Putting a 30MM Carb on a CSC 2021 TT250

[Bob Kelly]

I saw a bunch of videos on guys putting a 28mm to 30mm carb on the hawk 250 and I have always thought that the carb on the TT250 was way too small
so I watched them with interest !
I followed the link one gave and found a 30MM Nibbi carb on Amazon and a intake manifold too that was supposed to fit the Hawk anyway so I got them
for less than $75.00 ...
Anyway they arrived in 2 days which was really fast for here !
and I now have the TT250 in the shop and all tore down...
but the intake manifold doesn't fit right... it bolts on fine but it puts the carb at a real steep angle which I don't like... (that's with the manifold upside down)
with the manifold on the way it should go.... the carb won't go on the manifold
as it hits the frame.... and with the TT250 it has a vacuum port on the stock manifold.... the new manifold I got doesn't have a vacuum port at all
.... so.... I've decided to make an intake manifold for it.
I scrounged around in the steel pile and found a 3/16" piece of plate just the right size to make the flange part and got it all cut out and smoothed up nicely... I then found a 1" piece of water pipe to use as the part for the carb to Hook on too... but it has to be at a different angle than the other one so the carb doesn't hit the frame.... and I got that all cut at the approximate angle and will probably weld it up this afternoon and see if it fits or not
....it's rather tight quarters so I may just tack it on there real good and then try test fitting it before I weld it completely on there... that would be prudent I think. <GRIN>
this carb should make a real big difference in the performance I would think
as the slide is much bigger than the stock slide ! (like almost a 1/4" larger in diameter !) the only thing I am worried about is ....it being too much carb for it ! LOL.... but that SHOULD be able to be tuned out with the jetting
but I have no idea if I can even get more jets for this carb or not... but I shouldn't have much trouble there.
.....
in the past I put a 200cc carb on a 90cc Honda and it made such a big difference it was unreal ! although it has a horrible sogg spot just off idle that was impossible to get rid of... but that was because the carb WAS too big... about 2 times what it should have been... this isn't the same at all
yes it's bigger but it is not so big that it should give me any trouble like that.
....I am hoping that won't be an issue....
I have already opened up some of the back pressure that they love to incorporate into the exhaust systems on motorcycles on this bike and I figure I have at least doubled it's ability to get rid of the exhaust...
as for the air intake , I want to continue to use the stock air box but I am thinking the top hood is a bit on the small size so I may open the snorkel at the top under the seat ... the rest I think will be able to handle the added air flow...
....left to do is make up a vacuum port for the CA. air pollution B.S. as I do live in California ! UGH !!!!
which shouldn't be too hard as I have a lathe and can just drill and tap a bolt hole and then take a bolt that thread size and trim it down and drill a 1/8" hole through it and lock-tight it in with red lock-tight !
.... the problem is ....it is cold in the shop now and I detest getting cold anymore .... so I may put it off a while.
.....
it should be an interesting experiment to see how much it helps the TT250
as acceleration right now is lacking and you could not possibly wheelie that machine without dumping the clutch ! ...there is no way !
I am hoping that this change will fix that ....
We shall see I guess.
....
Bob......

[JerryHawk250]

First of the PE30 is too big for the stock engine. You can get it to work but very hard to tune. You should get the PE28FL which will bolt right up like the stock carb without the need for an adapter.

https://www.amazon.com/Motorcycle-Ca...d670b6bc&psc=1

[Megadan]

Engine size alone is not a good indication of carb size match.

Larger carbs =/= more power either.

The CRF230F makes 19hp with a smaller 26mm bore venturi style carburetor than the CG250 that makes 15hp with a 30mm bore venturi style carburetor.

Fact is you will get more power from head porting and an exhaust than you ever will from a carburetor. People sell the carburetor thing as some miracle of power. It's easy to sell because it's easy to do. A ported head and a good exhaust on a stock carb will blow the doors off a stock engine with a bigger carburetor every single time.

[JerryHawk250]

Originally Posted by Megadan

Engine size alone is not a good indication of carb size match.

Larger carbs =/= more power either.

The CRF230F makes 19hp with a smaller 26mm bore venturi style carburetor than the CG250 that makes 15hp with a 30mm bore venturi style carburetor.

Fact is you will get more power from head porting and an exhaust than you ever will from a carburetor. People sell the carburetor thing as some miracle of power. It's easy to sell because it's easy to do. A ported head and a good exhaust on a stock carb will blow the doors off a stock engine with a bigger carburetor every single time.

Exactly!

