Air box mod what the?

[anthonyMember]

Ok I have a new klx450r with 330ks on the clock. The other day I took the std muffler insert out. I can now hear the bike and it’s goes no worse probably a tiny bit better. Then I decided to remove the air box snorkel. After I did this I changed the oil and filter and put a new twin air air filter in. Now when I putt around in second gear and give the throttle a good twist the bike pops/coughs once then it goes like it should. Before the air box mod and new air filter it would rev out and go as fast as you could twist the grip. Any opinions on what could be causing this would be greatly appreciated.
The bike is stock apart from what I’ve mentioned here.

[GregMember]

Sounds for all the world like you have leaned it out now that you are allowing more air in the the carby than it is jetted for. You will need to change the jetting if youre going to continue with the snorkel removed. I would refit the snorkel for a while. Maybe get your suspension dialed in or maybe get it setup for your weight.

For jetting check this out

Check this out by clicking here

You maybe able to adjust some of it out with your air screw, but more than likely you will need to raise the needle by lowering the clip position at the top of the needle this will richen the mixture. The main jet will be fine because thats only wide open stuff and by the sounds you arent reaching that yet

Good luck and with jetting keep it simple

TB

[DudeMember]

Ant dude

Could be bad fuel :dry:

My KLX450 only uses 98 BP ultimate fuel and no dramas but once I put bad fuel ‘not even sure what it was’ and for the next hour and a half of riding it was back firing and stalling,was quite concerning but came good and now happy days. :laugh:

[DudeMember]

moto wrote:

Trailboss wrote:

You maybe able to adjust some of it out with your air screw, but more than likely you will need to raise the needle by lowering the clip position at the top of the needle this will richen the mixture. The main jet will be fine because thats only wide open stuff and by the sounds you arent reaching that yet

I agree mainly with TB though you don’t have an airscrew, you have a fuel screw, this is an important difference when trying to tune your carby.

As far as the needle goes, this can get confusing depending on which way you look at it. To raise the needle and lower the clip as TB suggests you need to put the needle circlip in the next slot down from where it currently is. Typically there are 5 slots at the top of the needle, 1 being at the top and 5 being at the bottom and 1 being the leanest, 5 being the richest respectively.

The current jetting will most likely be casuing ‘lean bog’ and a subsequent little backfire or pop. Adjust your fuel screw first and then have a crack at the needle too.

I have the same bike and the big muffler and taken out the snorkle as well as drilled a heap of hole in the air box……….this may help the guy I bought the bike off said the mechanic adjusted the fuel screw 2 1/4 turns from the bottom and said later I may have to turn it to 2 1/2…..which I have not done a this time ,it still goes too good for me.. :laugh: :laugh:

[anthonyMember]

I fitted a 48 pilot jet yesterday the std one was 45
Down low it’s better with a smoother transition from low to high rpm.
It starts easier and sounds smoother at idle.
The colour of the exhaust is on the dark side of gray so I think it’s running quite well as far as mixture goes.

[anthonyMember]

I’m quite happy with how the bike is going. I have one question though, I noticed that when the bike is started cold it blows a tiny amount of black smoke. It is only a very small amount and is hardly noticeable but it is there. When the motor is hot it does not do this. So I am thinking it may be a tiny bit rich at idle. I was wondering if I need to go down a size with the pilot or try adjusting the fuel screw? All the jetting and other mods are as stated in the above posts. Any suggestions are welcome thanks.

[GregMember]

Your bike spends 99% of its life warm / hot you shouldn’t do adjustments or set mixtures for when its cold cause thats not where its ridden or rev’ed or supposed to operate.

Sounds like you have it sussed

TB

[drewMember]

i may be wrong here, but i thought since super/ leaded fuel was phased out, the rule of thumb of a grey pipe = a good/ correct tune went out the window?

[Author]

Posts