gggGary wrote:
Ran through this helpful posting stem to stern. In some other threads I found mention of the float height and how it changed early to late. I have a 2002 carb on the bench so wondering if resetting the float to the late spec or some in between height would be advantageous?

My vacuum cap was significantly warped, found a few mentions of that, it didn't take long to straighten the sealing surface by stroking it on a piece of 160 grit on a flat surface.

A link to manifold mods in the original post might be good?

I swear the main is plainly marked as a 165, no markings on the other brass. I still need to look at the needle jet see if it's a stocker or has adjustments. Might these be some weird after market stuff? The PMS cap had been removed when I started. screw was 3 1/4 turns out. The float bowl screws are stock phillips, not burred up.
There was carbon build up on bore, slide and even inside the pilot jet..

You want to set the float for the later spec. It applies to all years of the carb models. Check out Curts Site On the projects tab are several zip files with great info. You will find the manifold porting and surfacing there.

Rod

There are a couple of outfits selling "just like Mikuni" brass out there, so it's possible to have off brand jets with no markings. We all tend to go Genuine Mikuni only around here. I'm away from the lap top just now, but I'll hook you up on manifolds in a short bit. Raising the float is a matter of taste mostly. I raised mine a long time ago to the later spec, not due to troubles, but just because I was there. No influence on fueling noted. I have since done the pump less mod. If I had starvation on top end or hard acceleration I'd consider it a first move.

#165 main jet means .165mm

Google inches =mm

So that means a 165mm= (.0165mm) main jet has a hole in it that is .4190 thousandths.

A #40 idle jet is #40 (.040mm) or .0157 thousands of an inch ( Fifteen thousands) size hole.
A 37.5mm idle jet would be about (.014 thousandths and change.) size hole.

gggGary wrote:
Ran through this helpful posting stem to stern. In some other threads I found mention of the float height and how it changed early to late. I have a 2002 carb on the bench so wondering if resetting the float to the late spec or some in between height would be advantageous?

My vacuum cap was significantly warped, found a few mentions of that, it didn't take long to straighten the sealing surface by stroking it on a piece of 160 grit on a flat surface.

A link to manifold mods in the original post might be good?

I swear the main is plainly marked as a 165, no markings on the other brass. I still need to look at the needle jet see if it's a stocker or has adjustments. Might these be some weird after market stuff? The PMS cap had been removed when I started. screw was 3 1/4 turns out. The float bowl screws are stock phillips, not burred up.
There was carbon build up on bore, slide and even inside the pilot jet..

Yamaha changed the spec on the carb float setting, so that all are to be set at the 04 and later setting.

By "vacuum cap", do you mean the cover on the Coasting Enricher, on the side of the carb?

The stock main on a 99-03 Roadie, is a 165 *Mikuni*. It will also have a Square in a Square, and an "R" stamped on it, if it is a *Mikuni* jet. All Mikuni jets, have the Square in a Square and R.

The Pilot jet, is in the carb bowl. It is a tall thin bodied jet. The size is stamped on the side, and you may need a magnifying glass, to read it.

The Starter jet, is the only other jet. It doesn't get messed with, unless somebody does it accidentally on purpose(if you follow my drift). It is either a 56, or is blanked off, if it is stock. We have had more then one incident, where a main jet was installed in the Starter jet hole. When that happens, the Enricher won't work properly at all. The bike will be difficult to start, or won't want to start at all, when this has happened(this shouldn't be confused with people not knowing how to start the Roadstar, according to the Yamaha manual).

It's not uncommon to have a carbon residue in the carb throat, from the chuffing back through the carb, when the pilot circuit is to lean, or the clip is set to high on the needle. It can also get that way from blipping the throttle. Are you calling the PMS screw, the pilot jet?

You can search the forum, for threads about surfacing the flanges on the intake manifold, and porting. Or, buy one of Curts manifolds, that will have the surfacing, porting, and will have the vacuum port soldered shut as well. He has an ad in the classifieds.

LuckyDon wrote:
#165 main jet means .165mm

Google inches =mm

So that means a 165mm= (.0165mm) main jet has a hole in it that is .4190 thousandths.


Actually, Mikuni sizes their jets according to fuel flow, not size of hole. This is why Mikuni jets differ in fuel flow, from DJ's. The comparrison chart on the Tech articles page, offers some insight. A 165 Mikuni, is larger, then a 165 DJ.

Gary knows a thing or two about carbs y'all. He's just talking out loud about his jets! Lol. Over in XS650 land, he's all over those old BS carbs, so no basics required. Curt's site (under his avatar above) has some great info for sure.

I think I gave you this link before:

http://weislake.com/sig/mucker/instructions.htm

Here's a Mikuni 170. Note the "R" and the square in square that SKWEARpeg references. The pilot jet has these stamped around the outside of the brass. In the photo below, you can see it's in the lower half of the protruding shoulder, so not the easiest to see installed, if it's Mikuni brass.





Grizzly float valve:



Road Star version of "The Carb Guide"
http://weislake.com/sig/mucker/carb/carb%20tech3.pdf

N224.103.35 for pilots (the 35 is the size, comes in 2.5 steps, so a 37.5 is the next step up) and N100.604.165 (165 is the stock size. Comes in 2.5 steps as well. 167.5 is next)for mains

vacuum cap, the big black cap over the diaphragm, mine had a major warp, the screw flanges were sucked down leaving a gap on each side. Ordered a replacement enricher cap cause this one has the warp/crack starting. New float bowl o-ring on order also. Will check and set float to "late spec". Looking over the curt manifold file and printed that, and the HS40 manual pages.

Good call on the Mikuni = square in a square Yup these are some aftermarket brass parts, into the dust bin they go. Still need to look at the needle.
Jetsrus here I come. I guess I'll pull the carb off the "parts bike", see what's in that one.

A possible alternative to Jets-r-us:

http://www.pjmotorsports.com/mikuni-jets.html

They also carry the oval and round "generic" K&N filters we use like the RA-66V, RA-76V, RC-1980 types if you want some bigger air for a ported manifold to sing with, for little cabbage.

I had never considered the possibility of a leak with the top hat over the upper chamber. I thought the distortion was just a by product of only two screws, the palstic cap and a fat oring flange on the diaphragm. I can see, where if it was leaking, it'd slow down the response of the slide.

I used a grey scratch pad, dipped in Seafoam to clean the backs of my slides.

Here is the Odo dry set float setting method. I like it, but it is susceptible to some interpretation error. The tube on the bowl drain, with the bike on a lift or held upright, is the yamaha approved method.
http://weislake.com/sig/mucker/carb/carbfloat/carbfloat.htm