Airbox modifications.

So my 462 is running a bit rich. Black soot on my numberplate and plug is blackish and a bit wet. I haven't cut my "E" airbox yet. I'm going to cut the top out tomorrow. Should this lean it out due to a drop in pressure in the carb, drawing less fuel up?

Also what kind of hp am I missing at the moment?

Oh and it is popping a lot on deaccelaration. All exhaust bolts are tight. There is a tiny leak coming from the slip joint.

Cheers

The poping on decal is normal if you have the ce removed from the carb. You didn't mention what jetting or carb you are using.

The poping on decal is normal if you have the ce removed from the carb. You didn't mention what jetting or carb you are using.

sorry, I'm using an fcrmx 41. Yea I thought the popping was normal. It kinda sounds cool :thumbsup:

180 main jet

200 main air jet

EMR needle

clip 3

48 pilot jet

no pilot air jet

2 turns fuel screw

Drop your main jet to a 175 and try that...That's what I have installed on my 485....

Your stroker may be calling out "give me air"...I drilled my side cover to let it breathe...

DSC02334-1.jpg

DSC02333.jpg

Drop your main jet to a 175 and try that...That's what I have installed on my 485....

Your stroker may be calling out "give me air"...I drilled my side cover to let it breathe...

Crap. I stuffed up on that last post. I'm actually running a 172 main jet.. The rest is correct though. What's Ur thoughts on my airbox mod? (cutting out the top)

Edited by seemus7
Slow Internet!!
Crap. I stuffed up on that last post. I'm actually running a 172 main jet.. The rest is correct though. What's Ur thoughts on my airbox mod? (cutting out the top)

I doubt that's the problem. Why don't you just remove the air box cover and ride around and see what happens?

What altitude are you?

Steve

I doubt that's the problem. Why don't you just remove the air box cover and ride around and see what happens?

What altitude are you?

Steve

I don't doubt it at all....

What Steve has suggested is good for you to try first before modding your s/cover..

I did mine on the dyno 1st ,w/out the side cover, the air /fuel was sweet..:thumbsup:

172mj should be close...

Yep I'l be sure to take it off before I cut away. Ur right Craigo. It is crying out for air I think. Will try tomoz

Edited by seemus7
Retarded iPhone keypad
I don't doubt it at all....

What Steve has suggested is good for you to try first before modding your s/cover..

I did mine on the dyno 1st ,w/out the side cover, the air /fuel was sweet..:thumbsup:

172mj should be close...

No kidding, so you obviously don't play in the dirt then, right? I guess those who do get dirty could just have two covers, one for SM with holes in it, and one that's stock.

Steve

Yea I play in the dirt. That's why I want to cut the top out instead. Probably will still get filthy in there though.

Most bikes need no more air than the 3X3 provides. A fully worked engine needs no more than a 4X4. As the OP alluded to, opening more causes a pressure drop and therefore a larger main and very possibly, a richer needle.

Main Jet

Starting with the recommended main, remove the airbox door and go for a ride (bike fully warmed up, 3rd or fourth gear, up a slight hill). Is it better or worse?

If it is better, you need a smaller main.

Go down one size, replace the airbox door, ride. Remove the airbox door and test again. Better or worse? If better, go down a size again. Keep repeating this till the test with the airbox door is worse.

If it was worse with the airbox door removed, tape over 1/3 of your airbox opening, test (airbox door on, of course).

If it is worse now with the tape and was worse with the airbox door off, your main is just right. You are done!

If it seems better, you need to go up a size in main jet. Then test it again (remove the tape). Replace the tape, test again. If with the tape on it is better, go up another size in main. Keep repeating this till having the tape on is worse than with it off.

To finish up and ensure you are set accurately, retest the bike with the tape off (airbox door on), ride it, then remove the airbox door (tape off, of course). Best performance should be with the airbox untapped, airbox door on.

Remember, the main only operates at WOT. Ideally, you want to be in 3rd or 4th gear doing the tests, hitting max revs (just shy of the limiter) for at least 10 seconds to get an accurate representation of the jet status.

Yea I play in the dirt. That's why I want to cut the top out instead. Probably will still get filthy in there though.

