Hello I am new to the forum, and I am needing a little help with a bike that I have been working on. My father in law has a 2003 Roadstar. He bought a stage 1 kit from Yamaha, a Speedstar kit containing air box with k&n filter, ignition module, and jet kit. Also he bought some aftermarket cobra pipes, and an intake. The intake pretty much looked like the stock one. I pulled the carb apart and it had a 35 pilot and a 165 main jet. I replaced these with a 50 pilot and 170 main also put a needle in with the c clip in the third groove. I started out with the pms screw backed out 3.5 turns. I put this all back together and its back firing through the carb. It seems Idle fine and the upper rpm range is also great, but if you crack the throttle open about .25 it will start back firing. I have adjusted the screw as much as all the way in and 6-7 turns out with no help. I then took the carb back off and replaced the pilot with a 60, and it seemed to help somewhat, but just not enough I can adjust the screw out until it black smokes and I still get a back fire @ .25 throtle. I have checked for air leaks a number of times, so I am at a loss any help would be greatly appreciated..

I'm not a carb guru.. BUT, I can tell you what I know.... and think, and I may get corrected from one of our carb guru's. First question, did you remove the AIS? The AIS allows air to be pumped into the exhaust allowing excess gas to burn off... with after market pipes this causes some awful backfiring...

OH WAIT, JUST REREAD YOUR POST... I've got a 1700 and you've got the 1600... well most of what I wrote applies also. as a matter of fact even more so...

I've got the Speedstar K&N intake, but with drilled out stock pipes.. here's my carb settings I've got baron's jet kit (mikuni jets, baron's needle *caution we have 2 different needles*) I run 167.5 with the needle on the 3rd ring. Stock pilot. 1.75 turns out. Bike is a touch on the lean side. still able to start in very cold conditions with the choke. takes about 5 minutes to warm up.

These bikes tolerate very rich conditions... (until the valves stick) I think with a 50 or 60 pilot you are way to rich. Can you start the bike without using the choke? If so I think that would confirm you are to rich on the pilot circut.

You may also want to mess with the accerator pump screw... some people have had sucess with getting rid of a cough / back fire by screwing it all the way in.... on mine, it did not help, I think if your accelerator pump is making you rich enough to backfire, then you're to rich on the pilot... but this is an opinion the accelerator pump fires to prevent / fix a momentary lean condition at the moment of throttle opening when the engine is pulling air, but no fuel is flowing through the main jet. So if you watch the accelerator pump dumps fuel into the carb throat the moment you open the intake, (even before the butterfly opens) before the venturi effect is fully pulling fuel via the main jet. so I THINK if you're drowning the engine when the accelerator pump fires you've got to much gas in the mixture to begin with.

Well I hope this helps... ~Dave

Put the stock #35 pilot back in and try the 170 main on the 3.5 or 4 th clip setting. PMS about 3.5 turns out.

I've found the 170 to be a bit rich and believe that Dave's setup (167.5 main) to be better but it also depends how retrictive your pipes are.

There are a number of carb articles in the Tech Tips section that I would encourage you to read to understand the functions of the various 'parts'.

Normally carbs require a bit of 'fiddling' after getting them in the ballpark but in the end you'll get there.

Doc