C & D Taper Needles

[Jeb]

I'm gonna be doing some serious jetting soon.

I've read a bunch of posts where C & D needles are compared on bikes with head/carb mods. I'll attempt to summarize: C-taper = earlier hit, D-taper = later hit. Different tapers from what I understand.

My bike: '03 220 w/ many air box holes & no snorkel, gnarly rev (K-30), stock silencer. I currently run Mobil 1 full synthetic at 32:1 with premium pump gas. Current needle is stock. Once I get the premix down, I've got some jets and several plugs for some serious plug chopping.

4 questions:

Would either needles have much impact on my current setup, i.e. even without the head/carb mods yet? Yeah, I know, go see for yourself, but I didn't want to get too involved in something that wasn't going to change things very much.

If the C and D needles are worth a go, anybody got the part numbers?

Premix Q1: I've seen the postings regarding the Amsoil Interceptor. My current selection for oil is so I can share premix with my son (Suzuki JR80). Any disadvantage using the Interceptor in the non-exhaust valve bike like the JR80? The mix ratio would change with the Interceptor . . .

Premix Q2: I'm considering dabbling with VP Racing's C12, like mixing some with the premium pump gas. Comments? I suspect - perhaps wrongly - the race gas makes more of a difference in more modified bikes, but I'm considering having a little fun with the race gas to see what happens. I don't suppose there's any disadvantage with having some C12 in the aircooled JR80 (again, we'd use the same premix)? The whole thing with race gas is just too cool not to consider . . . if there's enough indication it might make a difference.

As always, thanks for any input !!

And, yes, I'm eventually gonna go for some RB work in the future.

[m0rie]

Give a CEL a try with the stock carby and a #5 slide. I think you'll like the change...

Race fuel gives you more consistant jetting.

[Jeb]

Race fuel gives you more consistant jetting.

Why is this the case? In my feeble brain this is not immediately intuitive !

[m0rie]

Fuzzy could throw a better explanation out than I could but generally speaking race fuel is more consistent batch to batch than the stuff you buy at your local quickie mart. This consistency lets you run leaner on the edge jetting than you normally could because you don't have to worry (as much) about the octane and makeup of the fuel changing. When you start heavily modifying an engine and want to get that last little bit of extra performance out of it that consistency plays a key roll in jetting for that performance.

[fuzzy]

Morie got it dead on. Say you have a consistent environment(which doens't exist in the real world) where the air density is the same. You could jet to the gnat's butt with C12 because it's so consistent and run this jetting forever. Where as if you tried this with pump gas you could potentially stick the motor due to the fuel's inconsistency. In the real world we don't get the same air every day so minimal carb tuning is always required on any given day for your tune to be its best, and in this case you might as well be running pump gas. Keep in mind this is pertaining to C12 from sealed small drums....I wouldn't trust the C12 from a 2000gal tank at the drag strip in this manner.

In any engine you're best to run the fuel the engine was built to run. American cars? Don't waste your $ on anything above 87. KDX? Built to run in the low 90's 'octane wise.' Race gas won't hurt anything. You will have to jet leaner, will gain a bit of throttle response, and will lose top end power(would darn near need a dyno to see it though). Won't hurt JR, and yes running the same fuel/oil should be no problem at all no matter what 'blend' you cook up. That thing is probably on the rich side in which some race gas could make it run better. I think this is why some folks think race gas is better.....When they put it in their richly jetted bike it does in fact run better! Read up on tolulene on this site. A bit of tolulene mixed into your pump-gas premix will give nice throttle response without having to shell out big $ for C12. In conclusion the only time you should really run race gas (unless you have a fat wallet) is if you had your engine physically altered to take advantage of the fuel. In this case it's generally irreversable, and you say goodbye to pump gas forever. Oh, how sweet a 2T does run when it's been built for C12/etc though!!! Noticable power gains though the entire band, and that wickedly violent throttle response.

I've been wanting Gorr to 265 my WR for a while, and I think I might just take it up to him soon. If this is done 'mo tractability' porting will be requested along with having the head/etc cut for C12. I run it in my karts, and always have fuel left over (probably half of what I mix on a given day) that ends up getting burned in my tractor. Might as well cut the left over 12:1 kart fuel with fresh gas and use it in the bike. Yeah, that's cut as in double the quantity...LOL! The 12:1 fuel does help the slightly burnt valve in the john deere though.

[Mr. Wibbens]

And, yes, I'm eventually gonna go for some RB work in the future.

You won't regret it!

I just went from a CEK to a DEK

CEK to me was like a lght switch, either on or off, can't really get anywhere when you are sideways and spinning

DEK is more like one of those rotary dimmer light switches, just nice and smooth

[Indawoods]

I am getting my brother a CEL for Christmas... that's right I said "CHRISTMAS!"

I presently am using the DEK as well... very predictable but opens up nice. I like the CEK also but reserve it for more open areas....

[Indawoods]

Didn't the 89-94 models come with 1173 needles and the 95's come with 1174 needle tapers?

I recall swapping out the 92 I had with a 1174 needle.....

[Mr. Wibbens]

Didn't the 89-94 models come with 1173 needles and the 95's come with 1174 needle tapers?

I recall swapping out the 92 I had with a 1174 needle.....

