DT250 Carb Choice

[Jumpjuly]

Hello,

Im in the process of building my DT250.

Current mods are:

- Mx250 Barrel & piston ( Highly Ported )
- Boyesen Reeds
- New Rear Shocks
- Custom Expansion Chamber
- New Coils

I am now at the stage of sorting out fuel delivery, what are peoples suggestions ?
What works best ? For the wank factor I would love a flatslide, but not imperative.

any suggestions would be great ! thanks.

[Nathan S]

What are you using the bike for?
If it has to stay Pre-75 or Pre-78 legal, then the only question is what size Mikuni round slide you fit: 34, 36 or maybe 38.

[Jumpjuly]

Im making it as a street / dirt tracker, something to scoot around the city on the take it into the fire roads and have a bit of dirt fun.

[Nathan S]

Hard to beat a PWK then.
Will idle at the lights, have better throttle response than virtually anything, hold its tune well (regardless of temp/altitude), is easy to get parts for, and still make about as much grunt as anything.

[cyclegod]

DT standard carb was a 30mm and MX was a 34mm, why not comprimise with a 32mm ? still streetable without being too thirsty.

[Jumpjuly]

Ok cool, the PWK sounds like the goods, the engine wouldn't need more fuel due to the porting and pipe ? I would assume I should go atleast the same size as a standard MX.

[Nathan S]

I'd go for a PWK35 or 36, subject to what physically fits*, what the porting is actually like, and how pleasant you want it to be at light throttle/cruising/etc. A 38 still wouldn't be completely out of the question.

*The PWK35 has a smaller body than a PWK36.

[Jumpjuly]

I do currently have a Mikuni TM flatslide, but I am at a loss on how to find out how big the carb is and whether or not it will work with my bike.

[shelpi]

The Sudco 5th Edition Tuning Manual is a great thing to have its got it all in there, will help in every way,
have a look! and its cheap

[Jumpjuly]

cool, $25 on ebay, sold !

[Nathan S]

There's numerous versions of flat slide Mikunis called "TM". The later TMX/TMXX are pretty good, I'm not so impressed by the earlier ones.
They're much harder to get jets for, and there's way less publicknowledge about needles, compared to the PWK. The Aussie Mikunis importer is GREAT to deal with, which eases the pain.

[Lozza]

All fall well short of the tunability and outright HP of either a round slide PHBE and flat slide VHSB Dellorto.




ultimate two stroke carby

[LWC82PE]

When were those Delortos first available? Would they be better than a Lectron?
What website can I find all the various dimensions on those?

[Nathan S]

Lozza loves his Dellortos, but they give me the shits:
Hard to get parts for;
Minimal knowledge base/publically available info;
Needle and seat will last a ridiculously short period of time;
Sensitive to temp/altitude changes.

I'm happy to accept that they're the best for performance - but the extra performance just isn't worth it to me.

[FourstrokeForever]

Lozza loves his Dellortos, but they give me the shits:
Hard to get parts for;
Minimal knowledge base/publically available info;
Needle and seat will last a ridiculously short period of time;
Sensitive to temp/altitude changes.

I'm happy to accept that they're the best for performance - but the extra performance just isn't worth it to me.

And I second that!

After years of tuning Dellortos on my early Husaberg(s) , I can honestly say that when Dellortos are new, they are great and hold their tune well. They are very sensitive to atmosphere conditions but a quick fiddle with the mixture screw usually cures hiccups. Once they start to wear, they are a pain in the brain (and wallet). It doesn't take long for the slide, needle and seat to start wearing.
Once I bit the bullet and forked out for a 41mm Keihin FCR, the difference is amazing. Easy to start, much better response, no hiccups on nasty hills.....

If your not worried about race eligibility, put a flatslide on it. I'd personally go for a 36mm as with the reeds, porting and pipe, the engine will love more fuel.