[CheapThrills]

I have the PE30 (https://mymotorcycleblog.com/nibbi-c...allation-tbr7/) took more tweaking than my Mikuni but I do LIKE it.



hth,

[flopsweat]

I've also been toying with the idea of replacing my stock carb. What exactly kind of performance change would happen if I went with the PE28FL? There's a lot that I want to do aside from this, so I'm kinda figuring out the order of priority and whether or not changing the carb should be high up on the list. Would I need to find a jet kit as well? I think I went up one size from the super lean jetting that CSC has in their TT's.

[Deckard_Cain]

Originally Posted by flopsweat

I've also been toying with the idea of replacing my stock carb. What exactly kind of performance change would happen if I went with the PE28FL? There's a lot that I want to do aside from this, so I'm kinda figuring out the order of priority and whether or not changing the carb should be high up on the list. Would I need to find a jet kit as well? I think I went up one size from the super lean jetting that CSC has in their TT's.

Port the head and upgrade the exhaust... then worry about the carburetor. I put a VM26 on mine and then did the aforementioned upgrades, it was night and day. And the vm26 is nothing to write home about.

Just adding a carburetor without corresponding and complimentary changes isn't going to give the results that you're likely looking for.

[Megadan]

Originally Posted by flopsweat

I've also been toying with the idea of replacing my stock carb. What exactly kind of performance change would happen if I went with the PE28FL? There's a lot that I want to do aside from this, so I'm kinda figuring out the order of priority and whether or not changing the carb should be high up on the list. Would I need to find a jet kit as well? I think I went up one size from the super lean jetting that CSC has in their TT's.

The TT250 does have a better head casting than the Hawk but the exhaust is still a bit of a restriction. I would personally do an exhaust before I ever bothered with a carburetor. Only then would a carb upgrade possibly show any real advantages. Even then it's honestly not enough to justify it in my mind. Only after porting and even a cam does the need for better induction really start to show in my own experiences. Even then it's not much of a change.

You would likely need some jets but the real Nibbi carbs actually come with a small number of jets that are sized fairly close for a stock engine.

You also need to keep in mind that upgrading the carb means you will either need to run a pod filter or modify the intake tube and/or air box if you desire to retain it.

[flopsweat]

Ah see that's what I was wondering about, if just swapping the carb doesn't do much, then I probably wouldn't do it. I know nothing about porting a head, so that will likely not be in my foreseeable future. Would changing JUST the exhaust make any noticeable difference? I think I read I'd have to go up another level on the jetting with an aftermarket exhaust, which would be easy enough to do. I know a lot of people swap them just because of sound, but I couldn't care less about how it sounds, so just wondering if there's enough of a performance difference to even bother.

[Wild Dog]

Just to add more into what's been told already.

Like they said cc alone is not a good measurement for carb size or jetting, not even compression ratio is.
On a stock cg engine you are going to get better performance from something smaller than a true 30mm.
The stock exhaust headers on these motorcycles is way too restrictive, not just because they have a cat.

That's not carbon build up but solder that's there on purpose

the other end of the header.


In my case i wanted to keep the stock carb when i changed the whole exhaust for 304 stainless steel with a power bomb.

But unlucky me, it is a teikei mv28.
They make jets for 3 type of motorcycles 125, 230, 600. I dare anyone to find jets for it.. Some folks found out that some main jets by mikuni may work, but not ideal.
Full system exhaust, the head was worked on and matched to the new exhaust.
Dyno tested each time and the best setup was the pwk 28 (sudco copycat) with a 35 pilot and 120 main, the engine went from 17 something hp to 20 something hp.
Even with the work done on the head for my engine 35 is barely on the rich side.


If your motorcycle came with a carb that takes keihin jets, just get new jets and fine tune it.

Originally Posted by flopsweat

Would changing JUST the exhaust make any noticeable difference? I think I read I'd have to go up another level on the jetting with an aftermarket exhaust, which would be easy enough to do. I know a lot of people swap them just because of sound, but I couldn't care less about how it sounds, so just wondering if there's enough of a performance difference to even bother.

Most of these motorcycles are lean from the factory, if you put a slip on, you can get away with the stock jettings. But if you change the header, it will be way too lean, not to the point of destroying the engine in a few seconds but it will cut the lifespan of the engine

[CheapThrills]

I never really looked at my TBR7 stock exhaust piping, for those restrictive welds since I upgraded the piping pretty early in my riding. But, for my Boom Vader, I had to wait for the piping to come in after taking time to brake the motorcycle in, so I found a the stock exhaust had very restrictive weld joint.



Tried dremeling one out, but the metal was was very hard. Better to upgrade the piping.