I wasted hours trying to fix it! Thanks for all the help.

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