Does anybody agree that the air adjustment screws on the Raptor are very hard to turn. They are so hard sometimes they almost strip. What's up with that?[img]i/expressions/face-icon-small-mad.gif[/img]

 

have not experienced that on mine but I have seen posts from others who had the same problem, one individual said his were screwed all the way in from the factory (????)

 

Yes, they are a pain adjusting while mounted on the quad. Are you having some type of trouble?

 

Yup, me too, I even bought one of those long screw drivers from the Yam dealer so I could adjust the air screws while the bike is running to obtain the "optimum setting" but like you said it doesn't feel right & when I think I am close to 3 turns out I was really 5+ turns out & it was running like crap. The only way I was able to set it with any confidence was to flip the carbs over & set them to 3 turns out & hope that was the optimum setting. By the way, if you do have any luck adjusting them while the bike is running, you can definitley hear the difference. If you manage to turn them all the way in you will stall the bike. As you approach the optimum setting the rpms will peak out & if you go too many turns out(too rich) it will kill the rpms as well.
I have no confidence that those screws can take any abuse & yet if you read about jetting they say you should adjust the air screws everytime you ride, what a joke! I just installed larger pilot jets(25's) & leave the air screws @ 3 turns out. Most of the racing mfgs agree with those settings, some actually use 27 pilot jets.

 

So, from what you just said, there is a set number of turns from the totally closed position. It looks like you have some reference to the service manual. Do you know the recommended settings for the screws from the totally closed position for each carb?[img]i/expressions/face-icon-small-smile.gif[/img]

 

Chimmer....I have found that when RPM's peak, after a couple of more turns, the RPM's only become slightly more erratic. The carbs are more prone to blowing off with the idle slightly more erratic....even though the condition is Rich.
I found peak RPM along with the least erratic idle easiest with a vacuum guage.
Dawg...a good baseline would be 2-2.5 turns out on the left carb and 3-3.5 turns out on the right carb.

 

Gary, I agree about more turns past ideal only causes erradict idle, just a slip of the fingers/lazy too. My manual says to set each carb @ 3 turns out from all the way in & I have read that it is a good baseline as well. I spoke with CT Racing about it & they also recommend setting the right carb a little richer but more like 3 1/4 turns on left carb & 3 1/2 turns on the right. I like your idea of using a vacuum gauge because it makes much more sense than guessing, the only problem is I don't have a guage & don't know how to use one either. Maybe you can elaborate on this a little. I like to do all my own work as well & don't like paying anybody to just guess when I can do better myself for free. Also, I have read numerous posts about fixing the boot blowing off the carb problem being resolved by going a little richer on the air screws not leaner & by increasing idle RPM. However, experience is much more valuable & if you don't mind I think we all can benefit from your experience/comments.

 

A vacuum guage can be picked up at any auto parts store. A decent one can usually be picked up for around $20. The numbers on the guage need to read from 0 to +20-25. The guage will have a small vacuum line attached that's maybe 15 inches long. THis line attaches to the nipple thats exposed on the top of the left intake boot.
I will give the run-down on the tuning process for my Raptor. First, I attach the line to the nipple and lay the guage somewhere you can see it while tuning. I use a flexible screwdriver.....now I get set up to adjust one mixture screw and start the engine. The vacuum guage is extremely erratic at first.....I turn the screw almost all the way in and start to back the screw out......the engine RPM goes up slightly and the erratic condition gets better.....now I turn the screw a little more and the erratic condition is more evident by the guage....I have went too far....I back up and feel pretty confident. I go to the other side and do the same process. I am close.....I do this process one more time on each carb and the vacuum needle is only slightly erratic.....I attribute this slight erratic condition to primarily the cam specs. For MY RAPTOR the optimum settings are 2 3/4 and 3 1/2 turns out with 27.5 pilots.
I used to have major trouble with carb blowoff......this is researchable....this process has eliminated my problems.

 

Also, after mine was adjusted correct.....I have not re-adjusted them since this past spring and even in the cold weather now, it runs like a top with crisp response.

 

Gary, thanks for the info, I will have to give the gauge method a try, sounds like Yamaha should take a few pointers from you as well but I guess they realy don't want to teach us how to modify our bikes & mess up the warranty.
I had heard two different reasons why the boots were blowing off the carb. One was that the air screws were set a little too lean & the other was that it was time for a valve adjustment. I know the person who said it was a valve adjustment problem & he said when he had the problem, he could see the boot breathing in & out, kinda of like the eratic idle you described. Anyway, thanks again for the info.