mikuni rs34 tuning

I am needing some help tuning a set of mikuni rs34 carburetors on a 78 kz1000 ltd. The only mods are Denco 4 into 1 header, Kn pods, Dyna S ignition, Dyna Coils.The pilot jets are 115, mains are 130 and the needles are still set where they were when purchased. Right now it seems to hesitate when you first hit the throttle. Mid range and top end is pretty smooth. I do not know much about tuning carbs so any help would be appreciated. Thanks Jumbulias

Follow the link for the RS tuning manual...

kzrider.com/index.php?option=com_docman&...d&gid=481&Itemid=108

The manual is actually for the HS series but is used for the RS series as well.... Pretty much all I could find on the web for tuning Mikuni RS series carbs....

As depicted on the first page, for idle and low rpm ranges pilot system.... from 1/16th to 1/4 throttle, Needle jet & jet needle... Possibly the accelerator pump... See image below red boxed text...

Then there's the consideration where may just be due to the issues of too large a carb for a stock 1000 engine without any head porting, performance cams and such, they will stumble at low rpm's....

Use the search function and you'll find postings on it...

Good luck,

OMR

I have (or had, at least) a very similar engine combo as you, and my RS34s acted exactly the same way. Work fine from 4-5k on up, but smack the throttle open below that and you get a big bog and THEN it goes.

3 things:

-Bench sync your carbs. Don't even bother using vacuum gauges on these - the slides rattling back and forth and sucking air from the top cover as you adjust them will drive you nuts and you'll have a crappy running engine to boot. Take the whole rack off you bike. Go to the hardware store and get 4 NEW ball bearings about 1/8" to 1/4" in diameter. Pop off the tops of the carbs and adjust 1 carb a a time, referencing it to the master carb by slowly screwing the idle adjuster in and making the ball bearings fall through at the same time as the slides are lifted. Get it PERFECT, lock it down, and never touch it again.

-Adjust your accelerator pump to maximum. Have it start squirting as soon as you crack the throttle open, and adjust it so it uses as much of the stroke as you can, this will keep it squirting almost all the way up to 3/4 throttle. I have never had any problems with too much fuel. These bikes love gas when you are snapping the throttle open, so provide it!

-Check your valve clearances, and make sure they are all spot on. You'll be suprised at the difference it makes.

Doing these three things helped a whole lot with my bike. It still gets mad if you really try to pour on the gas at like 2500, but remember, these carbs are significantly larger than these ones originally on the bike, and they are a top-end / bottom-end compromise until you really get some flow with either a big bore kit, higher compression, or some careful port work.

-Dave

Dave pretty much nailed it.