Motorcycle Repair: Spuddering, pet cock, honda cbr900rr

Question
Hey,

I have a 1998 Honda CBR900RR.  The upgrades are stage 2 jet kit, intake pod kit (K&N), full 2bro's exhuast system.  

The question i'm having is every once and awhile, i'll go to get on the gas and it will spudder for just a second or two at max, then resume with its power.  I have had the jets replaced, re-synced the carbs and floats, cleaned the filter pods out, cleaned out the pet-cock valve, check and adjusted the throttle cable, still does it every once and awhile.  I live in Phoenix az, so it stays hot all year round pretty much, which makes me think it has nothing to do with weather conditions.  I can't replicate it ever, it just happens on its own.  It will only happen in 1st gear right off the line, or if i'm cruising down the highway in 5th and i try to just roll back the throttle.

any ideas?

thanks,


Answer
Hi Colby,

The problem is either ignition or carburetion related. With the described modifications, I suspect a fuel problem.

The problems you're experiencing is common with such performance mods. Engineers designed the stock engine configuration to work very well in a variety of climates and conditions. Adding a pipe and changing the air/fuel mixtures results with such problems. Once installed, performance parts change the tunability and reliability of the engine as you knew it when stock.

It is my experience that drop-in jet kits get the A/F mix in the ballpark. Additional tuning is necessary to correct the A/F mixutres. Getting the air/fuel mixtures dialed in may be an on-going process.

If the problem occurs rarely, maybe the fuel has a spec of water of other fuel contaminate that causes the problem.

Respectfully,
Mark Shively