Well, I just cut out the restrictions in the intake boot going into the airbox. It seems to run worse than before. It bogs when changing gears if you wind it out in the gears as you would during a drag. It is just like a slight hesitation and then it picks back up. I wasn't sure if it was due to me removing the inner flaps in the boot, so I put some tape over the intake opening and it seemed to bring the crispness back.

Now what do I do? Does it sound like it's runing lean? Will a lean condition cause it to stuble when going into the next gear like I described?

Thanks for you help. I'm at 400ft above sea level if that helps with the jetting.

 

Check your plug. It is probably running lean.

 

I don't think you'll ever be 100% satisfied with the stock carbs. Dual flatside 37mm carbs w/accelerator pumps would rock.

 

37mm? Wouldn't that be a little large? The stock ones are 33mm.

 

Bash, I won't pretend to diagnose or prescribe for your Raptor; however--CV carburetors depend upon airflow to raise the slide and needle--the air current creates a partial vacuum used for this purpose. Messing with the air intake ("removing restrictions") might affect the pressure gradient throughout the system and honk up the mid-to-high fuel-air mixing and delivery system.

Don't know if that's what happened; just a possibility, proving once again, "It's not nice to fool Mother Nature," or the Yamaha engineers, either.

As Scooby says, slide carbs with accelerator pumps attack the hesitation problem, dumping raw gas into the engine when you hammer the throttle, immediately raising the slide and needle instead of waiting for the vacuum effect to do its thing; however, as tdporter mentioned above, beware of over-carbureting if you go that route.

Keep us advised of your progress as you super-tune your Raptor. Good luck!

Tree Farmer

 

bash, i thought the same thing when I cut mine out, but then it seems to pull top gear alot harder, I may rework the boot and see if there is a difference. Keep in mind also that you will have to rejet after adding the exhaust in the future, so it may not be that big of A deal. it may come back to life with an air screw adjustment, since it is minor. Also since temperatures have finally dropped below the 80's here Ive notice it takes a bit to warm up. But I guess thats what happens to a 660 at 60 degrees. Let us know what happens.

 

Bash I think I will restore my air obstruction, have you had any luck, I think I will try and fashion a couple of L shaped aluminum pieces and attach one to each side of the vertical piece. Let me know if you have found a different way yet? After riding today I tried to pay attention and in most conditions I sometimes would notice the difference so Im going to put back the obstruction and see how it feels.

 

Yamaraptor,

For the time being, I took a piece of duct tape that was about 2" across. I cut it so that I could cover the same amount of area that the rubber we cut out covered. If you stick it to the airbox lid and then slide the boot over it, it is not visible and seems to stay in place well.

I'll keep it like this until I rejet or get a pipe and have to rejet anyway. If down the road, this temp. fix doesn't work, I'll just order a new rubber boot. My bet is that the jetting will take care of it.

What's your altitude? I'd bet that we noticed a slight degradation of performance because we are already running leaner than the guys at the high altitudes.

 

You know reading this is really starting to make me think about mine. I cut that restriction out and changed to 12 tooth front sprocket at the same time. From the getgo I noticed that it didn't seem to loft the fronts as easy as it did with the 13 tooth, I know it didn't make any since but I really didn't think to much of it. Last weekend I went riding at the dunes, and I felt that "bog" when drag racing between 1st and 2nd, We were racing a steep dune and I stayed in 2nd to the top when racing.....the previous weekend I had went but didn't race... but I didn't notice the bog when I got on it a couple of times....

I am going to do the duct tape thing in the morning.... I am going to check the plug befor I do just to see what it looks like......

Lets keep the info flowing.... I to want to wait till I get a pipe before messing with the jetting..

 

It's posts like these that make me glad that my Raptor is still on a truck somewhere. By the time I get mine, YaMaHaRaPtOr will have most of the performance bugs down to a science, and Bash will have taken care of the two or three that YaMaHaRaPtOr missed!

Thanks for good info, and let me know if I should leave the obstruction in or not.