Im new here and this is my first post, I have had to read a few posts to figure out bikes I was working on before though. So here goes nothing…
I’m currently working on a 2006 Bruin 250. The guy brought it to me and said that neutral, 1st, and 2nd he has full range on the throttle, 3rd 4th and 5th the throttle has to be “babied”. He had replaced the carburetor with an OEM carb and continued to have the same issue. He also replaced the spark plug.
i tested the unit and found that first and second have full throttle range, once you shift to third it feels like the engine is governed unless you ease into the throttle. If you need the power and open the throttle quickly, it loses rpm and power. It won’t stall but it runs roughly just above an idle rpm.
I found an air leak on the carburetor joint and replaced it. I have tried 2 different spark plugs and various gaps from .028” to .033”. I have tested the resistance on the ignition coil and the spark plug cap. All was within spec. I’ve checked the valve lash clearance, also within spec. Fresh gas and good flow from the tank to the carb. I’ve inspected all vacuum lines and the throttle and choke adjustments. The choke being on or off doesn’t affect the issue at all.
Many ideas before I give up and send him to someone else???
thanks!