The previous owner of my bike said his son jetted the bike to make it run better. The problem is that his son lives on the other side of the country. So............ This bike is completly stock so what kind of jets do you think he installed in it?? Leaner or richer jets?? What kind of aftermarket jetting would you do to a stock bike to make it run better?? Make it run leaner or richer?? 1990 CBR600F

 

Does it have a K&N filter? Does it have aftermarket exhaust? Most of the time you re-jet with bigger jets because you added stuff to make it breathe easier. If it is stock, it should probably stay with stock jets.

 

I know mine was jetted, but i have a K&N filter, and Yoshi exhaust on mine. It was done right before i bought it so i am not sure what is in it though.

 

i said it was stock

 

If it is stock then no jets. It should have been left alone with the stock jets and needles. No change to air flow=no reason to add fuel with a jet kit. The carbs were probably all snotted up and he thought jetting it would fix them, instead of a good old fashioned take the whole damn things apart carb cleaning. More than likely, depending on the kit, wether it had adjustable tapered needles or just jets, he probably put bigger mains in it. People think jetting carbs is gonna add all kinds of power, but it only doesif the bike is breathing easier, i.e. UNI or K&N filter, and a pipe. Is there black smoke coming out of the tailpipe when you rev it up? What do the plugs look like? If the plugs are black, then it is running too fat, you may want to try to get more air in by adding a filter and using a hole saw to make holes in the top of the air cleaner box. If it is the other way and the plugs are looking crispy, it is running too lean and you'll have to jet it back to normal. I am betting on the mixture being fat.

 

I just changed the plugs about 300 miles ago and they all looked a perfect shade of brown. I thought maybe there was a kit out there that was just an easy carb upgrade without installing any hardware.

 

yeah, there would be no reason to change the amount of fuel being delivered if you didnt change the amount of air being delivered. when you add air, you add more fuel, and vice-versa, but not one without the other. i have seen a dynojet, and a yoshimura stage 1 kit, i have the yoshi kit as i plan to install it alongside my V&H ss2r.

 

Yeah, I just read the DynoJet stage 1 kit can be used with STOCK motors.

Stage 1 Kits

 

It's really not worth a 5% increase to jet a bike. Things is, every bike is different. What works when jetting one bike, may not work on another. You could end up taking the carbs off and on like 10 times to get it right, and it may still never be 100% right. I am STILL messing with the carbs on my Hurricane1000 and I started tinkering with the jets over a year ago. Have had the carbs off so many times it's rediculous. Instead of spending a bunch of time trying to get 5% more HP, go for a ride. Trust me, unless you are extremely bored or just bought a K&N and a yoshi slip on, leave it alone. Especially if your plugs look the way you decribed. That means it is running almost perfect. You won't feel 5%. Another thing is Dynojet will say just about anything to sell you a jet kit [&:]