TOPIC:

Guys, need some help on these carbs. I need to set the float level correctly and I know that I can use the Mikuni HS manual for tuning procedures but there is one thing about this that is unclear to me. I know that with the carbs upside down, from the top of the float to the carb body mating surface to the bowl that the distance should be roughly 19mm. Here's my question: is the 10-20 degree angle shown in the picture critical and does that have to do with the small amount of play on the needle valve's actuator tab? Should this 19mm be measure with the float fully pushed down on the needle valve so that the slack is taken up in the pin and the needle valve completely seated, or should the 19mm be taken with absolutely no pressure on the float other than gravity (and perhaps the carbs at a 10-20 degree tilt, if that makes much of a difference in the pressure it puts on that pin?)? Any insight into this would be most appreciated, thanks in advance guys!

David

As with other style carbs, would ignore the float height and instead concentrate on getting the fuel level to specs inside the float bowls, using the clear tube test.

A carb cares about actual fuel level inside the float bowl, and couldn't care less about the dry-measured-upside-down-on-the-work-bench float height.

Good Fortune!

u set the fload hieght with gravity on needle only. this is only a rough setup. then u do as Patton said and do the clear tube test. which is the only real good way to be acurate. but it is a pain.

Ok Patton, I know I could do a search and find it somewhere on the forum but since we're here anyway, would you be so kind as to school me on the clear tube test? Would really appreciate it. Also, I read on another post on here that the best way to sync these particular carbs is to use (4) 1/8" to 1/4" ball bearings and get them to drop throught the carbs at the same time using the pilot carb. Agree? Thanks!

www.kzrider.com/forum/3-carburetor/447154-poor-fuel-economy

The ball bearing test you mention is like the float height business, just a way to get close.

this is the clear tube taest as posted by patton.u can buy or make this tool. just put a line on the tube if u make your own, this will insure the same amount of fuel comes out of the bowl each time. and set the fuel level to the manufactures spec.




as for setting the slide level, any small drill bit will work fine. then u sync the carbs with a vacuum gauge later.

The bench sync is to get the slide heights equalized, knowing that the later "running" sync will re-adjust each of them to thereby obtain equal performance among the cylinders (as measured by carb vacuum produced by each cylinder).

When doing the bench sync, it's okay to use some readily available device in each carb, such as a paper clip wire. So each slide's closed height is set at the width of a paper clip wire.

An important thing to remember when doing the bench sync is that the later engine running sync will ofter necessitate one or more of the slides being lowered even more than the paper clip width setting during the bench sync.

To allow for this likely scenario during the running sync, do this:
While doing the bench sync, assure the idle thumb screw is adjusted with sufficient thread remaining to allow further slide height reduction as and when later necessary.

Good Fortune!

Just now had a chance to check back in on the replies here. Thanks for the info guys. I will be seeing what I can do with these carbs tomorrow. One thing to note; RS's don't have an idle thumb screw, believe it or not.

My RS's have a thumbscrew

Yea, that was an ignorant statement on my part. Its been about a year or more since I touched these carbs and I remember reading somewhere that someone said they didn't have a thumbscrew. But they do. Just like the ones in your pic. What they DON'T have for sure is a small bowl drain screw, only the large drains similar to 29 smoothies to access the main jets easy.

At the end of the day, I got the bike running pretty well but its still not right. I moved the jet needles 3 seperate times, starting with them being in the middle, which caused the bike to fall on it's face HARD when hitting on the gas much past 1/4 throttle. Raised the needle up a notch and it corrected most of this problem, but still some hesitation if too hard. Decided to raise it to the last position (Needle highest) and that started to go the other way and make it worse, drowning it out so I put them back to the #4 position (if counting down from the top of the needle).

Still not really happy with the way its running though and I would think my bike could handle 34's at this point. Just put a 1075 kit in it and had a mild port/polish job done on the head, making sure to match the larger boots to the head's intake ports, no spots for the gas to puddle up. Also running a kerker header and pod filters of course. Anyway, not really sure where to go from here as I know I can't set the needle in any better position than what I just described. According to the tuning manual (HS tuning manual), I don't think my main jets have much to do with the issue as I start to get issues I'd say right past the 1/2 throttle position and the manual says the main jets don't even really matter until about 3/4 throttle. Anyone have any thoughts? Also, the accelerator pump is adjusted to start working as soon as the throttle is pulled and to work as long as it is possibly able to (the stop screw is adjusted all the way out). I have no issues up until about 1/2 throttle or so.

the main will affect from 1/2 to 3/4 ,just not that much. i would try to dial in the main now. hopefully it will need to go in the direction that will help u.

what main and pilot are u running ?