Q9: Any keihin needle experts?

A reference for the PWK carbs...
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freeindeed
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Q9: Any keihin needle experts?

Post by freeindeed » 01:02 pm Aug 17 2018

Assuming everything on my 2001 KDX220 is working well, I figure my next step in jetting would be a DGQ or EGQ needle.

The stock needle (R1173L or BGP), CEN needle and CEQ needle in the 5th needle clip position all make the bike run too lean from 1/4 RPM to 3/4 RPM, too rich from 1/8 to 1/4 RPM

So according to charts, it looks like DGQ would be next in line and then EGQ after that. There are no needles higher than Q for the 3rd letter.

DGQ:
(D=2 steps leaner from stock at 1/4 throttle-should help & 2 steps richer at 3/4 throttle-should help)
(G= 5 steps richer from stock at 1/4-3/4 throttle-should help)
(Q= 1 step leaner from stock at 1/8-1/4 throttle-should help)

Does that sound right?

John_S
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Re: Q9: Any keihin needle experts?

Post by John_S » 03:14 pm Aug 17 2018

This whole thing doesn't sound right to me. The 1/8 to 1/4 should be able to get close with any of those needles and the right size pilot jet. I don't mean to insult you but is this your first two stroke? One thats jetting really good will crackle along (not smooth and sound rich) if you're going at a constant speed with a constant throttle input, such as 10 mph with 1/8th throttle. But...as soon as you change the throttle position even a little it should pick up smooth until it stops accelerating (for your throttle input) and then its back to crackling along. All of these needles being lean at the 5th clip makes me wonder also. I think either you're heading in the wrong direction or the carb is worn out or something else is going on. Elevation and temps make a difference but the 220 should run pretty great (I would think) with the stock needle in one of the 5 clip positions with the right pilot and main. My stock needle on the 220 was either at 2nd or 3rd. The 1st clip was pinging lean and the 4th clip was blubbering rich.

D is a richer taper than stock at 1/4-3/4 all the way through. Its not leaner at 1/4 and richer at 3/4
G is the same L1 (39.95) if stock is BGP, not 5 steps richer
Q is one step leaner like you mentioned at 1/8-1/4

freeindeed
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Re: Q9: Any keihin needle experts?

Post by freeindeed » 03:59 pm Aug 17 2018

You are right. It should be DCQ or ECQ.

DCQ:
(D=2 steps leaner from stock at 1/4 throttle-should help & 2 steps richer at 3/4 throttle-should help)
(C= 4 steps richer from stock at 1/4-3/4 throttle-should help)
(Q= 1 step leaner from stock at 1/8-1/4 throttle-should help)

Yes, it makes sense that a D needle with a larger taper should be richer all the way through its taper.
But according to Canadian Dave on dirtrider.net:
"Jet Needle Taper – Taper changes are made to " rebalance" fuel delivery between 1/4 and 3/4 throttle.
This is an area a lot of mistakes are made. It’s important to remember we are talking about a taper (angle). Changing tapers doesn’t result in a linear change. Changing to a needle with a smaller taper, say a B taper (1 degree 15 minutes), to a smaller taper A (1 degree), richens the jetting at lower throttle setting (1/4 throttle) and leans the jetting at higher throttle settings (3/4 throttle). Going to a larger taper leans the mixture at lower throttle setting and richens higher settings."

I do not understand this because going from a (1 degree 15 minutes) taper to (1 degree) taper should be leaner all the way through? Except maybe where the taper ends and it transitions to the sharp pointer on the end?

No its not my 1st two stroke as I own a KDX400 and have previously owned KDX200's.
So I know you have to clear the extra fuel mix out by revving it now and then if the going is slow.
At the Mora, MN enduro, the bike was running so rich in the low end, I was having to pull in the clutch and rev up the motor every 15 seconds or so because of concerns of the bike flooding or fouling a spark plug. At the same time the bike was pinging in the midrange and had a peaky powerband which was a concern also.

I am hoping jetting will fix the problem.
Otherwise, it could get expensive.
The bike is nearly completely gone through and restored. Not the bottom end though.

But it could be:
1) An air leak. I have not had a leak down test done yet. But I did spray starter fluid mist all over while it was idling and did not find any problems.
2) The exhaust port was modified, without modifying the other ports. I would think this would throw the fuel and air flow out of balance. the only way to find out is put in a new cylinder? $600.
3) that possibly the stock carburetor does not work well with the RB designs head, exhaust port modified, gnarley woods pipe, Boyeson 607 reeds & airbox top and snorkel intact. A Lectron carb is $465.

John_S
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Re: Q9: Any keihin needle experts?

Post by John_S » 08:26 pm Aug 17 2018

That needle info is interesting how it affects the different ranges. I've read that post from Canadian Dave but i think I sort of glaze over when it starts getting too deep into the needles. I'm sorry to hear that you're putting in all the work and not getting the typical results. I had a heck of a time tuning my 220 and it ended up being an air leak (there were other things) that threw me off the most. It was leaking at the oring for the left side slotted KIPS cover. You would think if the shaft seals that press into the cylinder were doing their job that the oring on that cover wouldn't make that big of a difference. A leak down test showed i was losing a pound every couple minutes from that slotted cover. A new oring with no air loss, and the engine became predictable to jetting changes.

KDXDave
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Re: Q9: Any keihin needle experts?

Post by KDXDave » 02:25 pm Aug 19 2018

I wouldn't call myself an expert but I have played around with Sudco needles a bit on my KDX200 & KDX220. I haven't listed these needles yet but was thinking about it as I read this. Both my KDX's have R&B Carbs with R&B Head Mods (shaved for altitude and shaped for torque) V-Force 3 reeds. I'm usually riding at 7500 to 9000FT...I like the DEL, DEK best. BUT you are running at 200-300 feet.....Unknown to me? What I have are DDK, DDL, DDM, DEJ, DEL, DEK in the D series. I also have BEL, and a CEK. The BEL was rich everywhere for me. The CEK really woke up both the 200 & the 220! I ride mostly tight single track and the CEK was a liitle rich on the low end and came on too quick in the woods when the KIPPS opened. The run Gnarly Torque pipes that are kinda finished at 6200-6400RPM. If any of this interests you I'd sell you 3 needles shipped snail mail for $20... I have Paypal..... Thank you KDXDave
Member of the BlueRibbon Coalition, NMOHVA, Blackfeathers Trail Preservation Alliance Jemez Mountains NM single track rider: KDX200 KDX220 KTM200EXC

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