ATA-250D with Mikuni 30mm - what jets you running?

[Rule308]

Anyone with a 250D or similar running a Mikuni 30mm carb? Can you list your pilot jet size, needle clip position, mods and typical weather/temp?

Just curious for a comparison. I'm running in high-80's and 90's deg F (high humidity) for ambient temperature.

Only have a K&N filter with Uni foam sleeve, Mikuni 30mm with stock mikuni VM28/486 number 20 pilot and that's way too lean. Took it out earlier and it fell on its face all the way through the throttle (lower 1/4 and up to 3/4, didn't go WOT). I probably need to jump at least 2 jets up to a 25 on the pilot jet, and drop the needle clip (raise the needle) by 2 clip positions (all gut feel).

[Weldangrind]

I presume that your 250 is actually a 223 or a 230. If so, I'd feed it with a 115 main and a 30 slow jet to start. I'd also put the clip in the middle.

[culcune]

Taotao tends to name many of their products with the 'wrong' size, the named size being 'over.' This quad is a 200 according to their own specs, if that makes a difference as far as jets go. Wade Liu of Excalibur had pointed this out for me when we were discussing one of their older '250' quads which had the specs listing it as a 200.

[Mudflap]

Hard to imagine it's a 200 with a bore of 71mm. If so it would be a very much oversquare engine, just what you don't want when low end torque is needed.

Also the engine number is 171FMM with the second M indicating 250cc class. It would be an L if it was 200cc class.

[Mudflap]

I just went out and measured as accurately as I could without removing the head. I did it by inserting a 1/4" dowel into the spark plug hole, holding it as vertical as possible (about 10 degrees from vertical), marking it with a sharp knife layed flat against the cooling fin. Then I did the same thing with the piston at the bottom of the stroke. The distance between the 2 marks is 66.26mm.

With a bore of 71mm a stroke of 66mm would be 261cc. Since my measurement isn't perfect I could see the actual stroke being 65mm (257cc) or maybe even 63mm (249.4cc) but there is no way the stroke is 50mm (197cc).

My conclusion is the engine used in the Taotao ADA-250D is indeed larger than 200cc, probably larger than 230cc, likely 249cc.

[Weldangrind]

Knowing that, I might try a 120 main and a 35 slow, assuming you're anywhere near sea level.

[Rule308]

Whatever that stands for. I think its a 230cc. Yes, I'm at sea level, Houston, Humid as hell everyday.

So what do you think? I want to say my main jet was 100, needle is near top if not in top groove (deepest needle, low) and pilot (slow) jet is 20.

Planning to try clip in middle of needle, pilot jet at 30 if that's one of the sizes I bought and Main jet 120 if I got that size ordered. What do you think?

I probably need to jet it rich, by the time deer season gets here Llano should be fairly cooler than Houston, can get downright cold, so I better "lean" towards "rich" in my tune.

Better order more jets from the sound of it.


Just checked, the richest jets I have are 120 main and 35 pilot. Will try those first and middle clip position. Thanks for the input guys,

[Weldangrind]

Originally Posted by Rule308

I probably need to jet it rich, by the time deer season gets here Llano should be fairly cooler than Houston, can get downright cold, so I better "lean" towards "rich" in my tune.

Ha.

I'd try a 115 main and a 30 slow to start.

[Mudflap]

Is that a 167 FML or 167 FMM? An FML engine would be the 200cc and an FMM would be the 230cc.

[culcune]

Thanks for clarifying the engine size. I was going by a conversation I had probably over a year ago with one of their dealers/distributors, as well as their own site lists the engine as a 200cc. I am hearing better and better things about them from even a few short years ago, so I would definitely consider one no matter what the stated engine size is vs. what they name the bike, vs. what is actually attached to the bike Anyway, sorry to hi-jack, and thanks for clarifying!

[Rule308]

God almighty this is a hard pilot screw to get to on the 30 mm Mikuni. Either you burn yourself on the head fins or the exhaust and thats with the exhaust wrapped. I think I've boogered up the pilot screw slot. Fiddling around with several short screw drivers, several right angle screw drivers, several other ways and still can't adjust the pilot screw.

On top of that I had the choke on when I had it running the other day, the filter kept me from seeing the choke position. Took a look at the original stock Keihin carb and its a sealed unit. Can undo the bowl because the screws don't have heads, slots, nothing. Looks like they were safety type screws where the head shears off after you torque them to the right amount. Can only adjust the air mixture on the side of the Keihen Carb.

I saw some weird S-shaped intake manifolds online for the vertical engine and since only 13 bucks buying one on a whim to see if I can relocate Mikuni external to the body to reach the damn pilot screw. Wonder if they make an extended pilot screw. Still don't have it running right, since I can't adjust it without pulling carb.

[Rule308]

Just bought this
http://www.ebay.com/itm/Air-Fuel-Mix...-/161790414165

Hope it works, but looks like I'll have to cut the head off to fit. The starter is pretty close to bottom of carb, so looks like I'll chop it if I have too.

[Rule308]

I notice there are several different manifolds for sell but can't tell for sure if any will fit this model. Tempted to buy a few and see if any will fit. Who has tried this?

[Weldangrind]

The weird S-shaped intake is for a quad like mine. They're tough to start, but they're ok once the engine is warm.

Please let me know how the extended pilot mixture screw works for you. If it's a win, I'll buy several.

[Rule308]

http://www.amazon.com/Racing-Product...et+screw+R%26D

Bought this R&D Jet Screw also. I plan to use it first. Sounds like a God-send for these carbs.

Isn't the Mikuni with the pilot screw in the back an air screw. It adjusts air flow?