KDXRIDER.NET

Will idle forever if setting and returns to idle fine if just cruising around not getting revved out, but as soon as it gets run up into powerband for any length of time it dies upon returning to idle. It has only recently started doing this, no tweak of the Air screw makes any difference, if setting and you give it a quick opening of the throttle it will hesitate for a second, at first I was thinking to rich but I am not sure and getting more confused every ride. After dying it will start first kick with a little blip of the throttle and after a few boggy revs its right back to idling properly. Any educated help will be very appreciated. FMF Gnarly Woods pipe, power core silencer, needle on highest (leanest) notch, main up one cant remember pilot size.

fresh wiseco top end btw.

Sticking floats?

Doesnt act like other float issues I've had, I'm thinking maybe float level if it turns out to be float related, planning to tear it down tomorrow :(

It just kinda sounds like it's running out of fuel at higher rpm's? That what made me think it was floats. Could be a clogged jet? But it sounds like a fuel problem of some sort.

Runs perfect everywhere, even at idle, except when returning to idle after engine braking or when closing the throttle after a brisk run

That is odd!

03MoneyPit wrote:Runs perfect everywhere, even at idle, except when returning to idle after engine braking or when closing the throttle after a brisk run

You said when you " give it quick throttle it will hesitate for a second " from idle - so it's not working 'perfectly everywhere'.
If it were me I would take the following steps:
-start with a clean air filter
-clean carb (jets, choke, float valve) and verify float level is set correctly.
-reference the jetting guide and start tuning. Perhaps getting rid of the off idle bog will solve the other issue.
-may also want to inspect the reeds

Reeds have about 40 hours on them, I'll look them over too, I'm hoping to find the float level off and I think I'll raise needle a notch for the first correction attempt. You really have to crack it open fast to get the hesitation, so yes its not perfect, but at no time would a person whip the throttle way open from idle like it requires to get the bog lol. I'm thinking it might be a hint lean off idle, so maybe it picked up some trash in the pilot and the needle needs raised. Fingers crossed its that simple anyway lol.

Finally got to work on it awhile today, no signs of crank seal leaks and I did find the pilot was pretty clogged. I raised the needle from top to middle clip position and the bike would idle much better and didnt try to die but the middle was so rich it stuttered, dropped the needle one notch (to second from top) and it seems lean on the bottom again. I'll pull the carb tomorrow and pull jets and check sizes, as is I'm thinking pilot is too small and main is too big. The midrange hit is there but it runs out before the bike has revved out noticeably more than when the needle clip is centered.

I should also add that all hesitation off idle completely disappeared with the needle clip in the middle slot.

Tore back into it today, using a .010 shim, needle on second slot from top, it is a much better machine, no more dieing on decel or hills, I adjusted the floats a little more and Air screw out 2.25 turns. I pulled the jets and the previous owner has 38 pilot, 160 main.

Setup is Open airbox, Twin Air Filter, FMF Gnarly Woods pipe and power core silencer, 40:1 with Castor 927, switching back to Motul 800 after this batch.

03MoneyPit wrote:Tore back into it today, using a .010 shim, needle on second slot from top, it is a much better machine, no more dieing on decel or hills, I adjusted the floats a little more and Air screw out 2.25 turns. I pulled the jets and the previous owner has 38 pilot, 160 main.

Setup is Open airbox, Twin Air Filter, FMF Gnarly Woods pipe and power core silencer, 40:1 with Castor 927, switching back to Motul 800 after this batch.

2.25 turns out means the pilot is too rich (big). but, since you already have a 38 in it, i would expect you have a leaking needle seat, and/or jet block gasket, and/or incorrect float height.

if you put the airbox lid back on, it will be really rich. even worse with the stock pipe+stock silencer. when mine was in a similar situation where everything had to be leaned to the max, i finally replaced the carb and things improved exponentially. check the simple things first before you do, though:


float height = 16mm +/- 1mm ?
jet block gasket = the torx screws (3 of them) can be cut with a hack saw to allow a common head screw driver to turn them ?
float needle (the one attached to the float assembly) - is it sealing perfectly ?
is the tip of the needle perfectly sharp, no wear rings on it's tip ?
is the slide tight in it's grooves ?
is the pipe completely free flowing, no blockage in the arrestor's packing ?

if all of those are confirmed, and you still can't run a larger pilot jet, i would bet it's another worn out carb.

Float height is an issue, the floats bottom out (compress the spring on the needle) so setting it has been a booger, I have it set atm to where the float needle seats as the floats reach 18mm and currently the bike runs the best it has since I've owned it, I think the main is too rich and the needle requires lowered because of it, also seems like raising the needle helps the bike from closed to nearly WOT where it gets a little blubbery. Blowing through the fuel inlet operating the float manually I can hear the air stop passing through the inlet and det rerouted to somewhere else. I do plan on just picking up a new carb asap for the sake of the bikes name, but the prior lean bottom end was pretty noticeable compared to its behavior now and its willingness to tractor up a hill below powerband vs rough run (compared to now) and require powerband to make climbs that the bike will put up now. I may order the jetblock gasket and a new set of floats just to experiment. $30 shipped for floats and jet block gasket is a cheap enough expenditure to warrant throwing parts at it lol.
I believe the eshaust needs repacking, as rich as it is running up top and as bad as it was loading up down low I dont see how it couldnt be, but I plan to off the power core and run the turbine core so I'll postpone repacking the PC. It is tempting to gut the silencer now though LMAO