Carb Tweaking

My XJ650R runs pretty darn good, all things considered. Smooth idle at 1050-1100, warms up quick and runs good at speed. But when I first take off, from a stoplight for example, the bike is very hesitant, almost like a miss, but not from spark issues. I haven't had the carbs synced yet, and with Memorial Day weekend here anyway, I want to ride. I've run SeaFoam through the system...can anyone offer any suggestions to a somewhat mechanically impaired XJ owner to get a little bit smoother action from this ride?

A proper sync tool and new bank of carbs are in my near future, just not for the holiday.

Thanks and regards,
Furyus

 

Does this bike have the Hitachi carbs? If so - I just saw the inside of my brother's carbs. All 4 of the screens in the carbs were eaten away. These could be clogging passages.

Maybe the mid-range circuit?

I don't think it is the sync though. I had one carb way out of sync, and it made it run rough at idle, but it performed well accelerating.

Also - how fast are you twisting the throttle? On mine, if you instantly pop it open, it takes a split second before it gets going. This is carbureted, not fuel injected. I like that because I am less likely to kill myself from a slip of the wrist. :lol:

 

i can almost garuntee you its a sync problem. Heres what my bike used to do that syncing took care of:
after starting from a stop it accelerates fine, unless i try to acelerate QUICKLY! then it sputters, almost coughs once or twice (the bike would vibrate a little) and THEN the power would come on. it would basicly hesitate. Also it had a very sporadic idle, and would sometimes die when not warm after coming to a stop. After syncing the carbs all these were eliminated.

These bikes run very strange when not synced. Dont write your carbs off jsut yet. A proper sync and tune might be all you need.

 

My bike performs fairly well.

It doesnt seem to have squat for low end torque. For it to get up and go I need the RPMS of 5K, below it I feel like an old man driving a caddy pulling away from the green light as fast as soemone can walk...

(No offense to the older men here driving cadilacs!)

 

Thanks for all the replies. The bike idles super nice, and runs good at higher rpms, but is very flat at low end and is getting horrible mileage (30-33 around town). New plugs and new airfilter have been installed. For the most part, I can live with the way she runs considering her age. Having just come off a 2005 fuel-injected Ducati with instant throttle response probably doesn't help my impressions. Interestingly, today was hot around here (upper 80's-90) and she ran like a champ, even at parade speed.

Regards,
Furyus

 

Your gas mileage is not uncommon.

I get 100 miles before I refuel. I never try to push it past that. Once you run out and have to walk miles you learn these lessons

 

Have you colortuned the carbs? A slight stumble off of idle to about 3k RPM is usually a lean mixture. Yours sounds like it is only one or two carbs. Either way a colortune followed by a sync is exactly what you need.