K&N carb setup
 

Hi doods, I've just installed a K&N in my bike and already had a viper end can. Thinking in advance I decided to setup the carbs to accomodate for the extra air, so I upped the card needle one notch so its now in the middle and turned out the pilot by one turn.

Is this suitable and has anyone else got the same setup?

Ideas on a postcard please ... :D

Not the same, but do have k&N filter with Renegade exhaust. It ran lean so had bigger jets put in.

I'd expect you'll need bigger jets too. A full turn on the mix screws is a pretty big difference but there's no reason it can't work.

Here's some things I've heard/figured out. This isn't exhaustive but I've used all of these to good effect.

With the mix screws, you can get an idea of how well set up they are by how well it idles, and how quickly the needle falls back to idle from around 3000rpm. Rich causes a slow drop, usually.

With the mids, much the same- rich will cause the needle to drop slower than before. Also, you'll tend to get more backfires on overrun

With my bike, there's a really good indicator when it's running lean up top- if I cruise at around 5000rpm for a few seconds then crack the throttle open, it gives me a big stutter before it picks back up.

And of course, check your plugs, check your exhaust tip. I put the standard filter and baffle into my bike for its MOT since hte system's a bit rude- not terrible, just a bit too loud- and the baffle was basically black from the over-rich running by the time it came out.

Go find a shop with a dyno and get a base run done. Without tuning anything most shops will run it and give you a printout. Shouldn't cost more than £20-

If you want to replace main jets, I'd suggest 138DJ-140DJ as a start.

OK well i've been running this for a while now, I put the pin up one and turned the pilot out one full turn and it feels like its running too rich .. correct me if im wong as someone surely will :wink: im getting very poor running at low speed and the bike sounds and feels a lot different than before when im coming to a stop. Does this mean too rich or too lean? Without the correct tools to check im a little in the dark.

Usually with carb tuning, you start with the full throttle check to get the main jet correct then deal with the lower ranges. I could tell you what to do with an old Amal carb - uphill blast under load, kill engine PDQ and do a plug chop. If a Mikuni has the same sort of circuits in it as an Amal, the air screw deals almost solely with tickover and throttle just opening. Needle height with 1/4 to 3/4 throttle approx. All circuits tend to overlap.

A full extra turn on the pilot screw is a pretty major change, like I said earlier... I'm not sure what stock is, but I'm running 2 3/4 turns IIRC with a full system and Race RS filter. It sounds like most of your difficulties are at low revs?

Yeah doesn't seem to be any problems top end, and I've regulary revved it that high and cough riden at high speed offroad. All the problems feel and sound at low range. too rich I think? I put the needle up one to allow more fuel, so do you think I should drop the pilot back half a turn? Without doing a major re-jet or shimming just yet as im off to Germany on Thursday :shock:

I'd start with the pilot screw for sure, since youcan be pretty sure there's something amiss there.

Thanks northwind, i'll have a play with it tomoz and see how I get on :D Also do you or anyone else know what size the scres for the carb casing is two of them seemd to die on me while I was doing it :(