yzf 750 carb gurus

YZF750flyer · Post by **YZF750flyer** » Tue Jan 24, 2006 12:20 am

Ok, I have a 97 YZF 750. Whats the best way to lean out the low end? Keep in mind, all of my checks have been done in neutral on a stand but it seems like from about 4-5K on up, the mixture seems good, but coming off of idle it seems real rich. Sitting at idle (about 1200 rpm) when you hit the throttle fast, like a quick blip, it almost wants to die, then comes up. If you roll it on at a medium speed, it comes up in rpm just fine. Im actually not sure of its rich or lean at the low end, but when I ran it with the airbox off, the overall feel and sound of the bike made me think it had leaned out just a tad (exhaust note got a little raspier and started popping a little) and the low end response improved just ever so slightly. I have the stock needles installed (no grooves to move the e-clips on) and everything else is stock except for the emulsion tubes (I just installed those from Factory Pro hoping that would fix the problem). Im trying to get rid of the hesitation and burble off of idle. Any help would be appreciated.

dragracer1951 · Post by **dragracer1951** » Tue Jan 24, 2006 8:50 am

sync them

YZF750flyer · Post by **YZF750flyer** » Mon Jan 30, 2006 12:50 am

Thanks for the tip. I did sync them along with installing the needles from a dynojet kit and it has improved things a bit. I also opened the mixture screws a full turn and have just about gotten rid of the lag but now I dont have the top end power I should have. I think a needle position change migh take care of that, but its going to be a guess as to which way I need to move them. Above 70 mph, I cant hear the bike so I cant tell whats its doing mixture wise. Any tips or things to look for to help determine if its rich or lean? Thanks,
Eric

dragracer1951 · Post by **dragracer1951** » Mon Jan 30, 2006 12:26 pm

Man...You can tell the mixture by listening to it????

Look at the plugs

YZF750flyer · Post by **YZF750flyer** » Tue Jan 31, 2006 2:58 am

Yeah, I guess that might sound a little far fetched and may not work in this case. Most of my piston engine experience is with RC helicopter engines which in those cases you CAN determine mixture problems by the sound of the engine, (i.e. popping, gurgling, or raspy type sounds) you just have to know what to listen for. Forgive my ignorance for I am just a lowly noob.

YZF750flyer · Post by **YZF750flyer** » Thu Feb 02, 2006 1:10 am

Well, thanks to the help from everyone here on the board and the invaluable archives, I think I have gotten the bugs worked out of my 750. The hesitation is almost completely gone, the top end pull is back and it idles wonderfully. That said, I feel like Im only about 95% of the way there. I think I could get it just a little bit better if I keep tweaking the mixture screws and adjusting the needles, but at this point I have no idea what else to do to get it perfect. I think Im just going to ride it for awhile and see how it does. Thanks again to everyone who helped me out, directly or indirectly.

Eric