Keep in mind that when you "Cut your teeth" with hard core racers they weren't looking for longevity, They weren't looking for pulling up a long steep grade or accelerating to pass a vehicle at hwy speeds. they were looking to win a race and were tuning to do just that. That isn't your goal at least I don't think it is. If your bike runs so great then I guess there really wasn't a need to start this thread. As far as the screw in the carb put a screwdriver or allen(whichever it is) in the screw and with something supporting the bowl lip hit the screwdriver or allen with a hammer. That should break the screw loose. if you have an impact driver that will also work to get it out.

davej wrote:
Keep in mind that when you "Cut your teeth" with hard core racers they weren't looking for longevity, They weren't looking for pulling up a long steep grade or accelerating to pass a vehicle at hwy speeds. they were looking to win a race and were tuning to do just that. That isn't your goal at least I don't think it is. If your bike runs so great then I guess there really wasn't a need to start this thread. As far as the screw in the carb put a screwdriver or allen(whichever it is) in the screw and with something supporting the bowl lip hit the screwdriver or allen with a hammer. That should break the screw loose. if you have an impact driver that will also work to get it out.

Yeah I used to rely pretty heavily on my impact screw driver back in the day when I was working on a lot of different types of vehicles. I went through a long draught of avoiding engine work after the kids parted home and we went from five vehicles plus boats and a vintage firetruck that I was restoring to instead just having a couple of bikes and a Toyota truck, perhaps working on outboard motors once in a while for fun and profit.

I guess I went on strike for a bunch of years. Really scaled down in the last ten years and a lot of my tools went with it. Time to pick up another impact driver I guess. It did wonders more times than not. But those screws and fittings inside carbs can freeze up and some are so fragile that they just break rather than cooperate, creating new problems. Believe it or not I had a hell of a time just breaking the screw loose that holds the throttle pull cable from sliding out of the throttle grip housing. An impact driver would have been the ticket.

The bike truly DOES run great. I started this thread just to be sure that an emergency hadn't arisen which would spell the doom of my upper end if I didn't make some immediate changes. I'm not trying to go leaner, only dealing with what I got when I bought the bike six weeks ago.

The bike idles great whether at 2.5 or 3.33 turns out, just a bit smoother and quieter when further in. Kind of like a sewing machine vs. a thumper.

Right now I'm taking a 'if it's not broke don't fix it' breather. I've been dealing with what I considered necessary repairs and upgrades since buying the bike in early July, while getting familiar with its design and characteristics in the process. I'm going to keep a jetting upgrade on my mind until I'm ready to go that route and I'll probably stack some other upgrade or two in at the same time. But I'll pull the plugs periodically just to keep an eye on things.

When I was referring to my buddies who raced Harley's years ago, I was doing so to illustrate how they used the plugs to take the pulse of what was going on in the motor, as we all should be doing. I'm not trying to replicate what they were seeking back in the day, however performance is performance. I may upgrade my igniter so I can get some more revs out of the motor (I have the 1600). Those extra 500 RPM that the 1700's pull might be fun once in a while.

Not sure what I have inside the carb but if my main needle is adjustable, as I'm guessing it will be, I should be able to drop the clip a notch or two to richen it up on acceleration. I spend most of my time on the road putting around in 5th gear when possible so I'm not too worried about what's going on under higher revs. But I may just step up to a 42-45 after rolling it around in my head for a while. I'm in no hurry.

Thanks again for your thoughts and insight fellas! Always appreciated!! Now I've got to figure out how to burn the next tank of gas. Maybe head north to take in the eclipse? I probably shouldn't pass that up.

I was serious about the real world AFR numbers that have been accumulated. I like the CV carbs, because they are almost as simple as a hammer. If you step to a 42 or 45 HSR, then there is a variety of combinations, that you can run. Its never interested me to mess with it. I like hammers.

For a 1600, at least a 37.5 Mikuni Pilot. You won't need anything larger then a 40. For the Main, a 167.5 for the stock igniter is sufficient. This would be with intake and exhaust mods that create a more free flowing system. As JD pointed out the other day, the extra revs at the top end with a 1700 igniter, go real well with a 170 Mikuni. It allows for the extra fuel on top, when you need and want it.

Notice I keep mentioning Mikuni. Mikuni jets flow more fuel, then say DJ in a straight up comparrison of the number size alone. Mikuni sizes their jets according to flow rates, DJ sizes theirs, according to the size hole they drill. For example, a 35 Mikuni Pilot, will flow an equal amount of fuel as a 37.5 DJ (hat tip to davej for that tidbit). If you look on the Tech Articles page, you will see a comparrison chart for Mikuni's and DJ's. This is why whenever somebody starts out with "I was looking at this cheap jetting alternative from "Mothers Best Jetting Solutions", most of our eyes glaze over. Just say no. Its a Mikuni carb. Do the right thing.

