Why Reject And What Is the Effect

[jlearning1]

Hello Everyone:

I have been reading a lot on rejetting. I have a 1980 Yamaha XS400SG. I have it running pretty good. I was wondering what is rejetting, and what effect does it have on the bike. I was considering rejetting my bike, no changes to the exhaust. I will continue to run stock pipes and stock air filters. If I decide to rejet, do I have to make any modifications to my air filters or exhaust? Do I have to go with pods? If I rejet, will increase the power of the bike or what does it actually do. Im going to order me a rejet kit from that guy on Ebay, and install it and see what happens.

Thanks

 

[leedutcher]

you only need to rejet if u make any kind of modfication to the exhaust of intake. people rejet because u mes up the air/fuel ratio. oen exaust cause less back pressure causing u to lean out. same wth putting on pod filters runnign to lean will backfiring, alo of popping, bad mpg, poor performance, and eventully will damge your exhaust and intake valves, and possibly engine failure....

 

[OliverB]

If you are going to stay with stock pipes and air filters, don't re-jet. In my opinion, it is not worth all the fuss. You do need to replace the idle air mix o-ring if you have Keihin carbs and set idle air mix screw at 3-3.5 turns out on each carb. Properly set up stock, these engines will start easily and run beautifully.

 

[HoughMade]

I have a stock bike and I am running stock jets....and it runs really, really well.

 

[jlearning1]

I have the Mikuni B34 carbs. I notice at times when my bike is idling, I hear a pop coming from the right side exhaust pipe. Could that be because I am running to lean or to rich? What does running to lean or to rich mean?

Thankz

 

[leedutcher]

lean= not enough fuel rich means too much fuel.... u can always tell if ur running lean or rich from your spark plugs.... black and wet means rich and white means your too lean... brownish tan is what u want...

 

[jlearning1]

Which one would cause the popping and low idle?

 

[HoughMade]

lean, usually.

 

[xschris]

Sometimes if the carbs are out of sync they can pop like that as well. I went one size up on my main jets (137.5) these bikes came from the factory very lean. I have factory air filters and factory mufflers. Read your plugs as well you want them to be an even brown, white is lean and black is rich.

 

[leedutcher]

check the bottom of your exhaust. somtimes tiny rust holes will make a popping sound as well.

 

[jlearning1]

No holes in exhaust. Spark plugs are brownish tan with a lilltle black around the housing.

Thanks