Hello whomever, I'm a nubee to this forum and I'm hoping to get a little advise and possibly offer some as requested. I have an 04 KFX700 built to 800cc with 11:5 compression pistons, re-ground cams, mild head work, K&N, HMF Dual exhaust, Dalton clutch kit, run VP C-12 fuel. But my jets are only a couple numbers over stock. I ride primarely sand (Dumont Sand Dunes) at approximately 2200 ft alltitude. Should I go larger on the jetting ? If so how much ? Any recommendations to air/fuel mixture ? I have about maxed this bike out but always looking for that extra little punch. Thank You for your consideration, if you have any questions I'll do my best to answer them.

 

Is it running smooth? If it's not showing signs of being lean, why would you feel the need to go with larger jets?

 

You must be in need of larger jets....just my intake and exhaust mods made me go up almost 35 sizes....is she popping? backfiring? being boggish?

 

Thanks for your responce; It did a lot of popping especially when I had the after market CDI box on. On our last tripI put the stock box back on & the popping dropped off quite a bit. Still does a lot of popping especially when I'm coming back down comp using the engine as the break (probably just loaded up after the all out up the hill ?).
The people who built my bike (Crower Power out of Lake Elsinore) recommended I take it to Denton Racing out of Riverside. Apparently they have a dyno for quads and they should be able to dial in the jetting and mixture.

You said you went up 35on yours, did you have to seriously play with your air/fuel mixture to get it right ? If so what worked for you.

 

I strongly recomend a dialajet for your kfx.this is the coolest thing since fuel injection,and they sell a tpi for 9.99 thats a must the dialajet runs 129.99 i think for the kfx and its a cool clean easy instalation.this will allow you to adjust it perfectly even better then fuel injection, and not much more then a jet kit

 

I would buy a few jets the next size up. Seat the pilot screw completely and turn it out approx 2 turns. Then fine tune it until the popping is gone. If you have to turn it out more than 3 turns and it still pops, go up another jet. The popping could also be a result of an air leak. Make sure your head pipe, air intake, etc are all secure.

 

you should be atleast 145/148 your way to lean now, popping = lean.

 

I can't believe someone who spent all that time and money modding up his V is missing out on one of the biggest HP gain mods he can do. Not putting you down man, but you absolutely need to mod your airbox and run WAY bigger jets than stock. Alot of the big bore V guys are running carbs off of street bikes just to be able to get enough fuel into the motor. The only way mine will run the way it's supposed to at sea level with the stock carbs is to drill out the jets with a 3/32 drill bit. They don't make keihin jets bigger than a 200 and 200 is still a little lean for mine. In NM where I usually ride at 5000-6000 feet, my V is running jets 175/180. I think your going to kick yourself when you feel the HP you've been misssing out on. Good luck!

 

Thank You from New Mex, that's good advise. You said you drilled out your jets with a 3/32. When I bought my HMF pipes it came with a UNI air filter and a bag of jets. In the assorted bag there was only one size that was bigger than the stock jets, so I put those in. Funny/not so that the guys from Crower who built my bike didn't say anything about needing a lot more air and fuel for maximum performance (then again it was the first KFX700 they built). Not to be too ignorant, but when you see a jet size of 148 is that in thousandths of an inch ? You mentioned air box mods, can you be more specific ? Thanks again for your advise

 

Can you tell me how it works ? I don't want to seem stupid but all I can envision is a bag of various size jets and you just keep changing them out till one works. This isn't an electronic devise ?