K&N air filter and HMF exhaust

[clint Wolverine]

Guys, I just bought a K&N air filter, HMF Exhaust, and the HMF Jet kit. Now, I don't think the jet kit is going to get delivered before I go on a trip up to Coal Creek (TN). Is it safe for me to go ahead and run the K&N and Exhaust without jetting?

The jet kit is all about getting the proper Air/Fuel ratio right? How does elevation affect the A/F ratio?

If I'm understanding it correctly, the free flowing intake and exhaust will lean it out some, then I'll need to jet it richer to get it back to a good ratio? Does elevation make it more lean or more rich?

 

[ctateusa1]

I believe elevation would make it richer due to lower air pressure up in higher elevations.

I would definetly change jetting if you ad the exhaust and filter.

 

[fireman69]

definatly take the stock pipe with you incase you need to change back, im running a kn filter with stock exhaust, and no jetting, so i know your ok there, but if you wanna try it with the new exhaust i would take all the stock stuff with so as not to ruin a wheelin trip, you could change it back if needed in less than an hour........

 

[clint Wolverine]

thanks for the replies, I checked on the HMF site and it says to use a 145 Main Jet?, also I think the stock is like a 131? Since I only have to change the main jet, is this something I can get from a atv dealership? Also anyone have tips on how to jet it? I've never done it before, I'm sure I can replace it relatively easily, but what procedure should I go through to make sure it's jetted correctly?

 

[ctateusa1]

yhea you can get the main jet at a dealership, I think I went up to a 136 with my pipe and filter, and when I did the big bore kit, and head work I went to a 140.

Jetting is not too much trouble you just need to either pull the carb out or loosen up the allen head clamps enough to turn it 90 degrees so that you can remove the float bowl and replace the main jet. I also went up one size on the pilot jet at the same time.

 

[deepriggin]

Yeah, just remember that Mikuni jets go by different #s than DynoJet or HMF, so when aftermarket kits "recommend" 145, its usually thier own brand. I ended up buying a handfull of spark plugs and a couple bigger jets, did a few runs and inspect the plugs if its lean or rich, basically trial and error... Good luck bud. As for elevation, the higher up you go, the thinner the air is, and the richer you'll end up running.

 

[clint Wolverine]

HMF's numbers match mikunis numbers. Looks like their jets will get to me before I leave, so I'll be putting them in. I think I will get a couple extra spark plugs and check the plugs. I'll let you guys know how it turns out.

 

[clint Wolverine]

I got my K&N filter and HMF Exhaust (145 Jet) on and headed up to Coal Creek TN for a couple days. I really like the exhaust, makes it sound pretty mean but not too loud to stand. It was a royal pain to get the exhaust on, it just wouldn't go all the way on, but after taking it off sanding it, then beating the crap out of it we finally got it on. The jet was easy to change also.