hey guys,
by no means new to dealing with carb issues but new to rejetting.
so... recently purchased myself a K&N lunchbox and rejetted, bought the jets separate rather than in a kit, did the research and went with the pilots up to 40 and the mains up to 140, it's a 2000 btw and it's on the standard exhaust/endcan.
with minimum fettling i've got the spark plugs running the right colour so i'm pretty confident that the jets are pretty much bang on :D air mix screws are set to somewhere in the 4-5 turns out region.
it's runnable but i'm a bit of a nazi when it comes to things being done right,
my issue is primarily with mid-range bogging, i lifted the needle one notch, definitely made a difference but the issue is still there, lifted it another notch and the mid-range is slightly less boggier however the low-end has in return bogged down a little and will backfire and konk out if you give the throttle a quick flick when cold, however not when warm.
i know that in particular with dynojet kits the instructions require that you drill the slides and insert the ''correctors'' and i've read that they make a significant difference to the low end responsiveness however they don't seem to be purchasable outside of their kits, go figures. which i declare :bs: haha
anything to do with rejetting is always going to be trial and error, i'll get there in the end but any input to make the process just that bit quicker would be greatly appreciated :icon_mrgreen: :bowdown:
K&N induction roar is somewhat satisfying to say the least :thumb:
4-5 turns out on the mixture screws sounds a little excessive to me, but I don't own a 500 so I'll let others chime in on that.
Every jet circuit is actually linked at all throttle ranges - but obviously some are more pronounced. If you have the mixture, pilot, and needle settings absolutely PERFECT, but you main jet is too large, it will make everything else rich as well. So with a 140 main jet you keep richening the needle position, but it's never rich enough? Try a larger main jet. A 142.5 main will allow more gas past the needle as soon as the slides raise up.
Just checking: have the carbs been vacuum synced and valves checked?
Quote from: Big Rich on July 28, 2013, 06:34:37 PM4-5 turns out on the mixture screws sounds a little excessive to me, but I don't own a 500 so I'll let others chime in on that.
Confirmed. If the pilot jet is properly sized, 3 turns should be plenty.
Quote from: Big Rich on July 28, 2013, 06:34:37 PM
4-5 turns out on the mixture screws sounds a little excessive to me, but I don't own a 500 so I'll let others chime in on that.
Every jet circuit is actually linked at all throttle ranges - but obviously some are more pronounced. If you have the mixture, pilot, and needle settings absolutely PERFECT, but you main jet is too large, it will make everything else rich as well. So with a 140 main jet you keep richening the needle position, but it's never rich enough? Try a larger main jet. A 142.5 main will allow more gas past the needle as soon as the slides raise up.
Just checking: have the carbs been vacuum synced and valves checked?
a previous jetting set up i had ended up with 5-6 turns out, ran spot on and was told by a few reliable sources that it shouldn't matter that the air/mix is so far out as long as it's running right.
it's a steep learning curve but yeah i find it really interesting how it all works... most people think it's a bit sad but ahwell haha :D
all bikes of the same model will be slightly different case to case but general consensus seems to be that the 142.5 mains are too rich with a stock pipe and lunchbox and the 137.5s are too lean.
but i think you just inadvertently raised something i may have overlooked :cookoo: *facepalm* i had it set to burn the right colour but i've not checked the plugs since i've messed about with the needles! i thought i did but in retrospect i needed use of the bike and it was runnable... totally forgot i was going to do that... to state the obvious, raising the needle increases fuel and it will be running rich in the 1/4 to 3/4 throttle, it was lean hence i put it out further on the air/mix before messing with the needle position which would correlate with it being a couple of turns out in the first place. haha sometimes you need to just step back or sleep on it... for a week. i'll have a tinker with that in the morning. thanks for the epiphany!
also i balanced the carbs about about a month back but will be sure to do it again once i get the jetting dialled in and valves are supposed to be checked every 8,000 in accordance to the manual if memory serves, bikes done 20,000 and i doubt the previous owners bothered so it's definitely on the to do list.
still looking to see what the deal with drilling slides is if anyone can suggest what to do about it, chime in if you know what the deal is :thumb:
Your sources are correct about it running right. Here's the problem though with having mixture screws out too far though: while the screws are threaded, they are also spring loaded. Those springs not only keep a washer & oring in place, but it also puts pressure on the mixture screws as well. Too far out = not enough pressure on the screw = screw vibrates loose. And if a mixture screw falls out, it causes all sorts of running issues.
I've never drilled the hole in slides so I can't speak for exactly what it does. But PeteGS has on his GS450 carbs, so maybe look for his thread on the GSResources (just "Pete" over there though). Have you considered cutting a little off the springs on top of the slides? Just an idea....