Topic: Do K&N airfilters have big impact on jetting mixture?

[hevykevy420]

Calling all K&N filter people out there...

I searched for this topic...didn't come across anything so here goes.  I think I'm the slightest bit rich on my main jet.  I'm sick of taking off the carbs and putting them back on, not to mention retapping stuff everytime I strip a bowl bolt.  I have a hesitation if I whack the throttle at speed, but its not so bad as to want me to go leaner on my jets (I'm already down to the stock #110's).

I'm using the stock airbox, i'm not fond of cross winds or the effects of shifting your legs around with the pods (no offense pod people).

Do K&N filters flow more air then the stock filter element?  Anyone have experience using a K&N element?  Could this give me the perfect mixture?

[MRieck]

It will lean the mixture out....it may help.

[ofreen]

Installing the K & N filter in the stock airbox on my '75 750F had no adverse effect on the carburetion.  In fact, I didn't notice much difference one way or the other.  K&N claims no jetting changes are needed.

[eldar]

Generally, not much jetting is needed on the 77/78. You did not say at what rpm this happens or speed.  Is it better when it is cooler? Mine does that and I think it is actually the lows that are too rich, not the mains. Mine does it at about 70 mph which is about 5000 rpm or so, maybe a bit less.

[HondaMan]

I love my K&N, 95,000+ miles later. The K2 early bikes with 657A carbs had 110 mains, which I moved down to 105 after using the K&N for a season, just to lighten the plugs a little. Went to a 100 at 6000 feet when I moved to Colorado.

That hesitation could be a lagging throttle slide: try running some BG44K (a few ounces at a time) for a whole can and see if it helps.

[eldar]

Never seen a lagging slide. At least not on my carbs but my linkages all operate as one and the only cables are the throttle cables. No chance for mechanical lag. Do I get lucky sometimes!

[hevykevy420]

The slides all move smoothly with action from the throttle, I don't think there's any lag.

The slight hesitation happens when I'm going about 60-65 mph with rpms around 4k-4.5k.  If I whack the throttle, it just bogs.  If I give it throttle, but smoothly (no wacking : ) then there is no hesitation.  during normal riding, the jetting seems pretty spot on (at least i think).  Its always hot here in Texas, so I'm not sure if it would do it when colder.  I have noticed the hesitation even when the bike has reached operating temperature.

I'm using #110 mains, the stock airbox and filter element and the other mods i have are listed in my trailer.  Cam is A Web cam, stage III.

How could it be my idle jets?  I thought these had no effect on 1/2 to WOT jetting?  I have noticed that the best way to start the bike cold is to turn up the idle screw, give it 1/2 choke, then immediately take the choke off, and turn down the idle when warming up.  I have noticed a little smoke coming out of the pipe when it it warming up, then it goes away after i start to adjust idle down.

i've heard that with a racier cam, you have less suction, that is why i figured i have to start the bike this way, i didn't think of the possibility that my idle jets were to rich, is that why I may have smoke at start up?  Am I burning/not burning gas or oil? I have a fresh rebuild and redone head so I didn't think it was oil leak down in the cylinder.

what is BG44k?

[eldar]

That light smoke on idle with choke is poorly or unburnt fuel mix. I doubt it is oil. Did you tune your idle mix using a shop tach or dwell/tach? You should, it will help. I have to do it too but I have very little time but I know it will make a big difference. I know it is a too rich as I get about 40 mpg when I should get 45 or so maybe more.

[hevykevy420]

aha!  That makes too much sense.  So thats what those little screws are for.  This was the last thing on the list to do for me, I will have to go out and get a shop tach, otherwise that stinky warm up exhaust will annoy me 

[eldar]

Yeah it is a little stinky. I used to reak of gas till I got things leaned out some. Now it is not too bad but once in a while I still smell the fumes.