Carb tweeking after Hot Cam install?

5 replies to this topic
  • bultaco

Posted June 02, 2009 - 12:45 PM


I installed an autodecompression exhaust cam in my 1999 WR 400F. Easy now to push starter down...just that the prior carb settings are not quite right...Could the new piston pressure/air/fuel mixture while starting require new settings? It takes about 30-40 kicks to get it started...same once warm and trying to start again after shut down. A remote fuel screw was installed on the carb at the same time...not sure if it is seated exactly as the prior screw.:crazy:

Thanks for any help.

  • William1

Posted June 02, 2009 - 01:00 PM


If the problem does not care if the bike is warm or cold, I suggest first confirming valve clearances are correct. Confirm them, do not assume.
Then, I'd confirm the spring/washer and oring are on the fuel screw, then I'd try the original one.

  • bultaco

Posted June 02, 2009 - 02:18 PM


This is the fuel screw which replaced the original one...joe


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  • rich1167

Posted June 02, 2009 - 03:34 PM


Could be that your getting too much decomp from the cam.

  • Birdy426

Posted June 02, 2009 - 04:18 PM


I didn't have to make any jetting changes when I went to the hot cams auto decomp cam on my 426. Agree with William1, check the clearence. Hard starting as you describe is usually a valves hangin open a bit issue...

  • William1

Posted June 02, 2009 - 04:42 PM


Far as I know, that screw is supposed to be OK. I'll ask a dumb question that has to be asked. When you took your old screw out, you removed the spring/washer/oring, put them on the new screw, right. I ask because sometimes they fall off and guys neglect to have them, in other instances, the oring has remained behind up in the hole and a second one ended up being installed.


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