Pilot screw setting and other crimes...

[Treb]

Well after getting a whopping 32 mpg on my last run over to the hills and back I decided it was time to have a look at the carbs. Other than being dirty on the outside, everything looks pretty good inside the bowls. No plugged jets and float valves appear to be in good shape. Also did a bench sync check and it's set as good as any I've ever setup with the paper feeler gauge method.

 

Then I checked the pilot screws for blockage and found all of them at a little over 4 turns out. No blockages but 4 turns out? I checked the spec sheet I have and it shows some nonsense about 15 something or other...After searching here I found many threads asking the question of how many turns out but no answers. So I started turning them in first 1/4 turn at a time and test riding it. No difference noticed except maybe a touch quicker acceleration for the first two tries then I just decided to go with the old standby 2.5 turns out. It starts easier and does not backfire on decel. I will read the plugs after my next run to make sure it's not too lean but I'm pretty sure it was waaay too rich.

 

So I'll preface this by saying that I live at over 4,800 ft and almost always go up from here to something around 10K to sometimes over 12,000 ft. If anything I would think the factory jetting and or pilot screw setting would be a touch rich for me in the first place?

 

P.S. If you guys think getting the carbs off of a RSV is a pain in the neck you should try a Magna...

Edited November 15, 2018 by Treb

[BlueSky]

I'm surprised you got 32mpg with the idle mixture screws set at 4 turns out.

[sldunker]

Just a reference for you. I checked my screws on my 2007 RSV and they are all at about 2 turns out. Starts good, no popping and very good gas mileage.

[RSTDdog]

If you look at the head pipes on the RSV (and RSTD, the early Ventures, Royales, Vmax, etc) they all have threaded access ports (10mm head). Back when I worked for a Yamaha dealer, we had the Yamaha Exhaust gas analyzer, analog gauges, and set up with 4 sensors, so you could set the CO value exactly the same on all 4 carbs with the mixture screws. Yamaha had published specs for setting CO with EGA.

 

Absent an EGA, you can set them by ear, or set them using a good tachometer and your sync gauges. Lean Drop method is the typical where you adjust the mixture lean for maximum RPM and then richen to drop RPM by 50 ( you need a good tach). You can see changes in the mixture at idle in the sync gauges as well. Adjusting mixture for highest vacuum reading on that cylinder is equivalent to leanest (before miss sets in) mixture setting on that cylinder.

 

And as all of that is a bit fiddly and will drive the OCD among us crazy, 2-2.5 turns out is usually good on clean and properly functioning carbs.

[Marcarl]

Maybe some to help understand what is happening as you go along. During idle, the primary circuit has all the control over fuel mixture, well nearly all, but as you open up the throttle plates the secondary or running circuit has it's input. The higher the rpm, the less percentage the primary, or idle circuit has an impact. It never cuts out, just has less of an effect. Sooo, when in idle mode, the primary circuit and it's adjustments has a profound effect on the running, but once over 1500 rpm, not so much, it's all on a percentage basis. Air mixture settings have very little to do with running down the highway, but a lot to do with sitting still and moving on from standstill. It also come into effect when the throttle is released and the throttle plates close, because then the primary circuit is the only one working. Keep in mind, that the circuits are more governed by the throttle plate position than the engine rpms.

Hope I'm right and this helps.

[KAWoodworth]

Does anyone have pictures of where the pilot screws are located on the second gen carbs?

 

Thanks

[Treb]

Marcarl Yes I understand how the jets overlap in duty as the throttle is opened. Here is a little graphic that that popped up on another MC forum that shows it quite nicely.

 

As far as a pic of the pilot jet adjustment screw location...Its not easy to take a pic of it while the carbs are on the bike, Heck it's even a challenge just to get a screwdriver on them. You have to look thru underneath the carbs to the back of the opposite side and it's a cross tip brass screw so you can use a flat tip from vertical or horizontal.

 

P.S. If they haven't been adjusted they might have some brass caps on them that you have to remove.

Edited November 16, 2018 by Treb

[Du-Rron]

Does anyone have pictures of where the pilot screws are located on the second gen carbs?

 

Thanks

 

https://www.venturerider.org/forum/showthread.php?115048-Carburetor-float-bowl-covers&highlight=pilot+screws

 

shows a pic

[Treb]

UPDATE: Took it out for a 150 mile trip and the mpg is up to 39 with a mix of highway and twisties. Now as far as the other crimes go... I notice a different noise I think coming from the front end when I make turns, even just banking back and forth on a straight away. Is there a history of worn wheel bearings at over 60K miles? And has anyone actually gotten good sound from modifying the stock exhaust or is there a reasonable replacement that won't make my ears bleed and empty my wallet but has a little rumble to it?

Edited November 17, 2018 by Treb

[Du-Rron]

UPDATE: Took it out for a 150 mile trip and the mpg is up to 39 with a mix of highway and twisties. Now as far as the other crimes go... I notice a different noise I think coming from the front end when I make turns, even just banking back and forth on a straight away. Is there a history of worn wheel bearings at over 60K miles? And has anyone actually gotten good sound from modifying the stock exhaust or is there a reasonable replacement that won't make my ears bleed and empty my wallet but has a little rumble to it?

 

I get from 26 to 40 mpg depending on my driving, load, wind, etc... Some brands of tires, like Dunlop 404's, will sing, moan, to you in the curves and turning corners. Everybody usually puts a HD exhaust on (not me) and there are several articles on here about it.

[Graywulf]

Depends how far you want to go, I have V&H Monster ovals {LOUD} but a really nice 'rumble' with an Ivan's jet kit.

 

{not my bike} -->

[Treb]

Depends how far you want to go, I have V&H Monster ovals {LOUD} but a really nice 'rumble' with an Ivan's jet kit.

 

{not my bike} -->

 

Did you choose to re-jet or was it a requirement for using the monster ovals? I love the sound but they are too rich for my blood

[Graywulf]

Did you choose to re-jet or was it a requirement for using the monster ovals? I love the sound but they are too rich for my blood

 

I don't know if others have run 'Ovals' on standard jetting, but as they are a lot more 'free flowing', and I fitted K&N's also, so I did the jet kit as a matter of course. I can start the bike with no choke at all 'non winter/cold' from cold, and certainly have plenty of low down pull.

[BlueSky]

Sounds like a V8!