carb question....pleeeeze help ?!?!

[Slingshot560]

ok...heres the deal....87 lt 500, fmf pipe and silencer, bored .60 over.....when im riding and get into the upper rpm range, the motor bogs down like it runs out of gas, then when i slow down sometimes it revvs way the hell up...like when a 2 stroke is runnin out of gas, but the tank is full and it flows right out of the tube no prob, i cleaned out the carb and went from a 480 to a 490 main jet, and it still does the same thing, but now it feels like it floods itself out sometimes and sometimes will just shut off and it takes 5 thousand kicks to get it goin again, and you allways have to choke it to start it...somebody please help...i bought it and it has been apart more than it has been together and its pissing me off...please help

[zillaguy89]

OK I'm not trying to sound like a dick here, so please don't take it that way, some people do get this confused. You say its bored to a 560? like with a big bore kit, or is it just .060 over? Next question. If it is really a 560, are you still running the stock carb? Hopefully not, if not can you give the size of the carb in millimeters, or even better,the model of carb?

I hate to bring up the dark side of the Quadzilla (if there really is a good side reliability wise) But you may be yet another victim of the dreaded "Stator Side Crank Seal" issue. Did the quad run fine and then just start doing this out of nowhere?

[zillaguy89]

Hey, just for kicks, check the color of your spark plug to make sure we're headed in the right direction here....black is too rich, white is too lean.

[flotek]

your stock carb should be called a tms38 its a 38mm flatslide carb ,not sure of your mods but that main sounds very rich , dont quote me but i beleive stock is 300 ,your like 18 sizes up , a bog in wot is your too rich ,a hesitation in wot your lean ,that strange high idle is due to your large flat slide is made from soft aluminum ,id be willing to bet its worn and when that happens you get a condition called free rev and its not cool and makes jetting shitty for you ,that stock carb is an excellent rever and a good size its just old and wears over 17 yrs . to often aguy wants to go fast and thinks he needs a 40 something millimmeter carb to drag when all yo udo is lose torque and midrange ,and esentially slow your bike down ,if you narrow it down to the carb and want to replalce it hy-tech atv sells the keihin d slide 39pwk ( like what dt has ) for 169$ and will add 3 hp to a piped motor .

[sblt500r]

I had the same problem with mine. It has a fmf pipe and silencer, k+n filter fmf ram valve, and bored 100 over with a wiesco piston. I put on a new ricky stator, coil, left crank seal, and it kept doing it. I had a stock carb, so i finally got a new keihin 39 mm pwk. Put it on kicked it 4 times and started right up. That was in 10 degree weather!!!! It now runs great. No more kicking my leg off to get it started. A new carb should help.

[Zilladude]

Stock 87 carbs are junk, throw it away. Get a 39 or 41mm PWK from Sudco or carb parts warehouse. You may need a different needle in the Keihin's though. I had a 230 main in mine & it seem lean on top, changed the taper of the needle & am down to a 190.

[Flattrack]

Check out Pro-Flo Great people to deal with good prices and super fast service....

[flotek]

if i still had my zilla id do things different knowing what i know now ,id get a 38mm air stryker carb ,the y are the shizzle goto keihins website look at that airstryker in comparison to the pwk carbs ,one of the many improvements is the intake has guided high wings that shoot(direct) air to the center of the jet needle ,cool as hell youll see what im talkin about go look if your debateing on a carb ,they only make an airstryker in 35 and 38 mm ,theyre kickass i may get the 35 A.S keihins for the she next year!

[zillaguy89]

Originally Posted by eviltwin

your stock carb should be called a tms38 its a 38mm flatslide carb ,not sure of your mods but that main sounds very rich , dont quote me but i beleive stock is 300 ,your like 18 sizes up , a bog in wot is your too rich ,a hesitation in wot your lean ,that strange high idle is due to your large flat slide is made from soft aluminum ,id be willing to bet its worn and when that happens you get a condition called free rev and its not cool and makes jetting shitty for you ,that stock carb is an excellent rever and a good size its just old and wears over 17 yrs . to often aguy wants to go fast and thinks he needs a 40 something millimmeter carb to drag when all yo udo is lose torque and midrange ,and esentially slow your bike down ,if you narrow it down to the carb and want to replalce it hy-tech atv sells the keihin d slide 39pwk ( like what dt has ) for 169$ and will add 3 hp to a piped motor .

I agree. I was probably trying to be too technical, haha. I just wanted to detirmine whether it was a 560, or .060 over, that would make a big difference on what carb to use.

That "free rev" your talking about is from air actually working its way around the worn out slide, making it act like the throttle is open even if its not, correct? I was thinking about going back to the stock carb after the rebuild, but after hearing that, I'll stick with the PWK.

[ReeperLT500]

If your carb is not sticking then it's the jets. Yes your 480-490 it's way too big. I have a 440 and mine is bored .80 over. When I first got my 500 I too had to choke it to start it even when hot. I increase my idle jet to a 35 or 40 can't remember, problem solved. It's not getting enough fuel on the low end(thus high idle) and bog on the high end(too rich). Although as eviltwin stated that's an old carb so it could be sticking. But try the jets first since it's cheaper to buy a set of jets than a new carb. -Mark