As far as clip position on the needle, most here are more then happy with the clip in the 4th, and the fat spacer and a single silver washer under the clip to set the elevation. If you wanted to be slightly leaner on the needle, then you can either remove the silver washer under the fat spacer, or, you can move the clip to the third groove from the top, and add a second silver washer(spacer/shim) under the fat plastic spacer. Either of those, will give you something around 3.5.

More then 4, and you get into sloppy rich territory, and less then 3.5, and many have trouble getting their bikes to run well off idle.

As far as Multi groove needles go, the DJ or Barons needles are almost identical. They are slimmer and have a faster taper then the fat stock needle, and have multiple grooves(either 5 or 6). All the jetting choices I mentioned above, are using a DJ or Barons needle. Speedster made(makes?) kits for the CV carbs also. Their needle is fat like the stock needle, but also has multiple grooves. When using a Speedstar needle, you will need to run fatter Mains. On a 1700, a 180 or even the stock 182.5 will work. Based on that, I'd think you would need to be richer then the 170, with a fat speedster needle on a 1600. The reason being, with a slimmer needle you have taken a step up from 165 to 167.5 Mikuni Main. It seems reasonable, that a 170, 172.5, or maybe even a 172, may be a better choice for a fat speedster needle, in a 1600.

As far as messing with the float, unless you check it and know its wrong, don't mess with it. I'd encourage checking it.

+1 on the 37.5 pilot with your setup and the CV carburetor. The HC setup also came with a reduced size primary pilot air jet which is up top under the diaphragm. Stock is a 2mm. It's possible that jet wasn't replaced because the slight discoloration at the tip of the insulator which is the idle and primary circuit would be darker.

Reducing pilot air jet sizes richens things up quite a bit. If it's not idling real smooth with the screw at 2 1/2 turns cover the secondary air jet at the mouth of your carb with your finger and you'll see quite a difference.

As far as removing the carburetor for jet changes I've found that I can do anything necessary with the carb on the bike with the exception of course removing a stuck screw.

I wish I could get up there and see the eclipse but that won't happen. Maybe we'll get a little bit of a shadow down here.

OK, my brain's a little on autopilot this morning, taking in the news as I catch up online and still not fully in gear, so let me ask you a question about this pilot screw. Thanks for your input, it's been awesome.

Keep in mind that I had a lot of projects going on at once, with the bike as well as beyond it, so adjusting the pilot screw was something I did as an experiment without knowing which setup I actually have in my carb or what the PMS setting for the HC and pipes should actually be.

But let me make clear, when I took the screw to 2.5 turns the bike purred like a kitten. I was stunned. It sounded like another bike, a NORMAL bike if you will. In some ways I liked it and in others I didn't. I like the growl of a richer idle.

But I messed with the PMS only to see what would happen with the backfire on deceleration. To my memory it completely eliminated it. I took the screw out another 1/2 turn and found that perhaps a bit of backfire returned but the bike seemed to have more power.

Let me backtrack a bit. With 2.5 out there may have been a slight hesitation when hitting the throttle, almost like I was concerned that it was going to die. I had to nurse the throttle to raise the revs before leaving a stop sign. So I fattened it up and that problem was gone.

But another result of 2.5 turns out was that the bike seemed really lean on acceleration. It ran great and when I was in 5th gear on the freeway I was looking for another gear at 80 MPH because it had fooled me that much. I may go back down to 2.5 turns just to try it again now that I've had the bike longer and am more familiar with its power band.

When I backed the screw further out to 3.33 turns, the richer the idle sounded, which I like, and the more fuel it seemed to have on acceleration. It was a much throatier growl, didn't sound like it was starving for fuel. Not a lot of difference in the higher revs, only on bottom end acceleration. So that's where I've kept it.

So two questions...

How deeply through the revs do you think the pilot setting can affect performance?

If I go back to 2.5-2.75 turns do you think it will affect or lean out the motor in a negative way compared to what I'm running now, or is it truly only the lower revs affected and not going to hurt the overall band width of the motor?

Reason I ask is without putting the bike on a dyno I really don't know if the quieter, leaning sounding motor is actually making MORE power than the throatier richer mix, of if it is indeed starved for fuel. I just left it fatter because it seemed like a safer setting and seemed to have more grunt on acceleration compared to the leaner setting (it is LOUDER).

Is there more chance of hurting the motor if I go back to 2.5+ turns for now, without changing anything else? I know the pilot is designed for idling but I was surprised how broadly it affected the entire powerband altogether when I fattened it up.

Regarding all of your jetting tips and insights, I know that at some point I'm going to have to pull it all apart just to see what's in there. I am living under the assumption that whoever spent the $$ to do the HC, pipes, and other upgrades probably had enough sense and advice to upgrade the jets as well. I can't know without going through it all.

But like I said, it runs great and is a lot of fun so short of concerns for hurting the motor I'm fine with where things are at right now.

