OK, advice would be appreciated as to which way to go:

2004 LTZ250 with standard airbox and snorkel:

K&N jet kit or Dynojet kit?
K&N oiled air filter or Unifilter foam filter?

Do atv's have mas air flow sensors like cars as I have heard that the oil from the K&N filters can mess these up.

 

I would (will) go with cheapest jet kit, like I said I think the K&N and Dynojet are the same product.
I prefer the foam filters, they do not require any special cleaning solutions or special oils as K&N leads one to believe. I have never had a K&N filter so I cannot offer true opinion, but I do know they sell a separate cleaning kit for their filters.

Mass air flow sensor, I think that is only used on fuel injected motors.

 

Thanks for that, looks like dynojet and Unifilter then.

Why are the atv's not fitted with the correct jets from new?

Are these jest pure unscrew, refit new ones and off to play or is there any 'messing around' afterward?

 

Just looked at the Unifilter site and you have to oil these filters too! Anyone know a reason which I should buy?

 

Mass air sensors are strictly for fuel injection. The Z250 (as well as most other quads) use a carb.

87

 

Thats good, no problem with oiled filters then. Juts need to decide which one, Unifilter or K&N. I am not too woried about price.....just want the best one for the job, same goes with the jet kit too. Any recommendations?

Am I going to notice much difference on the 250 with only jet kit and filter but with standard airbox and snorkel?

 

The stock bikes come corked up on both ends (intake and exhaust) due to EPA noise and emission laws. They are jetted properly from the factory for that. But when you start opening things up your air/fuel ratios are not correct so that is why the re-jetting takes place. The jet kits come with instructions to get you in the ball park, usually that works well enough. The jets are just screw in, but you do have to remove the float bowl and the top of the carb for the needle replacement. You will also have to drill out a brass plug to get to an air screw. It is not hard, but wrestling the carb into a position where you can work on it or remove it is the hardest part.

Throttle response is usually the most notable change after jetting. I think it will be a decent improvement even w/o an aftermarket pipe.

 

Well, I ordered the Uni Filter and the K&N Jet Kit. I'm removing the Airbox lid also, so I'll let you guys know what the jet size is. I've already removed the Spark Arrester and just added a .8 washer under the needle jet (same as jetting for an Alba Slip-On), and that seems to be right-on with the airbox lid on and the stock air filter.

 

what if u got it jetted after the exhaust, would would it still need to get jetted again?

 

ofcourse...everytime you do a mod to increase either intake flow or exhaust flow you need to re-jet.. its not a one time thing and your done.