Ledar Air-Correction Kit - what is it?

[Mitch]

Mrs R's bike (Kwak GT750) has still got a bit of a flat spot when trying to pull away. Sometimes the bike gets all boggy as you open the throttle. I've replaced the inlet rubbers from the carb to the engine but it still isn't quite right

On the piles of paperwork we got with the bike, it mentions something about the aforementioned kit.

How does it work? Also, how would it affect the jetting on the bike?

The bike's got K&N's on it and I'm wondering if it's set up correctly :confused:

[Dougie]

A LEDAR kit (for GS550 slide garbs at least) contains bigger main jets and small jets to fit in the air side of the pilot circuit.It's necessary when fitting pod filters such as K&Ns.A thought,have you checked your diaphragms?

[MrFluffy]

People usually use air corrector kits to get round huge flat spots that k&n and 4-1 exausts introduce. It sort of works usually but it DOES take a awful lot of patient setup to dial out each and every one of the flat spots.
The air corrector kits are usually different jets, and depending on which carbs its for etc, they can contain little drills to alter the size of the vent holes in the slide, a different pilot jet, different emulsion tubes whatever. Theyre different for each bike.
Your flat spot is probally down to the k&n's (and a 4-1 if you have one), the stock carbs were designed to draw air from a still air chamber that allowed the vacumn created at throttle to pass the intake for the diaphragm chamber creating the correct amount of lift, the air corrector drills are intended to try and compensate for this lack of vacumn when you fit k&n's or the like and try and restore stock responses to certain conditions. Stock airboxes work well for these reasons, even if theyre a pain to work with. Id rather fit reverse cone bellmouths than k&n's, if your going to be shot it might as well be for a decent gain.....
If its any consolation I have a stock gt with a motad 4-1 and thats got a niggly flat spot at lower revs, that wasnt there with the stock 4-2 system. And I cant be arsed taking off the carbs 10 zillion times to tune it out :(

[dracken1]

if you have a standardish exhaust system. and you only fit k&n airfilters you can often clear a flat spot by adjusting the mixture screws. if the flat spot is above 2200 rpm then you may be able to cure it by raising the slide needle a notch..

[Mitch]

if you have a standardish exhaust system. and you only fit k&n airfilters you can often clear a flat spot by adjusting the mixture screws. if the flat spot is above 2200 rpm then you may be able to cure it by raising the slide needle a notch..

Damn, that means we need a rev-counter Mrs R! (does anyone sell those cute little custom ones that go with the speedo that's already on there?)

The exhaust that's on her bike (same as mine) is a Motad 4-1; whereas my GT has a standard airbox on there still and Mrs R's has got all this electrickery built in place of the airbox (including an alarm, ignition switch and all sorts). I suppose the ideal solution would be to retro-fit an original airbox (would one off a GT550 be enough - as they're smaller - or would I have to put a 750 one back in?) and switchgear. We may just do that anyway as we have more than enough wiring from various donor bikes...

I think the jets Dougie refers to are the ones in the right-hand hole in the back of each carb. I suppose they can be taken out but I would have thought there'd be a lot of work to set the carbs up properly. I suppose someone with a Dyno could do the fine tuning (at a price).

Say, we were able to start again... what would be the best way to go? back to standard jets & filter and work from there?

What do Reverse Cone Bellmouths do then that K&N's don't Mr Fluffy? Me no comprende. I've seen them on a few bikes in the past but don't know much about them. I've also see people make up an airbox to suit in place of filters and that seems to work

[dracken1]

umm minitach 48 or 60mm stainless steel like the one below.this guy is a really nice person to buy off..
http://www.jwmotorcycles.com/C0036.html

ok ok its me.
£21.95 less 10% plus shipping for forum members only.

with a motad exhaust and just filters you should not need to rejet at all.
nor change the air correctors

standard carb settings for the gt750 are
main jet 110
needle position 3
pilot screw 2 turns out.

if your mixture screws are 2 turns out. turn them out a half turn then try the bike if better try another 1/4-1/2 turn. if it feels worse it needs to be turned in an 1/8th of a turn can make all the difference...

before doing anything though ensure all the jets/airways in the carbs are clear

[Mitch]

with a motad exhaust and just filters you should not need to rejet at all. nor change the air correctors

standard carb settings for the gt750 are
main jet 110
needle position 3
pilot screw 2 turns out.

if your mixture screws are 2 turns out. turn them out a half turn then try the bike if better try another 1/4-1/2 turn. if it feels worse it needs to be turned in an 1/8th of a turn can make all the difference...

before doing anything though ensure all the jets/airways in the carbs are clear

OK... I think I've got the hang of this... (carbs have never been my strong point and the haynes book of lies hardly helps matters, and as for the Kwak KZ750 service manual...) - I think I've done this before but am not totally sure.

Main Jet 110 - to get to that, am I right in saying you undo the float bowl underneath and take it out with a screwdriver? If so, I've done that before on the ZL.

The Needle is the one that goes from the top of the carb through the throttle valve assembly - that's fairly straight forward (well it was on't sprog's 125 as that only had a single carb), only there's four of them

And the pilot screw, you say two turns out... Do you start by turning it clockwise or anticlockwise before you start (as in all the way clockwise then two turns out or vice versa?). I think I learned about this years ago - but someone kept calling it the mixture screw (are they the same thing?)

