I have an 86 250r and it was just rebuilt. I have been trying to find the ideal fuel air mixture and everything I do results in my plug burning black. I still have stock pipe and a ct silencer. It also still has stock reeds and carb. I am at a 148 main and a 38 pilot. Stock says the main is 150. I move the needle and it still burns black. It also doesn't have the power it should on the upper half of the throttle. It sputters after half throttle. Anyone have any idea on what to do?

 

check your reeds also what ratio of gas are u running

 

Check your float height and your needle and seat.Also your jet needle and needle jet for wear

 

You should also check your air mixture screw on the side of your carb, it should be aprrox. 1.5 to 2 turns out to start with. ( turn the screw all the way in GENTLY till it bottoms out, and then back it out 1.5 turns.) Start with this and see if your plug gets any better

 

I am running a 32:1 fuel ratio. I am also running a rad valve for a reed cage. What exactly am I suppose to check on the reeds. Are they suppose to be tight against the cage or can there be space in between.

 

What exactly does the air screw do and what does it affect. When you put after market parts in does the jet size go up or down or does it depend.

 

The air screw controls the air- fuel mixture ratio that the engine see's in the RPM range. The ideal ratio is 14:1 (14 parts air 1 part fuel) but real world conditions are usually 12:1. That 1.5 turns is just a base line to start with in tuning your carb. If more air is needed to go with the fuel, you turn the screw out approx 1/8 turn at a time. Set the screw at 1.5 turns and then start your bike and let it idle, now listen to your engine if the engine runs a little rough turn the screww out a little at a time till you hear the idle get smoother. If you have gone more than 2 1/4 turns you have gone to far for a stock engine. 1 3/4 turns should be just about right for a stock engine. If you add a aftermarket pipe on you will need to go up on your main jet approx 2 sizes over stock. If you port the cyl you will have to jet the carb again. Thats done by trail and error. Also take your clip on the needle and put it in the middle slot to start with.

 

What I had before is not going to work now because I put on an aftermarket pipe and a rad valve. On the reeds of the rad valve I could see light when I looked through the carb end. Is this bad. Another thing. It idled before I put the pipe and reed cage in and now it doesn't idle at all. Any suggestions on where to start. The main is stock and it is burning black still. The needle is on the second clip from the top and the pilot is a 38. The Air screw is turned out to about 1 5/8 turns. Not sure if that is correct because it don't idle at all. I would appreciate any help I could get guys. Thanks.

 

I dont know if your bike came with the instructions for the rad valve, but they say you will have to drop your main usually 2 sizes, but up to 4. This could be what your problem is. I know it does not sound right because most mods make you increase the jetting. Anyway try dropping two main sizes. I run my 87 air screw at 1 7/8 turns, it works good.

 

Thanks for the help guys. I adjusted the float. Changed the reeds on the rad valve. Put in a smaller main jet and a smaller pilot jet. I reset the needle to middle position and now all I have to do is put it all back together and see what happens. I let ya know the results. Again thanks for the help.