Pros & Cons: Pilot Jet Increase

[sfcrader]

I'm wondering what advantages/disadvantages I would see bumping-up the pilot jet size in my 2nd Gen? I was thinking of ordering 1 size up from current stock jets. Next weekend I am planning on setting the floats and cleaning the carbs. Thanks for any information provided.

[camos]

I'm wondering what advantages/disadvantages I would see bumping-up the pilot jet size in my 2nd Gen? I was thinking of ordering 1 size up from current stock jets. Next weekend I am planning on setting the floats and cleaning the carbs. Thanks for any information provided.

The first question I would ask is why?

What do you hope to accomplish by increasing the size of the idle jets?

 

Any time someone messes with the stock configuration of the fuel system, the air intake system or the exhaust system they open a Pandora's box of adjustments that usually end in worse performance or MPG than there was to begin with. Those systems were designed to work together in harmony so any tweaking of one will require adjustments to the others as well. It can be done but it is rare that anyone ends up with a better running engine without making extensive changes.

[sfcrader]

I had really bad backfiring on deceleration; I have check and rechecked everything I have read here and even had a local shop here in Massillon checked her over. The few things I was able to check and find and whatever the local shop as able to do did help with the backfiring. I read somewhere that increasing the pilot jet up 1 size could help with this. But before I do this I would like to know other pros and cons.

[Freebird]

Bad backfiring just isn't normal. I don't think that it is a problem on most bikes that are not modified in one way or another. I know you have checked a lot of things but if it's happening on your bike but not on others that are set up the same way, there is something that you haven't found yet.

[utadventure]

I had pretty consistent backfiring on the '99 until I put the stock mufflers back on.

 

That solved 99% of the backfiring. After completing a tune up and carb adjust/sync, no more backfire.

 

Dave

[Ace]

I've increased the pilot jet size one size on both of the RSV's I've owned. Neither were backfiring but it really improved cold starting and really really improved off idle throttle response. Didn't affect MPG at all, just made the bikes run better.

[cowpuc]

Hey Crader,,, it always amazes how one tiny little air leak at an exhaust gasket can cause huge backfiring issues - it dont take much fresh air to get drawn into the pipes and cause this ailment. If I were dealing with backfiring - thats the first place I would check. Another common spot to check is manifolds for air leaks (causing lean condition) or vacuum lines.. Truthfully though,,, make sure your exhaust system is sealed tight with no pin holes first

As far as tweeking on the low speed circuit - I always like fine tuning on the metering rod before rejetting.. I have no idea if your dealing with a 2nd Gen as I type this and have never had 2nd Gen Carbs apart. I do know that U.S. models of the 1st Gens did not have normally "e" clipped metering rods but - lots of us have fine tuned very successfully with nylon washers. IMHO - the metering rod adjustment makes a little more sense because it can be manipulated and tuned without removing the carb to rejet and,, in my case - been fine tuning off the metering rods on scoots for years..