Road Star Forum
Welcome, Guest
Please Login or Register.    Lost Password?
Go to bottom Post Reply Favoured: 0
TOPIC: Re:fuel air mixture
#497083
Just Dave (User)
Expert Boarder
Posts: 439
graphgraph
User Offline Click here to see the profile of this user
Gender: Male Location: Port Richey, Fl Birthdate: 1965-02-05
Re:fuel air mixture 1 Year ago  
Ttown wrote:
After reading your post concerning how you set the PMS reminded me of something we used to do to our race cars setting the idle and fuel air mixtures consecutively until you reach an equal point between the two. I'm going to give that a shot tomorrow after work.

The pilot needle is set in the 5th grove, and I am using the 172.5 main jet, due to running straight pipes and a low restriction air filter.

I am going to go through it another time using starter fluid to be sure there is no vacuum leaks. Between the best setting for air fuel mixture and vacuum leak it has to be one or a combination of the two.


I'm sorry, it does say 3 1/2 turns on thew barons sheet, I was looking at Shanes instructions. I had both of them sitting right here at my desk. Wonder why his says 2 turns???

Hope you get it sorted out soon.
 
Logged Logged  
 
Last Edit: 2012/05/29 22:00 By Just Dave.
 

A Happy Traveler has no Particular Destination
  The administrator has disabled public write access.
#497209
SKWEARpeg (User)
Platinum Boarder
Posts: 5902
graphgraph
User Online Now Click here to see the profile of this user
Gender: Male Location: Milton, Florida Birthdate: 1958-00-00
Re:fuel air mixture 1 Year ago  
Ttown wrote:
After reading your post concerning how you set the PMS reminded me of something we used to do to our race cars setting the idle and fuel air mixtures consecutively until you reach an equal point between the two. I'm going to give that a shot tomorrow after work.

The pilot needle is set in the 5th grove, and I am using the 172.5 main jet, due to running straight pipes and a low restriction air filter.

I am going to go through it another time using starter fluid to be sure there is no vacuum leaks. Between the best setting for air fuel mixture and vacuum leak it has to be one or a combination of the two.


Your on the right track. The PMS controls the fuel, and the air is a constant on these carbs. By backing the PMS out, you make the mix richer, and turning it in leans it. The motor should quit or almost die when the PMS is turned in all the way. You are essentially cutting off the fuel.

Okay here goes. You can probably get by with the 170 main(99-03), but you should move the clip to the 4th groove from the blunt end. That will reduce the rich part in the over lap. The 172.5 will work fine, it just provides more fuel at WOT. If it's still running fine there, you can bump the clip to the third, and put another/second silver washer under the white spacer on the needle....that gives you a half step, so you'll actually be at 3 1/2. The further from the blunt end of the needle, the richer the overlap in the circuits. The closer to the blunt end, the leaner. The needle, is like a cork in a bottle. The further down the needle is, the more it chokes of the fuel in the overlap.
When your messing with the PMS, make sure the bike is warmed up good. The idle should be between 800 and 900 RPMs. 10 to 30 minutes of harder riding..not poking around. When its warmed up good, and idling, turn the PMS in until you get a lean stumble, and then back it out(counting the turns) until you notice the rich stumble....It might be subtle, so pay close attention. Then, turn the PMS halfway back towards the lean stumble. In theory, that should have you at the midpoint. After some riding and testing, you can turn the PMS in some more, until you start noticing lean issues. When you thinnk your at the sweet spot, shut off the bike, and then turn the PMS in until lightly seated(counting the turns), and then back it out to where you were. Now, you have a reference point for where your bike runs the best.
When tinkering with the main, and the pilot circuits, you are trying to get to the point where you have lean issues, and then back up to where you were before you noticed the lean. Its best to mess with one at a time. I'd concentrate on the pilot first, but still move the clip to the 4th groove now.

It's possible, that with the clip in the 5th groove, and your idle at 950 rpms, you were pulling more fuel up through the main circuit in the overlap, and creating a rich condition. It may be, that the extra fuel was causing the idle to sag, and then rev as it catches up....that's just an alternative to the check for a vacuum leak thingie.

Once you get on top of this and the PMS adjusted, you can actually turn the idle down to 700 or there abouts, and the bike should still idle fine. When it gets down to 650 or 700, it gets the definitive V-twin lope
 
Logged Logged  
 
  The administrator has disabled public write access.
#497364
Ttown (User)
Fresh Boarder
Posts: 17
graphgraph
User Offline Click here to see the profile of this user
Re:fuel air mixture 1 Year ago  
I will give it a shot as soon as I get a day free from work Thanks
 
Logged Logged  
  The administrator has disabled public write access.
Go to top Post Reply
Powered by FireBoardget the latest posts directly to your desktop
...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... ...................................................................... -->
New Forum Posts




The Road Star Clinic is a collaborative community of riders who archive and publish user contributed technical data about Yamaha Road Star motorcycles.

We also sponsor the creation and support of other community websites similar to our own. Inquiries about availability of a website for your community can be submitted to us via any "Contact Us" option on the Clinic.

Copyright 2003-2007 Road Star Clinic and its respective authors. Road Star Clinic is sponsored by the folks at MLSHomeQuest.com.