O.K., I 've been trying to dial in my raptor. I just modded my air box (another post) and got a Dyno jet kit. The springs and needels are different, but apparently the jet sizes are too.... I have stock sizes 140,145,150,155,160,165,170,175. Kept having flat spots so I got the Dyno kit stage 2. It comes with several main jets up to 150...I have 148/150 in now and my plug looks new. It runs good, pulls hard but I think it is still lean since I can't get the plug to color.... I dont want to order more jets from dynojet... I think I might just use the stock jets with dynojets needles...has anyone done this....I have the Graydon airbox, K&N Filtercharger, outerwears prefilter, outerwears Airbox lid.... Anyone else run this setup? All help is greatly appreciated......

 

Yes actually I tried that and it doesn't work well at all. You get a huge flat spot in the midrange and if you go to drastic it wont rev out (wayy to lean). It seems the Dynojet needles don't work well with the Yamaha jets. I am running 148/150 dynojet mains with the needles and springs. I also have a full race exhaust system, no airbox lid, and a proflow kit. It seems to run great! If your not noticing any problems with how the quad runs I wouldn't chenge the kit.

 

The Dynojet setup is a "system", designed with a lot of R&D to work well together. Using DJ needles with stock jets or stock needles with DJ jets will screw up the fuel curve leading to performance troubles. The numbering system between the two does not correspond, i.e. the stock 175 is not way larger than a DJ150, so stick with one or the other and it should run fine. I'd recommend the Dynojet system though...

 

The jets are definatly different sizes, you can see it if you put them side by side, your plug may stay "uncolored" due to the gas you are running, you can try the larger jets but some of them will not work well with the dynojet needle, its sort of a trial and error method, if you are at sea level or close you should be able to get close to 170/175.

 

actually, I went riding yesterday, and put the bike to the test every situation I could find.....and decided I will stick to th 148/150 dynojet jets. The bike pulls real hard and no flat spots....rode real tight woods like a snake through mangrooves and it stalled on me twice, dont know if it was my error or if it loaded up a little in the low rpm's.... When I got done riding I checked the plug and its like a light chocolate....so I think I'm fine....

 

Mine would stall a bit in low gear/low rpms for a while, I upped my pilot jets and the problem went away

 

i just installed a 170 mikuni main jet in my 660 grizz.
i also have the dynojet kit with the biggest main being 160. the 170 mikuni is bigger flowing jet then the 160 dynojet. since i modify my airbox i needed more juice. will be testing tomorow.somebody send me these specs.

160 d/j .063
160 mik .067
170 mik .071

 

Hey Vraptor,

What did you up your pilot jets too. I am getting ready to do the same and just wondered.

Thanks KD

 

I went up to 25 on the pilots, it really cleared up a small flat spot that liked to come on about 6' from the top of really steep hills, or when I dropped rpms into sharp turns. I ride at 5000'->8000' altitude so you may be able to go to 27.5

 

Mine acts the way u described yours before u upped your pilot. What size comes stock???? did u up just one size?? Thanks up front...