I think these carbs may have been f'cked about with because of the K&N's so as you can imagine, the jets are probably way out...

I'm off to the Pissed Indian for a lie down!!!! (we've got a MAG stall there so we're hopefully off there this aft to set up!). I know which way I'm going to go with my GT - standard filter etc. Phew!

[odie]

Turn the mixture screws in till they wont go any further (not to much or you will nacker them) then turn them out 2 FULL turns of your screw driver, that will be your datum point to work from.
every thing else you have said is correct, the needles etc.

[MrFluffy]

What do Reverse Cone Bellmouths do then that K&N's don't Mr Fluffy? Me no comprende. I've seen them on a few bikes in the past but don't know much about them. I've also see people make up an airbox to suit in place of filters and that seems to work
Flow gas properly and work in the rain, plus if your going to go to all that effort of redoing the carbs might as well get some power gains out of it ;)
The reverse cone of the bellmouth creates a really good way for the gas flow to get into the carb mouth from the infinately large space (outside) into the throat without having loads of eddy's in the gas flow and the like, the reversal on the bellmouth alone is usually worth a few bhp..
Downside, they let all the crap into the motor and it wears out quicker, but generally my motors dont live long enough for it to be a real issue so I just run with a mesh screen over (which also stops flashbacks) to catch the really big bits like stones etc. The only bikes I run with filters on have either turbo's or superchargers cos bits in there get really really expensive and get really upset by particles of crap....

The whole k&n myth really bugs me, I used to work at a bike shop and we had hundreds of bikes in over the years where someone had started to "tune" them, and the first thing anyone does is throw away the standard still air chamber that the japs spent millions developing and in reality is very very good, especially on more modern stuff, and replacing it with a crappy cone filter that makes less flow rate than the same airbox and a freeflow filter element, end result huge flat spots all over the rev range that you have to dick about trying to tune out, not always completely sucessfully. You still see adverts where the seller explicitly mentions k&n filters like its some big improvement and I just think "I bet thats got more flat spots than a hedgehog on the m25".... Pet hate, sorry I probally am ranting..

[dracken1]

to a point i must agree with mr fluffy.
a standard airbox with any internal baffling removed and fitted with a direct relacement filter such as k&n will give you a performance increase but with a much smoother power delivery

[BikerGran]

Someone mentioned diaphragms - I would check those (cos it's easy) before starting to mess about with jets etc. My GT550 wasn't pulling very well, took the tops off the carbs and all four diaphragms had splits about an inch long in them! Amazed it was running at all - and it had only done 25000 miles at that time.

But don't get genuine Kwak replacements - they cost the earth!

[Mrs Reject]

I'm fed up with it all to be honest! Every dealer we go to doesn't seem to know how to fix it up right. I'm tempted just to say bollox to it all and get a new bike. If i get stuck behind a slow driver on a big hill the feckin' bike just dies and stops. One guy told me my engine only has 80% compression in the cylinders and it needs new piston rings so could the problem be that or is it more likely to be carbs do you think? Bike problems are so much worse if you don't know much about the workings of bikes.......it's all witchcraft, if I burn the little old lady next door the bike will probably be ok :D

[dracken1]

ok according to autodata the compression for your bike is between 8.5-13.1 bar, which near as dam it is 127-185 psi.
20% below the upper end of the scale would mean you would still have 148psi.
20% below the lower end would be 101 psi (not good)

don't know why the mech gave you the results of the comp test in that manner.
most, myself inc would have said what the readings of each cylinder were.
saying 20% down, as you can see above does not mean it's knackered


an electrical prob would usually appear at certain revs, carb prob by throttle position and engine load.

have you made sure that the tank can get air into it either throgh a breather pipe or a vented fuel cap?
is the prob worse with the lights on?
there are a few things that could be causing it.

[Mitch]

ok according to autodata the compression for your bike is between 8.5-13.1 bar, which near as dam it is 127-185 psi.
20% below the upper end of the scale would mean you would still have 148psi.
20% below the lower end would be 101 psi (not good)

don't know why the mech gave you the results of the comp test in that manner.
most, myself inc would have said what the readings of each cylinder were.
saying 20% down, as you can see above does not mean it's knackered


an electrical prob would usually appear at certain revs, carb prob by throttle position and engine load.

have you made sure that the tank can get air into it either throgh a breather pipe or a vented fuel cap?
is the prob worse with the lights on?
there are a few things that could be causing it.

I think to be honest m8, where we took it wasn't ideal as they only half sorted a problem - as in they got the bike running, where at one point it wouldn't go for more than a mile or so. This was put down to a dodgy fuel filter.

I've got a good mind to have a look at the jets this next couple of days then take the bike up to Galea Camchains in Essex this Friday as they are supposed to be experts on GTs due to when they were in London, they used to sort out all the courier bikes (nearly all GTs or CXs at one point),

The breather pipe's OK as far as I know. The bike is running dog rough because of the camchain rattle - another good reason for visiting Galea

The worst thing about the bike is where you're going up hill slowly, so you're in first gear and stuck behind a tractor and the revs have died under load, making it stall - though now I sorted out the carb intake rubbers (or carb holders according to the packet) it's not as bad but it's still running rough