rejet with no other mods

Hey guys, new klx450 owner here. Start off by saying this is the most awesome bike I have ever been on. Putts around with the kids well, hangs with the big boys well too. With that said I have been following the jetting threads and have a question. Where we ride there are SEVERE noise restrictions so I dont want to increase the bark at all, this means no removing the pea shooter or opening the airbox. Besides, the bike has enough power for its intended use already. My main concern is the bike running hot. I have never overheated the bike that I can tell but I am all about engine durability and heat kills. The only thing I have done so far is unplug the headlight so my second battery charges during rides better. Has anyone had satisfactory results just going up one size on the pilot or main jet for heat reduction or is a new fuel screw and/or needle absolutely necessary? Sorry for the ignorance but although I have been riding for many years, I have kept my bikes mostly stock and most of them have been two strokes. Again, not looking for any more power just reliability and this site is the best I have ever seen. Thank you guys in advance.

Jd jetting kit and a adjustable fuel screw is a great way to go. Also opening the air box doesn't make these bikes noticably louder.

I would say that the pilot is ok stock - 45- as I am still running that without the pea-shooter and

without the airbox restriction

the JD jet kit also uses the 45 pilot - with a 165 main jet and their special needle

you could try a 155 main and work up to the 165 if needed for stock restricted exhaust & air box

stock the klx450 has a 145 main

as far as a needle you can get the NCVU needle which I think is the stock needle that is in the

austrailian klx450 - it is the same as the nlzu (which is stock here) but it has multiple clip grooves

so you can raise the needle - the stock needle only has one grove -no adjustment

I seem to remember someone adding shims under the stock needle to raise it up

these shims were common use from snowmobile jetting

or buy the Jd kit as that seems to be the most common - for some reason?????

I can't see spending the money if all you get is a needle and a couple main jets

Thanks to everyone for the info, I was wondering if someone had just gone up one size on the main without messing with the unadjustable needle and not had any adverse effects. The carb looks like a PIA to get to considering that I am not looking for any more power or noise.

easy to change main jet with out taking off carb - just remove plug in bottom of float bowl

if you want to shim or change needle - again you do Not have to remove carb

just remove gas tank -easy access to needle under top cap of carb

Also - scrap the AIS if you can, helps get rid of the overheating, while keeping stock exhaust.


the Air Injection System only adds a small amount of air into exhaust to

completely burn off any unburnt gas left over from combustion process

there is no way it can make engine temp increase

if your jetting is OK it should not have any adverse effects

Every one thinks that "Because its a polution control it must suck power etc"

this is not true - it only reduces the carbon monoxide levels

this is good for the environment and I would challenge anyone to prove it hurts performance

I ran the 155 main without any mods and it helped. Removing the AIS helps even more. Hope this helps. Happy Trails

The AIS increases the temp of the exhaust, therefore increase engine temps somewhat. It doesn't suck power and it shouldn't effect the way the bike runs, but it will increase engine temps slightly.

All I know is when I first got the bike, it overheated FREQUENTLY. I rejetted and it still overheated some. Then I removed the AIS and it was much better. If you you can get a quiet aftermarket exhaust it will help even more. Info on here indicates that the Pro-moto insert helps alto with not much extra noise. i am running KX can with a db dawg insert and it runs 92db. I haven't boiled it for a long time now.

I agree that the ais more than likely doesn't directly affect engine temp, but it does increase exhaust temperatures which should increase engine temps ever so slightly I would think. I think I am going to ditch the ais and increase my main one size and leave it at that, besides I love the bike as is and a small improvement in heat is all I am looking for. Thanks for your opinions and knowledge guys, I really appreciate it and keep chiming in if you have other experiences to add.

I'd up the pilot one size before changing the main jet if running stock exhaust. If you open up exhaust, (highly recommended) you will then need to increase the main jet size.:smirk:

Take the AIS off and go with a 155 main and you will be happy. It will run way cooler. The AIS makes the bike run very hot so it will burn the unspent fuel at the exhuast port. Look were the AIS goes in at. Then you will understand why it runs so hot. Happy trails.

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