Air / Fuel Mixture

[cloud2blue]

I have a 2000 m750, which is carbureted. When I purchased it used, the airbox lid had been chopped and it had Conti Replica Trumpets. I recently installed a Quat-D Ex-Box and now the mixture is lean. (White spark plugs, "backfires" from exhaust when I chop the throttle, correct me if I'm wrong)

As I understand it, I have 2 options: 1) re-jet to increase fuel, or 2) restrict the air coming into the airbox.

Is there a reason I should pick one option over the other? Is there a better option I'm forgetting?

I'm hoping restricting the airbox, because it would be something I could do myself.

[ducpainter]

I have a 2000 m750, which is carbureted. When I purchased it used, the airbox lid had been chopped and it had Conti Replica Trumpets. I recently installed a Quat-D Ex-Box and now the mixture is lean. (White spark plugs, "backfires" from exhaust when I chop the throttle, correct me if I'm wrong)

As I understand it, I have 2 options: 1) re-jet to increase fuel, or 2) restrict the air coming into the airbox.

Is there a reason I should pick one option over the other? Is there a better option I'm forgetting?

I'm hoping restricting the airbox, because it would be something I could do myself.

Either way you are richening the mixture.

Restricting air to the airbox will reduce power...theoretically.

[Norm]

The more air you can ingest, the more fuel and more power. Less air = less fuel = less power.
I think the ratio is about 14:1, but tuning is usually done by feel and plug readings.

[Oldfisti]

The more air you can ingest, the more fuel and more power. Less air = less fuel = less power.
I think the ratio is about 14:1, but tuning is usually done by feel and plug readings.

Or a dyno with an A/F probe.   

[clubhousemotorsports]

Before re-jetting take a second look at the new exhaust I have had more than a few bikes come in with leaky exhausts backfiring up a storm.

Ideally you would get it dynoed after checking for leaks, checking air fuel ratios.

For a quick test throw a stock lid on and see how she runs.

[Norm]

With an open air box lid, you can take a roll of duct tape with you and add strips of it to cover the filter until you get the best throttle response. I usually do this before I start the plug reading process because unleaded fuels can be a pregnant dog to read.
Of course, I ain't got one of them new fangded dino units you speak of.

[clubhousemotorsports]

Norm
you don't always need a dyno but it sure speeds up the process.

I have seen bikes de-tuned because the dyno tuner tuned the bike to run great when sitting in a pressurized room.