Jetting questions

[Bush0102]

Ok if my jetting is too rich, will it sputter when i punch the throttle? I can't snap into the high RPMs without bogging and sputtering, but if i ease it into the top of the powerband there is no problem. Some of the mechanics at the honda shop say i'm too lean and some are saying i'm too rich...so i dont know what to do.

Currently I'm running a 180 main jet (stock pilot and needle settings) with my airbox lid on, K&N, and a HMF slip on.

I have a 172 so i might try that, but this has been tough to get the jetting right so i want to make sure i'm too rich before i drop back down.

Also, when i ride at higher altitudes do i need to decrease or increase my main jet size?

thanks

[nosliw]

yes it will sputter if you snap it if your too rich.

at higher altitudes you need to lean your jetting out. thinner air=less oxygen

[Bush0102]

OK sounds like i need to get that 172 in there. thanks.

[sickmojave]

with my HMF slip-on and stock air filter with holes in the lid. I run a 155. :eek:

[wilkin250r]

Rich or lean will show up on the spark plug.

Your main jet size will have very little effect with a quick snap of the throttle. At that point, you're actuating the accelerator pump. If the accelerator pump isn't working properly (maybe a bad diagphram, or clogged) it's entirely possible to be too rich on the main, and STILL be too lean when you punch the throttle. However, if it IS too rich on the main, an extra shot of fuel from the accelerator pump could cause it to stumble. However, if the accelerator pump is working properly, I can't ever imagine it being too lean when you stab the throttle, even if the main jet is lean.

Check your accelerator pump first. Probably replace the diaphram with a new one. I think they even sell complete accelerator pump rebuild kits, complete with diaphram, o-rings, ect.

After that, check your accelerator pump.

Third, check your accelerator pump.

THEN, after all that, check to see if your main jet is too rich.

Are you running the stock carb? I know the FCRs had a problem with the accelerator pump.

And what is your spark plug telling you about your WOT jetting?

[Bush0102]

Originally posted by sickmojave
with my HMF slip-on and stock air filter with holes in the lid. I run a 155. :eek:

yeah i ran the stock jet for a while but i started having problems. how do you like that XR cam?

[sickmojave]

Originally posted by Bush0102
yeah i ran the stock jet for a while but i started having problems. how do you like that XR cam?

It's alright but didn't add much. when I replace my piston I'm going to find a better cam..;)

[Bush0102]

Originally posted by wilkin250r
Rich or lean will show up on the spark plug.

Your main jet size will have very little effect with a quick snap of the throttle. At that point, you're actuating the accelerator pump. If the accelerator pump isn't working properly (maybe a bad diagphram, or clogged) it's entirely possible to be too rich on the main, and STILL be too lean when you punch the throttle.

Check your accelerator pump first. Probably replace the diaphram with a new one.

After that, check your accelerator pump.

Third, check your accelerator pump.

THEN, after all that, check to see if your main jet is too rich.

where is the accelerator pump located and how much does a new diaphram cost? everything in the carb looks pretty clean (only ridden it once since it got cleaned in the winter) so i dont think theres any junk in there.

This is starting to piss me off, i'm having so many issues with this damn carb i just cant seem to get things right.

[wilkin250r]

Are you using the stock carb?

If I had a picture, I could show you. It should be right next to the float bowl, on the right side.

[Bush0102]

yeah, its just the stock carb.

So is there any chance it could just be a simple as the main jet is too big an when the accelerator pump is opened up there is just simply too much fuel? I dont want to go through a bunch of complicated stuff i'm not familiar with if it could just be a problem with the main jet in the first place.

can you see it in any of these pictures?

http://www.atvriders.com/images/articles/pilotjet/pilot1.jpg

http://www.atvriders.com/images/articles/pilotjet/pilot2.jpg

http://www.atvriders.com/images/articles/pilotjet/pilot3.jpg

[cals400ex]

in the top pic you posted, it is the round piece on the left side that is held on by 3 screws. be careful with those screws, they strip easy.

[Bush0102]

ok anyone else have an opinion? I need to get this straightened out today...