2nd phase of carb/exhaust mods

[mdsuave13]

thanks a ton, i will do this when i have the opportunity, and get back to you on the results.. i do have a bit of a surge when i give throttle like its not pulling smoothly.. so maybe i am still running lean.... ???

[fatboy250]

Originally Posted by red2003

FYI, stock jet is an 8mm long Keihin type #109.

So what would be the next step up if you were gonna replace the main jet? I know I have the same carb, but have only done the clip and air mixture screw.

Jason

[red2003]

Sudco has the jets we need here:

http://www.sudco.com/keihin_mj.html#393

We need type 99101-393-xxx, so 2 jets up would be a 99101-393-112 (019-183). That's what I would recommend, or ream that bad boy out like I did for free!!!

[chris5150]

i love i when things are free. also i am going to be doing mostly soft sand and mud riding. i do not want to just have the uni-filter attached to the carb. so i was wondering would it work if i used the crate my bike is coming in to make a new air filter box. that box would be covered in slits to let air in but not on the bottom and contain the uni-filter. so i can keep splashing water out. and red you should post a video of how your bike sounds in action. i am really curious about that muffler.

[ambassador]

Chris,
Unless your new Lifan is really running like crap, drop the c-clip, adjust the carb and drill some holes in the muffler...
As for me, I drilled the muffler out 2 5/8 holes, backed out the carb screw 1/2 turn and I sleep alot better now....

[chris5150]

people on here have said that the air box are brittle, attach poorly, and do not let much air in.

it is hard for my to keep anything stock.

if i can fabricate something better, why not? but if anyone thinks this will not improve things, look better, or increase performance let me know.

[red2003]

Originally Posted by chris5150

people on here have said that the air box are brittle, attach poorly, and do not let much air in.

it is hard for my to keep anything stock.

if i can fabricate something better, why not? but if anyone thinks this will not improve things, look better, or increase performance let me know.

Chris, the stock airbox on my Roketa wasn't all that bad. If you plan on doing a lot of sand riding, leave it stock. I ride street and back roads so not much to contaminate the filter. I don't have a way to video the sound. If you've ever heard a stock YZ250F, it sounds just like that, only not as snappy. Same deep tone without the compression. Sounds really good though!!!

[chris5150]

thanks red.

[red2003]

Originally Posted by chris5150

thanks red.

[fatboy250]

Originally Posted by red2003

Sudco has the jets we need here:

http://www.sudco.com/keihin_mj.html#393

We need type 99101-393-xxx, so 2 jets up would be a 99101-393-112 (019-183). That's what I would recommend, or ream that bad boy out like I did for free!!!

Maybe you can bring me up to speed on the what the numbers designate. The stock is a 109 and the up size would be the 112. Do these correlate to the i.d. for the jet? If I asked Dad to take this stock jet to work and use a small bit to drill it out, what would be the i.d. dimension?

Jason

[red2003]

Originally Posted by fatboy250

Maybe you can bring me up to speed on the what the numbers designate. The stock is a 109 and the up size would be the 112. Do these correlate to the i.d. for the jet? If I asked Dad to take this stock jet to work and use a small bit to drill it out, what would be the i.d. dimension?

Jason

Hey Jason,

The bigger jet # means increased flow. It's not just the size of the hole that determines this. Different jet sizes may have the same size hole but different taper, and that changes the flow characteristics. Be careful with a drill. Remember doubling the size of the hole QUADRUPLES the flow of gas through it. The tip cleaners worked well because they have such small graduations between sizes. Looking at the jet, I couldn't even tell the hole was any bigger, I just know it is since the the files obviously took off a little material at each step. Two sizes up on files has made it plenty rich. I increased the hole diameter by about the thickness of a piece of paper maybe. The correct thing to do would be order new jets, but I had it all apart and didn't feel like waiting a week to get parts. And it was FREE!!!!!!!!!!!!!!

[mdsuave13]

not to mention that that site that has the jets says that they are selling them in quantities of 4 only.. so if 3 other people want to do this, i'll go in with you all to get some. Let me know.

[fatboy250]

Originally Posted by red2003

Puffs a little if you punch it off idle, but the plug is nice golden brown.

Would you consider replacing the pilot jet to correct this? Or are you content with it at this point?

[mblas3]

mdsuave13, I would go in with you.

Mark

[red2003]

Originally Posted by fatboy250

Would you consider replacing the pilot jet to correct this? Or are you content with it at this point?

No, its fine. Sitting there idling, if you goose it, it puffs a little black smoke, but I'd much rather have that then a white spark plug. No need to change anything else. Every bike I've ever owned and modded puffed off idle. I could probably run the air screw back in to 1.5 turns, but I don't care enough to mess with it. There's no stumble off idle, so I think I'll leave it alone.