See if this helps?
http://www.mikuni.com/pdf/hs40_manual.pdf

The PMS adjustment, should be done as follows.
The bike should be well warmed up....as in burn your pinkies hot... for your initial set.
The idle needs to be between 850 and 900 rpms.
With the bike running, turn the PMS in until it is lightly seated. The bike will run a bit rough, but it will run. There are three other small holes at the base of the throttle plate on the floor of the throat, fed by the Pilot circuit.
Now, start backing the PMS out about a quarter turn or less at a time, keeping track of the number of turns out, and letting the idle settle after each small change. You're listening for the first best smoothest highest idle. Most people find that around 1 1/2 to 1 7/8 out from lightly seated.
This will generally be a bit lean. The factory sets them around 2 3/8 out. As temps cool in the fall, some may notice just a bit of decel popping at 2 3/8, and can tweak it out a bit more.
If after the initial setting, you want to tweak it some more, you can do that when the bike is cold. Just keep track of how much you turn it in and out from your baseline.

Keep in mind, this is just a mixture adjustment, with a closed throttle, and the idle set correctly. If after all this messing, you think you are seeing some benefit from backing it out further, in hopes of fixing something else, git-r-done. But, you'll have just wasted all the time setting the idle mix, which is what the PMS does. I think you would be better off tweaking either the clip elevation on the needle, or bumping the Pilot size, for off idle hesitation.

It's possible the decel popping may be related to either a vacuum leak, or possibly an exhaust gasket leak. It wouldn't be the first time somebody spent a lot of time chasing a "jetting" issue, only to find out they had extra air getting in from somewhere.

Keep in mind as well, the Roadie is a long stroke air cooled v-twin, with a single carb trying to do it all. They aren't partial to the Maserati style throttle blipping at stop lights or in the driveway. They are just not that kind of a performance machine. They will pull like a freight train though.

SKWEARpeg wrote:


Keep in mind, this is just a mixture adjustment, with a closed throttle, and the idle set correctly. If after all this messing, you think you are seeing some benefit from backing it out further, in hopes of fixing something else, git-r-done. But, you'll have just wasted all the time setting the idle mix, which is what the PMS does. I think you would be better off tweaking either the clip elevation on the needle, or bumping the Pilot size, for off idle hesitation.

It's possible the decel popping may be related to either a vacuum leak, or possibly an exhaust gasket leak. It wouldn't be the first time somebody spent a lot of time chasing a "jetting" issue, only to find out they had extra air getting in from somewhere.

Keep in mind as well, the Roadie is a long stroke air cooled v-twin, with a single carb trying to do it all. They aren't partial to the Maserati style throttle blipping at stop lights or in the driveway. They are just not that kind of a performance machine. They will pull like a freight train though.

Keep in mind that regardless of the PMS settings that I've used, from 2.5 all the way out to 3.3, I'm fine with the results of idle. It runs and sounds fine. I used to run an even lower speed idle because I liked the loping sound, but in reading the RSC posts I've gleaned that the motor may have oiling issues at too low idle so now I run it faster. It used to speed up a bit when it got hot but now with the higher idle speed it doesn't change much.

I'm just trying to figure out how far up the power band the idle mix affects performance and whether leaning out the idle can really affect the higher revs much as it relates to running leaner.

My next experiment may be running it from about 2.0 out to 4.0 to see what results I seem to be getting under the entire throttle range. I think the screw was about 4.0 out when I bought the bike last month and that produced some annoying backfiring. But tweaking the PMS did show that it was causing the backfire because it completely disappeared as I turned the screw in, eliminating any thoughts of gaskets or a cracked manifold. That's all I was really trying to chase down with the PMS adjustment to begin with, and that put that issue to rest.

davej wrote:
As far as the screw in the carb put a screwdriver or allen(whichever it is) in the screw and with something supporting the bowl lip hit the screwdriver or allen with a hammer. That should break the screw loose. if you have an impact driver that will also work to get it out.

I used to be a certified Yamaha Electronics tech. Even the electronics side of Yamaha used the same type of soft metal screws.
What I would do to prevent from rounding out a screw head was make sure that I had a Good fitting Phillips screwdriver, I used snap on.
If I still stripped it out, I would use my diagonal wire cutters. Place the cutters over the head of the screw in the middle, squeeze the cutters and turn it sharply ccw. That usually would break the screw loose. It is all about torque. Handheld impacts, I used to use on my dirt bike, but I would not want to use on a carb, since everything is soft/brittle metal.

Rg

Nocolorbrother wrote:
See if this helps?
http://www.mikuni.com/pdf/hs40_manual.pdf

That's an awesome link! That's exactly what I was looking for. It didn't show up the first time you posted so thanks for coming back and adding it in.

I'll read through that for a while and make some decisions. Looks like the pilot only affects things through 1/4 throttle which is what I seemed to experience.