Yeah, that dyno jet kit seems like a rip off. $50 for a few jets when they are only a buck or 2 for individual main jets from the dealer.

 

Danyeo,

I use to have the same problem with DynoJet's power kit. It didn't like the needle for some reason. I've since gone back to stock jetting components, and the problem is gone. Each engine is different though. Some run fine with the DynoJet kits and some don't. That's why it's hard for a person to recommend jetting to a person when they start to add a pipe and new filter and stuff. With it backfiring like that, I would say your lean on the main. With just a slip-on and a aftermarket filter, you shouldn't have to touch your stock needle setting. Just up the main until she boggs at WOT and keep going down a main jet size until you get good throttle response. Then I'd put in a fresh plug and do a plug reading. I also upped the pilot jet to a 42 and re-adjusted my airscrew. If your turning it more than twice around, then you need to up the pilot jet. Currently I have the WB E series, modified airbox lid, UNI filter, removed my choke, and I'm running a 42 pilot, needle position stock, and a 162 main. Now my neighbor has the exact same setup, but he needed a 170 main. Jetting is not fun! Good luck, let us know how she came out.

Bdutch,

I'd go back to stock jetting, I don't think your quad is responding to the DynoJet kit in a good way either. I played around with mine for 2 days before I gave up on it. It sounds like a main jet problem though. Also though, have you checked for airleaks? If your carb boot or anything is cracked, it'll suck in more air leaning it out. And make sure all of the fuel passage ways are clear.

 

jcv400ex -

Good points. One thing though, you should turn the air/fuel mixture screw out four turns before going up a size with the pilot (from lightly seated position, of course). Two turns out doesn't completely open the curcuit.

You've got my vote regarding dynojet. Charging too much for their system isn't what really bothers me, its their bad customer service. What you get for $50 is a small set of main jets (using their sizing system, of course), and a redesigned needle. After buying a dynojet kit for my previously owned mojave, I found out that needle variants are only really useful in HIGHLY modified engines - stuff most of us will never touch. Plus, even when you highly modify an engine, you'll need to customize your needle size much more than dynojet can ever provide.

Expanding on the customer service...

My mojave ran awful after installing the needle. I called dynojet (after testing every clip position) hoping to receive helpful advice, and instead, I was told basically I had no idea what I was doing. I had jetted this machine before, and had a good working knowledge of jetting and corresponding circuits. Needless to say, dynojet spewed inaccurate info on how to properly jet a machine, along with belittling me any chance they could. Granted, this was only one salesman/tech guru - but nonetheless, it left a really bad taste in my mouth.

To anyone that's considering modifying their machine (e.g., pipe), don't just assume buying a $50 kit will solve your jetting needs. Look a little further into info regarding jetting, you'll find that a kit will never replace jetting your machine properly. Sometimes the kit works, other times it doesn't - it's really a potshot. There's plenty of resources on this site and others that will give you an understanding of jetting principles. You'll find that factory main jets, along with adjusting the needle that came with your machine will give you the results you're after.

ogre

 

Hey, i thought i would post my results from the weekend. My setup now is, K@N air filter, air box lid on because I'm worried about all the sand that gets in there, and i have a 150 main, I'm not using the dynojet mains anymore. BUT i did install a WB rev kit. Easy 2 minute install and i think it really helped. I dont bog or hiccup at WOT. I think the problems i was having were i was just hitting my rev limiter and my carb settings were ok, I'm not sure. Lots of people seem to use a larger main than what I'm using but i am going to keep my air lid on for now to keep dirt out. I know taking off the lid would require a larger main. But it ran great on Sat and i was ripping around concentrating on riding and not worried about my machine. Thanks for all the help.