I believe so, I had a 1174 before I got RB'd

[Jeb]

. . . You will have to jet leaner, will gain a bit of throttle response, and will lose top end power(would darn near need a dyno to see it though) . . . That thing is probably on the rich side in which some race gas could make it run better. I think this is why some folks think race gas is better.....When they put it in their richly jetted bike it does in fact run better!

One thing: I'm probably misunderstanding something about which you have a deeper understanding, but why would I need to jet leaner if running race gas tends to cure rich jetting?

Whatever the case, thanks!! I may just skip using race gas at least for now.

The toluene thing - interesting!! I literally use millions of gallons of the stuff as a solvent in one of our polymer processes at work (a piece of useless trivia).

[Jeb]

I am getting my brother a CEL for Christmas... that's right I said "CHRISTMAS!"

Is the CEL that good or that expensive ?

The part number: is it "CEL 017-017" or is it "N427-48-1'34-38.15-2.705" or am I crazy and just call a dealer?

[Indawoods]

It's not the cost thing... it's the thought. It's something he would not go out of his way to get but would like what it does.

Part number I haven't looked up yet, but will probably get it from SUDCO along with some various other things like gaskets and such....

[Jeb]

It's not the cost thing... it's the thought. It's something he would not go out of his way to get but would like what it does.

Part number I haven't looked up yet, but will probably get it from SUDCO along with some various other things like gaskets and such....

Your ARE a thoughtful brother . . .

BTW, what exactly does the CEL do?

[Colorado Mike]

might want to grab one of their jet boxes, pretty handy.

[Indawoods]

I seen those.... Pretty nice.

[canyncarvr]

RE: 'BTW, what exactly does the CEL do?'

Meaning compared to the OEM needle?

It's a taper thing, mostly. The 'C' being steeper angle-wise (changes diameter faster when the taper starts) it starts taperling later (farther down) the needle than does a 'B' needle.

That keeps the thicker (leaner) part of the needle in the needle jet longer in the throttle pull. BUT..that thicker part is indeed richer than the OEM needle.

The most important part of needles (sez me) is to understand that the L1 is NOT the length of the straight section of the needle. It is the length of the needle TO a given diameter, 2.515mm.

Now you can see why different taper angles matter so much..the taper starts in different places on the needle (with a given L1 and diameter).

The carb is pretty complicated considering the different circuits, how they overlap, when and how they work. What you want to get to is a place where one circuit doesn't smash/overshadow the other (WAY too rich coming off of WAY too lean). You want them to link smoothly.

That said, different needles will give your bike its 'personality'. Like Inda and Wibby said, a 'C' series is a lot of fun..and a real handful, too. Fun in the right places. A 'D' series is more forgiving, doesn't switch on/off quite as fast AND in higher throttle ranges where traction is less an issue.

It indeed comes down to what it is you want to get done..and then tune accordingly!

Try some toluene! You'll like it!!

Have fun!

[Bailey28]

Had a CEK set up from Ron's carb mods. Changed to a DEK and loved it, as CC said, it is smoother with more forgiving power delivery.

I will try an EEK I have laying around to see if it smooths it even more.

Currently---- 40/155, DEK-4, 2 9/16 SSS. runs great, very responsive. 70*F temp

[Jeb]

'Believe I'll try some toluene, this coming weekend perhaps . . . got a CEL and a DEL on the way!

How'd you guys start getting into needle changes, anyway? Many fiddle with jets, but few seem to tweak the needles (in my limited experiences).

Anybody ever fool with a jetting kit (for the KDX)? JD Jetting has kits for the 200 and the 220. I don't suppose there's anything magical in the kit that would take me beyond the knowledge base on this website, just curious . . .

[canyncarvr]

Re:'How'd you guys start...'

The needle being part of the jet setup...if you're going to 'rejet', might as well get that part figured out, too!

The needle being 'right' from Maw Kaw makes about as much sense as every other jet selection they made being right....they're not.

A needle tweak is a big fat deal. The few (however many) that do dial their bikes in needle-wise are happy campers!!!

I don't know what's in JD's kits. He is largely responsible for the trend toward the C and D angles. He's the first I recall mentioning the use of them.

Ron is responsible for a whole lot of it, too. Between his dyno and Dan's (Acutemp) seat-of-the-pants testing, 'we' got a Keihin that actually works!!

Did you ever happen to read JD's input on the RB Carb jetting thread of a few years back? He made a lot of sense of the senselessness of the 1173/4 needles Kawi used, more exactly what they had in mind, why they designed such a needle..and more importantly...why it DIDN'T WORK!

JD is responsible for finally getting it through my head that L1 had nothing to do with the section of needle that is actually straight! I mean...it's CALLED the 'straight section', so why wouldn't it BE STRAIGHT!!??



Needles can indeed be magical. Especially when you don't know what it is (not marked). It's not something you're likely to figure out with a set of calipers too easily. You CAN, it's just not easy.

When you have RB-Designs work on your carb, ask Ron to sell you a DEK and CEK as part of a 'try this' package. I think Ron generally sends his carbs out with a CEK needle. Not sure about that. The 'K' part of it works due to the throttle valve (slide) being machined to a 7mm cutaway in Ron's carbs.

Have fun!!

[Indawoods]

He sends the CEK to blow your mind!

It did mine... I thought I was back on the KTM 250!
Lots and lots of fun but will flat wear you out.

Then someone sent me a DEK, It is a much tamer hit and works extremely well in the woods... the right needle I might add.

I drop the CEK in on occasion for the addreline rush!