Try 27.5 pilots - I think you will solve your problem!

 

Ritchie,

Your mains are probably in the right range. 160-180. I think you need to go back to the beginning. Start with 160-165, stock needles, and stock clip position. You can test the mains jettings by doing a high speed run and cutting it off, pulling the plug and checking. You should be close, and may even need to go up one size, as that Yosh flows pretty well.

The midrange 1/4-3/4 is probably most dependent on the needles and their position.

The idle ~1/2 involves the pilot jet, on which I (and most who responded) think you need to richen. (Notice that the midrange and the idle overlap somewhat).

Go back to the beginning and start from there. Where did you get your Yosh? Any support from them?

RM

 

RitchieRoadRash,

You definitely could be on to something with the choke problem. You should disconnect it from the carb and take a close look. KNOWSALOT posted an upgraded choke cable for the Raptor that doesn't allow water to go down the cable and into the choke chamber of the carb. He posted the service bulletin about it too.

I had a similar problem going on with the Kodiak. I couldn't keep it idling the same from one day to the next. One day it idled fast and the next day I would have to increase the idle on it. Turns out that I had corrosion going on in the carb where the choke cable connects along with a totally wasted spring that was supposed to push a needle into the carb thus shutting down the air flow whent the choke was in the off position. The needle would pull out properly with the choke "on" but then wouldn't push back in with it "off".

Good Luck.

/NotuRaptor

 

i saw what knowsalot posted. sounds like something i'll surely check into. but first i want to lay this on you guys. i called my mechanic today. keep in mind he's got pretty much all the business in this town so he realy works on what he wants when he wants. don't get me wrong this guy is really good but he's got to be in the mood to give some advice on things, especially over the phone. this was the third time i've called. besides all that this is what he said today...... he rally didn't feel the pilots would help this problem. his conclusion was since none of the jetting i've done changed anything he believes with the airbox removed the air is entering the engine before the fuel has time to catch up (especially going from zero throttle to full so quickly) resulting in an extremely lean condition at the beginning. he said it was something i would just have to deal with unless i could find a carb with an acclerator pump to keep constant pressure. (surely it was sarcasm) o.k. it sounds very plausible. i can see the logistics since with even the slightest amount of throttle before i nail it the stumble doesn't occur. i'm new at this jetting bit but it would seem to me that if you increased the pilots it would in turn increase the amount of fuel present at the time just before "punching" it.??? it seems there would be that little extra fuel in there that would compensate for the sudden flow of air.??? i know, i know, buy some freakin' new pilots and find out! eraptoid suggested 27.5. is there anything between that and stock so i could order both. don't want to be too rich. oh yeah, there is a pilot jet in both carbs right? never delt with them before. thanks.

 

oh yeah...rennym, i got my pipe straight from yoshimura research and development. i went to the web site and i didn't see my pipe and a few other models anymore. i haven't called them because of all the other mods i have done. so hey that should speak volumes on my opinion of you guys' input. i posted this rather than call yoshimura. hehe. later.

 

Richie,

Well, before buying another carb, remember that there are many guys on this board who run the stock one with all types of different combinations. And a new carb could be $400 or so, so there is tons of room to try more jetting.

I was recommended to go with the 27.5. Mine is stock right now and I haven't had a reason to change it. I think the stocks are 22.5 or something like that. I think there is a ~25 you can order as well.

I am starting to lean with Notu, that there may be something else wrong other than the jetting. Check the carb operation, choke cable, etc, and make sure it works properly.

From your description, you should be jetting in the correct 'range', and you seem to be having too much trouble.

I would try the pilots as it is the only Jetting setting you haven't tried yet. If you don't get it to work right, I would start to look at the carb operation.

Man, good luck. This has to be killing you....

RM

 

RRR you can order the 25s but I wouldn't even bother. I am running with less air requirements as you and am running 27.5s and have no indication of being to rich at idle. It also would help to be a little rich to make it run cooller at idle. I don't know if a plug test will work at idle but you could try it, use a fresh plug it helps.

 

RichieRoadRash, I have had the exact same problem. I am running the full yosh exhaust system, Prodesign foam filter/billet connecting plate, no air box lid except for an OuterWears cover, Dyno jet needles/springs, clip pos=3, 155/160 mains, 25 pilots. I had low rpm problems just like you & cured it some by making sure the idle was set @ spec of 1400-1600 rpm, that's higher than most models & sounds high to the ear as well. However, the problem didn't go away completely until I turned the fuel screws out around 4 turns each. According to most literature I've read, the next step was to go to bigger pilots(27.5) & then turn the fuel screws back in for best idle. I am waiting for the 27.5 pilots in the mail & after I get them installed I will let you know what the best fuel screw settings are, at least for my atv that is but should be close on yours as well. I'm sure you've heard this before but your valves need to be adjusted correctly as well. Also, summer time the air is thinner which means you need to jet a little leaner & winter time the air is denser so you'll need to be richer then. I'd be interested in knowing how you fixed your problem so keep us updated!

 

RM, it's not exactly killing me. i'm always up to a challenge and learning new things, but yeah i'm ready to put this one to bed. i hope the pilots will work.
chimmer if you get yours sooner than i do let us know if it worked.
ward, i was wondering if i would here from you since were pretty close in alt. thanks everyone. i'll get back to you guys soon. seriously, thanks for all the help.

 

i just pulled the choke cable off and the thing looks like it's been sitting next to the titanic for a few years. i can't believe all the crap in there. i guess there IS a severe design flaw with this. this may be the problem. i wanted to check it before i ordered te new pilots. it's soakig in gum out right now so i'll let you guys know something soon. by the way i jetted back up to 165/170.