Sluggish T250

[Vintageman]

You mean when you said this -> "The carbs are Mikuni VM26 two-stroke carbs and are brand new" I did see that and forgot in between post ltimes sorry and embarrassed about my ever growing senility combined with permanent A.D.D.

Are these aftermarket carbs (e,g, SUDCO ourchase) or new OEM? I should stop here and await your reply, but can't

If new OEM than no carb jetting worries other than some tweaking for pods. My experience more tweaking needed for higher end circuit versus lower speed circuit

To me it sounded like issue was very similar to junked out OEM carb parts in areas i said when I missed the fact they were new!

If aftermarket, how did size of needle jet/ jet needle compare with OEM? Slide cut too (2.0, 2.5, 3.0?)
Do these have an air jet that feeds Needle Jet? What about jet needle tapering versus OEM?

My guess not same as OEM if aftermarket (OK if I am wrong again, but if not imight be key things to look at).

[Tripleking]

Needle jet is probably too big as it is the only thing I have not changed. I am running a 110 main jet (a little bigger because I am using foam filters) and a 30 primary jet (this is similar to stock. I tried bigger primaries, but it runs better
with the 30 jets). The needle is the #5F21 which came with the carbs and the needle jet is the #182-N8 which came installed.

The carbs are Mikuni VM26-8074

thx

P.S. Since I cleaned the filters an oiled properly, the engine rise pretty will. It pulls nicely from 3,000 to about 5,500 (I have not taken in above as I am still breaking it in. However, it is pulling strongly and smoothly approaching 5,500 RPM. I there is any complaint, it is low rpm throttle response. Not much of a complaint though.

[JFISHSOLEVIBE]

Very interesting thread pertinent to my GT380...

All last year I used cone shaped fabric pod filters.

Decided to replace them this year and tried something different, I got shorter pods. At first I noticed the motor clearly running rich, and it has since slightly evened out (I'm assuming due to the oil on filters being minimized as I've ridden it).

Does filter shape have a great deal to do with how air is drawn in and at what rate?

[Tripleking]

Not sure. I know surface area matters. My pods have a 1-7/8 flange and a 2 inch body. They are four inches long. I would have preferred to use the stock air box, but mine was MIA when I bought it. I also have a GT380 and run K&N filters in the stock air box. I have mild expansion chambers and runs fine on stock jetting. However, slightly bigger jets might improve performance.

[Vintageman]

I depends how the stock jet needle starting dia compares to the one you have now if the Jet Needle is too big if you have to use that needle. It does sound like things are off down low where jet needle is deep in Jet needle. Also depends where taper begins on needle too versus EOM. Have you ever compared needle to OEM #5CN3 I think

Not sure if they are here -> http://www.iwt.com.au/MIKUNIjn.HTM" onclick="window.open(this.href);return false;

Those foam filter when you oil the get more restrictive of course but, if you had extra area you would not notice. And you don't have much area. You can jet for that but, kind of defeats the purpose of pods if for performance.

On dirt bikes and kart engines that need that oil to filter well I like foam but longer lengths and I usually have plenty of room so don't care about looks. I like foam oiled as I think it should be for know dusty applications, Grabs dirt better.

I like and K&N for road (less dirt), more area per size (folded, thinner), look nice just my opinion. Actually now days I like stock air box. You can mod for more flow too and still have OEM look too. Usually on eBay. What state/country are you in?