Bikes poping like a mofo!!!!

7 replies to this topic
  • ShadyatBest

Posted September 23, 2005 - 12:57 PM


here is the deal. its a wr450, 3500', 70 degrees. There is no exhaust leaks, and there is an after market Dr d exhaust. Other mods are power now, air box cut open, and backfire screen removed. The needle has been raised a clip, the pilot has been brought up one size bigger and the main is 2 sizes bigger, the airscrew has been adjusted from 1.5 turns all the way out to 3.5-4 turns.Now of decel it pops like crazy. The pipe turns red hot from the cylinder and back just about to the connection with the silencer. The cases even get hot enough to boil water. If you spit right about the clutch side case it will boil.It boils over at idle. It is friggin hot!!!! Where do i go from here? its ryno66's bike but he refuses to ask these questions. Hes going to melt his bike!!!

  • clark4131

Posted September 23, 2005 - 01:34 PM


It obviously way too lean, but we need more info...

  • Pilot Jet Size
  • Main Jet Size
  • Type of needle
  • Needle clip position

Now I'm talking numbers here, not generalities. "Up one, down two" really means nothing without a point of reference. Here's a good starting point to pass on to your bud...

Elevation 0 to 4,000 feet

30 to 45 degrees: 172 main, JD Blue #5, 48 Pilot, 2.0 turns, 75 starter jet, #0 leak jet
45 to 60 degrees: 170 main, JD Blue #4, 48 Pilot, 1.75 turns, 72 starter jet, #0 leak jet
60 to 75 degrees: 170 main, JD Blue #3 or JD Red #5, 48 Pilot, 1.5 turns, 70 starter jet, #40 leak jet
75 to 90 degrees: 168 main, JD Red #5, 48 Pilot, 1.25 turns, 68 starter jet, #50 leak jet
90 degrees plus: 165 main, JD Red #4, 45 Pilot, 2.0 turns, 65 starter jet, #60 leak jet

Also, just a little FYI, 4-strokes have fuel screws, 2-strokes have air screws, and they work opposite of one another :banghead: ...SC

  • ShadyatBest

Posted September 23, 2005 - 01:40 PM


its my buddies bike so i will have to check on the sizes. He said the main was up 2 from stock. He did get a different needle and the pilot was one size up from stock. Is this usally a problem that is adjusted throughout the whole range of the carb or is it strickly a pilot jet issue.

What brings you down to that shit hole la paz??? My aunt lives just south of todos santos facing the ocean

  • clark4131

Posted September 23, 2005 - 08:58 PM


What brings you down to that shit hole la paz???

Pardon me? What's wrong with La Paz? Considering it's thought of as one of the top 10 places in the world for Americans to retire, you obviously have some personal issues with the place. I have 1.5 acres in a waterfront subdivision there that has tripled in value in the last 6 months, so I don't know where I went wrong. Maybe you can enlighten me :banghead: .

If your buddy is running a 170 main (+2 above stock), and a 48 pilot(+1 above stock), but is still popping on decel with his fuel screw cranked out, then he likely has internal engine issues. Most likely a few tight valves, if there truly is no exhaust leak. Overheating the way it does may be indicative of a cooling system issue as well, bad water pump, bad radiator fluid, etc. Like I said before, we're gonna need those numbers to be sure...SC

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  • ShadyatBest

Posted September 24, 2005 - 07:32 AM


you ever go to la ventana? There is that cove east of there with the giglin marlin. I like that area but have never been a big fan of la paz.

  • ovrrdrive

Posted September 24, 2005 - 05:43 PM


Make sure the hot start is inserted correctly. I put mine in once and it bound up and I had the exact same problem as you describe.

Try pulling it when the engine is running and see if there is any difference. The rpm should rise and it should sound different.

If it doesn't, that's most likely the problem.

  • ryno66

Posted September 24, 2005 - 09:41 PM


This is my bike. I am running a 50 pilot jet, 170 main, GYTR needleat third clip (from bottom), and a zip ty screw at 3.5-4 turns out, air box cut out with snorkle removed, power now, grey wire, Dr. D exhaust, ais removal kit. I want to try a larger pilot but a 52 seems pretty large from what I have heard. I just replaced the exhaust gasket so that is new. My bike does run pretty hot and at idle it will boil over even at low 70's temp. Should I try messing with the leak jet, start jet, or pilot air jet. Will the JD needles make a difference? I want to get a handle on my bike. It runs great with no bogs anywhere right now. With the zip ty at 1.5 turns out it pops at decel, at 4 turns out, no problem. My hot start plunger broke and I replaced it, seems to be functioning correctly.

  • Indy_WR450

Posted September 25, 2005 - 03:52 AM


Your problem is that you are using the pilot jet to compensate for a lean needle! The Dr.D pipe and other high flow pipes require JD needles. Go back to a 48 pilot with JD needles. The Blue needle is much richer at 1/4 throttle than the red. So I would start with JD Blue in clip #4 or 5 with a 48 pilot and report back. main looks close enough. :banghead:


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