I'm running around the same set up as you but with +1 intake, RHC 187 and porting.

Same jetting but with 180 main bike runs like a champ.

With my 3x3 airbox in the dirt I have noticed a lot more dirt and needing to clean it pretty much after every dusty day.

I'm running around the same set up as you but with +1 intake, RHC 187 and porting.

Same jetting but with 180 main bike runs like a champ.

With my 3x3 airbox in the dirt I have noticed a lot more dirt and needing to clean it pretty much after every dusty day.

Yea I also have RHC's, fcr41mx and porting. I can't be too far from perfect as it ruNs well. Pulls well from low revs at full throttle etc. It's just a bit of black soot Iv noticed collecting on the number plate and the spark plug is a bit blackish and wet??

Most bikes need no more air than the 3X3 provides. A fully worked engine needs no more than a 4X4. As the OP alluded to, opening more causes a pressure drop and therefore a larger main and very possibly, a richer needle.

Main Jet

Starting with the recommended main, remove the airbox door and go for a ride (bike fully warmed up, 3rd or fourth gear, up a slight hill). Is it better or worse?

If it is better, you need a smaller main.

Go down one size, replace the airbox door, ride. Remove the airbox door and test again. Better or worse? If better, go down a size again. Keep repeating this till the test with the airbox door is worse.

If it was worse with the airbox door removed, tape over 1/3 of your airbox

opening, test (airbox door on, of course).

If it is worse now with the tape and was worse with the airbox door off, your

main is just right. You are done!

If it seems better, you need to go up a size in main jet. Then test it again (remove the tape). Replace the tape, test again. If with the tape on it is better, go up another size in main. Keep repeating this till having the tape on is worse than with it off.

To finish up and ensure you are set accurately, retest the bike with the tape off (airbox door on), ride it, then remove the airbox door (tape off, of course). Best performance should be with the airbox untapped, airbox door on.

Remember, the main only operates at WOT. Ideally, you want to be in 3rd or 4th gear doing the tests, hitting max revs (just shy of the limiter) for at least 10 seconds to get an accurate representation of the jet status.

thanks for the tips william1. Will try this out. Would u call a 462 "fully worked"?

Almost fully worked, Bigger bore/stroke, ie a 470+

FYI:

My 470, with a 3.5 X 4.5 opening, FCR39 and Yosh Ti ran a 155. I tested using a wideband A/F tool.

Black can come from the AP. If you are off the gas, one the gas a lot, that explains it. If you want to confirm that is wat it is, after you do teh MJ test I gave you, hi the highway for 30 minutes, see if the pipe color goes from wet black to dry.

If you can afford it and have one available Dyno testing is the best way to sort out your jetting and accurately check for hp gains/improvements.....

That's presuming the engine tuner/dyno operator is competent....

I am reasonably confident you are going to need larger than 3x3....

Running it without the side cover will be an indicator..

So my 462 is running a bit rich. Black soot on my numberplate and plug is blackish and a bit wet. I haven't cut my "E" airbox yet. I'm going to cut the top out tomorrow. Should this lean it out due to a drop in pressure in the carb, drawing less fuel up?

Also what kind of hp am I missing at the moment?

Oh and it is popping a lot on deaccelaration. All exhaust bolts are tight. There is a tiny leak coming from the slip joint.

Cheers

I didn't see where anyone pointed this out, but the E airbox doesn't need to be cut out. Just remove the snorkel and you'll have the 3x3.

Yea I'm aware of that. That's why I wrote "E" airbox :thumbsup: it never had a snorkel anyway. Good ol Aussie E models don't have them. Was considering cutting even more out...

If you can afford it and have one available Dyno testing is the best way to sort out your jetting and accurately check for hp gains/improvements.....

That's presuming the engine tuner/dyno operator is competent....

I am reasonably confident you are going to need larger than 3x3....

Running it without the side cover will be an indicator..

That would be ideal... There is only one dyno in town that I know of. I'm not to sure that he likes working on dirtbikes...

I you do dyno it you will have fit a road tyre on the rear to obtain correct readings/traction...So it will only be half a dirt bike..lol

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