Hey there

Someone else might have something similar to this problem but I havent found one yet, so forgive me if this is a repeat post.

My 93' CBR 900RR was not feeling well with her sounding a little like a twin and she tended to bog down on the first gear. I just had her carbs cleaned and fuel drained. I didnt replace the plugs as I had just ridden for about 10km on these babies, but they were black as the night. After I have put her all together again she ran beautifully for a few minutes. Then she started acting up like before. Fine on the idle but a little nervousness in her revvs. She revvs fine if I twist the throttle at standstill but once i start to pull away in first gear she is erratic and jumpy. After another few minutes she starts to sound like a twin again.

I recently added an inline fuel filter to her as the previous owner didnt have one and shot her carbs to ****. Plus he was running crap fuel in her with out the filter and you can just imagine what happened inside the engine. This was all discovered when I cleaned her out previous weekend.

Does anyone have an idea as to what would make my bike fine when she is cold but once she warms up starts acting up?

 

CHECK THE PLUGS AGAIN SOUNDS LIKE THERE GETTING FOULED OUT SOMEHOW IF SO YOU WILL HAVE TO FIND OUT WHAT THE CAUSE OF THAT IS ALPHA

 

if its only happening once warm it sounds like a degrading coil to me, when it goes down does it go down on 1-4 or 2-3? cylinder 1-4 are fed by one coil and 2-3 by another. that would be the first thing i would look at mate. there cheap as **** an easily available on evilbay, just geat a pair n replace em both. only take an hour to do

 

ok cool, thanks for the info. I have checked on old forums now till about 2006 and other guys have also mentioned coils once bikes have warmed up.

Will check it out as soon as I can. I cant wait for her to purr again, then Im off to the mountains.

thanks a lot

 

if your unsure about wireing, make sure you have new ones before you remove old one, that way you cant make a mistake

 

Might want to go to a hotter plug if you are still running regular plugs just an idea hope ya figure it out

 

Hey there fellow bikers

Would just like to thank everyone who helped with the great info. After running carb cleaner through my system and listening to a noob (wannabe expert) at the bike shop who told me to switch fuels and totally screwed my carbs. Plus the ******* who had her before totally skrewed the air fuel mixtre when he installed the DynoJet and she was running so rich, she soiled her plugs within a week of riding and started that v-twin sound that all in line 4 riders hate to hear coming from their engines.

I stripped the carbs, installed a fuel filter(why the hell was this not installed earlier), flushed out the other fuel, cleaned every possible part of the carbs (Needles, Jets, disphrams), correctly set my air/fuel mixture, installed new plugs and put in the lower octane fuel back in and she is running like a brand new bike again. As I have personal experience, the CBR900RR Firebalde runs best on lower octane fuels. Higher octane fuels cause it to bog down heavily on the first gear once warm (or maybe its just my bike), that knowledge cost me two ignition coils and you can imagine how frustrating that must have been to see her react exactly the same with the new coils on. Lower octane fuels definately burn much better in the 900RR.

Thanks everyone for your input and maybe I'll be seeing fellow South African members in the mountains this weekend.

Cheers