30MM CVK CARBURETOR Question

[outcrydrummer]

I can't find any info on these carbs to figure out what the stock settings are. I know thats not the optimal setting for any one engine but I'm totally and utterly lost right now on the air/fuel and need a starting point.

I bought a carbide with a ton of mods and took it for a ride to find it not reaching above 4k rpm and being very slugish, then after a few seconds of wot it would fall on its face and stumble almost to the point of stalling. It would do this back and forth for a few seconds and eventually die.

I removed the plug and replaced it, ran it and found no sign of fuel ( didn't smell like fuel ) and was not black. Funny thing is the plug wasn't white either. It was just the color it was when installed minus some discoloring from heat which made me believe it was running lean. So i richened ( turned the air fuel out 1/4 turn )

This made it worse. went back the other direction to no help. Eventually got to the point now where it won't even crank at all. I'm getting good fuel to the carb, I removed the carb and pulled of the bowl and found absolutely no dirt or grime and a spotless carb.

Put it all back together with a new plug and tried again.....still won't crank. It will backfire 1 out 5 times trying to start it but thats it.

Don't even know what to do at this point. I know its probably just not the right air/fuel but I've tried going to the extreme side of what should be rich and working my way back until I get it right but like I said I can't even get it to start and run at this point on literally and sort of air/fuel adjustment.



Any and all help is appreciate because at this point I'm ready to roll it in the street in front of moving car

[metalstudman1]

My standard start point on an unknown carb is 1-1/4 turns out from closed.

[outcrydrummer]

Well it turned out to be the cdi. Swapped back to the stock and it runs just fine. I've had to turn it out about 3 full turns now from 2 1/2 out to get it just about right. With all the performance mods on this thing It's no surprise its pulling a lot of fuel.

I'm just glad I got it figured out.

Now does anyone know of a really good aftermarket dc cdi that won't fail at the drop of a hat lol?

[ckau]

Originally Posted by outcrydrummer

Well it turned out to be the cdi. Swapped back to the stock and it runs just fine. I've had to turn it out about 3 full turns now from 2 1/2 out to get it just about right. With all the performance mods on this thing It's no surprise its pulling a lot of fuel.

I'm just glad I got it figured out.

Now does anyone know of a really good aftermarket dc cdi that won't fail at the drop of a hat lol?

If you got to go that many turns out on the air screw you need a larger pilot jet. , A turn and a quater to half is about right.
Any cdi is a crap shoot. they either work 100% or non at all so there's no particular brand that stands above the rest

[outcrydrummer]

I'm still messing with it. I need to really let it run they way its set right now and read the plug. I ran it about an hour maybe and the color was nice and beige so if it stays that way I'm not going to mess with it.

I'm not familiar with these carbs but I'm assuming the pilot jet is the main jet? In that case I will look into getting another or just drilling out the one I have now.

Can anyone out there maybe suggest to me what springs, rollers, etc etc etc I should run for just having fun on flat fields?
I have 1000 1500 and 2000 clutch and main springs. I only have whats in the buggy which is unknown and 11 and 12g rollers.

Thanks

[ckau]

Originally Posted by outcrydrummer

I'm still messing with it. I need to really let it run they way its set right now and read the plug. I ran it about an hour maybe and the color was nice and beige so if it stays that way I'm not going to mess with it.

I'm not familiar with these carbs but I'm assuming the pilot jet is the main jet? In that case I will look into getting another or just drilling out the one I have now.



Thanks

No, the pilot jet and main are two separate metering jets. In a nutshell, the pilot basically meters flow from idle up into midrange while the main kicks in for top end. Hence, the over adjustment on the air screw to compensate for lean pilot flow. if you ran a wide open plug check the plug will show the effects from the main not the pilot. The right pilot will give you stronger acceleration and power through out the rpm range.

[outcrydrummer]

Ok I appreciate the info. Do you know where I could get the pilot jet and any idea on what size jet I would need with my mods?

[ckau]

Originally Posted by outcrydrummer

Ok I appreciate the info. Do you know where I could get the pilot jet and any idea on what size jet I would need with my mods?

for the Kehin 30 mm pumper carb,
main jet # 99101-393
pilot jet # N424-21

To get it dialed in right , you will need mains in the 138 to 148 range (5 jets). pilots in the 35 to 42 range (4jets). They run about 3 to 4 dollars a piece. Any cycle shop can get them. With your mods, you will probably fall in this range.
See whats in your carb then work with the pilot until you get the air screw into the turn and a quater to half range The idle and acceration should be smooth and crisp. Don't use the wide open run method to check the plug. thats good for hard acceration and drag racing . Run the buggy as you normally would, in operating temps for a while. After the enrichener circut (choke) is fully closed properly then check plug. Adjust main at that point.
you'll know when it's right, it packs one heck of a punch.

[outcrydrummer]

ok I appreciate the info. I think I'm going to order a color tune from gunson and just tune it that way after the jet or just drop it off at the local atv shop and let them do it as my work schedule during the week is hectic to say the least so I'd like to be able to ride on the weekend rather then tune lol.

I really think I might be messing up with the tuning somewhere along the line because they had that carb running on this kart with a 170 big bore kit so it must be more then enough fuel for this 150 kit. I know they said it was rejetted. maybe its just time I busted it open and looked at the jets.

It has really crisp throttle response and smooth acceleration but I don't have enough open road or area to really let it wide open and I don't have a clue to what rollers and springs are in it right now.

[outcrydrummer]

Well a new piston and rings later i have another question. Is the black slider that goes up and down in the carb suppose to go all the way up when reving it? When i rev it and look in the carb it only bounces up under half way. The kart cranks right up and runs fine now just missing power and still not spinning up past 4 to 5k rpm

[outcrydrummer]

Also could it be anything else? The previous owner had it running great with the exact setup i have so i shouldnt have to re jet the carb. Is there another vacum line besides the one that goes from the carb to the fuel valve? Any common issues that result in lack of power and low rpm? The cdi is good timing is good piston and rings are good spark is good so that only leaves vac and carb or intake stuff but ive rechecked all the clamps for the intake